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<P style="MARGIN: 0in 0in 0pt; mso-layout-grid-align: none"
class=MsoNormal><SPAN
style="FONT-FAMILY: 'Trebuchet MS','sans-serif'; COLOR: black; mso-bidi-font-family: 'Trebuchet MS'"><?xml:namespace
prefix = o ns = "urn:schemas-microsoft-com:office:office" /><o:p><FONT
face="Times New Roman">Greetings and a good day to each of you!
</FONT></o:p></SPAN></P>
<P style="MARGIN: 0in 0in 0pt; mso-layout-grid-align: none"
class=MsoNormal><SPAN
style="FONT-FAMILY: 'Trebuchet MS','sans-serif'; COLOR: black; mso-bidi-font-family: 'Trebuchet MS'"><o:p><FONT
face="Times New Roman"></FONT></o:p></SPAN> </P>
<P style="MARGIN: 0in 0in 0pt; mso-layout-grid-align: none"
class=MsoNormal><SPAN
style="FONT-FAMILY: 'Trebuchet MS','sans-serif'; COLOR: black; mso-bidi-font-family: 'Trebuchet MS'"><o:p><FONT
face="Times New Roman">As I read through the most recent postings about the
"perfect engine" for our wood gas, I was reminded of a study done a few years
ago. Those involved, the authors of the abstract below are quite respected in
their field, while pioneering work that has contributed to many of the
small successes in our industry.
</FONT></o:p></SPAN></P>
<P style="MARGIN: 0in 0in 0pt; mso-layout-grid-align: none"
class=MsoNormal><SPAN
style="FONT-FAMILY: 'Trebuchet MS','sans-serif'; COLOR: black; mso-bidi-font-family: 'Trebuchet MS'"><o:p><FONT
face="Times New Roman"></FONT></o:p></SPAN> </P>
<P style="MARGIN: 0in 0in 0pt; mso-layout-grid-align: none"
class=MsoNormal><SPAN
style="FONT-FAMILY: 'Trebuchet MS','sans-serif'; COLOR: black; mso-bidi-font-family: 'Trebuchet MS'"><o:p><FONT
face="Times New Roman">Though a bit lengthy, the abstract is quite
revealing and may add something to the conversation. Respectfully, Bill Klein -
3i </FONT></o:p></SPAN></P>
<P style="MARGIN: 0in 0in 0pt; mso-layout-grid-align: none"
class=MsoNormal><SPAN
style="FONT-FAMILY: 'Trebuchet MS','sans-serif'; COLOR: black; mso-bidi-font-family: 'Trebuchet MS'"><o:p><FONT
face="Times New Roman"></FONT></o:p></SPAN> </P>
<P style="MARGIN: 0in 0in 0pt; mso-layout-grid-align: none"
class=MsoNormal><SPAN
style="FONT-FAMILY: 'Trebuchet MS','sans-serif'; COLOR: black; mso-bidi-font-family: 'Trebuchet MS'"><o:p> </o:p></SPAN></P>
<P style="MARGIN: 0in 0in 0pt; mso-layout-grid-align: none"
class=MsoNormal><SPAN
style="FONT-FAMILY: 'Trebuchet MS','sans-serif'; COLOR: black; mso-bidi-font-family: 'Trebuchet MS'"><o:p><FONT
face="Times New Roman"> </FONT></o:p></SPAN></P>
<P style="MARGIN: 0in 0in 0pt; mso-layout-grid-align: none"
class=MsoNormal><SPAN
style="FONT-FAMILY: 'Trebuchet MS','sans-serif'; COLOR: black; mso-bidi-font-family: 'Trebuchet MS'"><FONT
face="Times New Roman">Biomass and Bioenergy 21 (2001)
61–72<o:p></o:p></FONT></SPAN></P>
<P style="MARGIN: 0in 0in 0pt; mso-layout-grid-align: none"
class=MsoNormal><SPAN
style="FONT-FAMILY: 'Trebuchet MS','sans-serif'; COLOR: red; FONT-SIZE: 18pt; mso-bidi-font-family: 'Trebuchet MS'"><FONT
face="Times New Roman">Biomass derived producer gas as a
reciprocating<o:p></o:p></FONT></SPAN></P>
<P style="MARGIN: 0in 0in 0pt; mso-layout-grid-align: none"
class=MsoNormal><SPAN
style="FONT-FAMILY: 'Trebuchet MS','sans-serif'; COLOR: red; FONT-SIZE: 18pt; mso-bidi-font-family: 'Trebuchet MS'"><FONT
face="Times New Roman">engine fuel—an experimental
analysis<o:p></o:p></FONT></SPAN></P>
<P style="MARGIN: 0in 0in 0pt; mso-layout-grid-align: none"
class=MsoNormal><B><SPAN
style="FONT-FAMILY: 'Trebuchet MS','sans-serif'; COLOR: blue; mso-bidi-font-family: 'Trebuchet MS'"><FONT
face="Times New Roman">G. Sridhar <I>_</I>, P.J. Paul, H.S.
Mukunda<o:p></o:p></FONT></SPAN></B></P>
<P style="MARGIN: 0in 0in 0pt; mso-layout-grid-align: none"
class=MsoNormal><B><SPAN
style="FONT-FAMILY: 'Trebuchet MS','sans-serif'; COLOR: blue; FONT-SIZE: 10pt; mso-bidi-font-family: 'Trebuchet MS'"><FONT
face="Times New Roman">Combustion Gasification and Propulsion
Laboratory,<o:p></o:p></FONT></SPAN></B></P>
<P style="MARGIN: 0in 0in 0pt; mso-layout-grid-align: none"
class=MsoNormal><B><SPAN
style="FONT-FAMILY: 'Trebuchet MS','sans-serif'; COLOR: blue; FONT-SIZE: 10pt; mso-bidi-font-family: 'Trebuchet MS'"><FONT
face="Times New Roman">Department of Aerospace
Engineering,<o:p></o:p></FONT></SPAN></B></P>
<P style="MARGIN: 0in 0in 0pt; mso-layout-grid-align: none"
class=MsoNormal><B><SPAN
style="FONT-FAMILY: 'Trebuchet MS','sans-serif'; COLOR: blue; FONT-SIZE: 10pt; mso-bidi-font-family: 'Trebuchet MS'"><FONT
face="Times New Roman">Indian <?xml:namespace prefix = st1 ns =
"urn:schemas-microsoft-com:office:smarttags" /><st1:place
w:st="on"><st1:PlaceType w:st="on">Institute</st1:PlaceType> of <st1:PlaceName
w:st="on">Science</st1:PlaceName></st1:place>, <st1:City w:st="on"><st1:place
w:st="on">Bangalore</st1:place></st1:City> 560 012, <st1:country-region
w:st="on"><st1:place
w:st="on">India</st1:place></st1:country-region><o:p></o:p></FONT></SPAN></B></P>
<P style="MARGIN: 0in 0in 0pt; mso-layout-grid-align: none"
class=MsoNormal><B><SPAN
style="FONT-FAMILY: 'Trebuchet MS','sans-serif'; COLOR: blue; FONT-SIZE: 9pt; mso-bidi-font-family: 'Trebuchet MS'"><FONT
face="Times New Roman">Received <st1:date w:st="on" Year="2000" Day="28"
Month="6">28 June 2000</st1:date>; accepted <st1:date w:st="on" Year="2000"
Day="13" Month="12">13 December 2000</st1:date><o:p></o:p></FONT></SPAN></B></P>
<P style="MARGIN: 0in 0in 0pt; mso-layout-grid-align: none"
class=MsoNormal><B><SPAN
style="FONT-FAMILY: 'Trebuchet MS','sans-serif'; COLOR: black; FONT-SIZE: 11pt; mso-bidi-font-family: 'Trebuchet MS'"><FONT
face="Times New Roman">ABSTRACT<o:p></o:p></FONT></SPAN></B></P>
<P style="MARGIN: 0in 0in 0pt; mso-layout-grid-align: none"
class=MsoNormal><FONT face="Times New Roman"><SPAN
style="FONT-FAMILY: 'Trebuchet MS','sans-serif'; COLOR: black; FONT-SIZE: 10pt; mso-bidi-font-family: 'Trebuchet MS'">This
paper uncovers some of the misconceptions associated with the usage of producer
gas, a lower calorific gas as a reciprocating engine fuel. This paper
particularly addresses the use of producer gas in reciprocating engines at high
compression ratio (17 : 1), which hitherto had been restricted to lower
compression ratio (up to 12 : 1). This restriction in compression ratio has been
mainly attributed to the auto-ignition tendency of the fuel, which appears to be
simply a matter of presumption rather than fact. The current work clearly
indicates the breakdown of this compression ratio barrier and it is shown that
the engine runs smoothly at compression ratio of 17: 1 without any tendency of
auto-ignition. Experiments have been conducted on multi-cylinder spark ignition
engine modified from a production diesel engine at varying compression ratios
from 11:5: 1 to 17: 1 by retaining the combustion chamber design. As expected,
working at a higher compression ratio turned out to be more efficient and also
yielded higher brake power. A maximum brake power of 17:5 kWe was obtained at an
overall efficiency of 21% at the highest compression ratio. The maximum
de-rating of power in gas mode was 16% as compared to the normal diesel mode of
operation at comparable compression ratio, whereas, the overall efficiency
declined by 32.5%. A careful analysis of energy balance revealed excess energy
loss to the coolant due to the existing combustion chamber design. Addressing
the combustion chamber design for producer gas fuel should form a part of future
work in improving the overall efficiency. c</SPAN><I><SPAN
style="FONT-FAMILY: 'TrebuchetMS-Italic','sans-serif'; COLOR: black; FONT-SIZE: 10pt; mso-bidi-font-family: TrebuchetMS-Italic">_
</SPAN></I><SPAN
style="FONT-FAMILY: 'Trebuchet MS','sans-serif'; COLOR: black; FONT-SIZE: 10pt; mso-bidi-font-family: 'Trebuchet MS'">2001
Elsevier Science Ltd. All rights reserved.<o:p></o:p></SPAN></FONT></P>
<P style="MARGIN: 0in 0in 0pt; mso-layout-grid-align: none"
class=MsoNormal><FONT face="Times New Roman"><B><SPAN
style="FONT-FAMILY: 'Trebuchet MS','sans-serif'; COLOR: black; FONT-SIZE: 10pt; mso-bidi-font-family: 'Trebuchet MS'">Keywords</SPAN></B><SPAN
style="FONT-FAMILY: 'Trebuchet MS','sans-serif'; COLOR: black; FONT-SIZE: 10pt; mso-bidi-font-family: 'Trebuchet MS'">:
Biomass; Compression ratio; De-rating; Producer gas; Spark ignition
engine<o:p></o:p></SPAN></FONT></P>
<P style="MARGIN: 0in 0in 0pt; mso-layout-grid-align: none"
class=MsoNormal><B><SPAN
style="FONT-FAMILY: 'Trebuchet MS','sans-serif'; COLOR: black; FONT-SIZE: 11pt; mso-bidi-font-family: 'Trebuchet MS'"><o:p><FONT
face="Times New Roman"> </FONT></o:p></SPAN></B></P>
<P style="MARGIN: 0in 0in 0pt; mso-layout-grid-align: none"
class=MsoNormal><B><SPAN
style="FONT-FAMILY: 'Trebuchet MS','sans-serif'; COLOR: black; FONT-SIZE: 11pt; mso-bidi-font-family: 'Trebuchet MS'"><FONT
face="Times New Roman">1. Introduction<o:p></o:p></FONT></SPAN></B></P>
<P style="MARGIN: 0in 0in 0pt; mso-layout-grid-align: none"
class=MsoNormal><SPAN
style="FONT-FAMILY: 'Trebuchet MS','sans-serif'; COLOR: black; FONT-SIZE: 10pt; mso-bidi-font-family: 'Trebuchet MS'"><FONT
face="Times New Roman">With the renewed interest in biomass energy by necessity,
biomass-based technologies are achieving prominence not only as rural energy
devices but also as industrial power plants. Gasification is one such
process<o:p></o:p></FONT></SPAN></P>
<P style="MARGIN: 0in 0in 0pt; mso-layout-grid-align: none"
class=MsoNormal><FONT face="Times New Roman"><SPAN
style="FONT-FAMILY: 'MS Mincho'; COLOR: black; FONT-SIZE: 6.5pt; mso-bidi-font-family: 'MS Mincho'">∗</SPAN><SPAN
style="FONT-FAMILY: ArialUnicodeMS; COLOR: black; FONT-SIZE: 6.5pt; mso-bidi-font-family: ArialUnicodeMS">
</SPAN><SPAN
style="FONT-FAMILY: 'Arial','sans-serif'; COLOR: black; FONT-SIZE: 8pt">Corresponding
author. Tel.: +91-80-360-0536; fax: +91-80-3601692.<o:p></o:p></SPAN></FONT></P>
<P style="MARGIN: 0in 0in 0pt; mso-layout-grid-align: none"
class=MsoNormal><SPAN
style="FONT-FAMILY: 'Arial','sans-serif'; COLOR: black; FONT-SIZE: 8pt"><FONT
face="Times New Roman">E-mail address:
gsridhar@cgpl.iisc.ernet.in<o:p></o:p></FONT></SPAN></P>
<P style="MARGIN: 0in 0in 0pt; mso-layout-grid-align: none"
class=MsoNormal><SPAN
style="FONT-FAMILY: 'Arial','sans-serif'; COLOR: black; FONT-SIZE: 8pt"><FONT
face="Times New Roman">(G. Sridhar).<o:p></o:p></FONT></SPAN></P>
<P style="MARGIN: 0in 0in 0pt; mso-layout-grid-align: none"
class=MsoNormal><SPAN
style="FONT-FAMILY: 'Trebuchet MS','sans-serif'; COLOR: black; FONT-SIZE: 10pt; mso-bidi-font-family: 'Trebuchet MS'"><FONT
face="Times New Roman">where clean gas could be
generated<o:p></o:p></FONT></SPAN></P>
<P style="MARGIN: 0in 0in 0pt; mso-layout-grid-align: none"
class=MsoNormal><SPAN
style="FONT-FAMILY: 'Trebuchet MS','sans-serif'; COLOR: black; FONT-SIZE: 10pt; mso-bidi-font-family: 'Trebuchet MS'"><FONT
face="Times New Roman">using a wide variety of bio-residues as
the<o:p></o:p></FONT></SPAN></P>
<P style="MARGIN: 0in 0in 0pt; mso-layout-grid-align: none"
class=MsoNormal><SPAN
style="FONT-FAMILY: 'Trebuchet MS','sans-serif'; COLOR: black; FONT-SIZE: 10pt; mso-bidi-font-family: 'Trebuchet MS'"><FONT
face="Times New Roman">feed stock and in turn use the fuel gas for power
generation purposes. These are being used in standard diesel engines in
dual-fuel mode of operation so as to obtain diesel savings up to 85%. Operation
of engines on gas alone has been explored in some limited sense by a number of
researchers ever since World War II. In the<o:p></o:p></FONT></SPAN></P>
<P style="MARGIN: 0in 0in 0pt; mso-layout-grid-align: none"
class=MsoNormal><FONT face="Times New Roman"><SPAN
style="FONT-FAMILY: 'Trebuchet MS','sans-serif'; COLOR: black; FONT-SIZE: 10pt; mso-bidi-font-family: 'Trebuchet MS'">present
times, adopting these technologies has immense economic benefits; a route
pursued by a number of researchers is in </SPAN><SPAN
style="FONT-FAMILY: 'Arial','sans-serif'; COLOR: black; FONT-SIZE: 10pt">[1–5].<o:p></o:p></SPAN></FONT></P>
<P style="MARGIN: 0in 0in 0pt; mso-layout-grid-align: none"
class=MsoNormal><SPAN
style="FONT-FAMILY: 'Trebuchet MS','sans-serif'; COLOR: black; FONT-SIZE: 10pt; mso-bidi-font-family: 'Trebuchet MS'"><FONT
face="Times New Roman">Development of gas engines using producer gas has been
explored ever since World War II. It is estimated that over seven million
vehicles in <st1:place w:st="on">Europe</st1:place>, <st1:country-region
w:st="on"><st1:place w:st="on">Australia</st1:place></st1:country-region>,
<st1:place w:st="on">South America</st1:place> and <st1:place
w:st="on"><st1:PlaceName w:st="on">Pacific</st1:PlaceName> <st1:PlaceType
w:st="on">Islands</st1:PlaceType></st1:place> were converted to run on producer
gas during World War II. These engines were spark ignited engines, mostly in the
lower compression ratio bracket operating either on charcoal or biomass derived
gas. Extensive fieldwork has been carried at National Swedish Testing Institute
of Agricultural Machinery [1] by mounting gas generator and engine set on trucks
and tractors. There have also been sporadic installations at <st1:country-region
w:st="on"><st1:place w:st="on">Paraguay</st1:place></st1:country-region> and
<st1:country-region w:st="on"><st1:place w:st="on">Sri
Lanka</st1:place></st1:country-region> [1] for power generation
application.<o:p></o:p></FONT></SPAN></P>
<P style="MARGIN: 0in 0in 0pt; mso-layout-grid-align: none"
class=MsoNormal><SPAN
style="FONT-FAMILY: 'Trebuchet MS','sans-serif'; COLOR: black; FONT-SIZE: 10pt; mso-bidi-font-family: 'Trebuchet MS'"><FONT
face="Times New Roman">The question of power generation using producer gas has
been addressed in recent times by a few researchers [1, 2, 6] and attempts have
been made to convert standard compression ignition engine to a gas engine with
the relaxation imposed on the compression ratio (CR) and others [3] operating a
supercharged SI engine to realize the rated output. Also, one researcher [4] has
reported working on producer gas fuelled engine at high CR (16:5: 1) for water
pumping application without any sign of knock. There appears no earlier work on
a systematic study on the engine behavior using producer gas fuel. The other
important reason that appears responsible is the
non-availability<o:p></o:p></FONT></SPAN></P>
<P style="MARGIN: 0in 0in 0pt; mso-layout-grid-align: none"
class=MsoNormal><SPAN
style="FONT-FAMILY: 'Trebuchet MS','sans-serif'; COLOR: black; FONT-SIZE: 10pt; mso-bidi-font-family: 'Trebuchet MS'"><FONT
face="Times New Roman">of standard and proven gasification systems, which could
generate gas of consistent quality on a continuous basis for engine
applications.<o:p></o:p></FONT></SPAN></P>
<P style="MARGIN: 0in 0in 0pt; mso-layout-grid-align: none"
class=MsoNormal><SPAN
style="FONT-FAMILY: 'Trebuchet MS','sans-serif'; COLOR: black; FONT-SIZE: 10pt; mso-bidi-font-family: 'Trebuchet MS'"><FONT
face="Times New Roman">Systematic studies are essential from the viewpoint of
establishing the highest useful compression ratio (HUCR) for producer gas fuel
and also indirectly establish the octane rating for the fuel. This paper reports
work on a producer gas fuelled spark ignition<o:p></o:p></FONT></SPAN></P>
<P style="MARGIN: 0in 0in 0pt; mso-layout-grid-align: none"
class=MsoNormal><SPAN
style="FONT-FAMILY: 'Trebuchet MS','sans-serif'; COLOR: black; FONT-SIZE: 10pt; mso-bidi-font-family: 'Trebuchet MS'"><FONT
face="Times New Roman">engine converted from a production diesel
engine.<o:p></o:p></FONT></SPAN></P>
<P style="MARGIN: 0in 0in 0pt; mso-layout-grid-align: none"
class=MsoNormal><SPAN
style="FONT-FAMILY: 'Trebuchet MS','sans-serif'; COLOR: black; FONT-SIZE: 10pt; mso-bidi-font-family: 'Trebuchet MS'"><FONT
face="Times New Roman">A well researched, tested and an industrially proven
gasifier system capable of generating consistent quality was employed as the gas
generator for testing<o:p></o:p></FONT></SPAN></P>
<P style="MARGIN: 0in 0in 0pt; mso-layout-grid-align: none"
class=MsoNormal><SPAN
style="FONT-FAMILY: 'Trebuchet MS','sans-serif'; COLOR: black; FONT-SIZE: 10pt; mso-bidi-font-family: 'Trebuchet MS'"><FONT
face="Times New Roman">purpose [7, 8]. The engine has been tested and verified
at the highest compression ratio of 17: 1 in order to establish knock-less
performance by capturing the pressure-crank angle trace. Subsequently the engine
has been tested at varying CRs so as to arrive at an optimum CR for maximum
brake power and affiance. The overall energy balance has been analyzed and the
shortcomings identified. Also the emission levels in terms of CO and NO have
been examined.<o:p></o:p></FONT></SPAN></P>
<P style="MARGIN: 0in 0in 0pt; mso-layout-grid-align: none"
class=MsoNormal><B><SPAN
style="FONT-FAMILY: 'Arial','sans-serif'; COLOR: black; FONT-SIZE: 10pt"><FONT
face="Times New Roman">2. Misconceptions and
clarification<o:p></o:p></FONT></SPAN></B></P>
<P style="MARGIN: 0in 0in 0pt; mso-layout-grid-align: none"
class=MsoNormal><SPAN
style="FONT-FAMILY: 'Trebuchet MS','sans-serif'; COLOR: black; FONT-SIZE: 10pt; mso-bidi-font-family: 'Trebuchet MS'"><FONT
face="Times New Roman">Prior to this development there have been two
misconceptions regarding producer gas fuel and they are identified as follows:
(1) auto-ignition tendency at higher CR when used in reciprocating engine, (2)
large de-rating in power due to calorific value of the fuel being
low.<o:p></o:p></FONT></SPAN></P>
<P style="MARGIN: 0in 0in 0pt; mso-layout-grid-align: none"
class=MsoNormal><SPAN
style="FONT-FAMILY: 'Trebuchet MS','sans-serif'; COLOR: black; FONT-SIZE: 10pt; mso-bidi-font-family: 'Trebuchet MS'"><FONT
face="Times New Roman">It was thought that these perceptions had no reasonable
basis. Indeed, the basis for the contrary seemed to exist. Firstly, producer gas
being a mixture of many gas species with large fraction being inert should have
higher octane rating when compared to natural gas and biogas. The gas contains a
large fraction of inert gases like CO2 and N2 accounting to 12–15% and 48–50%,
respectively, and these could act as knock suppressors [9]. However, so far
there has not been any research of octane rating test conducted on producer gas
fuel. Moreover, it is not clear if any established test procedure exists for
producer gas like the Methane number test for natural gas and biogas. One crude
way of assessment is to test the fuel gas in standard engines and place them
accordingly in the octane rating table.<o:p></o:p></FONT></SPAN></P>
<P style="MARGIN: 0in 0in 0pt; mso-layout-grid-align: none"
class=MsoNormal><FONT face="Times New Roman"><SPAN
style="FONT-FAMILY: 'Trebuchet MS','sans-serif'; COLOR: black; FONT-SIZE: 10pt; mso-bidi-font-family: 'Trebuchet MS'">Secondly,
there is a general thinking that producer gas being a lower calorific fuel, the
extent of de-rating would be large when compared to high calorific value fuels
like natural gas (NG) and liquefied petroleum gas (LPG). The de-rating if any
could be due to two possible reasons. Firstly, with the lower energy density
fuels there is a net decrease in number of molecules when compared to
high-energy fuels like diesel, gasoline, NG or LPG. This contributes to some
de-rating in case of low energy density fuels [10]. De-rating of power on
account of calorific value will be small because of marginal differences in the
energy release per unit mixture (air+fuel gas) [11]. This can be explained as
follows. The calorific value of producer gas varies between 4.7 and 5:0 MJ N
m</SPAN><I><SPAN
style="FONT-FAMILY: 'TrebuchetMS-Italic','sans-serif'; COLOR: black; FONT-SIZE: 10pt; mso-bidi-font-family: TrebuchetMS-Italic">−</SPAN></I><SPAN
style="FONT-FAMILY: 'Trebuchet MS','sans-serif'; COLOR: black; FONT-SIZE: 10pt; mso-bidi-font-family: 'Trebuchet MS'">3
as against 30 MJ N m</SPAN><I><SPAN
style="FONT-FAMILY: 'TrebuchetMS-Italic','sans-serif'; COLOR: black; FONT-SIZE: 10pt; mso-bidi-font-family: TrebuchetMS-Italic">−</SPAN></I><SPAN
style="FONT-FAMILY: 'Trebuchet MS','sans-serif'; COLOR: black; FONT-SIZE: 10pt; mso-bidi-font-family: 'Trebuchet MS'">3
for NG. The energy density per unit (producer gas +air) mixture is only 15–20%
lower than NG and air mixture even though the calorific value of producer gas is
one-eighth of NG. This is because the stoichiometric air=fuel ratio for producer
gas is 1.2 as compared to 17 for NG. Hence the extent of de-rating with producer
gas would not be marginal compared to NG fuelled operation at comparable
operating conditions. This gap could be nullified by working producer
gas<o:p></o:p></SPAN></FONT></P>
<P style="MARGIN: 0in 0in 0pt; mso-layout-grid-align: none"
class=MsoNormal><SPAN
style="FONT-FAMILY: 'Trebuchet MS','sans-serif'; COLOR: black; FONT-SIZE: 10pt; mso-bidi-font-family: 'Trebuchet MS'"><FONT
face="Times New Roman">at higher CR when compared to NG. The upper limit of CR
for NG has been identified to be around 15:8: 1 based on a recent work
[10].<o:p></o:p></FONT></SPAN></P>
<P style="MARGIN: 0in 0in 0pt; mso-layout-grid-align: none"
class=MsoNormal><B><SPAN
style="FONT-FAMILY: 'Arial','sans-serif'; COLOR: black; FONT-SIZE: 10pt"><o:p><FONT
face="Times New Roman"> </FONT></o:p></SPAN></B></P>
<P style="MARGIN: 0in 0in 0pt; mso-layout-grid-align: none"
class=MsoNormal><B><SPAN
style="FONT-FAMILY: 'Arial','sans-serif'; COLOR: black; FONT-SIZE: 10pt"><o:p><FONT
face="Times New Roman"> </FONT></o:p></SPAN></B></P>
<P style="MARGIN: 0in 0in 0pt; mso-layout-grid-align: none"
class=MsoNormal><B><SPAN
style="FONT-FAMILY: 'Arial','sans-serif'; COLOR: black; FONT-SIZE: 10pt"><o:p><FONT
face="Times New Roman"> </FONT></o:p></SPAN></B></P>
<P style="MARGIN: 0in 0in 0pt; mso-layout-grid-align: none"
class=MsoNormal><B><SPAN
style="FONT-FAMILY: 'Arial','sans-serif'; COLOR: black; FONT-SIZE: 10pt"><FONT
face="Times New Roman">3. Earlier work<o:p></o:p></FONT></SPAN></B></P>
<P style="MARGIN: 0in 0in 0pt; mso-layout-grid-align: none"
class=MsoNormal><SPAN
style="FONT-FAMILY: 'Trebuchet MS','sans-serif'; COLOR: black; FONT-SIZE: 10pt; mso-bidi-font-family: 'Trebuchet MS'"><FONT
face="Times New Roman">Shashikantha et al. [2] has reported related work on a
converted diesel engine at CR of 11:5: 1. In addition to the change in CR, the
combustion chamber of the original engine i.e. bowl-in piston
(hemispherical)<o:p></o:p></FONT></SPAN></P>
<P style="MARGIN: 0in 0in 0pt; mso-layout-grid-align: none"
class=MsoNormal><SPAN
style="FONT-FAMILY: 'Trebuchet MS','sans-serif'; COLOR: black; FONT-SIZE: 10pt; mso-bidi-font-family: 'Trebuchet MS'"><FONT
face="Times New Roman">was modified to Hesselman (shallow W) with an aim of
achieving a higher level of turbulence by squish rather than swirl. With the
above modification a power output of 16 kWe has been reported in
gas<o:p></o:p></FONT></SPAN></P>
<P style="MARGIN: 0in 0in 0pt; mso-layout-grid-align: none"
class=MsoNormal><SPAN
style="FONT-FAMILY: 'Trebuchet MS','sans-serif'; COLOR: black; FONT-SIZE: 10pt; mso-bidi-font-family: 'Trebuchet MS'"><FONT
face="Times New Roman">made with efficiency in the range of 21–24% against a
rated output of 17 kWe in diesel mode. However, the same authors [6]
subsequently claim a lower output and efficiency of 11:2 kWe and 15%. These
authors do discuss the knock tendencies at higher CR but no experimental
evidence seems to be provided in support. Measurements have been reported of
various parameters including that of exhaust emissions; however no measurements
have been made with respect to gas composition, which is considered essential
from the viewpoint of establishment of input
energy.<o:p></o:p></FONT></SPAN></P>
<P style="MARGIN: 0in 0in 0pt; mso-layout-grid-align: none"
class=MsoNormal><SPAN
style="FONT-FAMILY: 'Trebuchet MS','sans-serif'; COLOR: black; FONT-SIZE: 10pt; mso-bidi-font-family: 'Trebuchet MS'"><FONT
face="Times New Roman">The first experimental work in the higher CR range has
been reported by Ramachandra [4] on a single cylinder diesel engine (16:5: 1 CR)
coupled to a water pump. A power de-rating of 20% has been reported at an
overall efficiency of 19% without any signs of detonation. This work does not
report any other measurement like the pressure-crank angle diagram in order to
rationalize some of the results. Work on gasoline engine operation on producer
gas has been reported by Parke [12] with de-rating claims of 34%, compared to
gasoline operation. The same authors [3] suggest supercharging
to<o:p></o:p></FONT></SPAN></P>
<P style="MARGIN: 0in 0in 0pt; mso-layout-grid-align: none"
class=MsoNormal><SPAN
style="FONT-FAMILY: 'Trebuchet MS','sans-serif'; COLOR: black; FONT-SIZE: 10pt; mso-bidi-font-family: 'Trebuchet MS'"><FONT
face="Times New Roman">enhance the engine output. Martin and Wauters [5] have
reported work using charcoal gas and producer gas on an SI engine with a
de-rating of 50% and 40%, respectively, at a CR of 7: 1. However, the same
authors claim 20% de-rating when worked with producer gas at a CR of 11: 1. The
authors present a CR barrier of 14: 1 and 11: 1 for charcoal and producer gas,
respectively, with inadequate experimental justification. From the literature
survey it appears that no experimental evidence is available to support the
phenomenon of knock in producer gas engines, even though it is believed knock
would occur at higher CR.<o:p></o:p></FONT></SPAN></P>
<P style="MARGIN: 0in 0in 0pt; mso-layout-grid-align: none"
class=MsoNormal><B><SPAN
style="FONT-FAMILY: 'Arial','sans-serif'; COLOR: black; FONT-SIZE: 10pt"><FONT
face="Times New Roman">4. Current
investigations<o:p></o:p></FONT></SPAN></B></P>
<P style="MARGIN: 0in 0in 0pt; mso-layout-grid-align: none"
class=MsoNormal><SPAN
style="FONT-FAMILY: 'Trebuchet MS','sans-serif'; COLOR: black; FONT-SIZE: 10pt; mso-bidi-font-family: 'Trebuchet MS'"><FONT
face="Times New Roman">It is a well-acknowledged fact that it is desirable to
operate an internal combustion engine at the highest possible CR so as to attain
higher overall efficiencies. But the gain in efficiency beyond a certain CR can
be expected to be marginal due to other influencing factors such as heat loss
and friction. In the case of an SI engine the limitation of CR comes from the
knock sensitivity of the fuel. It has been experimentally investigated that the
upper limit for compression ratio for SI engine operation is 17: 1 beyond which
there is a fall in efficiency [13]. The above
conclusion<o:p></o:p></FONT></SPAN></P>
<P style="MARGIN: 0in 0in 0pt; mso-layout-grid-align: none"
class=MsoNormal><FONT face="Times New Roman"><SPAN
style="FONT-FAMILY: 'Trebuchet MS','sans-serif'; COLOR: black; FONT-SIZE: 10pt; mso-bidi-font-family: 'Trebuchet MS'">is
based on extensive tests with iso-octane as the fuel also doped with anti-knock
agent. If one were to consider this as the upper limit and since no other work
has been conducted at higher CR for SI engines, choosing a production engine in
the above range for the current investigation seemed very appropriate. The
current investigation was conducted on a commercially available diesel engine so
as to explore the possibility of working at the existing CR of 17: 1 and
optimizing the same if required. At the onset of investigation, it was perceived
that increase in CR could have conflicting effects on the power output of the
engine. This could be explained as follows. It has been universally recognized
that turbulent flame speed [9] plays a vital role in the heat release rate
during the combustion process in an engine cylinder. The turbulent flame speed
can be treated as an enhanced form of laminar flame under the influence of time
varying turbulence [9] within the combustion </SPAN><SPAN
style="FONT-FAMILY: 'Arial','sans-serif'; COLOR: black; FONT-SIZE: 10pt">chamber
of the engine. The laminar flame </SPAN><SPAN
style="FONT-FAMILY: 'Trebuchet MS','sans-serif'; COLOR: black; FONT-SIZE: 10pt; mso-bidi-font-family: 'Trebuchet MS'">speed
is again a function of initial pressure, temperature and the mixture
composition. An earlier computational work by Mishra [14] indicated that the
laminar flame speed for stoichiometric producer gas and air mixture could
decrease by one-tenth as the initial pressure is enhanced by a factor of 40.
However, these calculations were made at an initial temperature of 300K, and the
initial temperature at which combustion starts is high in the case of internal
Combustion engines. The influence of initial pressure and temperature on laminar
flame speed can be explained in simple terms as follows. The increase in the
unburned gas temperature results in increase in adiabatic flame temperature and
hence the average reaction rates. The increase in the reaction rate is a result
of the increase in the number of radicals released—thus contributing to increase
in the flame speed, whereas the rise in pressure can result in reduction in the
amount of radicals released thus retarding the flame speed. Therefore, the
conflicting nature of the effects of initial pressure and temperature needs to
be recognized. The effect of these at varying CR is an additional feature that
needs to be recognized in order to arrive at the optimum CR. Consequently, the
present investigation was started with an assumption that the optimum
compression ratio would be between 12: 1 and 17: 1 for maximum power output and
overall efficiency.<o:p></o:p></SPAN></FONT></P>
<P style="MARGIN: 0in 0in 0pt; mso-layout-grid-align: none"
class=MsoNormal><SPAN
style="FONT-FAMILY: 'Trebuchet MS','sans-serif'; COLOR: black; FONT-SIZE: 10pt; mso-bidi-font-family: 'Trebuchet MS'"><FONT
face="Times New Roman">In the current investigation, CR was the parameter that
was varied. The influence of CR on power, efficiency and emissions has been
studied in some detail. Minimum ignition advance for best torque (MBT) has been
determined at different Rs. The variation of cylinder pressure with time has
been captured using a piezo-based transducer. The overall energy balance has
been projected.<o:p></o:p></FONT></SPAN></P>
<P style="MARGIN: 0in 0in 0pt; mso-layout-grid-align: none"
class=MsoNormal><B><SPAN
style="FONT-FAMILY: 'Arial','sans-serif'; COLOR: black; FONT-SIZE: 10pt"><FONT
face="Times New Roman">5. Conversion
methodologies<o:p></o:p></FONT></SPAN></B></P>
<P style="MARGIN: 0in 0in 0pt; mso-layout-grid-align: none"
class=MsoNormal><SPAN
style="FONT-FAMILY: 'Trebuchet MS','sans-serif'; COLOR: black; FONT-SIZE: 10pt; mso-bidi-font-family: 'Trebuchet MS'"><FONT
face="Times New Roman">A three cylinder, direct injection diesel engine of 3:3 l
capacity, with a CR of 17: 1 was converted into a spark ignition engine to drive
a 25-kVA alternator. The salient features of the engine are given in Table
1.<o:p></o:p></FONT></SPAN></P>
<P style="MARGIN: 0in 0in 0pt; mso-layout-grid-align: none"
class=MsoNormal><SPAN
style="FONT-FAMILY: 'Trebuchet MS','sans-serif'; COLOR: black; FONT-SIZE: 10pt; mso-bidi-font-family: 'Trebuchet MS'"><FONT
face="Times New Roman">Modifications attempted on the engine for conversion are
as follows:<o:p></o:p></FONT></SPAN></P>
<P style="MARGIN: 0in 0in 0pt; mso-layout-grid-align: none"
class=MsoNormal><SPAN
style="FONT-FAMILY: 'Trebuchet MS','sans-serif'; COLOR: black; FONT-SIZE: 10pt; mso-bidi-font-family: 'Trebuchet MS'"><FONT
face="Times New Roman">1. Insertion of spark plug in place of fuel injectors
without changing its location (centrally located).<o:p></o:p></FONT></SPAN></P>
<P style="MARGIN: 0in 0in 0pt; mso-layout-grid-align: none"
class=MsoNormal><SPAN
style="FONT-FAMILY: 'Trebuchet MS','sans-serif'; COLOR: black; FONT-SIZE: 10pt; mso-bidi-font-family: 'Trebuchet MS'"><FONT
face="Times New Roman">2. Adaptation of a distributor type battery based
ignition system with a provision to advance=retard ignition timing. The set
ignition timing was checked using a stroboscope.<o:p></o:p></FONT></SPAN></P>
<P style="MARGIN: 0in 0in 0pt; mso-layout-grid-align: none"
class=MsoNormal><SPAN
style="FONT-FAMILY: 'Trebuchet MS','sans-serif'; COLOR: black; FONT-SIZE: 10pt; mso-bidi-font-family: 'Trebuchet MS'"><FONT
face="Times New Roman">3. The combustion chamber design comprising a flat
cylinder head and bowl-in piston was retained. No attempts were made to change
the combustion chamber design except that the thickness of the cylinder head
gasket was varied to accomplish different CRs of 17 : 1, 14:5 : 1, 13:5 : 1 and
11:5 : 1.<o:p></o:p></FONT></SPAN></P>
<P style="MARGIN: 0in 0in 0pt; mso-layout-grid-align: none"
class=MsoNormal><SPAN
style="FONT-FAMILY: 'Trebuchet MS','sans-serif'; COLOR: black; FONT-SIZE: 10pt; mso-bidi-font-family: 'Trebuchet MS'"><FONT
face="Times New Roman">4. For in-cylinder pressure measurement, provision was
made on one cylinder head by drilling a 1:5 mm diameter hole for pressure
measurement and fitting an optical sensor on the crankshaft for crank angle
measurement.<o:p></o:p></FONT></SPAN></P>
<P style="MARGIN: 0in 0in 0pt; mso-layout-grid-align: none"
class=MsoNormal><B><SPAN
style="FONT-FAMILY: 'Arial','sans-serif'; COLOR: black; FONT-SIZE: 10pt"><FONT
face="Times New Roman">6. Experimental set-up and measurement
scheme<o:p></o:p></FONT></SPAN></B></P>
<P style="MARGIN: 0in 0in 0pt; mso-layout-grid-align: none"
class=MsoNormal><FONT face="Times New Roman"><SPAN
style="FONT-FAMILY: 'Trebuchet MS','sans-serif'; COLOR: black; FONT-SIZE: 10pt; mso-bidi-font-family: 'Trebuchet MS'">The
well-researched, tested and industrial version of IISc’s-open top down draft,
twin air entry 75 kg h</SPAN><I><SPAN
style="FONT-FAMILY: 'TrebuchetMS-Italic','sans-serif'; COLOR: black; FONT-SIZE: 7pt; mso-bidi-font-family: TrebuchetMS-Italic">−</SPAN></I><SPAN
style="FONT-FAMILY: 'Trebuchet MS','sans-serif'; COLOR: black; FONT-SIZE: 7pt; mso-bidi-font-family: 'Trebuchet MS'">1
</SPAN><SPAN
style="FONT-FAMILY: 'Trebuchet MS','sans-serif'; COLOR: black; FONT-SIZE: 10pt; mso-bidi-font-family: 'Trebuchet MS'">solid
bio-residue gasifier system [7] formed the gas generator. This state-of-the art
technology has undergone<o:p></o:p></SPAN></FONT></P>
<P style="MARGIN: 0in 0in 0pt; mso-layout-grid-align: none"
class=MsoNormal><SPAN
style="FONT-FAMILY: 'Trebuchet MS','sans-serif'; COLOR: black; FONT-SIZE: 10pt; mso-bidi-font-family: 'Trebuchet MS'"><FONT
face="Times New Roman">extensive testing both in <st1:country-region
w:st="on"><st1:place w:st="on">India</st1:place></st1:country-region> [8] and
overseas [15] and proven to be a world-class system. The system has qualified
for long hours of continuous operation in meeting the industrial requirements in
terms of generation of consistent quality gas. The overall details of the
gasifier system are presented in Fig. 1. As shown in the figure, the system had
the provision to test the quality of the gas prior to supply
to<o:p></o:p></FONT></SPAN></P>
<P style="MARGIN: 0in 0in 0pt; mso-layout-grid-align: none"
class=MsoNormal><SPAN
style="FONT-FAMILY: 'Arial','sans-serif'; COLOR: black; FONT-SIZE: 10pt"><FONT
face="Times New Roman">engine. At the engine intake, a carburetor is
provided<o:p></o:p></FONT></SPAN></P>
<P style="MARGIN: 0in 0in 0pt; mso-layout-grid-align: none"
class=MsoNormal><SPAN
style="FONT-FAMILY: 'Trebuchet MS','sans-serif'; COLOR: black; FONT-SIZE: 10pt; mso-bidi-font-family: 'Trebuchet MS'"><FONT
face="Times New Roman">the engine. At the engine intake, a carburetor is
provided for proportioning air and fuel flow. As there were no carburetors
commercially available to cater to producer gas, a locally made carburetion
system and manually controlled valve were used for
proportioning.<o:p></o:p></FONT></SPAN></P>
<P style="MARGIN: 0in 0in 0pt; mso-layout-grid-align: none"
class=MsoNormal><SPAN
style="FONT-FAMILY: 'Trebuchet MS','sans-serif'; COLOR: black; FONT-SIZE: 10pt; mso-bidi-font-family: 'Trebuchet MS'"><FONT
face="Times New Roman">Measurements were made with respect to the following
parameters:<o:p></o:p></FONT></SPAN></P>
<P style="MARGIN: 0in 0in 0pt; mso-layout-grid-align: none"
class=MsoNormal><FONT face="Times New Roman"><SPAN
style="FONT-FAMILY: 'Trebuchet MS','sans-serif'; COLOR: black; FONT-SIZE: 10pt; mso-bidi-font-family: 'Trebuchet MS'">(A)
Producer gas compositions using on-line gas analyzers. The gases analyzed were
CO, CO</SPAN><SPAN
style="FONT-FAMILY: 'Trebuchet MS','sans-serif'; COLOR: black; FONT-SIZE: 7pt; mso-bidi-font-family: 'Trebuchet MS'">2</SPAN><SPAN
style="FONT-FAMILY: 'Trebuchet MS','sans-serif'; COLOR: black; FONT-SIZE: 10pt; mso-bidi-font-family: 'Trebuchet MS'">,
CH</SPAN><SPAN
style="FONT-FAMILY: 'Trebuchet MS','sans-serif'; COLOR: black; FONT-SIZE: 7pt; mso-bidi-font-family: 'Trebuchet MS'">4</SPAN><SPAN
style="FONT-FAMILY: 'Trebuchet MS','sans-serif'; COLOR: black; FONT-SIZE: 10pt; mso-bidi-font-family: 'Trebuchet MS'">,
O</SPAN><SPAN
style="FONT-FAMILY: 'Trebuchet MS','sans-serif'; COLOR: black; FONT-SIZE: 7pt; mso-bidi-font-family: 'Trebuchet MS'">2
</SPAN><SPAN
style="FONT-FAMILY: 'Trebuchet MS','sans-serif'; COLOR: black; FONT-SIZE: 10pt; mso-bidi-font-family: 'Trebuchet MS'">and
H</SPAN><SPAN
style="FONT-FAMILY: 'Trebuchet MS','sans-serif'; COLOR: black; FONT-SIZE: 7pt; mso-bidi-font-family: 'Trebuchet MS'">2</SPAN><SPAN
style="FONT-FAMILY: 'Trebuchet MS','sans-serif'; COLOR: black; FONT-SIZE: 10pt; mso-bidi-font-family: 'Trebuchet MS'">.
The N</SPAN><SPAN
style="FONT-FAMILY: 'Trebuchet MS','sans-serif'; COLOR: black; FONT-SIZE: 7pt; mso-bidi-font-family: 'Trebuchet MS'">2
</SPAN><SPAN
style="FONT-FAMILY: 'Trebuchet MS','sans-serif'; COLOR: black; FONT-SIZE: 10pt; mso-bidi-font-family: 'Trebuchet MS'">concentration
was deduced by difference. The CO, CO</SPAN><SPAN
style="FONT-FAMILY: 'Trebuchet MS','sans-serif'; COLOR: black; FONT-SIZE: 7pt; mso-bidi-font-family: 'Trebuchet MS'">2</SPAN><SPAN
style="FONT-FAMILY: 'Trebuchet MS','sans-serif'; COLOR: black; FONT-SIZE: 10pt; mso-bidi-font-family: 'Trebuchet MS'">,
CH</SPAN><SPAN
style="FONT-FAMILY: 'Trebuchet MS','sans-serif'; COLOR: black; FONT-SIZE: 7pt; mso-bidi-font-family: 'Trebuchet MS'">4
</SPAN><SPAN
style="FONT-FAMILY: 'Trebuchet MS','sans-serif'; COLOR: black; FONT-SIZE: 10pt; mso-bidi-font-family: 'Trebuchet MS'">components
were determined using infrared gas analyzers and the H</SPAN><SPAN
style="FONT-FAMILY: 'Trebuchet MS','sans-serif'; COLOR: black; FONT-SIZE: 7pt; mso-bidi-font-family: 'Trebuchet MS'">2
</SPAN><SPAN
style="FONT-FAMILY: 'Trebuchet MS','sans-serif'; COLOR: black; FONT-SIZE: 10pt; mso-bidi-font-family: 'Trebuchet MS'">component
using a thermal conductivity-based analyzer. The O</SPAN><SPAN
style="FONT-FAMILY: 'Trebuchet MS','sans-serif'; COLOR: black; FONT-SIZE: 7pt; mso-bidi-font-family: 'Trebuchet MS'">2
</SPAN><SPAN
style="FONT-FAMILY: 'Trebuchet MS','sans-serif'; COLOR: black; FONT-SIZE: 10pt; mso-bidi-font-family: 'Trebuchet MS'">measurement
system was based on chemical cell.<o:p></o:p></SPAN></FONT></P>
<P style="MARGIN: 0in 0in 0pt; mso-layout-grid-align: none"
class=MsoNormal><SPAN
style="FONT-FAMILY: 'Trebuchet MS','sans-serif'; COLOR: black; FONT-SIZE: 10pt; mso-bidi-font-family: 'Trebuchet MS'"><FONT
face="Times New Roman">(B) In-cylinder pressure variation data synchronized with
the crank angle measurement was acquired<o:p></o:p></FONT></SPAN></P>
<P style="MARGIN: 0in 0in 0pt; mso-layout-grid-align: none"
class=MsoNormal><SPAN
style="FONT-FAMILY: 'Trebuchet MS','sans-serif'; COLOR: black; FONT-SIZE: 10pt; mso-bidi-font-family: 'Trebuchet MS'"><FONT
face="Times New Roman">on a computer for every one-degree crank
angle.<o:p></o:p></FONT></SPAN></P>
<P style="MARGIN: 0in 0in 0pt; mso-layout-grid-align: none"
class=MsoNormal><SPAN
style="FONT-FAMILY: 'Trebuchet MS','sans-serif'; COLOR: black; FONT-SIZE: 10pt; mso-bidi-font-family: 'Trebuchet MS'"><FONT
face="Times New Roman">The pressure measurement was accomplished
using<o:p></o:p></FONT></SPAN></P>
<P style="MARGIN: 0in 0in 0pt; mso-layout-grid-align: none"
class=MsoNormal><SPAN
style="FONT-FAMILY: 'Trebuchet MS','sans-serif'; COLOR: black; FONT-SIZE: 10pt; mso-bidi-font-family: 'Trebuchet MS'"><FONT
face="Times New Roman">a pre-calibrated Piezo based pressure
transducer<o:p></o:p></FONT></SPAN></P>
<P style="MARGIN: 0in 0in 0pt; mso-layout-grid-align: none"
class=MsoNormal><SPAN
style="FONT-FAMILY: 'Trebuchet MS','sans-serif'; COLOR: black; FONT-SIZE: 10pt; mso-bidi-font-family: 'Trebuchet MS'"><FONT
face="Times New Roman">(M=s PCB make).<o:p></o:p></FONT></SPAN></P>
<P style="MARGIN: 0in 0in 0pt; mso-layout-grid-align: none"
class=MsoNormal><SPAN
style="FONT-FAMILY: 'Trebuchet MS','sans-serif'; COLOR: black; FONT-SIZE: 10pt; mso-bidi-font-family: 'Trebuchet MS'"><FONT
face="Times New Roman">(C) Measurement of voltage and current
across<o:p></o:p></FONT></SPAN></P>
<P style="MARGIN: 0in 0in 0pt; mso-layout-grid-align: none"
class=MsoNormal><SPAN
style="FONT-FAMILY: 'Trebuchet MS','sans-serif'; COLOR: black; FONT-SIZE: 10pt; mso-bidi-font-family: 'Trebuchet MS'"><FONT
face="Times New Roman">three phases and frequency for power
output<o:p></o:p></FONT></SPAN></P>
<P style="MARGIN: 0in 0in 0pt; mso-layout-grid-align: none"
class=MsoNormal><SPAN
style="FONT-FAMILY: 'Trebuchet MS','sans-serif'; COLOR: black; FONT-SIZE: 10pt; mso-bidi-font-family: 'Trebuchet MS'"><FONT
face="Times New Roman">calculations—the load bank constituted of
resistors.<o:p></o:p></FONT></SPAN></P>
<P style="MARGIN: 0in 0in 0pt; mso-layout-grid-align: none"
class=MsoNormal><SPAN
style="FONT-FAMILY: 'Trebuchet MS','sans-serif'; COLOR: black; FONT-SIZE: 10pt; mso-bidi-font-family: 'Trebuchet MS'"><FONT
face="Times New Roman">(D) Air and gas Kow to the engine using
pre-calibrated<o:p></o:p></FONT></SPAN></P>
<P style="MARGIN: 0in 0in 0pt; mso-layout-grid-align: none"
class=MsoNormal><SPAN
style="FONT-FAMILY: 'Trebuchet MS','sans-serif'; COLOR: black; FONT-SIZE: 10pt; mso-bidi-font-family: 'Trebuchet MS'"><FONT
face="Times New Roman">venturimeters.<o:p></o:p></FONT></SPAN></P>
<P style="MARGIN: 0in 0in 0pt; mso-layout-grid-align: none"
class=MsoNormal><FONT face="Times New Roman"><SPAN
style="FONT-FAMILY: 'Trebuchet MS','sans-serif'; COLOR: black; FONT-SIZE: 10pt; mso-bidi-font-family: 'Trebuchet MS'">(E)
Engine exhaust analysis—O</SPAN><SPAN
style="FONT-FAMILY: 'Trebuchet MS','sans-serif'; COLOR: black; FONT-SIZE: 7pt; mso-bidi-font-family: 'Trebuchet MS'">2</SPAN><SPAN
style="FONT-FAMILY: 'Trebuchet MS','sans-serif'; COLOR: black; FONT-SIZE: 10pt; mso-bidi-font-family: 'Trebuchet MS'">,
CO</SPAN><SPAN
style="FONT-FAMILY: 'Trebuchet MS','sans-serif'; COLOR: black; FONT-SIZE: 7pt; mso-bidi-font-family: 'Trebuchet MS'">2</SPAN><SPAN
style="FONT-FAMILY: 'Trebuchet MS','sans-serif'; COLOR: black; FONT-SIZE: 10pt; mso-bidi-font-family: 'Trebuchet MS'">;
CO, and NO<o:p></o:p></SPAN></FONT></P>
<P style="MARGIN: 0in 0in 0pt; mso-layout-grid-align: none"
class=MsoNormal><SPAN
style="FONT-FAMILY: 'Trebuchet MS','sans-serif'; COLOR: black; FONT-SIZE: 10pt; mso-bidi-font-family: 'Trebuchet MS'"><FONT
face="Times New Roman">and temperature.<o:p></o:p></FONT></SPAN></P>
<P style="MARGIN: 0in 0in 0pt; mso-layout-grid-align: none"
class=MsoNormal><SPAN
style="FONT-FAMILY: 'Trebuchet MS','sans-serif'; COLOR: black; FONT-SIZE: 10pt; mso-bidi-font-family: 'Trebuchet MS'"><FONT
face="Times New Roman">with the crank angle measurement was
acquired<o:p></o:p></FONT></SPAN></P>
<P style="MARGIN: 0in 0in 0pt; mso-layout-grid-align: none"
class=MsoNormal><SPAN
style="FONT-FAMILY: 'Trebuchet MS','sans-serif'; COLOR: black; FONT-SIZE: 10pt; mso-bidi-font-family: 'Trebuchet MS'"><FONT
face="Times New Roman">on a computer for every one-degree
crank<o:p></o:p></FONT></SPAN></P>
<P style="MARGIN: 0in 0in 0pt; mso-layout-grid-align: none"
class=MsoNormal><SPAN
style="FONT-FAMILY: 'Trebuchet MS','sans-serif'; COLOR: black; FONT-SIZE: 10pt; mso-bidi-font-family: 'Trebuchet MS'"><FONT
face="Times New Roman">on a computer for every one-degree crank angle. The
pressure measurement was accomplished using a pre-calibrated Piezo based
pressure transducer (M=s PCB make).<o:p></o:p></FONT></SPAN></P>
<P style="MARGIN: 0in 0in 0pt; mso-layout-grid-align: none"
class=MsoNormal><SPAN
style="FONT-FAMILY: 'Trebuchet MS','sans-serif'; COLOR: black; FONT-SIZE: 10pt; mso-bidi-font-family: 'Trebuchet MS'"><FONT
face="Times New Roman">(C) Measurement of voltage and current across three
phases and frequency for power output calculations—the load bank constituted of
resistors.<o:p></o:p></FONT></SPAN></P>
<P style="MARGIN: 0in 0in 0pt; mso-layout-grid-align: none"
class=MsoNormal><SPAN
style="FONT-FAMILY: 'Trebuchet MS','sans-serif'; COLOR: black; FONT-SIZE: 10pt; mso-bidi-font-family: 'Trebuchet MS'"><FONT
face="Times New Roman">(D) Air and gas FLow to the engine using pre-calibrated
venturimeters.<o:p></o:p></FONT></SPAN></P>
<P style="MARGIN: 0in 0in 0pt; mso-layout-grid-align: none"
class=MsoNormal><FONT face="Times New Roman"><SPAN
style="FONT-FAMILY: 'Trebuchet MS','sans-serif'; COLOR: black; FONT-SIZE: 10pt; mso-bidi-font-family: 'Trebuchet MS'">(E)
Engine exhaust analysis—O</SPAN><SPAN
style="FONT-FAMILY: 'Trebuchet MS','sans-serif'; COLOR: black; FONT-SIZE: 7pt; mso-bidi-font-family: 'Trebuchet MS'">2</SPAN><SPAN
style="FONT-FAMILY: 'Trebuchet MS','sans-serif'; COLOR: black; FONT-SIZE: 10pt; mso-bidi-font-family: 'Trebuchet MS'">,
CO</SPAN><SPAN
style="FONT-FAMILY: 'Trebuchet MS','sans-serif'; COLOR: black; FONT-SIZE: 7pt; mso-bidi-font-family: 'Trebuchet MS'">2</SPAN><SPAN
style="FONT-FAMILY: 'Trebuchet MS','sans-serif'; COLOR: black; FONT-SIZE: 10pt; mso-bidi-font-family: 'Trebuchet MS'">;
CO,<o:p></o:p></SPAN></FONT></P>
<P style="MARGIN: 0in 0in 0pt; mso-layout-grid-align: none"
class=MsoNormal><SPAN
style="FONT-FAMILY: 'Trebuchet MS','sans-serif'; COLOR: black; FONT-SIZE: 10pt; mso-bidi-font-family: 'Trebuchet MS'"><FONT
face="Times New Roman">and NO and temperature.<o:p></o:p></FONT></SPAN></P>
<P style="MARGIN: 0in 0in 0pt; mso-layout-grid-align: none"
class=MsoNormal><B><SPAN
style="FONT-FAMILY: 'Arial','sans-serif'; COLOR: black; FONT-SIZE: 10pt"><FONT
face="Times New Roman">7. Experimental
procedure<o:p></o:p></FONT></SPAN></B></P>
<P style="MARGIN: 0in 0in 0pt; mso-layout-grid-align: none"
class=MsoNormal><SPAN
style="FONT-FAMILY: 'Trebuchet MS','sans-serif'; COLOR: black; FONT-SIZE: 10pt; mso-bidi-font-family: 'Trebuchet MS'"><FONT
face="Times New Roman">Experiments were initiated on the engine only after the
gasifier system stabilized i.e. attained steady state operation in terms of
generation of consistent quality gas. The typical time scale for attaining
steady state<o:p></o:p></FONT></SPAN></P>
<P style="MARGIN: 0in 0in 0pt; mso-layout-grid-align: none"
class=MsoNormal><FONT face="Times New Roman"><SPAN
style="FONT-FAMILY: 'Trebuchet MS','sans-serif'; COLOR: black; FONT-SIZE: 10pt; mso-bidi-font-family: 'Trebuchet MS'">of
operation from the cold start was 2–3 h. During this period the gas was flared
in a burner. The gas composition was determined using on-line gas analysers,
pre-calibrated using a known producer gas mixture. The calibrations of these
analyzers were checked at random time intervals so as to minimize errors in long
duration operation. Typically gas composition at the time of start of the engine
test was 19 </SPAN><I><SPAN
style="FONT-FAMILY: 'TrebuchetMS-Italic','sans-serif'; COLOR: black; FONT-SIZE: 10pt; mso-bidi-font-family: TrebuchetMS-Italic">±
</SPAN></I><SPAN
style="FONT-FAMILY: 'Trebuchet MS','sans-serif'; COLOR: black; FONT-SIZE: 10pt; mso-bidi-font-family: 'Trebuchet MS'">1%
H</SPAN><SPAN
style="FONT-FAMILY: 'Trebuchet MS','sans-serif'; COLOR: black; FONT-SIZE: 7pt; mso-bidi-font-family: 'Trebuchet MS'">2</SPAN><SPAN
style="FONT-FAMILY: 'Trebuchet MS','sans-serif'; COLOR: black; FONT-SIZE: 10pt; mso-bidi-font-family: 'Trebuchet MS'">;
19</SPAN><I><SPAN
style="FONT-FAMILY: 'TrebuchetMS-Italic','sans-serif'; COLOR: black; FONT-SIZE: 10pt; mso-bidi-font-family: TrebuchetMS-Italic">±</SPAN></I><SPAN
style="FONT-FAMILY: 'Trebuchet MS','sans-serif'; COLOR: black; FONT-SIZE: 10pt; mso-bidi-font-family: 'Trebuchet MS'">1%
CO; 2% CH</SPAN><SPAN
style="FONT-FAMILY: 'Trebuchet MS','sans-serif'; COLOR: black; FONT-SIZE: 7pt; mso-bidi-font-family: 'Trebuchet MS'">4</SPAN><SPAN
style="FONT-FAMILY: 'Trebuchet MS','sans-serif'; COLOR: black; FONT-SIZE: 10pt; mso-bidi-font-family: 'Trebuchet MS'">;
12</SPAN><I><SPAN
style="FONT-FAMILY: 'TrebuchetMS-Italic','sans-serif'; COLOR: black; FONT-SIZE: 10pt; mso-bidi-font-family: TrebuchetMS-Italic">±</SPAN></I><SPAN
style="FONT-FAMILY: 'Trebuchet MS','sans-serif'; COLOR: black; FONT-SIZE: 10pt; mso-bidi-font-family: 'Trebuchet MS'">1%
CO</SPAN><SPAN
style="FONT-FAMILY: 'Trebuchet MS','sans-serif'; COLOR: black; FONT-SIZE: 7pt; mso-bidi-font-family: 'Trebuchet MS'">2</SPAN><SPAN
style="FONT-FAMILY: 'Trebuchet MS','sans-serif'; COLOR: black; FONT-SIZE: 10pt; mso-bidi-font-family: 'Trebuchet MS'">;
2</SPAN><I><SPAN
style="FONT-FAMILY: 'TrebuchetMS-Italic','sans-serif'; COLOR: black; FONT-SIZE: 10pt; mso-bidi-font-family: TrebuchetMS-Italic">±</SPAN></I><SPAN
style="FONT-FAMILY: 'Trebuchet MS','sans-serif'; COLOR: black; FONT-SIZE: 10pt; mso-bidi-font-family: 'Trebuchet MS'">0:5%
H</SPAN><SPAN
style="FONT-FAMILY: 'Trebuchet MS','sans-serif'; COLOR: black; FONT-SIZE: 7pt; mso-bidi-font-family: 'Trebuchet MS'">2</SPAN><SPAN
style="FONT-FAMILY: 'Trebuchet MS','sans-serif'; COLOR: black; FONT-SIZE: 10pt; mso-bidi-font-family: 'Trebuchet MS'">O
and rest, N</SPAN><SPAN
style="FONT-FAMILY: 'Trebuchet MS','sans-serif'; COLOR: black; FONT-SIZE: 7pt; mso-bidi-font-family: 'Trebuchet MS'">2</SPAN><SPAN
style="FONT-FAMILY: 'Trebuchet MS','sans-serif'; COLOR: black; FONT-SIZE: 10pt; mso-bidi-font-family: 'Trebuchet MS'">.
The mean calorific value of gas varied around 4:65</SPAN><I><SPAN
style="FONT-FAMILY: 'TrebuchetMS-Italic','sans-serif'; COLOR: black; FONT-SIZE: 10pt; mso-bidi-font-family: TrebuchetMS-Italic">±</SPAN></I><SPAN
style="FONT-FAMILY: 'Trebuchet MS','sans-serif'; COLOR: black; FONT-SIZE: 10pt; mso-bidi-font-family: 'Trebuchet MS'">0:15
MJ N m</SPAN><I><SPAN
style="FONT-FAMILY: 'TrebuchetMS-Italic','sans-serif'; COLOR: black; FONT-SIZE: 7pt; mso-bidi-font-family: TrebuchetMS-Italic">−</SPAN></I><SPAN
style="FONT-FAMILY: 'Trebuchet MS','sans-serif'; COLOR: black; FONT-SIZE: 7pt; mso-bidi-font-family: 'Trebuchet MS'">3</SPAN><SPAN
style="FONT-FAMILY: 'Trebuchet MS','sans-serif'; COLOR: black; FONT-SIZE: 10pt; mso-bidi-font-family: 'Trebuchet MS'">.
The feedstock used for gasification is Causurina species wood with moisture
content between 12% and 15% on dry basis (sun-dried
wood).<o:p></o:p></SPAN></FONT></P>
<P style="MARGIN: 0in 0in 0pt; mso-layout-grid-align: none"
class=MsoNormal><FONT face="Times New Roman"><SPAN
style="FONT-FAMILY: 'Trebuchet MS','sans-serif'; COLOR: black; FONT-SIZE: 10pt; mso-bidi-font-family: 'Trebuchet MS'">Once
the gas composition stabilized, the engine was operated for a few minutes at
1500 RPM at no-load condition. All the tests on the engine were conducted around
a constant speed of 1500</SPAN><I><SPAN
style="FONT-FAMILY: 'TrebuchetMS-Italic','sans-serif'; COLOR: black; FONT-SIZE: 10pt; mso-bidi-font-family: TrebuchetMS-Italic">±</SPAN></I><SPAN
style="FONT-FAMILY: 'Trebuchet MS','sans-serif'; COLOR: black; FONT-SIZE: 10pt; mso-bidi-font-family: 'Trebuchet MS'">50
RPM. The throttling for speed control and air and fuel proportioning was
achieved using manually operated valves.<o:p></o:p></SPAN></FONT></P>
<P style="MARGIN: 0in 0in 0pt; mso-layout-grid-align: none"
class=MsoNormal><FONT face="Times New Roman"><SPAN
style="FONT-FAMILY: 'Trebuchet MS','sans-serif'; COLOR: black; FONT-SIZE: 10pt; mso-bidi-font-family: 'Trebuchet MS'">Experiments
were conducted at CRs of 17: 1, 14:5: 1, 13:5: 1 and 11:5: 1 and these CRs were
achieved by varying the thickness of the cylinder head gasket. The compression
ratio values are based on the cylinder’s geometric measurements and were
verified by matching the motoring curve with an engine simulation curve. The
engine was tested at different ignition timing settings to determine the MBT at
different CRs. With set ignition timing, the air and fuel were tuned to achieve
maximum power. Measurements were initiated 10–15 min after attaining stable
operation. The in-cylinder pressure data with a resolution of 1</SPAN><I><SPAN
style="FONT-FAMILY: 'TrebuchetMS-Italic','sans-serif'; COLOR: black; FONT-SIZE: 5pt; mso-bidi-font-family: TrebuchetMS-Italic">◦
</SPAN></I><SPAN
style="FONT-FAMILY: 'Trebuchet MS','sans-serif'; COLOR: black; FONT-SIZE: 10pt; mso-bidi-font-family: 'Trebuchet MS'">crank
angle was acquired on a computer in excess of 100–150 consecutive cycles. Prior
to the start of these tests, the TDC was accurately determined using a dial
gauge and synchronized with the optical crank </SPAN><SPAN
style="FONT-FAMILY: 'Arial','sans-serif'; COLOR: black; FONT-SIZE: 10pt">angle
measuring system with an accuracy of </SPAN><SPAN
style="FONT-FAMILY: ArialUnicodeMS; COLOR: black; FONT-SIZE: 10.5pt; mso-bidi-font-family: ArialUnicodeMS">±</SPAN><SPAN
style="FONT-FAMILY: 'Arial','sans-serif'; COLOR: black; FONT-SIZE: 10pt">0:5</SPAN><SPAN
style="FONT-FAMILY: ArialUnicodeMS; COLOR: black; FONT-SIZE: 5.5pt; mso-bidi-font-family: ArialUnicodeMS">◦</SPAN><SPAN
style="FONT-FAMILY: 'Arial','sans-serif'; COLOR: black; FONT-SIZE: 10pt">.<o:p></o:p></SPAN></FONT></P>
<P style="MARGIN: 0in 0in 0pt; mso-layout-grid-align: none"
class=MsoNormal><B><SPAN
style="FONT-FAMILY: 'Trebuchet MS','sans-serif'; COLOR: black; FONT-SIZE: 10pt; mso-bidi-font-family: 'Trebuchet MS'"><FONT
face="Times New Roman">8. Results and
observations<o:p></o:p></FONT></SPAN></B></P>
<P style="MARGIN: 0in 0in 0pt; mso-layout-grid-align: none"
class=MsoNormal><B><SPAN
style="FONT-FAMILY: 'Trebuchet MS','sans-serif'; COLOR: black; FONT-SIZE: 10pt; mso-bidi-font-family: 'Trebuchet MS'"><FONT
face="Times New Roman">8.1. Performance<o:p></o:p></FONT></SPAN></B></P>
<P style="MARGIN: 0in 0in 0pt; mso-layout-grid-align: none"
class=MsoNormal><SPAN
style="FONT-FAMILY: 'Trebuchet MS','sans-serif'; COLOR: black; FONT-SIZE: 10pt; mso-bidi-font-family: 'Trebuchet MS'"><FONT
face="Times New Roman">The first and the foremost result of these tests is that
the engine worked smoothly without any sign of knock at a high CR of 17: 1.
There was no sign of audible knock during the entire load range. Moreover, the
absence of knock was clear from the pressure-crank angle recordings both at full
load and part load.<o:p></o:p></FONT></SPAN></P>
<P style="MARGIN: 0in 0in 0pt; mso-layout-grid-align: none"
class=MsoNormal><SPAN
style="FONT-FAMILY: 'Trebuchet MS','sans-serif'; COLOR: black; FONT-SIZE: 10pt; mso-bidi-font-family: 'Trebuchet MS'"><FONT
face="Times New Roman">The engine delivered a maximum output
of<o:p></o:p></FONT></SPAN></P>
<P style="MARGIN: 0in 0in 0pt; mso-layout-grid-align: none"
class=MsoNormal><SPAN
style="FONT-FAMILY: 'Trebuchet MS','sans-serif'; COLOR: black; FONT-SIZE: 10pt; mso-bidi-font-family: 'Trebuchet MS'"><FONT
face="Times New Roman">17:5 kWe (20 kW shaft power) at a CR of 17: 1 with an
overall efficiency of 21% compared to 21 kWe (24 kW shaft power) output at 31%
efficiency in diesel mode. The overall efficiency calculated is based on the
ratio of the shaft output delivered to the energy content in the biomass. The
overall efficiency in gas mode is based on the ratio of mechanical shaft output
to the energy content in the biomass. The useful output and efficiency decreased
with the lowering of CR. A maximum output of 15:3 kWe (17:6 kW shaft power) at
an overall efficiency of 18% was obtained at a CR of 11:5: 1. The variation of
brake power with CR is shown in Table 2. The power output at an intermediate CR
of 14:5: 1 and 13:5: 1 were 16.4 and 16:2 kWe, respectively, and with overall
efficiencies being 20%. The overall efficiency at 13.5 CR is the same as that at
14:5: 1 on account of leaner operation.<o:p></o:p></FONT></SPAN></P>
<P style="MARGIN: 0in 0in 0pt; mso-layout-grid-align: none"
class=MsoNormal><SPAN
style="FONT-FAMILY: 'Trebuchet MS','sans-serif'; COLOR: black; FONT-SIZE: 10pt; mso-bidi-font-family: 'Trebuchet MS'"><FONT
face="Times New Roman">The extent of de-rating in brake power is about 16.7% at
a CR of 17: 1 and increased as high as 26% at 11:5: 1 when compared to diesel
mode of operation. The gain in overall efficiencies from CR 11.5 to 17: 1 works
out to be 16.6%, which means an increase of 3% per unit CR increment. However,
the incremental gain per unit CR from 14.5 to 17: 1 is 2%. These figures are
well within the range of 1 to 3% gains per unit incremental of CR [9]. The
fuel–air equivalence ratio (PHI) at which the maximum power was derived was
around 1.00–1.06 with the exception of 0.86 at CR of 13:5: 1. The air to fuel
ratio is tuned from the viewpoint of deriving maximum output and therefore the
efficiency figures are necessarily not the maximum that can be obtained. It may
be possible to achieve higher overall efficiencies by operating at leaner
conditions.<o:p></o:p></FONT></SPAN></P>
<P style="MARGIN: 0in 0in 0pt; mso-layout-grid-align: none"
class=MsoNormal><SPAN
style="FONT-FAMILY: 'Trebuchet MS','sans-serif'; COLOR: black; FONT-SIZE: 10pt; mso-bidi-font-family: 'Trebuchet MS'"><FONT
face="Times New Roman">The peak shaft output at varying CR was found to be
sensitive to the producer gas composition. The hydrogen fraction in the fuel gas
dictated the ignition timing setting. Therefore the minimum advance for brake
torque (MBT) varied with the change in hydrogen content in the fuel gas. A
higher fraction of hydrogen means that the ignition timing has to be retarded in
order to benefit from the increase in the flame speed. With a faster burn rate
the optimum spark timing has to be closer to the TDC, the mixture temperature
and pressure at the time of initiation of spark will be higher and hence the
laminar flame speed at the start of combustion will also be higher. Therefore
optimizing the ignition timing based on hydrogen fraction is vital from the
viewpoint of deriving maximum shaft output.<o:p></o:p></FONT></SPAN></P>
<P style="MARGIN: 0in 0in 0pt; mso-layout-grid-align: none"
class=MsoNormal><FONT face="Times New Roman"><SPAN
style="FONT-FAMILY: 'Trebuchet MS','sans-serif'; COLOR: black; FONT-SIZE: 10pt; mso-bidi-font-family: 'Trebuchet MS'">Since
the mixture flame speed is a strong function of hydrogen content in the gas, the
MBT will differ based on the actual fuel gas composition. For a gas composition
containing 20:5 </SPAN><I><SPAN
style="FONT-FAMILY: 'TrebuchetMS-Italic','sans-serif'; COLOR: black; FONT-SIZE: 10pt; mso-bidi-font-family: TrebuchetMS-Italic">±
</SPAN></I><SPAN
style="FONT-FAMILY: 'Trebuchet MS','sans-serif'; COLOR: black; FONT-SIZE: 10pt; mso-bidi-font-family: 'Trebuchet MS'">0:5%
H</SPAN><SPAN
style="FONT-FAMILY: 'Trebuchet MS','sans-serif'; COLOR: black; FONT-SIZE: 7pt; mso-bidi-font-family: 'Trebuchet MS'">2
</SPAN><SPAN
style="FONT-FAMILY: 'Trebuchet MS','sans-serif'; COLOR: black; FONT-SIZE: 10pt; mso-bidi-font-family: 'Trebuchet MS'">and
19:5 </SPAN><I><SPAN
style="FONT-FAMILY: 'TrebuchetMS-Italic','sans-serif'; COLOR: black; FONT-SIZE: 10pt; mso-bidi-font-family: TrebuchetMS-Italic">±
</SPAN></I><SPAN
style="FONT-FAMILY: 'Trebuchet MS','sans-serif'; COLOR: black; FONT-SIZE: 10pt; mso-bidi-font-family: 'Trebuchet MS'">0:5%
CO, the MBTs have been identified as shown in Table 2, the measurement accuracy
of MBT is within 3</SPAN><I><SPAN
style="FONT-FAMILY: 'TrebuchetMS-Italic','sans-serif'; COLOR: black; FONT-SIZE: 5pt; mso-bidi-font-family: TrebuchetMS-Italic">◦
</SPAN></I><SPAN
style="FONT-FAMILY: 'Trebuchet MS','sans-serif'; COLOR: black; FONT-SIZE: 10pt; mso-bidi-font-family: 'Trebuchet MS'">crank
angle. The MBT in the present case has turned out to be about
6–10</SPAN><I><SPAN
style="FONT-FAMILY: 'TrebuchetMS-Italic','sans-serif'; COLOR: black; FONT-SIZE: 5pt; mso-bidi-font-family: TrebuchetMS-Italic">◦
</SPAN></I><SPAN
style="FONT-FAMILY: 'Trebuchet MS','sans-serif'; COLOR: black; FONT-SIZE: 10pt; mso-bidi-font-family: 'Trebuchet MS'">BTDC
at a CR of 17: 1 and has gone up to as high as 14–16</SPAN><I><SPAN
style="FONT-FAMILY: 'TrebuchetMS-Italic','sans-serif'; COLOR: black; FONT-SIZE: 5pt; mso-bidi-font-family: TrebuchetMS-Italic">◦
</SPAN></I><SPAN
style="FONT-FAMILY: 'Trebuchet MS','sans-serif'; COLOR: black; FONT-SIZE: 10pt; mso-bidi-font-family: 'Trebuchet MS'">BTDC
for a CR of 11:5: 1. These values are much lower compared to 30 to
40</SPAN><I><SPAN
style="FONT-FAMILY: 'TrebuchetMS-Italic','sans-serif'; COLOR: black; FONT-SIZE: 5pt; mso-bidi-font-family: TrebuchetMS-Italic">◦
</SPAN></I><SPAN
style="FONT-FAMILY: 'Trebuchet MS','sans-serif'; COLOR: black; FONT-SIZE: 10pt; mso-bidi-font-family: 'Trebuchet MS'">BTDC
at a CR of 11.5 based on earlier work [2, 6, 12] but matches with
10</SPAN><I><SPAN
style="FONT-FAMILY: 'TrebuchetMS-Italic','sans-serif'; COLOR: black; FONT-SIZE: 5pt; mso-bidi-font-family: TrebuchetMS-Italic">◦
</SPAN></I><SPAN
style="FONT-FAMILY: 'Trebuchet MS','sans-serif'; COLOR: black; FONT-SIZE: 10pt; mso-bidi-font-family: 'Trebuchet MS'">BTDC
[4] at a CR of 17: 1.<o:p></o:p></SPAN></FONT></P>
<P style="MARGIN: 0in 0in 0pt; mso-layout-grid-align: none"
class=MsoNormal><SPAN
style="FONT-FAMILY: 'Trebuchet MS','sans-serif'; COLOR: black; FONT-SIZE: 10pt; mso-bidi-font-family: 'Trebuchet MS'"><FONT
face="Times New Roman">The mechanical efficiency of the engine at a CR of 17 : 1
is about 80% and increases to as high as 87% at a CR of 11:5 : 1. The increase
in mechanical efficiency is attributed to the reduction in rubbing friction [16]
due to lower cylinder pressures encountered at lower CRs. The mechanical
efficiency values are based on indicated power measurement (based on integration
of pressure–volume diagram) and these were found to be identical with the Morse
test results.<o:p></o:p></FONT></SPAN></P>
<P style="MARGIN: 0in 0in 0pt; mso-layout-grid-align: none"
class=MsoNormal><B><SPAN
style="FONT-FAMILY: 'Trebuchet MS','sans-serif'; COLOR: black; FONT-SIZE: 10pt; mso-bidi-font-family: 'Trebuchet MS'"><FONT
face="Times New Roman">8.2. Pressure–crank angle
data<o:p></o:p></FONT></SPAN></B></P>
<P style="MARGIN: 0in 0in 0pt; mso-layout-grid-align: none"
class=MsoNormal><FONT face="Times New Roman"><SPAN
style="FONT-FAMILY: 'Trebuchet MS','sans-serif'; COLOR: black; FONT-SIZE: 10pt; mso-bidi-font-family: 'Trebuchet MS'">The
pressure–crank angle recording at all the CRs did not show any trace of knock
for all ranges of load including that of peak load and this is visible from the
pressure–crank angle diagrams as shown in Fig. 2. Faster burn rate due to
presence of hydrogen in the fuel gas may be one factor for the non-knocking
performance at higher compression ratio. The faster burn rate accompanied by
retarded ignition timing setting obviates any auto-ignition tendency of the end
gas. Increasing the flame speed or retarding the ignition timing setting is one
possible way of reducing knock tendency and this is well acknowledged in the
literature [9]. The maximum indicated mean effective pressure (IMEP) was
obtained at ignition timing corresponding to the maximum shaft output. The IMEP
obtained at varying CR as a function of ignition timing is shown in Fig. 3. The
max IMEP recorded was 595 kPa at a CR of 17: 1 and declined to about 485 kPa at
a CR of 11:5: 1. The maximum IMEP was obtained at a PHI of 1.05 and this falls
well within the anticipated PHI of 1.0 to 1.1 [9]. The point of occurrence of
peak pressure at all CRs occurred at 18–19</SPAN><I><SPAN
style="FONT-FAMILY: 'TrebuchetMS-Italic','sans-serif'; COLOR: black; FONT-SIZE: 5pt; mso-bidi-font-family: TrebuchetMS-Italic">◦
</SPAN></I><SPAN
style="FONT-FAMILY: 'Trebuchet MS','sans-serif'; COLOR: black; FONT-SIZE: 10pt; mso-bidi-font-family: 'Trebuchet MS'">ATDC,
except that at 13:5: 1 which occurred at 17</SPAN><I><SPAN
style="FONT-FAMILY: 'TrebuchetMS-Italic','sans-serif'; COLOR: black; FONT-SIZE: 5pt; mso-bidi-font-family: TrebuchetMS-Italic">◦
</SPAN></I><SPAN
style="FONT-FAMILY: 'Trebuchet MS','sans-serif'; COLOR: black; FONT-SIZE: 10pt; mso-bidi-font-family: 'Trebuchet MS'">ATDC,
which is close to the generally acknowledged value of 17</SPAN><I><SPAN
style="FONT-FAMILY: 'TrebuchetMS-Italic','sans-serif'; COLOR: black; FONT-SIZE: 5pt; mso-bidi-font-family: TrebuchetMS-Italic">◦</SPAN></I><SPAN
style="FONT-FAMILY: 'Trebuchet MS','sans-serif'; COLOR: black; FONT-SIZE: 10pt; mso-bidi-font-family: 'Trebuchet MS'">ATDC
for MBT [9, 17]. Therefore, for CR of 17: 1, 14.5 and 11:5: 1 the MBT should be
more advanced<o:p></o:p></SPAN></FONT></P>
<P style="MARGIN: 0in 0in 0pt; mso-layout-grid-align: none"
class=MsoNormal><SPAN
style="FONT-FAMILY: 'Trebuchet MS','sans-serif'; COLOR: black; FONT-SIZE: 10pt; mso-bidi-font-family: 'Trebuchet MS'"><o:p><FONT
face="Times New Roman"> </FONT></o:p></SPAN></P>
<P style="MARGIN: 0in 0in 0pt; mso-layout-grid-align: none"
class=MsoNormal><FONT face="Times New Roman"><SPAN
style="FONT-FAMILY: 'Trebuchet MS','sans-serif'; COLOR: black; FONT-SIZE: 10pt; mso-bidi-font-family: 'Trebuchet MS'">(lie
within 2–3</SPAN><I><SPAN
style="FONT-FAMILY: 'TrebuchetMS-Italic','sans-serif'; COLOR: black; FONT-SIZE: 5pt; mso-bidi-font-family: TrebuchetMS-Italic">◦</SPAN></I><SPAN
style="FONT-FAMILY: 'Trebuchet MS','sans-serif'; COLOR: black; FONT-SIZE: 10pt; mso-bidi-font-family: 'Trebuchet MS'">)
from what was actually measured. The variation of IMEP or the net useful output
within this close range would be marginal. The peak cylinder pressures and their
point of occurrence is shown in Table 3. The peak pressure at 14:5: 1 CR is
lower than 13:5: 1 probably due to a slight departure from MBT. The coefficient
of variation of the IMEP at all CRs and ignition settings occurred well within
3–3.5%, implying low cycle-to-cycle variation. The reason for low cyclic
variation is the faster rate of combustion occurring inside the engine cylinder.
The faster rate of combustion is attributed to higher flame speeds due to the
presence of hydrogen in the gas and also to the bowl-in piston combustion
chamber design with increased<o:p></o:p></SPAN></FONT></P>
<P style="MARGIN: 0in 0in 0pt; mso-layout-grid-align: none"
class=MsoNormal><SPAN
style="FONT-FAMILY: 'Trebuchet MS','sans-serif'; COLOR: black; FONT-SIZE: 10pt; mso-bidi-font-family: 'Trebuchet MS'"><FONT
face="Times New Roman">squish effect.<o:p></o:p></FONT></SPAN></P>
<P style="MARGIN: 0in 0in 0pt; mso-layout-grid-align: none"
class=MsoNormal><B><SPAN
style="FONT-FAMILY: 'Arial','sans-serif'; COLOR: black; FONT-SIZE: 10pt"><FONT
face="Times New Roman">8.3. Energy balance<o:p></o:p></FONT></SPAN></B></P>
<P style="MARGIN: 0in 0in 0pt; mso-layout-grid-align: none"
class=MsoNormal><SPAN
style="FONT-FAMILY: 'Trebuchet MS','sans-serif'; COLOR: black; FONT-SIZE: 10pt; mso-bidi-font-family: 'Trebuchet MS'"><FONT
face="Times New Roman">Fig. 4 represents the overall energy balance at a CR of
17: 1. The energy balance at MBT showed that about 32.5% of the energy was
realized as useful output (indicated power); about 27% was lost through the
exhaust (including the CO in the exhaust) and the remaining 40% to the cooling
water (inclusive of radioactive losses, etc). As expected with the advancement
of ignition timing, the loss through exhaust mode reduced and increased to the
coolant route. The energy balance in gas mode showed that a large fraction
of<o:p></o:p></FONT></SPAN></P>
<P style="MARGIN: 0in 0in 0pt; mso-layout-grid-align: none"
class=MsoNormal><SPAN
style="FONT-FAMILY: 'Trebuchet MS','sans-serif'; COLOR: black; FONT-SIZE: 10pt; mso-bidi-font-family: 'Trebuchet MS'"><FONT
face="Times New Roman">the energy was lost to the cooling water when compared to
the diesel mode. Fig. 5 compares the energy balance in gas and diesel mode (at
rated output of 21 kWe) at a CR of 17 : 1, the energy loss at maximum power
delivered to the coolant and miscellaneous is about 40% compared to 33% in
diesel and whereas, the energy loss through exhaust in gas mode decreased by 5%.
The indicated power and thereby the thermal efficiency being higher in diesel
mode is evident from the pressure–time curve shown in Fig. 2. The energy
balance<o:p></o:p></FONT></SPAN></P>
<P style="MARGIN: 0in 0in 0pt; mso-layout-grid-align: none"
class=MsoNormal><FONT face="Times New Roman"><SPAN
style="FONT-FAMILY: 'Trebuchet MS','sans-serif'; COLOR: black; FONT-SIZE: 10pt; mso-bidi-font-family: 'Trebuchet MS'">at
varying CRs is shown in Fig. 6. There was an increase in the loss of energy
through exhaust (which includes the energy in the form of CO) with the reduction
in the CR, whereas, the loss through the coolant and miscellaneous was higher at
higher CR. The useful energy is 32.5% at a CR of 17: 1 and has declined to 25.7%
at a CR of 11:5: 1. The useful energy at a CR of 13:5: 1 has stood about the
same as that at 14:5: 1 due to a relatively leaner operation. The increased
amount of heat loss to the cooling </SPAN><SPAN
style="FONT-FAMILY: 'Arial','sans-serif'; COLOR: black; FONT-SIZE: 10pt">water
as a whole in gas operation<o:p></o:p></SPAN></FONT></P>
<P style="MARGIN: 0in 0in 0pt; mso-layout-grid-align: none"
class=MsoNormal><SPAN
style="FONT-FAMILY: 'Trebuchet MS','sans-serif'; COLOR: black; FONT-SIZE: 10pt; mso-bidi-font-family: 'Trebuchet MS'"><FONT
face="Times New Roman">could be attributed to the engine combustion chamber
design. It has been quoted in the literature [9] that with engine geometries
such as bowl-in-piston there will be 10% higher heat transfer. The heat transfer
to the coolant in the current case falls well within this range. With the
increase in compression ratio the overall conversion efficiencies must improve
thermodynamically, similarly, the heat loss to the coolant and exhaust should
have reduced. However, increased energy loss to the coolant at a higher
compression<o:p></o:p></FONT></SPAN></P>
<P style="MARGIN: 0in 0in 0pt; mso-layout-grid-align: none"
class=MsoNormal><SPAN
style="FONT-FAMILY: 'Trebuchet MS','sans-serif'; COLOR: black; FONT-SIZE: 10pt; mso-bidi-font-family: 'Trebuchet MS'"><FONT
face="Times New Roman">ratio is probably due to increase in heat transfer
coefficient.<o:p></o:p></FONT></SPAN></P>
<P style="MARGIN: 0in 0in 0pt; mso-layout-grid-align: none"
class=MsoNormal><FONT face="Times New Roman"><SPAN
style="FONT-FAMILY: 'Trebuchet MS','sans-serif'; COLOR: black; FONT-SIZE: 10pt; mso-bidi-font-family: 'Trebuchet MS'">accounted
for because it forms a small part (</SPAN><I><SPAN
style="FONT-FAMILY: 'TrebuchetMS-Italic','sans-serif'; COLOR: black; FONT-SIZE: 10pt; mso-bidi-font-family: TrebuchetMS-Italic">_
</SPAN></I><SPAN
style="FONT-FAMILY: 'Trebuchet MS','sans-serif'; COLOR: black; FONT-SIZE: 10pt; mso-bidi-font-family: 'Trebuchet MS'">5%)
of NOx generated [9]. The NO level has been represented in milligram per unit MJ
of input energy. These results have been compared to the Swiss norms because of
some earlier collaborative work with the<o:p></o:p></SPAN></FONT></P>
<P style="MARGIN: 0in 0in 0pt; mso-layout-grid-align: none"
class=MsoNormal><SPAN
style="FONT-FAMILY: 'Trebuchet MS','sans-serif'; COLOR: black; FONT-SIZE: 10pt; mso-bidi-font-family: 'Trebuchet MS'"><FONT
face="Times New Roman">Swiss scientists; it was indicated that Swiss norms were
stringent with respect to the emission levels. The NO level reduced with the
retardation of ignition timing and this feature was observed for all CRs.
The<o:p></o:p></FONT></SPAN></P>
<P style="MARGIN: 0in 0in 0pt; mso-layout-grid-align: none"
class=MsoNormal><FONT face="Times New Roman"><SPAN
style="FONT-FAMILY: 'Trebuchet MS','sans-serif'; COLOR: black; FONT-SIZE: 10pt; mso-bidi-font-family: 'Trebuchet MS'">NO
level was observed to be maximum at the highest compression ratio with advanced
ignition timings, whereas for the MBT range of 6–20</SPAN><I><SPAN
style="FONT-FAMILY: 'TrebuchetMS-Italic','sans-serif'; COLOR: black; FONT-SIZE: 10pt; mso-bidi-font-family: TrebuchetMS-Italic">◦
</SPAN></I><SPAN
style="FONT-FAMILY: 'Trebuchet MS','sans-serif'; COLOR: black; FONT-SIZE: 10pt; mso-bidi-font-family: 'Trebuchet MS'">BTDC
the NO was roughly about the same in almost all the cases. However, there was
one exception of NO being higher at MBT for a CR of 13.5 due to a leaner
operation.<o:p></o:p></SPAN></FONT></P>
<P style="MARGIN: 0in 0in 0pt; mso-layout-grid-align: none"
class=MsoNormal><SPAN
style="FONT-FAMILY: 'Trebuchet MS','sans-serif'; COLOR: black; FONT-SIZE: 10pt; mso-bidi-font-family: 'Trebuchet MS'"><FONT
face="Times New Roman">It is a well-known fact that NO generation is strongly
dependent on the temperature and also residence time in the combustion chamber.
With the flame speed of the gas mixture being high, the ignition setting is
retarded whereby the residence time in the high temperature combustion chamber
is automatically reduced. Therefore, the low NO levels at retarded ignition
setting is an expected and consistent behavior. The above results match well
with those quoted in the literature [9], which show small to modest variation of
NO with CR. The variation of carbon monoxide (CO) with PHI is shown in Fig. 8.
The CO levels have been represented in grams per MJ of input energy. The trend
of CO with PHI is clear from the figure. The CO levels were lower at the highest
CR, and this could be attributed to higher temperatures, leading to relatively
complete combustion.<o:p></o:p></FONT></SPAN></P>
<P style="MARGIN: 0in 0in 0pt; mso-layout-grid-align: none"
class=MsoNormal><B><SPAN
style="FONT-FAMILY: 'Trebuchet MS','sans-serif'; COLOR: black; FONT-SIZE: 10pt; mso-bidi-font-family: 'Trebuchet MS'"><FONT
face="Times New Roman">9<o:p></o:p></FONT></SPAN></B></P>
<P style="MARGIN: 0in 0in 0pt; mso-layout-grid-align: none"
class=MsoNormal><SPAN
style="FONT-FAMILY: 'Trebuchet MS','sans-serif'; COLOR: black; FONT-SIZE: 10pt; mso-bidi-font-family: 'Trebuchet MS'"><FONT
face="Times New Roman">Been smooth and it has been established beyond doubt that
the operating engines using producer gas in SI mode at higher compression ratios
is technically feasible. The cylinder pressure–crank angle trace has shown
smooth pressure variations during the entire combustion process without any sign
of abnormal pressure raise. A shorter duration of combustion has been observed
with producer gas fuel, requiring<o:p></o:p></FONT></SPAN></P>
<P style="MARGIN: 0in 0in 0pt; mso-layout-grid-align: none"
class=MsoNormal><SPAN
style="FONT-FAMILY: 'Trebuchet MS','sans-serif'; COLOR: black; FONT-SIZE: 10pt; mso-bidi-font-family: 'Trebuchet MS'"><FONT
face="Times New Roman">retardation of the ignition timing to achieve MBT. These
faster burning cycles are corroborated by low cyclic pressure fluctuations with
a coefficient of variation 3%. The faster burning process has been identified to
be due to the higher flame speed of the fuel gas mixture and the
same<o:p></o:p></FONT></SPAN></P>
<P style="MARGIN: 0in 0in 0pt; mso-layout-grid-align: none"
class=MsoNormal><SPAN
style="FONT-FAMILY: 'Trebuchet MS','sans-serif'; COLOR: black; FONT-SIZE: 10pt; mso-bidi-font-family: 'Trebuchet MS'"><FONT
face="Times New Roman">h<o:p></o:p></FONT></SPAN></P>
<P style="MARGIN: 0in 0in 0pt; mso-layout-grid-align: none"
class=MsoNormal><SPAN
style="FONT-FAMILY: 'Trebuchet MS','sans-serif'; COLOR: black; FONT-SIZE: 10pt; mso-bidi-font-family: 'Trebuchet MS'"><FONT
face="Times New Roman">content in the gas. So, increased quantity of hydrogen in
the fuel gas mixture is desired from the viewpoint of approaching an ideal cycle
operation. The perceived<o:p></o:p></FONT></SPAN></P>
<P style="MARGIN: 0in 0in 0pt; mso-layout-grid-align: none"
class=MsoNormal><SPAN
style="FONT-FAMILY: 'Trebuchet MS','sans-serif'; COLOR: black; FONT-SIZE: 10pt; mso-bidi-font-family: 'Trebuchet MS'"><FONT
face="Times New Roman">negative influence of pressure on flame speed at higher
CR does not seem to exist based on the above results. The maximum de-rating in
power is observed to be 16% in gas mode when compared to diesel operation at
comparable CR. The extent of de-rating was much lower when compared to any of
the previous studies [3–6]. This number matches with a similar kind of de-rating
reported with NG operation [10]. However, the overall efficiency drops down by
almost 32.5% compared to normal diesel mode of operation. A careful analysis of
the energy balance revealed excessive heat loss to the coolant at all CRs and
this resulted in engine overheating within 30–40 min of operation at full load.
This phenomenon of excessive heat loss could be attributed to bowl-in piston
combustion chamber design. Higher heat loss to the cylinder walls can be
expected because the combustion chamber is originally meant for diesel operation
with inherent swirl. Hence suitable modification of the combustion chamber is
essential from the view point of reducing the energy loss to the coolant.
Reduction in 10% heat loss to the coolant would amount to improvement in overall
efficiencies by 3%. The study of the engine combustion chamber and modifications
can be looked upon as future work.<o:p></o:p></FONT></SPAN></P>
<P style="MARGIN: 0in 0in 0pt; mso-layout-grid-align: none"
class=MsoNormal><B><SPAN
style="FONT-FAMILY: 'Trebuchet MS','sans-serif'; COLOR: black; FONT-SIZE: 10pt; mso-bidi-font-family: 'Trebuchet MS'"><FONT
face="Times New Roman">R<o:p></o:p></FONT></SPAN></B></P>
<P style="MARGIN: 0in 0in 0pt; mso-layout-grid-align: none"
class=MsoNormal><SPAN
style="FONT-FAMILY: 'Trebuchet MS','sans-serif'; COLOR: black; FONT-SIZE: 10pt; mso-bidi-font-family: 'Trebuchet MS'"><FONT
face="Times New Roman">[1<o:p></o:p></FONT></SPAN></P>
<P style="MARGIN: 0in 0in 0pt; mso-layout-grid-align: none"
class=MsoNormal><SPAN
style="FONT-FAMILY: 'Trebuchet MS','sans-serif'; COLOR: black; FONT-SIZE: 10pt; mso-bidi-font-family: 'Trebuchet MS'"><FONT
face="Times New Roman">mechanical wood products branch of FAO forestry paper No.
72, Food and Agriculture Organization of United Nations, Rome,
1986.<o:p></o:p></FONT></SPAN></P>
<P style="MARGIN: 0in 0in 0pt; mso-layout-grid-align: none"
class=MsoNormal><SPAN
style="FONT-FAMILY: 'Trebuchet MS','sans-serif'; COLOR: black; FONT-SIZE: 10pt; mso-bidi-font-family: 'Trebuchet MS'"><FONT
face="Times New Roman">[2<o:p></o:p></FONT></SPAN></P>
<P style="MARGIN: 0in 0in 0pt; mso-layout-grid-align: none"
class=MsoNormal><SPAN
style="FONT-FAMILY: 'Trebuchet MS','sans-serif'; COLOR: black; FONT-SIZE: 10pt; mso-bidi-font-family: 'Trebuchet MS'"><FONT
face="Times New Roman">GS, Kamat PP, Parikh PP. Development and
performa<o:p></o:p></FONT></SPAN></P>
<P style="MARGIN: 0in 0in 0pt; mso-layout-grid-align: none"
class=MsoNormal><SPAN
style="FONT-FAMILY: 'Trebuchet MS','sans-serif'; COLOR: black; FONT-SIZE: 10pt; mso-bidi-font-family: 'Trebuchet MS'"><FONT
face="Times New Roman">15 kWe producer gas operated SI engine. Proceedings of
Fourth National Meet on Biomass Gasification and Combustion, Mysore,
<st1:country-region w:st="on">India</st1:country-region>, vol. 4, 1993. p.
219–31.<o:p></o:p></FONT></SPAN></P>
<P style="MARGIN: 0in 0in 0pt; mso-layout-grid-align: none"
class=MsoNormal><SPAN
style="FONT-FAMILY: 'Trebuchet MS','sans-serif'; COLOR: black; FONT-SIZE: 10pt; mso-bidi-font-family: 'Trebuchet MS'"><FONT
face="Times New Roman">[3<o:p></o:p></FONT></SPAN></P>
<P style="MARGIN: 0in 0in 0pt; mso-layout-grid-align: none"
class=MsoNormal><SPAN
style="FONT-FAMILY: 'Trebuchet MS','sans-serif'; COLOR: black; FONT-SIZE: 10pt; mso-bidi-font-family: 'Trebuchet MS'"><FONT
face="Times New Roman">Biomass producer ga<o:p></o:p></FONT></SPAN></P>
<P style="MARGIN: 0in 0in 0pt; mso-layout-grid-align: none"
class=MsoNormal><SPAN
style="FONT-FAMILY: 'Trebuchet MS','sans-serif'; COLOR: black; FONT-SIZE: 10pt; mso-bidi-font-family: 'Trebuchet MS'"><FONT
face="Times New Roman">Engines—naturally aspirated and supercharged engines.
<st1:State w:st="on"><st1:place w:st="on">Michigan</st1:place></st1:State>:
American Society of Agricultural Engineers, 1981. p.
1–35.<o:p></o:p></FONT></SPAN></P>
<P style="MARGIN: 0in 0in 0pt; mso-layout-grid-align: none"
class=MsoNormal><SPAN
style="FONT-FAMILY: 'Trebuchet MS','sans-serif'; COLOR: black; FONT-SIZE: 10pt; mso-bidi-font-family: 'Trebuchet MS'"><FONT
face="Times New Roman">[<o:p></o:p></FONT></SPAN></P>
<P style="MARGIN: 0in 0in 0pt; mso-layout-grid-align: none"
class=MsoNormal><SPAN
style="FONT-FAMILY: 'Trebuchet MS','sans-serif'; COLOR: black; FONT-SIZE: 10pt; mso-bidi-font-family: 'Trebuchet MS'"><FONT
face="Times New Roman">Performance studies<o:p></o:p></FONT></SPAN></P>
<P style="MARGIN: 0in 0in 0pt; mso-layout-grid-align: none"
class=MsoNormal><SPAN
style="FONT-FAMILY: 'Trebuchet MS','sans-serif'; COLOR: black; FONT-SIZE: 10pt; mso-bidi-font-family: 'Trebuchet MS'"><FONT
face="Times New Roman">engine. Proceedings of Fourth National Meet on Biomass
Gasification and Combustion, <st1:place w:st="on"><st1:City
w:st="on">Mysore</st1:City>, <st1:country-region
w:st="on">India</st1:country-region></st1:place>, vol. 4, 1993. p.
213–8.<o:p></o:p></FONT></SPAN></P>
<P style="MARGIN: 0in 0in 0pt; mso-layout-grid-align: none"
class=MsoNormal><SPAN
style="FONT-FAMILY: 'Trebuchet MS','sans-serif'; COLOR: black; FONT-SIZE: 10pt; mso-bidi-font-family: 'Trebuchet MS'"><FONT
face="Times New Roman">[5<o:p></o:p></FONT></SPAN></P>
<P style="MARGIN: 0in 0in 0pt; mso-layout-grid-align: none"
class=MsoNormal><SPAN
style="FONT-FAMILY: 'Trebuchet MS','sans-serif'; COLOR: black; FONT-SIZE: 10pt; mso-bidi-font-family: 'Trebuchet MS'"><FONT
face="Times New Roman">Performance of charcoal<o:p></o:p></FONT></SPAN></P>
<P style="MARGIN: 0in 0in 0pt; mso-layout-grid-align: none"
class=MsoNormal><SPAN
style="FONT-FAMILY: 'Trebuchet MS','sans-serif'; COLOR: black; FONT-SIZE: 10pt; mso-bidi-font-family: 'Trebuchet MS'"><FONT
face="Times New Roman">combustion engines. Proceedings of International
Conference—New EnergConversion Technologies and their Commercialization’s, vol.
2, 1981. p24.<o:p></o:p></FONT></SPAN></P>
<P style="MARGIN: 0in 0in 0pt; mso-layout-grid-align: none"
class=MsoNormal><SPAN
style="FONT-FAMILY: 'Trebuchet MS','sans-serif'; COLOR: black; FONT-SIZE: 10pt; mso-bidi-font-family: 'Trebuchet MS'"><FONT
face="Times New Roman">[6<o:p></o:p></FONT></SPAN></P>
<P style="MARGIN: 0in 0in 0pt; mso-layout-grid-align: none"
class=MsoNormal><SPAN
style="FONT-FAMILY: 'Trebuchet MS','sans-serif'; COLOR: black; FONT-SIZE: 10pt; mso-bidi-font-family: 'Trebuchet MS'"><FONT
face="Times New Roman">Veerkar S. Design dev<o:p></o:p></FONT></SPAN></P>
<P style="MARGIN: 0in 0in 0pt; mso-layout-grid-align: none"
class=MsoNormal><SPAN
style="FONT-FAMILY: 'Trebuchet MS','sans-serif'; COLOR: black; FONT-SIZE: 10pt; mso-bidi-font-family: 'Trebuchet MS'"><FONT
face="Times New Roman">spark ignited producer gas engine. Proceedings of the XIV
National Conference on IC Engines and Combustion, <st1:place w:st="on"><st1:City
w:st="on">Pune</st1:City>, <st1:country-region
w:st="on">India</st1:country-region></st1:place>, 1995. p.
97–107.<o:p></o:p></FONT></SPAN></P>
<P style="MARGIN: 0in 0in 0pt; mso-layout-grid-align: none"
class=MsoNormal><SPAN
style="FONT-FAMILY: 'Trebuchet MS','sans-serif'; COLOR: black; FONT-SIZE: 10pt; mso-bidi-font-family: 'Trebuchet MS'"><FONT
face="Times New Roman">[7<o:p></o:p></FONT></SPAN></P>
<P style="MARGIN: 0in 0in 0pt; mso-layout-grid-align: none"
class=MsoNormal><SPAN
style="FONT-FAMILY: 'Trebuchet MS','sans-serif'; COLOR: black; FONT-SIZE: 10pt; mso-bidi-font-family: 'Trebuchet MS'"><FONT
face="Times New Roman">Open-top wood gasifiers,
renewable<o:p></o:p></FONT></SPAN></P>
<P style="MARGIN: 0in 0in 0pt; mso-layout-grid-align: none"
class=MsoNormal><SPAN
style="FONT-FAMILY: 'Trebuchet MS','sans-serif'; COLOR: black; FONT-SIZE: 10pt; mso-bidi-font-family: 'Trebuchet MS'"><FONT
face="Times New Roman">energy—sources for fuels and electricity. <st1:place
w:st="on"><st1:City w:st="on">Washington</st1:City>, <st1:State
w:st="on">DC</st1:State></st1:place>: <st1:place w:st="on">Island</st1:place>
Press, 1993.<o:p></o:p></FONT></SPAN></P>
<P style="MARGIN: 0in 0in 0pt; mso-layout-grid-align: none"
class=MsoNormal><SPAN
style="FONT-FAMILY: 'Trebuchet MS','sans-serif'; COLOR: black; FONT-SIZE: 10pt; mso-bidi-font-family: 'Trebuchet MS'"><FONT
face="Times New Roman">[8<o:p></o:p></FONT></SPAN></P>
<P style="MARGIN: 0in 0in 0pt; mso-layout-grid-align: none"
class=MsoNormal><SPAN
style="FONT-FAMILY: 'Trebuchet MS','sans-serif'; COLOR: black; FONT-SIZE: 10pt; mso-bidi-font-family: 'Trebuchet MS'"><FONT
face="Times New Roman">Shrinivasa U, Sharan H. Results of an
Indo-Swi<o:p></o:p></FONT></SPAN></P>
<P style="MARGIN: 0in 0in 0pt; mso-layout-grid-align: none"
class=MsoNormal><SPAN
style="FONT-FAMILY: 'Trebuchet MS','sans-serif'; COLOR: black; FONT-SIZE: 10pt; mso-bidi-font-family: 'Trebuchet MS'"><FONT
face="Times New Roman">qualification and testing of a 300-kW IISc–Dasag
gasifier. Energy for sustainable development, vol. 4, November 1994. p.
46–9.<o:p></o:p></FONT></SPAN></P>
<P style="MARGIN: 0in 0in 0pt; mso-layout-grid-align: none"
class=MsoNormal><SPAN
style="FONT-FAMILY: 'Trebuchet MS','sans-serif'; COLOR: black; FONT-SIZE: 10pt; mso-bidi-font-family: 'Trebuchet MS'"><FONT
face="Times New Roman">[9<o:p></o:p></FONT></SPAN></P>
<P style="MARGIN: 0in 0in 0pt; mso-layout-grid-align: none"
class=MsoNormal><SPAN
style="FONT-FAMILY: 'Trebuchet MS','sans-serif'; COLOR: black; FONT-SIZE: 10pt; mso-bidi-font-family: 'Trebuchet MS'"><FONT
face="Times New Roman">Internal combustion e<o:p></o:p></FONT></SPAN></P>
<P style="MARGIN: 0in 0in 0pt; mso-layout-grid-align: none"
class=MsoNormal><SPAN
style="FONT-FAMILY: 'Trebuchet MS','sans-serif'; COLOR: black; FONT-SIZE: 10pt; mso-bidi-font-family: 'Trebuchet MS'"><FONT
face="Times New Roman">International edition. <st1:State w:st="on"><st1:place
w:st="on">New York</st1:place></st1:State>: McGraw-<o:p></o:p></FONT></SPAN></P>
<P style="MARGIN: 0in 0in 0pt; mso-layout-grid-align: none"
class=MsoNormal><SPAN
style="FONT-FAMILY: 'Trebuchet MS','sans-serif'; COLOR: black; FONT-SIZE: 10pt; mso-bidi-font-family: 'Trebuchet MS'"><FONT
face="Times New Roman">Hill, 1989.<o:p></o:p></FONT></SPAN></P>
<P style="MARGIN: 0in 0in 0pt; mso-layout-grid-align: none"
class=MsoNormal><SPAN
style="FONT-FAMILY: 'Trebuchet MS','sans-serif'; COLOR: black; FONT-SIZE: 10pt; mso-bidi-font-family: 'Trebuchet MS'"><FONT
face="Times New Roman">[1<o:p></o:p></FONT></SPAN></P>
<P style="MARGIN: 0in 0in 0pt; mso-layout-grid-align: none"
class=MsoNormal><SPAN
style="FONT-FAMILY: 'Trebuchet MS','sans-serif'; COLOR: black; FONT-SIZE: 10pt; mso-bidi-font-family: 'Trebuchet MS'"><FONT
face="Times New Roman">Development of a natural<o:p></o:p></FONT></SPAN></P>
<P style="MARGIN: 0in 0in 0pt; mso-layout-grid-align: none"
class=MsoNormal><SPAN
style="FONT-FAMILY: 'Trebuchet MS','sans-serif'; COLOR: black; FONT-SIZE: 10pt; mso-bidi-font-family: 'Trebuchet MS'"><FONT
face="Times New Roman">engine for optimum performance. Proceedings of
institution of mechanical engineers, Part D, vol. 211, 1997. p.
361–78.<o:p></o:p></FONT></SPAN></P>
<P style="MARGIN: 0in 0in 0pt; mso-layout-grid-align: none"
class=MsoNormal><SPAN
style="FONT-FAMILY: 'Trebuchet MS','sans-serif'; COLOR: black; FONT-SIZE: 10pt; mso-bidi-font-family: 'Trebuchet MS'"><FONT
face="Times New Roman">[1<o:p></o:p></FONT></SPAN></P>
<P style="MARGIN: 0in 0in 0pt; mso-layout-grid-align: none"
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face="Times New Roman">Fuels from biomass and their rational utilization in
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gas fuelling of internal combustion engines. Energy from
Biomass<o:p></o:p></FONT></SPAN></P>
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w:st="on">Lake Buena Vista</st1:City> <st1:State
w:st="on">Florida</st1:State></st1:place>. p.
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face="Times New Roman">A new look at high compression engines. SAE Transactions
1959; 67:112–23.<o:p></o:p></FONT></SPAN></P>
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style="FONT-FAMILY: 'Trebuchet MS','sans-serif'; COLOR: black; FONT-SIZE: 10pt; mso-bidi-font-family: 'Trebuchet MS'"><FONT
face="Times New Roman">[14] Mishra DP, Paul PJ, Mukunda HS. Computational
studies on the flame propagation in producer gas–air mixture and experimental
comparisons, Proceedings of the XIII National Conference on IC Engines and
Combustion, <st1:place w:st="on"><st1:City w:st="on">Bangalore</st1:City>,
<st1:country-region
w:st="on">India</st1:country-region></st1:place>,<o:p></o:p></FONT></SPAN></P>
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style="FONT-FAMILY: 'Trebuchet MS','sans-serif'; COLOR: black; FONT-SIZE: 10pt; mso-bidi-font-family: 'Trebuchet MS'"><FONT
face="Times New Roman">1994. p. 256–62.<o:p></o:p></FONT></SPAN></P>
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style="FONT-FAMILY: 'Trebuchet MS','sans-serif'; COLOR: black; FONT-SIZE: 10pt; mso-bidi-font-family: 'Trebuchet MS'"><FONT
face="Times New Roman">Effects of engine speed on combustion in SI engines:
Comparison of predictions of a fractal burning model with experimental data, SAE
Trans. 1993; p. 2277–91.<o:p></o:p></FONT></SPAN></P>
<P style="MARGIN: 0in 0in 0pt" class=MsoNormal><o:p><FONT
face="Times New Roman"> </FONT></o:p></P></DIV>
<BLOCKQUOTE
style="BORDER-LEFT: #000000 2px solid; PADDING-LEFT: 5px; PADDING-RIGHT: 0px; MARGIN-LEFT: 5px; MARGIN-RIGHT: 0px">
<DIV style="FONT: 10pt arial">----- Original Message ----- </DIV>
<DIV
style="FONT: 10pt arial; BACKGROUND: #e4e4e4; font-color: black"><B>From:</B>
<A title=Doug.Williams@orcon.net.nz
href="mailto:Doug.Williams@orcon.net.nz">doug.williams</A> </DIV>
<DIV style="FONT: 10pt arial"><B>To:</B> <A
title=gasification@lists.bioenergylists.org
href="mailto:gasification@lists.bioenergylists.org">Discussion of biomass
pyrolysis and gasification</A> </DIV>
<DIV style="FONT: 10pt arial"><B>Sent:</B> Thursday, February 24, 2011 7:46
PM</DIV>
<DIV style="FONT: 10pt arial"><B>Subject:</B> Re: [Gasification] ideal wood
gas engine</DIV>
<DIV><BR></DIV>
<DIV><FONT size=2 face=Arial><STRONG>Hi Tony and
Colleagues<BR><BR></STRONG>> This may be my first post to this site, I
trust you will all not hope it is my last.</FONT></DIV>
<DIV><FONT size=2 face=Arial></FONT> </DIV>
<DIV><FONT size=2 face=Arial><STRONG>As a fellow New Zealander, lets hear more
from you, we cover a lot of engine "stuff", and new voices are most
welcome.</STRONG></FONT><FONT size=2 face=Arial><STRONG> </STRONG></DIV>
<DIV><BR>> Getting the Air/fuel ratio correct is also vital. Using a
"colortune" sparkplug is the best way to really know when you have the correct
mixture as you can see the flame color within the combustion chamber.</DIV>
<DIV> </DIV>
<DIV><STRONG>Fluidyne bought a Colortune 500 kit back in 1974-5, and I used it
to teach how exhaust temperatures and engine sound changed across gas/air
mixtures, using a single cylinder Iron Horse engine. I sent both Kevin
and Arnt a copy of the colour guide out of our kit, seeing as they were
interested in this subject.</STRONG><BR><BR>> A turbocharger can be used to
increase the volume of mixture which is drawn into engine but whether or not
they are practical given the possibility of contaminated gas is something I
cannot comment on.</DIV>
<DIV> </DIV>
<DIV><STRONG>This is a problem for producer gas in most DIY systems. We do
better at the commercial level with more sophisticated filtration systems, but
it is better to use naturally aspirated engines of larger cylinder capacity of
lower RPM, than undersized turbocharged engines relying on high RPM for DIY
projects.</STRONG></DIV>
<DIV> </DIV>
<DIV>> The Mean effective pressure within the engine during the combustion
stroke, is largely dependent on the length of stroke of the engine, the
compression ratio and the ignition timing.<BR>> The stroke cannot easily be
altered but the compression ratio can be changed on some engines by machining
the cylinder head.</DIV>
<DIV> </DIV>
<DIV><STRONG>Generally speaking, this would mainly be applied to very old
engines, probably pre-dating around 1949. The literature records a lot of work
in this area of compression ratios by Woods in the late 1930's early
40's (from memory), where it was established that around 11:1 was the
optimum for producer gas. At this point, the extra friction from compressive
forces consumed the "extra energy", and little was gained from higher
compression. </STRONG></DIV>
<DIV><BR>> If a petrol (spark ignited) engine is run on wood gas or any
other gas, the Ignition timing has to be altered. In general the
ignition timing will be advanced by several degrees, in order to ensure as
high a mean pressure as possible is reached during the combustion
stroke.</DIV>
<DIV> </DIV>
<DIV><STRONG>This is true, but remember that WW2 petrol was of lower
octane, and required ignition advancement. Modern engines have that
advancement already built in for the higher octane available today. Then,
separate charcoal gasifiers away from wood gasifiers, because the H2 content
again changes ignition behaviour. Most engines set up to operate on LPG or
natural gas, are from 10-12:1 compression ratio (of the smaller sizes), and
run without alteration on 110-120 octane producer gas perfectly. Having
said that, you can always tweak them if the situation demands that degree of
perfection. The engine is the least of your worries if the gas making is
unstable (:-)</STRONG></DIV>
<DIV><BR>> The benefit of using a computer controlled ignition system is
that most if not all computer controlled systems have a "knock" sensor.
The purpose of this device is to sense when the ignition of the fuel has
caused the pressure within the cylinder to rise so high that the remaining un
burnt fuel spontaneously explodes. This results in engine knock, the
resulting noise is commonly known as "pinking" Diesel engines
knock a lot of the time because the very design of the engine is to raise the
fuel temperature to point when it spontaneously burns.</DIV>
<DIV> </DIV>
<DIV><STRONG>Speaking "generally", producer gas has no problem in most
standard spark ignition engines, as the spontaneous ignition temperature for
producer gas in our experience, is around 600C. You find these compression
temperatures in diesels around 16:1 ratio, and again from experience, once you
go over 17:1, the spontaneous ignition temperature makes the engine very
unstable. We worked with Lister (NZ) to develop dual fuel conversion
kits for the Pacific region, converted to gas Ford diesels in the UK,
Ford natural gas engines in USA, and purpose built gas engines in Germany.
</STRONG></DIV>
<DIV><STRONG></STRONG> </DIV>
<DIV><STRONG>In all cases, the operating temperatures around the engine can
affect the behaviour of the ignition temperatures, as will the actual CO,H2,
and CH4 content. Any uncracked hydrocarbons will also affect the timing
behaviour, so be careful how you tinker with the timing. Nothing is written in
stone!</STRONG></DIV>
<DIV> </DIV>
<DIV>> Older engines that use a Distributor lack the anti-knock feature.
Commonly distributors have a simple mechanical advise mechanism, to advance
the ignition as the engine revs faster, and a >Vacuum Retard mechanism
which aids acceleration. Engines which are subject to varying loads, can
benefit from the retard mechanism if there is any kind of control valve
/butterfly on the >intake, which would alter the manifold vacuum.</DIV>
<DIV> </DIV>
<DIV><STRONG>My genset engine is a 1949 Hillman engine, one of the early
higher compression engines (8:1) out of the UK. The vacuum advance and
retard is disconnected, but we have not noticed any problems across a wide
range of outputs for 1,000's of hours. It is a moot point however, and I will
reconnect it next time I play to see if it makes any
difference.<BR></STRONG>> <BR>> Anyone setting the timing on an engine
with a fixed load-speed, needs to be sure the advance/retard mechanisms are
either working correctly or have been locked up. As fixed speed engines can
"hunt" if there is any faults in or if there is any small changes in the
loading or fuel supply.</DIV>
<DIV> </DIV>
<DIV><STRONG>Gensets have to operate at fixed speed, so use a governor on the
throttle butterfly, and as I said, our advance/retard control is disconnected,
so cannot in any way affect how the engine hunts on load or gas changes.
Producer gas has many surprises as an engine fuel, and we learn more by the
day.</STRONG></DIV>
<DIV><STRONG></STRONG> </DIV>
<DIV><STRONG>Most of the above comments apply to fixed speed (RPM)
applications used for electrical power generation, both base and variable
loads, from our installation experiences 1978- 2010.</STRONG></DIV>
<DIV><STRONG></STRONG> </DIV>
<DIV><STRONG>Doug Williams,</STRONG></DIV>
<DIV><STRONG>Fluidyne Gasification.</STRONG></DIV>
<DIV><STRONG></STRONG> </DIV>
<DIV><STRONG></STRONG> </DIV>
<DIV><STRONG></STRONG> </DIV>
<DIV><STRONG></STRONG></FONT> </DIV>
<P>
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