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<DIV><BR><FONT face=Arial size=2><STRONG>Hi Vakrant,</STRONG></FONT></DIV>
<DIV><STRONG><FONT face=Arial size=2></FONT></STRONG> </DIV>
<DIV><STRONG><FONT face=Arial size=2>Sorry for this slow response to offer
comment on your questions. </FONT></STRONG><FONT face=Arial size=2><STRONG>We
rarely get exchanges with those actually working for engine companies on this
forum, but privately I know of the frustration of engine manufacturers who have
tried working with producer gas. We all know engines run on PG, but with many
contradicting results, so we need to chip away at why you in an engine
laboratory would appear to be experiencing problems.<BR><BR></STRONG>>Doug, I
agree with you. We have engines on PG but more over we want to go for higher
capacity engines. Currently engines running on PG have the CR 11 for NA
>engines and For TC its 8.5 ..</FONT></DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
<DIV><FONT face=Arial size=2><STRONG>As others have commented, these are very
low ratios for a gas engine, and while 17: 1 CR is possible, this does
require the best quality of clean PG possible, and very stable operating
temperatures of the cooling system.</STRONG></DIV>
<DIV><BR>But fpr same case in NG we can go higher. </DIV>
<DIV> </DIV>
<DIV><STRONG>Using NG is a trap for engine operating specifications. The gas
quality depends on how much condensate they remove before it goes into the
pipeline. This was discovered during the commissioning of a power
station at Alice Springs in Australia. It took four days for the gas to reach
the engine, so every time it was precisely set up, it changed and shut the
engine down after a few days. This detail can be giving you a lot of false
information.</STRONG></DIV>
<DIV> </DIV>
<DIV>I am trying to think from combustion perspective to increase further to
sqeeze out more power and thermal eff. . So far i tried till 12.5 (though
literature mentioned about 17) and whatever thermodynamic state of mixture (PG +
Air) shows positive signs and CFD also support it..</DIV>
<DIV> </DIV>
<DIV><STRONG>My understanding of the Cummins range of gas engines, is that only
the biggest model PSV 91G has been optimized for PG. The fact that it can
extract more from PG than previously thought, is a very big advance, and
with a TC and CR at 11:1 sounds like your difficulty is at another
level. Remember that literature only reports what has been done, and in
some cases become more of a Bibliography collection. If it was of any value to
you in a engine laboratory, then all the problems would be
solved!</STRONG></DIV>
<DIV><STRONG></STRONG> </DIV>
<DIV><STRONG>At a guess, I suggest the gasifier you are using is making less
than tar free gas, and you rely on a gas cleaning system to remove all
condensable. If this is the case, then you are probably experiencing how the
differing gas mixtures spontaneously ignite at various CR.</STRONG></DIV>
<DIV><STRONG></STRONG> </DIV>
<DIV><STRONG>A huge amount of work was done in New Zealand on conversion of
diesel engines to gas and exported around the World for bus fleets. I had a
lot of exchanges of information with those guys, and their opinion of PG was
that it would offer the best performance at around 14:1 CR. This would
appear to me to be a tad low, but your engine has to be able to optimize the
most common denominator of the gas in the target market, which in the main, is
contaminated PG. In this instance, the difficulty is sometimes found in the
tuning of the inlet manifolds, where a pressure pulse can form which then
affects the VE of each cylinder. You won't see this with a single cylinder
engine, so you may need to review the engine used for compression
experiments.</STRONG></DIV>
<DIV><STRONG></STRONG> </DIV>
<DIV><STRONG>When I consider combustion issues, it sometimes helps to
look in other directions, and this I found a while ago which may offer a
clue to PG engine combustion. How one might relate shock wave ignition to
the chemistry found in PG, would probably fill a book, but purist
answers to resolve the problems just don't seem to work in practice, so we must
be missing something important. </STRONG></DIV>
<DIV> </DIV>
<DIV><STRONG><FONT color=#0000ff><A
href="http://www.princeton.edu/mae/people/faculty/dryer/homepage/research/hydrogen-fire-safety/movies/Dryer_et_al_CST_179_2007.pdf">http://www.princeton.edu/mae/people/faculty/dryer/homepage/research/hydrogen-fire-safety/movies/Dryer_et_al_CST_179_2007.pdf</A></FONT></STRONG></DIV>
<DIV><FONT color=#0000ff><FONT color=#000000></FONT></FONT> </DIV>
<DIV><FONT color=#0000ff><FONT color=#000000><STRONG>Hope this gives you a few
ideas to consider.</STRONG></FONT></DIV>
<DIV><BR></FONT><BR><STRONG>Doug Williams,</STRONG></DIV>
<DIV><STRONG>Fluidyne...</STRONG></FONT></DIV></BODY></HTML>