[Gasification] Benefits of boosting compression ratio with producer gas

Mark E Ludlow mark at ludlow.com
Sun Feb 27 18:45:22 CST 2011


Hi Toby,

There is no difference, really, between pressure and vacuum. If we just
start to think of anything that has no pressure at all as Zero Pressure;
normal Atmospheric Pressure as 14.69 PSIA (PSI absolute) and so forth, then
we  won't get into trouble. Pump sizing always considers the Absolute
Pressure (e.g. PSIA) at the inlet and outlet, not the Gauge pressure (e.g.
PSIG). A third concept is Differential Pressure (e.g. PSID). A pump
increases the pressure (measured across the Inlet and Discharge Ports) as a
differential pressure gain, more-or-less irrespective of the Absolute
Pressure environment that it operates in.

There is really no such thing as "Vacuum" conveying. This only refers to the
fact the transport network operates at or below the ambient pressure and is
operated this way to help reduce fugitive losses of transported materials. A
vacuum cannot move anything; it is the force of pressurized gas behind the
transported material that provides the propulsive energy. In the case of a
conveying system connected to a positive-displacement "vacuum" blower, the
force is a maximum of 14.69 PSI, enough to "lift" a water column 33.9 feet,
hardly any stretch at all for a pump, though the work done will be the same
regardless of the method used.

When someone says: "Gravity doesn't exist; the world sucks!", this is a very
special case of the above that awaits the practical manipulation of
anti-gravity.

Best, Mark

 

From: gasification-bounces at lists.bioenergylists.org
[mailto:gasification-bounces at lists.bioenergylists.org] On Behalf Of Toby
Seiler
Sent: Sunday, February 27, 2011 3:42 PM
To: gasification at lists.bioenergylists.org
Subject: [Gasification] Benefits of boosting compression ratio with producer
gas

 


Sorry Tom, I didn't ask the question correctly (or I may be off in left
field).  This comes from some time spent in a place called Flow Dynamics
Laboratory where inlet design of blowers was being tested.  My application
was sawdust material moving.  Dan, the owner, explained how pressure was
much more effective than vacuum for moving mass.  He explained that drag in
a vacuum is hard to overcome, while pressure fills the space with molecules
and can push materials great distances.  

 

When talking engines, for example on my 74 Ford f600, I watch the vacuum
gage and see that it is around 18-22" of vacuum, warmed up 1200 rpm or so
(driving hydraulic pump).  So what goes to the cylinders is not atmospheric
pressure, it is around half, perhaps less.  

 

I'm trying to understand how engine efficiency is related to both air and
gas pressure and density.  If producer gas is operating with 18/1 in a
normally aspirated engine, due to high octane, how will the ratio be
affected if one has positive pressure at one or two pounds?  

 

Seemingly this would involve air flow across an orifice, similar to a
butterfly valve (throttle), but I am at a loss for a good start point.  

 

Given a large quantity of air and gas to make comparable power (not large
derated), the flow of air/gas in a large displacement engine would seem to
be a much more critical factor than just saying the cylinder is seeing
atmosphere pressure and forgetting the drag that manifolds, throttle valves
and pulling gas from a gasifier creates (in a suction system).  I can hardly
see a direct linear relationship. 

 

My work is a low pressure system, so this is not an academic or theoretical
discussion that I will never act on and I'm at a point of determining engine
for a CHP and what internal modifications to plan, if any.   I have several
engines, a 345 International, a 460 Ford, a Cumins 5.7 (with needed repair),
a 7.3 International (in a ford truck also needing repair).  

 

Sorry if this is confusing or not cogent.  I'm trying.

 

Toby

seilertechco 

 

 

 

 

 

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