[Gasification] Prime movers -- The Slow Go diesel concept

[jim mason]

yes, a slower rpm at high load will give more time for blowby.  but
many marine and slow speed diesels have survived well with this.
likely depends on ring configuration.  halving the desired running rpm
is likely to not exceed the design parameters.

yes, having all combustion happen at the top of the stroke does create
the highest load on the motor, but also the highest efficiency, as the
entire expansion is mined.  the closer a diesel gets to the otto
cycle, the more efficient it is.

while we are complicating peter's project, maybe we should encourage
him to add a pyrometer to monitor exhaust gas temps, as well as a
oxygen sensor so that fuel consumption and exhaust gas temps can be
plotted against mixture.

after that, we should ask him to install an hour glass full of wheat
or rice flour over the intake, and sift it into the air intake.  the
flame front of grain dusts is likely pretty slow, which will work well
in the current slow speed scenario.  no guarantees on cylinder wear
while running grain dust though . . .

j





On 8/2/06, Art Krenzel <phoenix98604 at msn.com> wrote:
> Mike,
>
> I am not certain of the pressure/power peak comparison for a diesel engine
> burning diesel fuel vs producer gas at these low rpms but I feel that the
> rate of pressure rise for each fuel is probably quite similar .  When you
> compare the ignition/pressure rise time of each fuel compared to the total
> time of the power stroke, I would think that the ignition/pressure time
> would be much smaller part of the total time so the delivered power of the
> different fuels might be noticeable but not overpowering.
>
> This comes from an old low rpm JOHN DEERE tractor driver where we even
> burned "tractor gas" which you could barely light with a match.  It seemed
> to be some sort of kerosene derivative.
>
> Art Krenzel
>
> ----- Original Message -----
> From: "Mike Redler" <redlerm at yahoo.com>
> To: <GASIFICATION at LISTSERV.REPP.ORG>
> Sent: Wednesday, August 02, 2006 9:21 AM
> Subject: Re: [Gasification] Prime movers -- The Slow Go diesel concept
>
>
> > Art,
> >
> > That's a good point. The only thing that makes me wonder is the rate of
> > combustion. I'm sure the engine could be slowed down to the point that
> > all of the combustion occurs in a relatively small volume near the top
> > of the stroke, causing high stresses and low torque at the crank. If
> > you're "lugging" an engine with direct injection, your injection
> > pressures and oil temperatures might play a roll as well.
> >
> > What if other fuels (like producer gas) burn more slowly and allow the
> > pressure from the expanding gases to be better distributed to the piston
> > during the power stroke at slower speeds?
> >
> > I would imagine that having a cetane value less than that of diesel
> > might be an indicator but, I'm not 100% sure.
> >
> > ...my $.02
> >
> > Mike
> >
> >
> > Art Krenzel wrote:
> >> Ken and Peter,
> >>
> >> As an old Trucker who ran diesel engines for a few lifetimes, I am
> >> wondering
> >> if you are considering the reduction in ring life due to operating the
> >> engine under load at the reduced RPM.  As a trucker, the quickest way to
> >> get
> >> your hands slapped was to "lug" as diesel engine at low rpm under load.
> >> The
> >> high combustion chamber pressure would begin to blow by the rings and you
> >> would be staring an engine overhaul in the face after only a fraction of
> >> the
> >> normal life of the engine.  At the proper operating rpm, the time
> >> available
> >> for the high combustion pressure gasses to "blow-by" the rings was
> >> sufficiently short that the rings could retain the pressure without
> >> significant blowby.  At the lower rpm, blow-by can occur sort of like the
> >> Discovery Space Shuttle Booster Rocket failure (with the same final
> >> result).
> >>
> >> Check the flow of gases out of your crankcase and see how they vary with
> >> rpm
> >> over time.
> >>
> >> Art Krenzel
>
>
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