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

[Art Krenzel]

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


----- Original Message ----- 
From: "Ken Boak" <kenboak at stirlingservice.freeserve.co.uk>
To: "Peter Singfield" <snkm at btl.net>; <GASIFICATION at LISTSERV.REPP.ORG>
Sent: Wednesday, August 02, 2006 1:53 AM
Subject: Re: [Gasification] Prime movers -- The Slow Go diesel concept


> Peter,
>
> Thanks for your explanation regarding running the diesel at half rated
> speed. I had not made the conection that reducing the speed, allows the 
> air
> fuel ration to be reduced accordingly thus maintaining efficiency.
>
> I think some further experimentation is needed, and I now have the means 
> to
> run the engine at a range of speeds,and make electrical power measurements
> using the PM dc motor as a dynamometer.
>
> These I will plot against fuel consumption, so I can get specific fuel
> consumption figures for  various rpm figures - and not just the rated 
> speed
> (650rpm) as the manual quotes.
>
> I am still slightly sceptical of your figures, as the best fuel efficiency 
> I
> saw was at rated speed,  where 1 litre of vegetable oil (c.v. 
> 9.4kWh/litre)
> produced 2.125kWh of electricity,  giving an overall conversion efficiency
> of 22.6%.  All I can suggest is that more fuel consumption experiments 
> with
> measuring cylinders and fixed electrical loads are necessary  to qualify
> your findings.
>
> At part load, but rated rpm, I have found that the exhaust gas temperature
> is very low. I guess thist is because the air to fuel ratio is higher than
> needed, and the excess air has the effect of cooling the exhaust gases.
> Under these circumstances the engine will fail to reach a sensible working
> temperature.    By reducing the speed, and maintaining a more optimum air
> fuel ratio, does the engine run at a reasonable temperature?
>
> When I first installed the dc starter/generator, I was cranking it over at
> 36V.  The pm motor makes a great dc generator and produces a dc voltage
> proportional to the shaft speed.
>
> When the engine fired fired, the pm motor started to generate and force a
> lot of current back into the starter battery, and the resulting charging
> load was such that the engine rpm stayed low, about 180 rpm -effectively
> fixed by the terminal voltage of the battery, which slowly crept up 
> towards
> 42V.
>
> By adding additional batteries into my series string, I could get the 
> engine
> to run at several discrete speeds from about 180rpm at 36V,  up to 650rpm 
> at
> 130V.  I can measure the charging current and the battery terminal 
> voltage,
> and thus get the electrical power.
>
> I agree that reducing our electricity consumption to a minimum, and using 
> a
> woodgas fuelled gen set to provide that power is a worthy direction.
>
> I am running a fridge/freezer, a PC,  a circulation pump for the solar 
> water
> heater, some lighting, a cooling fan and my radio on about 300W.  My 
> highest
> wattage appliance is my kettle at 2500W, but this is only used for a few
> minutes per day.
>
>
>
>
>
>
> Ken
>
>
>
>
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