[Gasification] Producer gas octane

[Ken Basterfield]

Tom,
Only a minor detail which does not invalidate the rules. Aero engines,
Lycomings and Continentals, are typically 6.5 : 1 CR the old 80 Octane, and
~ 7.5:1 100ll Octane. They tend to overfuel to keep the aircooled heads
cool, and they also work at reduced atmospheric pressure.
Ken



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-----Original Message-----
From: gasification-bounces at listserv.repp.org
[mailto:gasification-bounces at listserv.repp.org] On Behalf Of Thomas Reed
Sent: 31 July 2007 00:55
To: Discussion of biomass pyrolysis and gasification
Subject: [Gasification] Producer gas octane


Dear Daniel and All:

I long ago observed that the required octane ratio for known engines is 
10X the compression ratio (1930 engines, 6/1, 60 octane; 2000 engines, 
80 octane 8/1; airplane engines, octane 110 so 11/1 CR). I therefor 
assume that a good approximation to octane requirement is that "Minimum 
octane = CR X 10"

Applying this to producer gas, it will NOT ignite in 18/1 CR engines, so 
the octane of PG is > 180!  The octane scale was only meant to go from 0 
(n-heptane, 7 carbon straight chain) to 100 (2,2,4 trimethylpentane).  I 
learned that in auto shop in 1943.  It has been extended by using g of 
tetraethyl lead to get into the 100-120 range.  The rule above takes it 
to 180, and since nothing else compares, there is no way to check. 

But in any case PG is VERY high octane and won't preignite.
------------------------------------------------------------------------
Here's another comment.  The reason the octane of PG is so high is that 
it is so dilute.   The A/F ratio for PG is about 1.5, so much of the 
combustion chamber is diluted with N2.  So the the power per stroke is 
way down.  This can be recovered by going to CR>12.  But I don't think 
this puts any more strain on the bearings than gasoline in an unmodified 
engine.

Comments?

TOM REED           BEF//BEC
------------------------------------------------------------------------
Daniel Nicoson wrote:
> Boy, this is a discussion of generalities!  First question, what is 
> your goal?  Least expensive hardware to take your house off the grid 
> with a gasifier?  Or, a well optimized gasifier genset that gets great 
> Kw/lb fuel?
>
> I would suggest for option number one, find a suitable auto motor 
> where you have full control of spark and fuel and don't change a thing 
> internally. Most modern auto engines (from the early 1990's on) are 
> running 9:1 compression or higher, especially if you choose an Asian 
> or European design. If you are really wanting to optimize you might 
> want to raise the compression ratio.  I don't know off the top of my 
> head what the "effective octane rating" is for producer fuel but I'm 
> thinking it isn't bad.  With an effective higher octane you could gain 
> some efficiency by raising the compression ratio, but that will assume 
> consistently good fuel quality.  You would have to answer if that is a 
> good assumption.
>
> Your mention of aircraft use of auto engines is actually at the other 
> end of the use spectrum.  In that case people are after high specific 
> power ratio's, meaning high hp/CID.  Here we know we are going to 
> operate at a low hp/CID right from the start, so a engine designed to 
> be "well behaved" in an auto will work fine.
>
> Keep it simple.
>
> Dan Nicoson
>
> -----Original Message-----
> From: gasification-bounces at listserv.repp.org
> [mailto:gasification-bounces at listserv.repp.org]On Behalf Of Bob Stuart
> Sent: Sunday, July 29, 2007 11:01 AM
> To: Discussion of biomass pyrolysis and gasification
> Subject: Re: [Gasification] Rebuilding engines (was Re: Charcoal 
> GasifierNo
> 2.)
>
>
> On 29-Jul-07, at 7:42 AM, Daniel Nicoson wrote:
>   
>> Final note.  Many light duty industrial engines are actually an 
>> automotive engine configured for the industrial use, they are built 
>> to cost very little, and they work for many hours on end simply 
>> because their operation
>> is a steady predictable load that doesn't work the engine very
>> hard.  They
>> can last a very long time.
>>     
>
> When automobile engines are used in aircraft, they run at 3/4 throttle 
> much of the time, in contrast to the car which usually runs at well 
> under 1/4.  Most people don't even use  3/4 for everyday acceleration.  
> It takes some experience to make them reliable at high power.  I'm 
> more interested in the industrial conversions, though. Are special 
> camshafts and/or tuned manifolds available that would help us?
>
> Best,
> Bob Stuart
>
>
>
>
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>   

-- 
ÐÏࡱá

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