[SEL] semi OT - acetone in gas for cleaner, better running?

Listerdiesel listerdiesel at gmail.com
Wed Sep 14 06:32:21 PDT 2005


On 9/14/05, Curt <curt at imc-group.com> wrote:
> Richard,
> As I understand it the problem of knocking is a burn rate problem. Too
> quick of a flame propagation/burn flexes the top of the piston and we
> hear the knocking sound.
> I've been told all gasoline is the same with the differences in regular,
> mid, and premium being the additive packages that slow the burn rate.
> We hear these called octane boosters. What exactly is an octane booster?
> It is hard to imagine that all gasoline is perfect C(8) carbon chains.
> I'm guessing that it is a mixture of volatiles of lower carbon chains
> and oils of higher carbon chains, with the average being C(8) long. Do
> octane boosters make an attempt to tie shorter chains together to reduce
> the volatility? Or is there some other mechanism at work to reduce
> knocking/slow burn rate?
> 
> I've been trying to correlate physical properties to knocking. At first
> I was wondering if there was a relationship between flash point and
> knocking. But kero has a much higher flash point than premium gasoline
> and yet it is prone to knocking, so that kills that correlation.
> 
> I've also been wondering if there is a relationship between knocking and
> the explosive range of a fuel. For example, propane has a fairly narrow
> mixture range at which it will explode. Gasoline has a moderate range.
> On the other extreme is hydrogen. With hydrogen almost any mix ratio
> with air will result in an explosive mixture. I don't think I've ever
> heard a propane engine knock (forklifts for example).
> 
> Your thoughts? What physical properties of a volatile represent burn
> rate? If we know this, perhaps Bill's question about acetone as a decent
> non-knocking fuel can be answered.
> Curt Holland

Try and get hold of one of Sir Harry Ricardo's books on High Speed
Internal Combustion Engines, they go into great depth about developing
engines and fuels, and the addition of tetra-ethyl lead as a knock
suppressant. Engine types are discussed, and there are plenty of
drawings, some very large and pull-out, of development engines,
including sleeve-valve types.

Also, Sam Heron and the Ethyl Corporation are another source of
information around that time, particularly pre-WWII. Heron produced a
couple of books on fuel development which I have, and also he wrote a
fuel section in a very good book after the War about piston engine
development which I also have.

Heron received an award after the war, and Ricardo went on to greater
things in engine development. They both worked together just before
and during the War to develop high octane fuels, ending up at around
155 octane (RON) It's a fascinating subject on work that was carried
out under great pressure during war conditions in the US and UK.

Development of Aircraft Engines, Schlaifer / Heron, Harvard Business
Press,1950
History of the Aircraft Piston Engine, Ethyl Corporation, Heron, 1950
High Speed Internal Combustion Engines, H Ricardo, Blackie, 1953

Peter
-- 
Peter A Forbes
Email: listerdiesel at gmail.com
Web: www.oldengine.org/members/diesel




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