Rather than raise the compression ratio of a wankel, would it be

possible to

have a two stage combustion process where gasoline is the initial fuel?

When

it combusts, the pressure in the combustion chamber is raised enough to

ignite

the diesel fuel. You would have gasoline burning in the rear portion of

the

combustion chamber(near the trailing apex seal) and the diesel charge

would be

near the leading apex seal. I'm no engineer, I was just wondering if any
engineers have toyed with such a scheme. Is this what you'd call a

stratified charge?

Brian Trubee

Not really stratified charge in the current definition. Interesting idea.
Sounds complicated.

Paul Lamar

I think that even with late injection, a highly boosted gasoline engine
would
detonate. Detonotion is by defination, the condition where the combustion
process goes "high order" ie acts as a high explosive rather than normal
combustion. Flame front velocity goes from a modest number of feet
persecond, up to MILES per second - such that a stick of dynamite
placed on a steel plate will puncture it based on the inertia of the normal
air on the back side. I believe that the high pressure, heated air with
gasoline very likly would detonate. I believe the cetane rating of
"Diesel fuel is the attempt to mitigate this tendency. Combustion
proceeding during expansion is a sizable efficiency loss. The theoretical
Diesel cycle at a given expansion (compression) ratio is less than the
Otto cycle for this reason. In actual fact, both "Diesel" engines, and
four stroke gasoline engines both run on a modified cycle that is
between these two cycles.

Boosting does not improve cycle efficiency since efficiency is really
a function of the expansion ratio, not the compression ratio (as
erroneously reported in most text books) Think about it and you will
readily see why that is true - and why compounding works.
Vance

 
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