I’ve brought this over from the TERS thread since it seems more appropriate here.Tommy Cookers wrote: ↑Thu Apr 18, 2019 11:26 amimohenry wrote: ↑Thu Apr 18, 2019 8:36 amI was clumsily trying to indicate that the crank power from the ICE has gone up considerably from around 30% to over 40% of fuel energy content. .....
So if the %age of fuel burned hasn’t changed what is it that has increased the crank ITE by 14 %age points? Crank work from the compressor, more complete combustion....
the % fuel burned (in-cylinder anyway) hasn't changed
conventional engines were/are designed to a leaning limit that gives about 95% combustion efficiency
ie even these F1 engines have their leaning limited this way (though their leaning is significantly more than conventional)
below 95% combustion efficiency there is a sharp increase in combustion intermittency
these F1 engines (designed for running unconventionally lean) dilute the in-cylinder heat (far more than conventional lean)
ie the mean in-cylinder temperature is lower
so the heat taken by coolant is disproportionately lower
(generally engines can still work even with heat rate lowered enough for no cooling to be needed)
the reduction in cylinder heat taken by coolant is an increase in available heat and so in heat converted to work
that's a big source of the great increase in the crank ITE and BTE
(the very high geometric compression/expansion ratio and reduction/elimination of CO2/CO dissociation also help)
This is the first time I have understood what you mean by heat dilution increasing output. If I understand it your explanation of the increased BTE, which I suggest is around 14%age points, is made up of:
Increased heat retained in the working fluid because of the excess air, reducing cooling with a side effect of reducing the vehicle cooling requirements
Increased heat retained because at the lower combustion temperatures unproductive chemical reactions, endothermic?, are reduced.
The higher energy content working fluid expands for longer because of the higher expansion ratio. I guess as well as the compression ratio, valve timings come into play here.
Thanks for this insight, it’s taken a long time for the penny to drop.