SameSame wrote:Postmoe wrote:SameSame wrote:
Ouch. Maybe that's proof they have a more efficient combustion concept and that it is really hurting their energy recovery.
Would that mean less recovery?
It os perhaps a stupid question, but I thought lean combustion was rich in gasses and subsequently, good for turbine harvesting.
The more efficient the combustion process is the less energy the exhaust gasses will have if I understand it correctly. More of the total energy is given to the ICE leaving less energy in the exhaust flow to be harvested.
Edit: I think Hasagawa said that one of the challenges of improving the ICE efficiency was that less exhaust energy was available and that this would require a turbine redesign.
afaik (as I like to say from time to time) ........
combustion efficiency is about 95% in all engines (unless they are using rich mixture)
the issue is eg in normal engines that the mixture cannot be very lean without combustion efficiency falling below eg 95%
Mahle claims better combustion not more efficient combustion
they mean that they can go very lean without the combustion efficiency falling below eg 95%
going very lean means our F1 fixed fuel rate/heat rate is diluted by the extra air in the cylinder
there's more mass of gas so its temperature is lower so less heat energy needs to be taken by the coolant
less heat taken means more heat energy left in the cylinder to work on the large mass of gas, so producing more crankshaft power
higher boost is needed to provide the greater mass of air to make the mixture very lean
so exhaust pressure is higher (and there's greater mass), creating more power at the turbine (despite the gas being less hot)
but of course more compressor power is taken
ie there is no gain in recovery
the big question is how much heat dilution/leaning is being used
ie broadly, how much boost is being used
imo
the heat dilution engine is an engine further downsized (beyond turbo downsizing) in heat loss to coolant terms
but because of eg the higher gas pressure throughout compression, not further downsized in friction terms