Combustion efficiency with E85

[black2003cobra]

Does anyone have any actual data of combustion efficiency vs equivalence ratio for E85? I have data for gasoline, but not E85.

Thanks in advance!

 

[black2003cobra]

Should have added that it would be best to have data for both fuels measured from the same engine, of course. Thanks again!

 

[GregLocock]

What is your definition of combustion efficiency?

Cheers

Greg Locock

SIGlease see FAQ731-376 for tips on how to make the best use of Eng-Tips.

 

[patprimmer]

And which fuel would you like the same engine optimised to.

Regards
Pat
See FAQ731-376 for tips on use of eng-tips by professional engineers for professional engineers

 

[black2003cobra]

The usual definition. Actual heat energy in divided by max heat energy available from the fuel, i.e., ?c = Qin/Qhv.

 

[GregLocock]

Well I'll have to bow out of this as the only combustion efficiency I've come across is what I use to measure the efficiency of a boiler, as can also be seen from your definition.

So, guessing that you aren't just using an engine to warm water with, what do you actually want to know?








Cheers

Greg Locock

SIGlease see FAQ731-376 for tips on how to make the best use of Eng-Tips.

 

[black2003cobra]

Greg. I'm looking for net chemical energy released vs total available energy for the two different fuels as used in a typical SI automotive engine. (And please forgive me....I left out the factor of mass in the denominator above. Should have been Qin/(mf*Qhv).) I appreciate any help!

 

[GregLocock]

No you aren't, unless you are heating water.

You are probably looking for the shaft work /out/ for a given LHV of fuel in. =Wout/Qhv=(Qhv-Qout)/Qhv=BSFC/mdot/LHV


As Pat says, which fuel is your engine optimised for?



Cheers

Greg Locock

SIGlease see FAQ731-376 for tips on how to make the best use of Eng-Tips.

 

[black2003cobra]

Hi Greg. I'm sorry, but no...that isn't what I'm looking for. That would include the thermal conversion efficiency as defined by Wc/Qin. I'm not looking for the fuel conversion efficiency. Perhaps a confusion over definitions. Do you have a copy of Heywood? If so, please refer to his section 3.5.5. Perhaps that will help explain what I'm after. Let's assume a typical gasoline powered engine.

 

[SomptingGuy]

You are basically talking about exhaust gas analysis then. Why should E85 behave any differently from octane in this respect?

- Steve

 

[black2003cobra]

That's correct, Steve. That's what I'm looking for. My suspicions are the same as yours - that they would be not different - but I was looking to see if anyone had any data to support that. Thank you for your reply!

 

[Silverbullet86]

blackcobra:
Qin/(mf*Qhv) is indicated fuel conversion efficiency

Would finding the adiabatic flame temp of gasoline VS ethanol at stoich combustion help you?

 

[black2003cobra]

Hello Silverbullet86,

For indicated fuel-conversion efficiency, I use the definition,

?fi = ?t*?c = Wc/(mf*Qhv)

where ?t = thermal-conversion efficiency, and ?c = combustion efficiency, i.e.,

?t = Wc/Qin
?c = Qin/(mf*Qhv)

I studied primarily from Heywood, so his are the definitions I tend to use.

Incomplete combustion reduces temps, and I’m interested in equiv ratios higher than stoich, so max adiabatic flame temp at AFRs does not help me, unfortunately. But I do really appreciate the offer to help!

Eric

 

[GregLocock]

Ah OK, yes I have got Heywood but not here. I wonder if the SAE has published anything on catalyst feed gas temperatures for E85 as opposed to E0?

Cheers

Greg Locock

SIGlease see FAQ731-376 for tips on how to make the best use of Eng-Tips.

 

[SomptingGuy]

I don't see how flame temperature comes into it. This is really a thermochemical equilibrium problem (with the added subtlety of a freeze temperature for the water gas reaction).

I'd be tempted to grab an engine simulation program that uses thermochemical equilibrium as a basis for its gas properties and create some combustion bomb experiments.

- Steve

 

[dcasto]

here is a table of thermo data

http://www.naftc.wvu.edu/technical/indepth/datatable.html

The combustion efficency should not be any different on the same engine that is capable of ingesting the fuel. What I mean by that is, if the engine is built with 11 to 1 compresion ratio to take advantage of e85 octane, when you put in 85 octane regular gasoline, there will be a loss in efficency due to retardation and the ECU running rich to keep from burning holes in the piston.

So a 9 to 1 compression ratio enegine tuned for each fuel should have the same thermal efficency or within tolerances of the measurement system.

 

[Lou Scannon]

"So a 9 to 1 compression ratio enegine tuned for each fuel should have the same thermal efficency or within tolerances of the measurement system."
No, the fuel will affect the ratio of specific heats which will affect heat release and work, albiet not a great deal.