Fuel Temperature Compensation 1

[Methusalah]

Hi All,

Can anyone guide me with the theory of the effects of fuel line temperature relative to fuel delivery of a/f?

Basically does the a/f richen or weaken as the fuel tempature increases?

Hope you can help

 

[patprimmer]

If the pressure remains the same, and the delivery system meters volume, then the hot fuel will have a lower SG due to expansion, so it will lean the engine if the air density has not also changed.

Regards

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[mpgmike]

It is my understanding that the "air/fuel ratio" is actually an "air/fuel VAPOR ratio". Therefore if the fuel is admitted into the air charge closer to phase change temps, then the "effect" would be an enrichment condition. Of course it would depend on how efficient your combustion chamber design is. An efficient combustion chamber will perform better at vaporizing the atomized fuel on the intake and compression strokes and therefore would have less of an enrichment effect than a poor chamber design.

Mike

 

[patprimmer]

Bunkum

Air to fuel ratio is the ratio of the mass of air to the mass of fuel.

For a chemical reaction to be in balance, the mass of each reagent must be correct.



Regards

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[whitevette]

Hi, mpgmike!
Air/fuel ratio is measured in pounds, isn't it? State (liquid / vapor) has nothing to do with it. -whitevette

 

[patprimmer]

Umm, I think pounds is just one unit for measuring mass.

Regards

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[CapeNor]

I think it depends:

If it is a carburetter engine, it is a must that the air and the fuel are hot enough. Otherwise the fuel will form droplets again. In cold area's, it can be good to preheat the fuel.

If it is an injector engine. The temperature of the fuel is important for the atomizing. If the viscosity of the fuel is to high, the fuel pump will have troubles with it, and after the injection, the average size of the droplets will increase. This will cause a greater delay on the ignition, resulting in loss of power, loss of efficiency and higher exhaust gas temperatures. In worst cases, it will cause a diesel knock that, if ignored for long time, can damage the crankpin bearings.

At sea, they use the lowest quality fuel, and we preheat it to over 130 °C before it reaches the fuel pumps.

 

[WGJ]

"At sea, they use the lowest quality fuel, and we preheat it to over 130 °C before it reaches the fuel pumps."

Yes, but I assume from the "At sea..." bit that these will be heavy-oil engines where the fuel in question is more like light tar than automotive diesel.

Musn't confuse the functional niceties of gasoline, diesel and marine heavy oil types.


Bill