How Does Combustion Rate Impact SI Engine Efficiency?

[blumist]

I wanted some help in finding out the time taken for a differential mass of gasoline being burnt in the cylinder during the power stroke. Also, does it depend on the residual temperature of the mixture?

I tried to find it out through Arrhenius equations but am having a problem finding out the Arrhenius constant for gasoline. Will it work?

Thanks!​

 

[brewnog]

Not sure. As a guide, the 50% mass fraction burned point is typically in the range 15 - 30 deg ATDC, and the 10-90% mass fraction burn duration is typically 5-25 deg crank. You will certainly see a reduction in burn duration with increasing charge air temperature.

 

[Vespa71]

I don't know if this is reliable or exact enough for you. I've used this page to grasp the general dynamics of the IC engine.


From http://mb-soft.com/public2/engine.html

It turns out to be sort of fortunate that the "speed" of the explosion of the gasoline-air mixture is relatively slow! Under the conditions that generally exist inside a cylinder (during highway cruising), the flame front velocity is usually around 90 feet per second, or 60 mph. Mark's Standard Handbook for Mechanical Engineers, Section 9, Internal Combustion Engines, Flame Speed. Depending on exactly where the spark plug is located, that flame front must travel two to four inches in order to ignite all the gases in the cylinder. At 90 ft/sec, this then requires around 0.002 to 0.004 second for the combustion to complete.