Hehe. Chemistry. It was my one time major in college. By the fourth year, it didn't make any sense to me either and I switched to economics.

To put it in English:

When you squeeze a gas, it shrinks and/or it gets warmer. Squeeze it enough, and it will combust. Like diesel in an engine.

 

Maybe what you meant to say is ; "squeeze it enough, and it will heat up the air charge enough to cause an 'introduced flammable' to combust".

 

squeeze it enough, and it will heat up the air charge enough to cause an 'introduced flammable' to combust".
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like i said .i never was good at foreign laguages

 

Not sure if I meant to say that or not. I don't know that the introduction of a heat air charge makes a flammable combust or not. I thought the air and fuel were in somewhat homogenious mixture, so the entire thing is heated via the volume/pressure change.

But I'm also not sure if that matters much

 

In a gas engine they are.

In a diesel like ours, the air is compressed about 18:1. Then the diesel is injected, and ignites as soon as it's injected. There is no "mixture" in the common sense.

 

Any good reference material (particulaly online) to illustrate what happens when during the cycle on a diesel vs. a gas engine? I'm also curious over what length of time the diesel is injected, when in relation to piston position, how you avoid flame propogation back through the injector.

Thanks.

 

yeah; there's a big difference....what you & I are thinking in terms of is what's know as the OTTO Cycle---the way a gasoline or jet fuel works......where the air/fuel is combined first then ignited with a spark---

the diesel combustion system seams very simple---- allowing just about anything that will burn to be used from peanut oil to diesel. I too would be interested in how/when exactly the fuel is injected in relationship to piston position, how the fire/explosion is prevented from traveling back into the fuel rail, and how much remaining chamber space is remaining when the pistons are at TDC? Assuming the fuel is injected exactly when the piston is TDC? otherwise, it too would be getting "compressed' during the compression stroke(along with the chamber air), which would seem to problematic---resulting in severe timing problems.

 

http://auto.howstuffworks.com/diesel.htm

http://en.wikipedia.org/wiki/Diesel_engine

The fuel injector pressure is rather substantial, even in older engines. I'm sure the injector is closed by the time max pressure has occured.

 

Thanks for the links. There went an hour of my life. (to read those two pages as well as other interesting links that branched off from there)

 

Maximum combustion chamber pressure is far lower than the fuel injector's "valve opening pressure".