Detonation is more the cracked piston route which can be
Diesels don't detonate, which is a flame front running faster than the speed of sound in the medium. (If I recall correctly.) Diesel fuel is sprayed into a hot chamber, and burns as it goes in. Late-coming fuel doesn't find any oxygen to bind with nearby, and so travels further until it does. It's a _very_ different combustion cycle than an Otto. The injector spray pattern is crucial, because you want the fuel to be well mixed and sprayed around so that it burns where it is supposed to, in the middle, rather than up against the piston directly.
The same basic principles of stochastic mixture apply in Diesel engines. So if you 'pump' in more air you will need more fuel.
No, they do not. Stoichiometric ratios might determine how clean-burning the engine was, but not how much power you got. You don't need to supply fuel to match all the air. That's the whole point of a diesel, and one of the big reasons they get better fuel economy in general. Apparently you can over- fuel a diesel and get more power, but at diminishing returns. Until you quench the thing entirely. See the smoke-belching monster diesel trucks. Those engines don't last long, but what do you expect with 60# of boost and 1200+ horses out of a rated 300 horse motor? (For example.)
As I attempted to explain earlier, it is the amount of air being compressed that determines temperatures. The amount of fuel does not influence temperature
Pre-ignition, yes. Once flame enters the picture that's not true, and the situation gets complicated. PV=nRT only where there aren't chemical (or other) reactions polluting the pool. Diesels don't have 'mixture'. The only mixture is determined by how good the spray pattern is. (And combustion chamber design.) They get less power per displacement (ceterus paribus) because they're not as efficient at using up the last of the air. They get better economy because they're not constrained to stoichiometric ratios in order to prevent detonation and too-high pressures (i.e. too-hot chambers) because lean _mixtures_ burn faster (and therefore hotter in a chamber that's not expanding fast enough to absorb the heat energy and convert it to mechanical energy. (Diesel also has somewhat more BTU/gallon, so that helps the economy figures a little, but not enough to explain away the observed differences.) If the motion of the piston can't suck away the heat fast enough and convert it to work, that heat will go into melting the piston instead. Any particular engine design will have a sweet spot where its burn rate has the optimum power extracted at some particular RPM and load. They'll vary. I find heat engine design theory fascinating. -- Jim _______________________________________ http://www.okiebenz.com For new and used parts go to www.okiebenz.com To search list archives http://www.okiebenz.com/archive/ To Unsubscribe or change delivery options go to: http://okiebenz.com/mailman/listinfo/mercedes_okiebenz.com
