what causeses deisel to fire

[Dave G]

What causeses deisel to fire ie petrol has a sprk plug

[Buenchico]

The pressure inside a diesel engine produces sufficient heat for the fuel mixture to instantaneously self-combust (i.e. explode). The pressure inside a petrol engine doesn't heat the fuel mixture to a sufficient temperature for combustion, so the addition of a spark to the process is required (which also means that lower pressures can be used).

More here:
http://www.articlesbase.com/automotive-article s/petrol-engines-compared-to-diesel-engines-66 8455.html

Chris

[Clanad]

Chris is essentially correct (as usual) except that diesel fuel (nor gasoline for that matter) doesn't "explode" in the cylinders. I realize Chris was probably using the term as an euphemism, but engineers spend millions of dollars and untold amounts of time perfecting "flame propagation" in internal combustion engines. Exploding fuel causes detonation and can severely harm an engine...

[scotman]

With reference to "doesn't explode" that is the objective but we all know that it can if things are not set up properly. This is then down to mixture ratios and other things

[123everton]

Convection of the molecules caues it to combust.
The pressure in a diesel cylinder is much greater than that of a petrol one, petrol would simply evaporate in a diesel engine (well the older ones) petrol needs a spark to ignite it dieslel does'nt.

[Dave G]

Many many thanks to you all it was very informative

[chas2008]

Diesel engines have a higher compression which causes the diesel to combust, hence the term compression ignition engine . Large diesel engines have a large stroke (ie piston travel) which gives high torque and low RPM, hence why HGV,plant & commercials use diesels as they require enormous amounts of power

From wikipedia

A diesel engine is an internal combustion engine which operates using the diesel cycle (named after Dr. Rudolph Diesel). Diesel engines have the highest rate of energy to fuel (kwh/lbs) compared to any internal or external combustion engine.


The defining feature of the diesel engine is the use of compression ignition to burn the fuel, which is injected into the combustion chamber during the final stage of compression. This is in contrast to a petrol (gasoline) engine, which uses the Otto cycle, in which a fuel/air mixture is ignited by a spark plug.

[Toureman]

Diesel engines also use the "Otto Cycle" chas.

Read the last paragraph in the fuel octane section.....

http://en.wikipedia.org/wiki/Four-stroke_engin e

[chas2008]

Toureman,
ok, so i didnt cut and paste all of it, just enough to answer the basic question,.......slap on wrist needed

ps really dont think Dave G gives a wotsit about the Otto cycle.........