Diesels have very high compression ratios. Usually starting at 14:1 and
going as high as over 20:1. Many have turbos or superchargers. This makes
them more efficient. The high compression makes it auto ignite the fuel
when it is introduced. Diesel fuel injection systems have very high fuel
line pressures to overcome the cylinder pressure when injecting fuel.
Diesels are not tolerant of any out of spec conditions in the rotating
components because of the high cylinder pressures. A gas engine may limp
home with a bad rod bearing, a diesel will self distruct in short order.

"Shortwave Sportfishing" wrote in message
...
On 1 Jul 2005 08:48:37 -0700, wrote:



K. Smith wrote:
zee-qi wrote:
hi people.
i would ask you something.Who can explain me how does work diesel
engine.?and what kind of system it need to work normally.
..thx for your ansver...


They use diesel fuel which has a very low auto ignition temp (about
200-210C) so if a "vapour" of diesel sees 200C it auto ignites without a
spark.

Petrol gasolene has a higher auto ignition temp (250-280C) so it needs
an electric spark to ignite it.


Are you sure you're explaining that correctly?

I wondered the same thing - I just read what Karen wrote.

It's my understanding that the auto-ignition point isn't relevant with
gas engines because it doesn't rely on compression for ignition - it
relies on a spark. Which, at least to my mind, would indicate gas
would have a low flashpoint and a high auto ignition temperature.
Conversely, a diesel has a high flash point and a low auto ignition
temperature which is why the compression is high.

Also, it's my understanding that the reason some gas engines have high
compression ratios is more for power production.

Or am I wrong?