Course: BFM 202 Biodiesel Production

Lecture

Diesel Combustion
Credits
BFM 202 Biodiesel Production Unit 2 Lecture has been adapted from "ENGY 131 Unit 2 Commentary: The Diesel Engine" by Southeastern Illinois College.

ENGY 131 Biodiesel Production course content by Southeastern Illinois College is licensed under a Creative Commons Attribution 3.0 Unported License. Except where indicated otherwise.

Diesel Combustion

A diesel engine is a compression-ignited engine where air and fuel
enter the cylinder through the intake system. This air is compressed
to a high temperature and pressure, and then finely-atomized fuel is
sprayed into that air at a high velocity.
When the fuel comes in contact with the high-temperature air, the fuel
vaporizes quickly, mixes with the air, and undergoes a series of
spontaneous chemical reactions that result in a self-ignition or
auto-ignition. No spark plug is needed. Some diesel engines are equipped
with electrically-heated glow plugs and are used to assist in starting
the engine under cold conditions. The engine's power is controlled by
varying the volume of fuel injected into the cylinder; therefore, a
throttle is not needed.
The combustion timing is determined by the fuel injection and the
ignition delay must be precise in order to ensure low emissions and
optimum fuel efficiency.

Four-stroke Engine Basics

This process shows one cylinder in a 4-stroke engine. This process is repeated in each cylinder, thus converting chemical energy to mechanical energy.

1 | Intake Stroke | Air and vaporized fuel are drawn in
2 | Compression Stroke | Fuel vapor and air are compressed and ignited
3 | Power Stroke | Fuel combusts and pistons are pushed
4 | Exhaust Stroke | Exhaust is driven out