Definition:
The concept behind compression ignition involves using the latent heat built up by highly compressing air inside a combustion chamber as the means for igniting fuel.
The process involves compressing a charge of air inside the combustion chamber to a ratio of approximately 21:1 (compared to about 9:1 for a spark ignition system). This high level of compression builds tremendous heat and pressure inside the combustion chamber just as fuel is primed for delivery. An injection nozzle plumbed into the combustion chamber sprays a mist of precisely metered fuel into the hot compressed air where upon it bursts into a controlled explosion that turns the rotating mass inside the engine.
Examples: Diesel engines use compression ignition.
The Alternative Fuel Bible: Find Answers to Your Fuel & Vehicle Questions
The Alternative Fuel Bible: Find Answers to Your Fuel & Vehicle Questions