IC engines are classified into two types based on the ignition which are Spark ignition engine (SI) and compression ignition (CI) engine.
The IC engines are of different types but based on the ignition, the IC engines are classified into the following two types:-
- Spark ignition engine (SI)
- Compression igniton engine (CI)
Spark ignition (SI) engine:
The spark-ignition (SI) engine is also known as the petrol engine since the spark ignition is used in petrol-fueled engines. This engine is works on the otto cycle.
The spark plug is used in SI engines to ignite the air-fuel mixture. The compression ratio of the spark-ignition engine is around 10:1 to 14:1.
When the fresh charge enters inside the cylinder, the piston compresses the charge to high pressure. At the end of the compression stroke, the spark plug produces the spark to ignite the air-fuel mixture, and in such a way, combustion starts.
Compression ignition (CI) engine:
The compression ignition engine is also called as the diesel engine since this engine is woks on the diesel cycle which is invented by Rudolf diesel.
In these engines, the air is compressed to high temperatures and then at the end of the compression stroke, the fuel injector sprays the fuel in hot air for auto-ignition of fuel.
These engines have a higher compression ratio around 18:1 to 23:1 because in this engine, the air is compressed to high pressure and temperature for auto-ignition of fuel.
As CI engine has a higher compression ratio hence these engines produce high torque. Therefore these engines are used at high torque applications. Example: Buses, trucks, etc.