What are the Spark ignition Engine and Compression ignition Engine?
Spark ignition Engine
- Spark ignition, requires a spark plug in combustion chamber.
- Works on Otto cycle Petrol (because of high self‐ ignition temperature).
- 6 to 10.5 upper limit of C.R. is fixed by antiknock quality of fuel.
- Fuel and air are mixed and introduced cylinder,
- required to mix the air and fuel.
Compression ignition Engine
- Self‐ignition due to high temperature caused by high compression of air when fuel injected (no need of spark plug).
- Works on Diesel cycle.
- Diesel (low self‐ignition temperature is desirable).
- 16 to 20 upper limit of C.R. is decided by weight and structure of engine also.
Fuel is directly injected to the cylinder at high pressure at the end of combustion.
- A high pressure fuel pump is required with an injector (Carburettor is eliminated).
Based on cycle : Spark ignition engine and compression ignition engine is based on Otto cycle and Diesel cycle respectively.
Merits of spark ignition engine :
1. S.I. engines arrangement are lighter than C.I. engines.
2. Vibrations in S.I. engines is lower than C.I. engines.
Demerits of spark ignition engine :
1. Due to lower compression ratio thermal efficiency obtained is lower.
2. Cost of fuel (petrol) is generally higher than Diesel.
Applications of spark ignition engine :
1. Mopeds, scooters and motor cycles.
2. In small pumping sets and mobile electric generating sets.
Merits of compression ignition engine :
1. Thermal efficiency of C.I. engines is higher than S.I. engines because of its higher C.R.
2. C.I. engines have major application than S.I. engines.
Demerits of compression ignition engine :
1. C.I. engines are heavier than S.I. engines for the same power output.
2. The vibration from engine and the unpleasant odour in the exhaust are the main drawbacks.
Applications of compression ignition engine :
1. In ship propulsion, jeeps, buses and trucks.
2. Tractors for agricultural application.