Diesel engines also called as compression ignition (CI ) internal combustion engine works on diesel cycle we will discuss about Four stroke diesel engine .CI engine use air only in first two stroke of the cycle while SI engine use air fuel mixture in whole cycle.
As name suggest there are four stroke in one power cycle those are same to otto cycle but difference in process .
- Intake or Inlet stroke .
- Compression Stroke.
- Expansion stroke.
- Exhaust stroke.
Intake or inlet stroke :- In this stroke inlet valve opens and air comes inside the cylinder due to vacuum created by piston displacement and piston travels from TDC to BDC .
Compression stroke :- In this stroke both exhaust and inlet valve remains closed and air compress inside the cylinder up to a certain limit called as compression ratio while piston travels from BDC to TDC .high temperature and pressure developed inside the cylinder
Expansion stroke :– During this stroke fuel is injected through fuel injector and burnt due to high temperature developed inside the cylinder and forces the piston so that power power is produced and stored in the fly wheel .
Exhaust stroke :- after the expansion process completed unburnt fuel residue inside the cylinder which is forces out of the engine by piston through exhaust valve .this completes the one power cycle this cycle is called as diesel cycle .
Difference between Diesel and Petrol engine.
- Compression ratio of diesel engine is high compared to petrol engine due to low self ignition temperature of petrol.
- Diesel engine compress air while petrol engine compress air and fuel mixture .
- petrol engine use sparkplug for combustion while diesel engine use fuel injector .
- thermal efficiency of diesel engine is higher than the petrol engine due to higher compression ratio.
- Diesel fuel have higher lubrication property than petrol .
- Life of diesel engine is twice as that of petrol engine due to higher part strength.