Mechanical Engineering - Thermodynamics - Discussion

Compression ratio for petrol 6 to 10.

For diesel 15 to 25.

Compression ratio (r) = it is the ratio of total volume of cylinder to the clearance volume of cylinder.methematically,

r = total volume/clearance volume.

Vt = Vs+Vc.
Then r = Vt/Vc.

Diesel fuel is much dense then the petrol or gesoline it is required high pressure and temp to burn so by using high compression ratio burning temp of the fuel is minimised. With the use of injector air and fuel mixture get inside in engine and burn with high compression in the range of 16-20 but in case of petrol engine which is much smaller size then diesel high compression is not possible so spark plug is used which is ignite the air fuel mixture comes from carburettor.

As per my knowledge, it is 16 to 20.

Both knocking and detonation are not same because the term knocking is define has when the piston is moves from TDC-BDC or BDC-TDC then the piston will deflects or it will get collides to cylinder due to this we feel some sound then we call its knocking.

Detonation is nothing but incomplete combustion.

Self-ignition temp of petrol is about 450°c. That is why a spark plug is needed in si engines. Whereas in CI engines diesel self-ignites at about 180°c soo as soon as the compression starts the diesel self-ignites.

What 5&8 stands for? Please explain in detail.

That's why the diesel engine mileage is higher than petrol engine.

What is the Maximum temperature range produced in an IC engine cylinder?

Please answer me.

What is the Compression ratio of CI engines?