Week 2 : Basic Calibration of Single cylinder SI-Engine

SI Engine – Spark ignition (SI) engine is a type of engine in which the combustion takes place by the spark generated by the spark plug. It uses petrol as fuel and works on Otto cycle. In the spark ignition engine, the air-fuel mixture is inserted into the cylinder with help of carburetor. The compression of the fuel takes place but it has low compression ratio. The fuel is ignited by the spark generated by the spark plug. SI engine produces less noise and vibration and their starting is very easy. They are light in weight and have less maintenance cost. They are mostly used in light commercial vehicles such as scooters, motorcycles cars, etc.

Model -

Casesetup -

After running the engine at 1800RPM we got following results -

Air Flow rate -

BMEP -

BSFC -

In-cylinder pressure -

Engine power depends on many factors like compression ratio, bore diameter, burn duration, AF ratio etc. In this study our task is to increase power by 10% with constant engine speed, which is 3600rpm. Power at 3600rpm is 16.7KW and desired power 18.37KW and above.

Parameter variables were created to change some parameters in case setup, as showing in following image.

We went with different bore diameter, compression ratio, Air-Fuel ratio and burn duration. For gasoline engine compression ration is a limiting factor, means we cannot increase after 12.5, it is not feasible. Compression ratio 12.5 is the maximum compression ratio, which was successfully tested with Ferrari 458 italia. So, we went with CR 12 with same bore diameter, but it did not work, means we did not get desired output value. At compression ratio of 12, slight increase in bore diameter, can increase power.

After increasing bore diameter from 85mm to 90mm, brake power was increased from 16.7KW to 18.4KW, which is desired one. Further, we simulated model with changing Air-Fuel ratio and burn duration, but we did not get promising results. At very high value of these can work, but that would be infeasible.

Result -