Assignment 4
1. Compare SI and CI Engine.
- S. I. Engine works on the Otto cycle whereas C.I Engine works on diseal cycle.
- In S.I. Engine air and fuel are mixed in a carburattor where as in C.I. Engine fuel is mixed with air inside the cylinder.
- S.I. Engine fuel ignited with an spark plug where as C.I. Engine ignition is achieved with the help of the hot, compressed air.
- S.I. Engine has relatively low compression ratio where as C.I. Engine have high compression ratio.
- S.I. Engine has relatively low amount of power produced where as C.I engine produced high power.
- S.I. Engine uses very highly volatile fuel where as C.I engine have low volatile fuel.
- S.I. Engine are used in light duty vehicles like motorcycle and cars whereas C.I. Engine are generally used for heavy duty vehicles such as truck or buses.
- S.I. Engine are generally have high fuel consumption whereas C.I. Engine have relatively low fuel consumption.
- Air is allowed to enter through the inlet and moves along the runner to meet at the throttle and then allowed to enter the cylinder.
- Fuel is injected directly into the cylinder for combustion to happen and exhaust gases are allowed to leave the outlet.
1. BSFC:-
- From the above table, BSFC value is low compared with that of an S.I engine running at the same speed which clearly indicates C.I. Engine have high fuel efficiency
2. Air Fuel Ratio:-
- From above table, air fuel ratio is on higher side because more air is enter in the engine and it is very essential to keep the mixture lean.
3. Exhaust Temperature:-
- When the cylinder is compressed to a higher pressure we can see that the temperature inside the cylinder have risen to very high values shown in the graph above. At the exhaust cycle, the temperature are around 1000 K which on the higher side and remain throughout exhaust place until fresh air is allowed to enter the intake after TDC phase.
3. Change MFB value and observe the effect.
- From Case 1 we can observe that C.I. Engine achieve better brake power, Torque and also when it comes to BSFC we see that having minimum burning duration which consumed less fuel.