Question

Discuss the various processes of an actual four strokes spark ignition engine. What are the assumptions under which ideal Otto cycle can be utilized for the spark ignition engine?

Answer 1

a four-stroke gn of operation piston inside engine the Cycle is completed bly four strokes of the Cylindes. In these four strokes fuel is Two and burnt inside the engine. of Crankshaft are completed. the SI four strokes that occur injected revolutions inside engine are: :) Suction stroke is a stroke. In piston Cylinders move is Cylinder head ii) Compression stroke To Expansion to powen stroke iv) Exhaust stroke. the stroke. this i) Suction head . dead center near the top to down. Now, the and it is about fitted in the inlet valve opened ond remain closed exhaust the value because the difference. Because of pressure of the downward movement of piston, pressure created inside the cylinder so that air-fuel mixture is drawn inside the cylinder. After the piston reaches stroke ends and inlet the bottom closed. و Suction Valve is.

from top Compression stroke :: In this stroke bottom dead center and moves dead Center . of upward of piston, air-fuel mixture gets the clearance volume of the Because piston starts towards movement Compressed into Cylinder. At the spark is generated end of this compression stroke fuel the burns the by spark plug which and releases large amounts Because of this heat, high of thermal energy. pressures are generated. is iii) Expansion is power stroke: High pressure generated in compression Stooke pushes the piston towards bottom dead Center. In this stroke actual power produced by the engine hence this is called power stroke. Here expansion of gases бесuѕ during this process so this Called expansion process. In this stroice inlet and exhaust valves closed. remain iv) Exhaust Stroke! Because of internal and external inlet pressure difference exhaust valve opens and value remains closed al the end of power moving upward all the residual gases which are stroke. Piston starts direction and left after the Stroke are swept outside the expansion Cylinder and escape through the exhaust chambes

end of this reaches stroke . Piston At the Centen and the starts in moving top dead direction to suck air-fuel mixture downward the Suction stroke. and complete air Asumphoის : 1) working fluid is considered ideal gas. as an 2) Air is ideal power cycles are 3) A11 the processes internally reversible. The four processes of cou ideal otto cycle i) Iso entropic compression volume heat addition ii) Constant vi) soentsopic expansion heat rejection, iv) constont volume