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  • IC Engine - ICE
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Text from page-3

WORKING PRINCIPLE A. Otto Engines: (SI Engines) • Used in petrol engines, gas engines, light oil engines in which the mixture of air and fuel are drawn in the engine cylinder. Since ignition in these engines is due to spark, so are called Spark Ignition Engines. The various strokes of a four stroke (Otto) cycle engine are:  Suction Stroke  Compression Stroke  Expansion or power Stroke  Exhaust Stroke 3 SKNAYAK

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WORKING PRINCIPLE • Suction Stroke: • Also known as induction stroke. The piston moves from TDC to BDC, the inlet valve opens and proportionate fuel air mixture is sucked in the engine cylinder. The exhaust valve remains closed throughout the stroke. Compression Stroke: The piston moves towards T.D.C. and compresses the enclosed fuel air mixture drawn in the engine cylinder during suction. The pressure of the mixture rises in the cylinder to a value of about 8 bar. Just before end of this stroke the operating plug initiates a spark which ignites the mixture and combustion takes place at constant volume. Both inlet and exhaust valves remain closed during the stroke. 5 SKNAYAK

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WORKING PRINCIPLE • Expansion (working) Stroke: • The hot gases produced by combustion which drive the piston from TDC to BDC and thus the work is obtained in this stroke. During this stroke other three strokes remain idle. The flywheel mounted on the engine shaft stores energy during this stroke and supplies it during the idle strokes. Both the valves remain closed during the start of this stroke but when the piston just reaches the BDC the exhaust valve opens. Exhaust Stroke: This is the last stroke o the cycle. The gases from which the work has been collected become useless after the completion of the expansion stroke and are made to escape through exhaust valve to the atmosphere. The removal of gas is accomplished during this stroke. The piston moves from BDC to TDC and exhaust gases are driven out of the engine cylinder, this is called Scavenging. 6 SKNAYAK

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