WORKING OF TWO STROKE CYCLE SI ENGINE (PETROL ENGLINE) - WEEK ONE AND TWO

WEEK ONE AND TWO

TOPIC - Working of Two Stroke Cycle SI Engine (Petrol Engine)

The working principle of two stroke SI engine is described as follows:

1. Upward stroke

2. Downward stroke

1. Upward stroke (suction and compression):

The upward stroke consists of the suction and compression processes: During the first stroke, the piston moves upward from BDC to TDC. When the piston is at BDC, the partially compressed air fuel mixture from crank case enters into the cylinder through a transfer port as shown Figure 1.1(a). Then, the piston moves upward and compresses the air contained in it till the piston reaches TDC. At the end of the compression stroke, the spark plug produces the spark; it will ignite the compressed high pressure fuel air mixture. When the piston is at TDC, the inlet port opens and the air fuel mixture from the carburettor enters into the crankcase as shown in Figure 1.1(b). Thus, one stroke of the piston is completed.

2. Downward stroke (expansion or power and exhaust stroke):

When air fuel mixture is ignited, both pressure and temperature of the products of combustion will suddenly increase.

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