Working of Four Stroke cycle Diesel Engine

The working cycle of the engine is completed in four strokes and diesel is used as fuel. In this engine, spark is not used to ignite the charge but high compression itself ignites the fuel mixture. The working of the engine is described below:

a.       Suction stroke

The suction stroke is similar to that of petrol engine except that only air is taken into the cylinder during this stroke.

b.      Compression stroke

Compression stroke is also similar to that of petrol engine, but at the end of compression stroke, pressure and temperature of air reaches about 60 bar and 600⁰c respectively.

c.       Expansion stroke

During this stroke, both inlet and exhaust valve is kept closed and fuel valve opens just before the beginning of the third stroke. The supply of fuel is continued during a small part of expansion stroke. The temperature of the air at the end of compression stroke is high enough to ignite the fuel (Diesel). The combustion of fuel is continued at the constant pressure (isobaric process) as long as the fuel valve is open. The high pressurized gases pushes the piston downward even the fuel valve is closed.

d.      Exhaust stroke

During exhaust stroke, inlet and fuel valve remains closed and exhaust valve opens. The upward movement of piston pushes the burned gases outside the cylinder body. When piston reaches TDC, exhaust stroke is completed and becomes ready for next cycle.