Four Stroke Cycle Diesel Engine

Four Stroke Cycle Diesel Engine Points : Four Stroke Cycle Diesel Engine, Suction Stroke, Compression stroke, Expansion or Working Stroke, Exhaust stroke It is also known as compression ignition engine cylinder at the end of compression stroke. The four strokes of a diesel engine sucking pure air described below: 1. Suction Stroke In this stroke, this inlet valve (I) open and pure air is sucked into cylinder as the cylinder a. the piton moves down wards from the top (lead centre (TDC). It continues till the piston reaches its bottom dead centre (BDC). 2. Compression stroke In this stroke, both the valves are closed and the air is compressed as the piston moves upward from BDC to TDC. As a result of compression, pressure and temperature of the air increases considerably (the actual valve depends upon the compression ratio). This completes one of the shafts. 3. Expansion or Working Stroke Shortly before the piston reaches the TDC (during the compression stroke), fuel oil is injected in the form of very fine spray into the engine cylinder, through the nozzle (N) known as fuel injection valve. At this moment, temperature of the compressed air is sufficiently high to ignite the fuel. It suddenly increases the pressure and temperature of the products of combustion. The fuel oil is continuously injected for a fraction of the revolution. The fuel oil is assumed to be burnt at constant pressure. Due to increased pressure, the piston is passed down with a great force. The hot burnt gases expand due to high speed of the piston. During this expansion, some of the heat energy is transformed into mechanical work. It may be noted that during this working stroke, both the valve are closed and the piston moves from TDC to BDC. 4. Exhaust stroke In this stroke, the exhaust valve (E) is open as the piston-moves from BDC to TDC. This movement of the piston pushes out the products of combustion from the engine cylinder through the exhaust valve engine cylinder through the exhaust valve into the atmosphere. This completes the cycle and the engine cylinder is ready to suck the fresh air once again.