Two Stroke Diesel Engines

The main difference between two stroke and four stroke engines is the power produced by both the engines. Two stroke engines fires once in one revolution of the crankshaft, whereas the four stroke engine fires once in 2 revolutions of the crankshaft. Therefore, the two stroke engines are capable of producing more power per revolution.

In a gasoline powered two stroke engine, we know that there is a disadvantage of some amount of gasoline escaping along with the exhaust gases without getting burnt during the process of scavenging.

In the case of diesel powered two stroke engines, only air is used as a fresh charge, so there is no fuel wastage. Diesel is injected with the help of a fuel injector only after the air is compressed up to 1/18th of the cylinder volume. The compression of air increases the temperature and pressure inside the combustion chamber high enough to burn the diesel without the application of spark plugs.

Working:

The two stroke diesel engine has an air inlet port through which air is constantly tried to be pushed inside the combustion chamber with the help of an air pump. Two or four exhaust valves are provided at the top which open at the same time to let the exhaust gases to escape. A diesel injector is provided at the top to inject the diesel at the precise timing. There is no spark plug.

Power Stroke:

1. When the piston starts moving towards the Bottom Dead Centre (BDC) from the Top Dead Centre (TDC), the exhaust valve opens by means of camshaft and the exhaust gases escape out through it.


2. Further moving down, the piston uncovers the air inlet port and allows the air to fill inside the combustion chamber. The fresh air charge also drives out the remaining exhaust gases out of the exhaust valve.

Compression Stroke:

1. After reaching the BDC, the piston starts moving towards the TDC. The exhaust valve is closed and no more fresh air escapes out through the exhaust valve.


2. Further moving up, the piston covers the air inlet port and starts compressing the air trapped inside the combustion chamber to almost 1/18th of its volume.


3. The temperature and pressure rises inside the combustion chamber and just before the piston reaches TDC, diesel is injected inside the combustion chamber.


4. The fuel is burnt and tremendous amount of energy is released and the steps in the power stroke repeats itself.

A two stroke diesel engine must have a turbocharger or a supercharger to push more air inside the combustion chamber. Thus it is more expensive than a two stroke gasoline engine.