Diesel Engine vs Petrol Engine
Petrol and diesel engines are the two most commonly used internal combustion engines. Even though their operation seems similar, they have some interesting differences, and each has advantages over the other. This video is aimed at exploring these differences and advantages from a scientific point of view. By the end of this session the reader will be able to predict what happens, if he puts petrol in diesel engine or vice versa.
A detailed webpage version of the video is given below.
The Basic Operation – 4 Stroke Engine
Before going to the main topic let’s have a look at the basic operation of a 4 stroke I.C engine. Both engines have the same basic 4 strokes: intake, compression, power, and exhaust. During the intake stroke fresh air is sucked in (or forced in) to the cylinder. The compression strokes compresses this gas and produces a hot gas. Fuel is burnt in this hot gas and the power stroke happens next. Please remember power stroke is the only stroke where the piston absorbs energy from the fuel. The last stroke is to eject the burn gas to the atmosphere. All these operations are depicted in Fig.1 in detail.
Why There Exists Two Different Engines ?
There are differences between the two engines due to the difference between the way fuels burn. Petrol is a volatile fuel, is readily evaporates, so it gets mixed with the air efficiently. As a result, just a spark is sufficient to produce smooth combustion in a well pre-mixed petrol engine. As you can note from Fig.2 petrol has a very low flash point. Flash point is the minimum temperature required for a liquid fuel to form a spontaneously combustible mixture.