Fuel supply system is a seperate system used to deliver diesel at correct time in correct quantity, to a diesel engine (or C.I engine), for smooth and efficient operation.
The operation of a diesel engine is different from that of a petrol engine. In a petrol engine, air-fuel mixture is supplied by a carburetor to the engine, at the beginning of the suction stroke. But in a diesel engine, fuel (without air) is supplied at the end of the compression stroke, by means of a fuel supply system.
Fuel supply system is the food pipe of a vehicle.
Fuel supply system in diesel engine is made of the following components:
- Diesel tank or reservoir
- Low pressure pump
- Fuel injection pump
- Fuel injectors
1. Diesel tank or reservoir:
Whenever you supply fuel to a diesel engine vehicle, it is stored in the diesel tank. Diesel tank temporarily stores diesel that is to be supplied to the engine.
2. Low pressure pump:
It pumps the diesel at a low pressure to the fuel injection pump through a filter.
Before diesel is supplied to an engine, it must be filtered to remove any unwanted impurities. Filter is used for this purpose.
4. Fuel injection pump:
This is the most important component of the fuel injection system.
Fuel injection pump pressurizes the fuel to the required level and injects it correctly at the end of the compression stroke, during each cycle of operation of the engine.
5. Fuel injectors:
Injectors are devices used to inject the fuel to the cylinder. In diesel engine, when fuel is injected, it is automatically atomized.
Diesel is pumped from the diesel tank by a low pressure pump. It is passed through a filter. The filter removes any unwanted impurities in the diesel.
Filtered diesel is supplied to the inlet port of the fuel injection pump. The fuel injection pump automatically pressurizes the diesel to the required level and supplies it to the fuel injector. The fuel injector forces the fuel into the cylinder at the end of the compression stroke, during each cycle of operation of the engine.
Fuel injection pump is operated by means of a cam shaft. CAV fuel injection is the most common fuel injection pump used in diesel engines.
Any leak-off diesel from the fuel injection pump is supplied back into the filter as shown in the diagram above.
Characteristics of a good fuel supply system:
- A good fuel supply system should be able to deliver the fuel correctly at the end of the compression stroke.
- It must be able to properly atomize the fuel.
- It must operate smoothly and sharply during each cycle of operation of the engine.
- It must be able to supply the fuel above atmospheric pressure.