Fuel Delivery System in Petrol Powered Automobile

A fuel delivery system is critical in storing and delivering the fuel that is required by the engine to function. For the engine to run efficiently and smoothly, it needs to be supported with the right amount of fuel mixture based on its wide range of demands. Generally, the type of ignition used in petrol engine is spark ignition, so it is also called as spark ignition (SI) engine. The spark plug in the engine is ignited for every cycle at the beginning of the expansion stroke.

*Components of a petrol fuel delivery system

*Fuel tank: The purpose of the fuel tank is to store petrol in it. It is a temporary storage unit for the fuel.

*Fuel filter: Fuel filter is used to remove impurities present in the fuel. It is present at the inlet of the fuel lift pump.

*Sediment bowl: The impurities filtered in the filter are stored in the sediment bowl. It has to be cleaned at regular intervals.

*Fuel lift pump: Fuel lift pump is used when the level of fuel tank is below the carburetor. Fuel lift pump helps to supply the fuel to the carburetor.

*Carburetor: It is a device that is used for mixing the fuel and air outside the cylinder. The phenomenon involved is called carburetion.

*Fuel pipes: Fuel is carried to different parts of an engine through the fuel pipes present.

*Inlet manifolds: Inlet manifolds helps to supply the fuel-air mixture to the cylinder.

*Working of fuel delivery system in a petrol engine

*In the first case, if the fuel tank is above the level of carburetor, the fuel flows due to the action of gravity. This system consists of two filters placed between the fuel tank and carburetor. Sediment bowl is equipped to hold the dust and dirt of the fuel.

*In the second case, if the fuel tank is below the level of carburetor, a fuel lift pump is used to force the fuel from the fuel tank to the carburetor. Fuel is directed from the fuel tank to the sediment bowl and then to the lift pump from where it goes to the carburetor. The fuel from the carburetor flows to the engine's cylinder through the inlet manifolds.

*In both the cases, a carburetor is used to mix the fuel and air. When air flows over the end of a jet containing fuel, a certain quantity of fuel is drawn into the air stream.

*If the speed of air flow jet increases and the jet is larger, the amount of fuel drawn into the airflow is greater. The level of fuel can be maintained by a float chamber. Fuel levels in the float chamber and fuel jet are always maintained same.

*The velocity of the air flow over the fuel jet can be varied by a construction called as venturi.

*Air fuel mixture is controlled by a butterfly throttle valve. When the butterfly valve is in accelerate position, the airflow over the jet increases and more fuel is drawn into the air stream.

*A second butterfly valve called as choke is used to provide richer mixture in cold conditions. Volume of air entering the venturi is controlled by the choke.

Petrol being less dense than diesel fuel is burned easily by using a spark plug. Petrol engine is lighter when compared with that of a diesel engine.

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