The fuel injection system can be divided into low-pressure and high-pressure sides.
The low-pressure components include the fuel tank, fuel supply pump and fuel filter.
The high-pressure side components include a high pressure pump, accumulator, fuel injector and fuel injector nozzle.
A number of injection nozzle designs and different actuation methods have been developed for use with different types of fuel injection systems.
Fuel Tank
The Fuel tank is the fuel reservoir for the engine which holds the fuel and it will help to maintain the temperature of the fuel below the flash point. It is also corrosion-resistant and leakproof to pressures of at least 30 kPa. The fuel tank will be provided with a safety valve to relieve the excessive pressure. It will be able to dissipate the heat from the fuel coming from the engine.
Fuel Feed Pump
The Fuel feed pump is used to feed the fuel from the fuel tank to the injection pump. It has the spring loaded plunger actuated through the push rod from a camshaft. When the push rod is at minimum position, the spring force on the plunger will create suction in the pump to flow the fuel from the fuel tank into the injection pump. When the cam is turned to its maximum lift position, the plunger is lifted upwards. The inlet valve will be closed and the fuel will be forced through the outlet valve. See the following schematic sketch of the fuel feed pump.
Injection Pump
The main function of the fuel Injection pump is to deliver the right amount of the fuel into the injector under high pressure. (usually, the range will be 120 to 200 bar) at the correct instance to the injector fitted in each cylinder head.
There are two different types of Injector pumps
Jerk type pump
Distributor type pump
Fuel Injector
The quick combustion will depend on the well-designed fuel injector. A good fuel injector will atomize the fuel into fine droplets and increase the surface area of the droplets and helps for mixing of the subsequent combustion.
The fuel injector consists of the following components.
Needle valve
Compression spring
Nozzle
Injector body
The fuel is supplied from the injection pump to the injector by means of a governor with sufficient force to lift the spring valve in the injector. The fuel will be sprayed as fine droplets into the cylinder.
Nozzle
The Nozzle is the part of the Injector through which the fuel is injected into the cylinder. Following is a schematic cross-section representation of the single hole Nozzle.
Any nozzle should fulfill a few requirements to be used in a CI engine. those are listed below
Should be able to proper atomize the fuel. (Mixing of fuel with air in the combustion chamber)
Fuel distribution in the cylinder against the cylinder pressure.
Prevention of fuel from impinging directly on the walls of the combustion chamber or piston.
Proper mixing of the fuel, even in the case of a non-turbulent type of combustion chamber.
These are the different types of components available in the injection system.
