Timing, pressure and quantity of fuel delivery are crucial for efficient combustion. The important task of fuel delivery is performed by the fuel injection Equipment.
Mechanically-Controlled Fuel Injection
Fuel is supplied to the injector by an injector pump. The injector pumps are mechanically driven from the crankshaft. The drive from the crankshaft is set so that the injector pump delivers fuel at the correct time in the engine operation cycle.
Single Element Injection Pump (Jerk Pump)
The simplest type of injection pump found on single cylinder engines. The single pumping element delivers fuel to the injector via a high pressure pipe. Multi-cylinder engines sometimes utilize multiple single element pumps. This is most often seen in stationary or marine applications.
In-Line Injector Pump
In-line pumps use a similar design to the single element pump, for a multicylinder engine. A number of jerk pumps are combined into a single component. The pumps are driven by a camshaft held within the pump body.
Rotary Injector Pump
Rotary pumps are similar in appearance to a petrol engine distributor. A single pumping mechanism rotates and supplies fuel to each cylinder in turn.
Electronically-Controlled Fuel Injection
Recently developed electronically controlled injectors can provide exact amounts of fuel at very high pressure, very precise timing and even multiple injections within each cycle to give greatly improved combustion and in turn increased fuel economy and lower engine noise and toxic emissions. Both in-line and rotary injection pumps have been developed with electronic components to help achieve more accurate injection timing and metering. By monitoring the engine using a number of sensors the electronic controller can modify the fuel injection characteristics to improve combustion.
Common Rail Injection Systems (CDI)
With this system a pump constantly supplies fuel at a very high pressure to the common rail – a tube with thick walls. From the common rail fuel is supplied to electronically controlled injectors. The higher pressure injection gives a finer spray and improved combustion.
Unit Injector System and Unit Pump Systems
Unit injector systems combine the pump and injector into one unit. The pump is driven from the engines camshaft. Fuel delivery is timed and metered by electronically-controlled valves. Unit pump systems are similar with the pump and injector separated and connected by a short high pressure fuel line.
Source: Darren Hill, “Vegetable Oil as a Fuel”