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How Do Fuel Injectors Work in an Aircraft?
Most modern vehicles, including aircraft, rely on fuel injectors to power their engines. These devices spray a mixture of air and fuel to be ignited in their combustion engines and can be driven either by springs or an Electronic Control Unit (ECU). As a key component in aircraft, it is important for pilots and engineers alike to understand how a fuel injector works to best maintain it.
What Are Fuel Injectors?
Fuel injectors are essentially electronically controlled valves supplied with pressurized fuel by a fuel pump. Their role is to supply the correct amount of fuel to the engine so that it can combust to power it. Because the engine requires an exact amount of fuel, fuel injectors are built to be extremely precise. As such, they are a type of valve which relies on electronic control and are placed at a certain angle to inject just the right amount of fuel into the combustion chamber. Not only does the amount of fuel being injected need to be accurate, but the angle it is placed at, the pressure, and the spray pattern all must be very exact to meet the needs for the perfect air-to-fuel ratio for combustion. Fuel injector design can vary depending on whether the engine operates on petrol or diesel fuel. While the fuel injectors for petrol-operated engines use an indirect mechanism to spray the fuel, diesel-operated engines use a direct mechanism.
How Do Aircraft Fuel Injectors Work?
Aircraft fuel injectors are powerful valves controlled by an ECU (Electronic Control Unit), that are capable of opening and closing several times per second. In the process, fuel is transported from the fuel tank to the injectors along fuel lines. Once the fuel has reached the injectors, it is pressurized to the right extent by using a fuel pressure regulator. The fuel is then divided into several cylinders and sprayed into the combustion chamber. This is a general overview of the process; however, the details differ depending on whether the fuel injectors are mechanical or electronic. In a mechanical fuel injector, a spring system is used to control the flow of both air and fuel into the combustion chamber.
Mechanical fuel injectors are still used today in many vehicles, but for their heightened accuracy, only electronic fuel injectors are used on modern aircraft. Both types of fuel injectors follow the same general process as described above, but they differ in two major ways: the amount of fuel they transfer and the tension used to open and close the valve using the spring. Rather than employing these two functions to control the spray of fuel, electronic injectors use an ECU that controls all the required functions. In electronic systems, sensors are used to keep track of things like air temperature, air intake pressure, engine temperature, engine speed, and accelerator position. According to these measurements and the calculations done by the ECU, it determines the specific amount of fuel that needs to enter the cylinders. All of this input is sent to the ECU in real time and is processed so fast that the extent by which the valves must be opened and closed is calculated almost simultaneously.
As data is fed to the ECU, it calculates the amount of fuel that needs to be injected and the number of valves that need to open for that to happen. When the electronic signals are sent from the ECU to the fuel injector pins, it creates an electromagnet inside the fuel injector which causes the plunger to move outwards and open a path for fuel to pass through. After the cycle of fuel injection is completed, the ECU stops sending an electronic signal to the fuel injector and therefore deactivates the electromagnet. Without an electromagnet pushing it outward, the plunger can then revert back to its normal position, closing the nozzle, and stopping the fuel spray.
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