In aviation discussions, the engine of a flying device has always turned this machine into an attractive subject due to its complexity and benefit of advanced technologies, and most aviation fans call the airplane engine one of their favorite components.
The public’s perception of an airplane engine is a device whose function is only to push the plane forward and has no other use, while only one of the functions of the engine is to create propulsive force. But did you know that the power of all electrical and electronic systems, including the communication and lighting systems of the aircraft, is supplied by the engine?
Or did you know that the air you breathe inside the airplane cabin is provided by the engine compressor?
Or even when the plane lands, the most braking force and reduction of the plane’s speed is the responsibility of the plane’s engine? Did you also know that the engine is responsible for powering the aircraft’s hydraulic systems to open and close the wheels and move the control surfaces? And these are only a part of the named tasks of the aircraft engine. Maybe now you can consider the engine as the beating heart of the plane and realize its high importance in the plane.
In order to get to know the engine, we must first introduce you how the engine generates the driving force and then we will discuss each of the engine components and their roles.
Creating a driving force
Newton’s third law can help us understand how propulsion is created. This law states that if some amount of air is pushed back by an object, that object will be pushed forward in proportion to the amount and speed of the air that has been pushed back. The simplest example is a balloon full of air that we release from the end, as a result, it is observed that the air is released at a high speed at any moment and its reaction causes the balloon to be pushed forward (thrown). Like the balloon in the example, the airplane engine pushes back a significant amount of air at a high speed, and its reaction causes the airplane to move forward. Therefore, the more air is pushed back by the engine at a higher speed, the more forward force we will have, which is called creating momentum.
Types of air engines
Air engines are designed in several ways based on different applications, which include:
Turbo-Jet: Turbo-jet engines provide most of their momentum production from the exhaust gases of the engine. These engines can create high speeds, but due to noise and high fuel consumption, their production is stopped for commercial passenger planes and nowadays they are used for military purposes.
Turbofan: Commercial passenger aircraft engines often use turbofan engines. These types of engines have a relatively large fan in front of them, which provides almost 80% of the driving force of the engine, and the rest of the driving force is provided by the reaction of the exhaust gases from the engine.
Turbo Prop (Turbo Prop): Turbo prop engines, in fact, use propeller power to produce propulsion power, and it includes about 90% of the production power. These engines produce much lower thrust and speed than jet engines, but the fuel consumption of turboprop engines is much lower (about two-thirds of turbofan engines). These engines are often used in light aircraft and passenger planes for short distances.
Turbo Shaft: Helicopters are the most users of these engines. The components of this engine are not different from other jet engines, but their mechanism is not the production of propulsive force, but the creation of torque, which leads to the turning of the helicopter propeller.
Engine components
Common engines in commercial passenger planes usually have the same structure and consist of three main parts:
Compressor: Increasing the pressure and temperature of the air entering the engine and transferring this air to the combustion chamber is done by the compressor.
COMBUSTION CHAMBER: provides a chemical reaction between air and fuel to create an energetic mixture and transfers it to the turbine.
Turbine (TURBINE): Its task is to take energy from the mixture of air and fuel produced by the combustion chamber in order to turn the compressor, the fan and the auxiliary components of the engine.
Engine side components
These components are mounted on a gearbox and the gearbox is powered by a shaft connected to the compressor.
These components are:
Generator (GENERATOR): Its task is to produce electricity consumed in the plane, such as communication systems, lighting systems and entertainment systems, etc.
Hydraulic pump (HYDRAULIC PUMP): It provides the necessary pressure to move the plane’s control surfaces and also to open and close the wheels.
Starter (STARTER): Its task is to rotate the shaft of the aircraft engine to start it, which is usually pneumatic in turbofan engines, because the size and mass of the shaft is so large that electric starters cannot rotate it.
THRUST REVERSER: It is another side component of the engine whose task is to change the direction of the air pushed back by the fan and as a result it reverses the direction of the forward force to create reverse thrust and reduce the speed of the aircraft. This device is used by the pilots when the plane lands on the ground, and passengers often notice the increase in the sound of the engine during landing, which is caused by the activation of the engine reverser.
Systems using compressor air
The hot and high-pressure air produced by the engine compressor (so-called bleed air) is one of the most useful aircraft fluids, and several examples of its applications can be mentioned:
The pneumatic system of the plane, which includes the engine start system for its initial start-up, uses this air.
The air conditioning system (Air Condition System), which has the task of providing fresh air to the passenger cabin, uses this high-pressure air.
The Anti-Ice system, which prevents the formation of ice pieces on the edge of the wing and the engine, uses this air when necessary.
Sina Behari – Flight Qualification Continuity Expert of Kamotech Flight Company
