Jet Engines: Working, Types and Usability

The need for an aircraft with greater power and solidity arose during the Second World War. However, in terms of fuel efficiency, the planes consumed an immense amount of fuel and lacked high-speed manoeuvrability.

What they needed was an engine that could produce more thrust and consume less fuel. The theory of jet propulsion eventually solved this dilemma by using two engines concurrently with individual compressors and turbines.

A comprehensive description of jet engines and their functioning has been discussed below.

Jet engines are high-powered apparatuses that allow air to be squeezed into the engine, which then combines with the fuel to get it ignited. The explosion of hot exhaust gases produces enormous thrust that propels the aircraft forwards.

The most primitive versions of jet aircraft could reach speeds up to 482 kmph. However, many countries exploited the success of jet engines by manufacturing spy planes like the Lockheed SR-71, which could reach 3530 kmph by flying at an altitude of 26,000m.

Turbofan is the most common type of jet engine now that is used in commercial and military aircraft alike. However, more powerful jet engines like a ramjet do not require compressors because the extremely high speeds automatically compress air entering the engines, although inoperative when the aircraft is at rest.

The working principle of a jet engine involves the conversion of the fuel’s chemical energy into kinetic energy that drives the aircraft forward.

The jet plane works on the principle of thrust with or without propellers while allowing cold air to enter, ignite, and exit at high temperatures.   Jet engines typically have three crucial components – compressor, combustion chamber, and exhaust nozzle.

While the compressor increases the air pressure and temperature of the air intake, a combustion chamber ignites the air-fuel mixture and releases heat energy. The exhaust nozzle powers the plane by increasing the speed of exhaust gases.

The following steps describe how a jet plane works:

Step 1: First, fans situated at the frontal part of a jet engine suck cold air, forcing it through the inlet, thus, slowing the moving aircraft.

Step 2: The compressor squeezes the air from the fans, raising its pressure and temperature.

Step 3: A fuel tank maintains a continuous supply of liquid fuel (usually kerosene) to the engine.

Step 4: The liquid fuel mixes with the compressed air in the combustion chamber and ignites. This reaction produces hot exhaust gases and significantly increases the temperature. The burning mixture attains a temperature of approximately 900 °C.

Step 5: The exhaust gases flow through a set of turbine blades, causing the blades to spin. As the turbine gains rotational energy, the gases lose the same amount of energy; accordingly, the gas cools down moderately and loses pressure.

Step 6: The turbine blades transmit power through an axle running along the length of the engine. Additionally, the compressor and fan are connected to this axle. Hence, the compressor and fan spin in tandem with the turbine blades.

Step 7: An exhaust nozzle oozes the hot exhaust gases and helps the aircraft reach up to 2100kmph. Afterburners in high-performance military jets squirt fuel into the exhaust jet, producing an additional boost to push the plane forward.

 Speeds reached by the most efficient turbojet engines almost equal the speed of exhaust gases. Depending on the engine’s power and positioning of propellers, there are five different types of jet engines.

• Turboshaft engine: This gas-powered engine is mostly used to turn turbines instead of generating thrust. Typically used in helicopters to turn the rotors, they also control the helicopter’s power by converting high-speed gases to mechanical energy.
• Turboprop engine: Perfectly suited for flying at mid-range latitude, this engine uses a gearing system connected to its propeller that saves fuel. Despite having propellers of a smaller diameter, turboprop engines have multiple blades that drastically improve the aircraft’s stability.
• Turbofan engine: These engines have large fans to suck in more air and squeeze it at high pressures to ignite the fuel. Unlike turboprop and turboshaft engines, the turbofan variant produces lesser engine noise and uses an additional thrust to cool down the engine.
• Turbojet engine: With a diffuser at its front end, this engine takes oxygen supply from the atmosphere. Like other engine types, the turbojet engine uses compressed air to ignite the fuel. However, they can reach up to 1600 kmph thanks to the reactive thrust in the opposite direction.
• Ramjet engine: Unlike other engine types, ramjet engines do not require a compressor or turbine. The diffuser drastically increases incoming air pressure and squirts it on a hollow tube containing the fuel. However, it must maintain a considerable speed to start the compression process.