Turbojet Engines produces all of its thrust by ejecting a high-energy gas stream from the engine exhaust nozzle. Most of the modern passenger and military aircraft are built with gas turbine engines, which are also called jet engines. Turbo engines worked by a large amount of surrounding air is continuously brought into the engine inlet and the compressor pulls air into the engine, the compressor acts like an electric fan, and at the exit of the compressor, the air is at a much higher pressure than free stream. In the burner, a small amount of fuel is combined with the air and ignited. The turbine works like a windmill. Instead of needing energy to turn the blades to make the airflow, the turbine extracts energy from a flow of gas by making the blades spin in the flow.
The basic function breakdown of the turbojet engine works – AIR INTAKE, COMPRESSION, EXPANSION, and THRUST PRODUCTION.
The parts and components contained in the turbojet engine:
·Diffuser – is used to slow down and increase the pressure of the incoming air before it enters the combustion chamber.
·Compressor – is designed to increase the pressure of the incoming air before it enters the combustion chamber. It improves engine efficiency by ensuring a higher air mass flow rate.
·Pump – It is designed to receive compressed air and mix it with a small amount of fuel to produce power.
·Fuel Injector – It ignites the mixture of air and fuel, which initiates the combustion reactions.
·Combustion chamber – is used to mix air and fuel and burn to produce high-velocity exhaust gases. The design efficiently mixes and burns the fuel with the compressed air, generating a high-temperature, high-pressure gas flow.
·Shafts – It transfers power from the high-speed turbine to the compressor, compressing incoming air and driving the engine’s overall operation. The shaft is connected with the compressor and turbine.
·Turbine – It is connected to the compressor by a shaft and uses the energy from the exhaust gases to drive the compressor and other accessories.
·Nozzle – It is used to reduce the pressure energy and increase kinetic energy, resulting in enhanced thrust and forward motion of the jet.
Advantages of Turbo Jet Engine:
Versatile Fuel Compatibility: Flexible in choosing fuel type, it can use low-grade fuel type also.
Reduced Wear and Tear: Turbojet engines experience minimal parts wear and tear, contributing to their durability.
High Thrust Output: It produced higher thrust compared to propeller engines.
High Operating Temperature: It enables efficient performance at high heat levels and handles elevated operating temperatures
Impressive Speed: Engines operate at very high speeds, suitable for fast aircraft.
Simplified Construction: It’s a very straightforward and relatively simple construction.
Favorable Weight-to-Power Ratio: The weight-to-power ratio is low in turbojet engines, contributing to their power output efficiency.
Low Maintenance Cost: Low maintenance cost and reduced operational expenses.
Absence of Unbalance Forces: Turbojet engines lack unbalanced forces, minimizing potential operational issues.
Supersonic Efficiency: Turbojet engines are highly effective for supersonic aircraft, enabling efficient supersonic flight capabilities.
Turbojet engines are used in various applications such as:
·Military Aircraft
·Supersonic Aircraft
·Experimental Aircraft
·Unmanned Aerial Vehicles (UAVs)
·Target Drones
·Missile Propulsion
·Jet Trainers
There are two major types of defense turbojet engines axial flows and centrifugal flow engines.
Axial flow engines are the most common type of engine, it contains a compressor, combustion chamber, and turbine. The air as it passes through the compressor, experiences an increase in pressure. The air is fed to the combustion chamber leading to an increase in temperature and the high-pressure and temperature gas is then passed through the turbine, where it is expanded and the required power is obtained.
Centrifugal flow engine compressors are designed perpendicularly to the axis of rotation, it with a single-stage compressor causes air to flow in a circular motion.
Types of defense turbojet engines:
Afterburning Turbojet Engines: Afterburning is achieved by injecting additional fuel into the jet pipe downstream of the turbine. The advantage of afterburning is significantly increased thrust, afterburning is also called a reheat system. The engine injects additional fuel into the exhaust stream after the turbine section. Ignited fuel increases the temperature and velocity of the exhaust gases, thereby providing extra thrust during take-off, combat maneuvers, or supersonic flight.
Low-bypass Turbofan Engines: This engine uses a multistage fan which generates a low volume but relatively high speed air stream whereas high bypass engines usually have a single-stage fan which generates a high volume but relatively low speed air stream. The engine features a relatively small bypass ratio, meaning that a significant portion of the incoming air bypasses the engine core and is instead directed through a fan and around the engine core. The engine configuration provides high thrust output and fuel efficiency.
High-bypass Turbofan Engines: It contains a large fan at the front which generates most of the thrust. The majority of the air drawn in by the fan bypasses the core engine, flowing around it rather than through it. These engines are mostly used in commercial and military surveillance aircraft. This design prioritizes fuel efficiency and quiet operation over raw thrust, making it suitable for long-range missions and reconnaissance flights.
Variable Cycle Engines: This engine is designed to optimize performance across a wide range of flight conditions from subsonic to supersonic speeds with low levels of fuel consumption. The engine with the characteristics of both a high-bypass engine (for subsonic flight speed) and a low-bypass engine (for supersonic flight speed). The engine has adjustable components, such as variable inlet guide vanes and adjustable bypass ratios, allowing them to adapt to changing flight regimes.
Supersonic Turbojet Engines: The engines for supersonic flight, featuring specialized air intakes, combustion chambers, and nozzles optimized for high-speed operation. In the defense sector, this engine is used in fighter aircraft and reconnaissance platforms capable of sustained supersonic speeds.
Revolutionary in defense with Mini-jet turbine engines:
In India, a start-up makes innovative mini-jet turbine engines for military applications with Morden technology. The company designed a mini jet turbine engine for unmanned aerial vehicles and other defense applications capable of generating up to 20kgf. It developed three different models such as DG J20, DG J40, and DG J60.
Conclusion
Looking ahead, ongoing advancements in propulsion technology, including the integration of advanced materials, additive manufacturing techniques, and artificial intelligence, promise to further enhance the capabilities of defense turbojet engines, ensuring continued dominance of the skies for military forces around the world.