1, different definitions
(1) The turbojet engine is a turbine engine. It is characterized by completely relying on airflow to generate thrust. Usually used as the power of high-speed aircraft, but the fuel consumption is higher than that of turbofan engine. There are two types of turbojet engines: centrifugal and axial. Compared with centrifugal turbojet engine, axial flow has the advantages of small cross section and high compression ratio. Today, most turbojet engines are axial flow.
(2) turbofan engine, also known as "turbofan engine". Refers to a gas turbine engine, in which the gas injected from the nozzle and the air exhausted from the fan generate reactive thrust. It consists of compressor, combustion chamber, high-pressure turbine (driving compressor), low-pressure turbine (driving fan) and exhaust system.
2, the working principle is different
(1) The structure of modern turbojet engine consists of inlet, compressor, combustion chamber, turbine and nozzle, and there is an afterburner between the turbine and nozzle of fighter. Turbojet engine is also a kind of heat engine, which must follow the principle of heat engine doing work: high pressure inputs energy and low pressure releases energy.
Therefore, from the principle of generating output energy, jet engines and piston engines are the same, and they all need four stages: intake, pressurization, combustion and exhaust.
The difference is that in piston engine, these four stages are carried out in time-sharing, while in jet engine, they are continuous. The gas flows through all parts of the jet engine in turn, corresponding to the four working positions of the piston engine.
(2) The turbofan engine consists of a fan, a low-pressure compressor (unique to turbofans), a high-pressure compressor, a combustion chamber, a high-pressure turbine driving the compressor, a low-pressure turbine driving the fan and an exhaust system.
Among them, the high-pressure compressor, combustion chamber and high-pressure turbine are collectively called the core engine. Part of the gas discharged from the core engine can be transferred to the low-pressure turbine-driven fan by energy, and the rest can be used to accelerate the gas discharged from the nozzle.
3. Different characteristics
(1) turbojet engine: It is characterized by completely relying on airflow to generate thrust.
(2) Advantages and disadvantages of turbofan engine: Advantages of turbofan engine: large thrust, high propulsion efficiency, low noise, low fuel consumption and long range. Disadvantages: The fan has large diameter and windward area, so it has large resistance, complex engine structure and difficult design.
Extended data:
Performance of turbojet engines;
1. overcomes the main shortcomings of the aviation piston engine with propeller, and the fighter successfully breaks through the "sound barrier", which provides conditions for the aircraft to fly at high altitude and makes the aircraft enter a new era of supersonic flight from subsonic speed. The turbojet engine has made an indelible contribution to the rapid development of aircraft.
2. While the turbojet engine gains thrust, a large amount of high-temperature gas with certain heat energy and kinetic energy is discharged from the engine at high speed, and a large amount of energy is lost in vain, which fails to convert the heat energy generated by fuel combustion into effective work to the maximum extent.
3. Therefore, the use economy of turbojet engine is poor, which is the fatal weakness that restricts its continuous development. Especially when the afterburner is used, although the thrust of the engine can be greatly increased, the temperature and velocity of the gas discharged from the tail nozzle are much higher than those without afterburner, which greatly increases the energy loss and makes its economy worse.
References:
Baidu encyclopedia-turbofan engine
References:
Baidu encyclopedia-turbojet engine