2. Turbine engine
(1) turboprop engine
(2) turbofan engine
(3) turbojet engine
(4) turboshaft engine
3. Ramjet engine [Edit this paragraph] The piston engine (1) consists of cylinder, piston, connecting rod, crankshaft, valve mechanism, propeller reducer, casing and other parts.
(2) Working principle: The farthest position of the piston top in the crankshaft rotation center is called top dead center, the nearest position is called bottom dead center, and the distance from top dead center to bottom dead center is called piston stroke. Piston aero-engines are mostly four-stroke engines, that is, a cylinder completes a working cycle, and the piston has to go through four strokes in the cylinder, which are intake stroke, compression stroke, expansion stroke and exhaust stroke in turn.
When the engine starts to work, it first enters the "intake stroke", the intake valve on the cylinder head opens, the exhaust valve closes, the piston slides down from the top dead center to the bottom dead center, the volume in the cylinder gradually increases, and the air pressure decreases-lower than the atmospheric pressure outside. So the mixture of fresh gasoline and air is sucked into the cylinder through the open intake valve. The ratio of gasoline to air in the mixed gas is generally 1 ~ 15, that is, it takes 15 kg of air to burn one kilogram of gasoline.
After the intake stroke of the piston engine is completed, the second stroke, namely "compression stroke", begins. At this time, the crankshaft continues to rotate due to inertia, pushing the piston to move upward from the bottom dead center. At this time, the intake valve is closed as tightly as the exhaust valve. The internal volume of the cylinder decreases gradually, and the mixed gas is strongly compressed by the piston. When the piston moves to the top dead center, the mixture is compressed in the small space between the top dead center and the cylinder head. This small space is called "combustion chamber". At this time, the pressure of the mixed gas is increased to 10 atmospheric pressure. The temperature has also risen to about 400 degrees Celsius. Compression is to make better use of the heat generated by gasoline combustion, so as to greatly increase the pressure of the mixed gas enclosed in the narrow space of the combustion chamber, thereby increasing its work capacity after combustion.
When the piston is at the bottom dead center, the volume in the cylinder is the largest, and the volume is the smallest at the top dead center (the latter is also the volume of the combustion chamber). The degree to which the mixed gas is compressed can be measured by the ratio of these two volumes. This ratio is called "compression ratio", and the compression ratio of piston aero-engine is about 5 to 8. The greater the compression ratio, the more gas compressed and the greater the power generated by the engine.
The compression stroke is followed by the "working stroke" and the third stroke. At the end of the compression stroke, when the piston is close to the top dead center, the spark plug on the cylinder head generates an electric spark to ignite the mixture, and the combustion time is very short, about 0.0 15 seconds; But the speed is very fast, about 30 meters per second. The gas expands violently, the pressure rises sharply, reaching 60 to 75 atmospheres, and the temperature of the combustion gas reaches 2000 to 2500 degrees Celsius. When burning, the local temperature may reach three or four thousand degrees, and the impact force of gas on the piston may reach 15 tons. Under the strong pressure of gas, the piston moves quickly to the bottom dead center, pushing the connecting rod to run downwards in Yemen, and the connecting rod drives the crankshaft to rotate.
This stroke is the only stroke that can make the engine work and get power. The other three strokes are all prepared for this stroke. An airplane with a piston engine
The fourth stroke is the "exhaust stroke". After the working stroke, due to inertia, the crankshaft continues to rotate, making the piston move upward from the bottom dead center. At this time, the intake valve is still closed, while the exhaust valve is wide open, and the burnt exhaust gas is discharged through the exhaust valve. When the piston reaches the top dead center, most of the exhaust gas has been discharged. Then the exhaust valve closes, the intake valve opens, and the piston descends from the top dead center to start a new cycle.
From the intake stroke to the exhaust stroke, the thermal energy of gasoline is converted into mechanical energy to push the piston to move and drive the propeller to rotate and do work. This general process is called "circulation". This is a repetitive movement. Because it involves the conversion of thermal energy into mechanical energy, it is also called "thermal cycle".
In order to complete the four-stroke work, piston aero-engine needs some other necessary devices and components besides the above components such as cylinder, piston, connecting rod and crankshaft.
The biggest difference between piston engine and turbine engine is air intake. Piston engine is intermittent air intake, while turbine engine is continuous air intake.
(3) Application of piston engine
Mainly used in aircraft, helicopters, airships and other aircraft before the 1950s to drive propellers or rotors. Later, it was gradually replaced by a turbine engine with higher power and better high-speed performance. At present, it is mainly used for small aircraft engines. Helicopters and ultralight aircraft. [Edit this paragraph] The turbine engine (1) consists of a compressor, a combustion chamber and a turbine.
(2) General components: compressors are usually divided into low-pressure compressors (low-pressure section) and high-pressure compressors (high-pressure section). The low-pressure section sometimes has the function of increasing the intake air volume by the intake fan, and the incoming airflow is compressed into high-density, high-pressure and low-speed airflow in the compressor to increase the efficiency of the engine. After the airflow enters the combustion chamber, the fuel is ejected from the fuel supply nozzle, mixed with the airflow in the combustion chamber and burned. The high-heat waste gas generated after combustion drives the turbine to rotate, and then the residual energy is taken out through the nozzle or exhaust pipe. As for how much energy will be used to drive the turbine, depending on the type and design of the turbine engine, the turbine will be divided into high-pressure section and low-pressure section like a compressor.
(3) Working principle: Although the turbine engine may have many different working principles, the simplest turbine type can only include a "rotor", such as a fan blade with a central shaft, which is placed in a fluid (such as air or water). When the fluid passes through, the force acting on the fan blade will drive the whole rotor to start rotating, so that the axial torque can be output from the central shaft. Windmills, waterwheels and other devices can be said to be the earliest prototypes of turbine engines invented by human beings.
(4) Application of turbine engine
Turboprop engine;
Turboprop engines are mainly used for aircraft below 800km/h, such as domestic Yun 8 series, xinzhou 60(MA60) series and American C 130 series. The advantages of turboprop are good economy, more fuel-saving than turbofan/jet engine, and higher propulsion efficiency when using turboprop at low speed and low altitude. The disadvantage is that it is noisy and not suitable for high-speed flight, and the propulsion efficiency of turboprop is also related to the flight altitude. Please refer to the manufacturer's technical manual for specific principles.
Turbofan engine;
The turbofan engine is mainly used for aircraft over 800km1000km. For example, B737/747/757/767 of American Boeing Company, A300/3 10/320/330 of Airbus Company, ARJ2 1/ Yun 10 of China, EMB145/of Brazil. Turbofan engine is the mainstream engine of civil airliner at present. Generally, Gao Han air-to-air ratio engine is adopted, which is more fuel-efficient than turbojet engine. At subsonic speed, the propulsion efficiency is higher and the noise is lower than that of turbojet engine. The disadvantage is that the engine has large windward area and large wind resistance, which is not suitable for hypersonic flight.
Turbojet engine;
Turbojet engines are mainly used in military aircraft, but also in civil aircraft, such as Olympus 593 turbojet engine used in Concorde; The typical application of turbojet engine is the Su -25 aircraft of the former Soviet Union, which uses the turbojet engine of Rurika Design Bureau as the power, and has set a fighter speed record of Mach 3.3 and a ceiling record of 37,250 meters. Compared with turbofan engine, high speed/high altitude performance is a major feature of turbojet engine. Disadvantages are high noise and high fuel consumption. At the same time, this kind of engine is not suitable for low-speed flight, and it is easy to cause engine stall when flying at low speed.
Turbine shaft engine;
Mainly used in helicopters, compared with piston engines, turboshaft engines have much larger power-to-weight ratio and generate much more power. The main disadvantages are complicated manufacture and difficult maintenance. Especially the turboshaft engine needs a bigger reduction gear to slow down because of its high power and high speed, and sometimes even the weight of the reduction gear accounts for half of the engine.
Turboshaft engine [edit this section] Ramjet engine (1) consists of inlet (also known as diffuser), combustion chamber and nozzle.
(2) Working principle: The general difference between ramjet engine and turbofan engine is that ramjet engine has no compressor and relies on high-speed air for ramjet intake. Generally, a ram air engine needs Mach 0.5 to start. The working principle is to use the oncoming air to decelerate after entering the engine, so that the static pressure of the air increases, and then it enters the combustion chamber for combustion. After the temperature rises, it is accelerated by jet expansion, and finally it is ejected through the nozzle to provide thrust.
Application of ramjet (3): Ramjet is simple in structure and large in thrust, especially suitable for high-speed and high-altitude flight. Because it can't start by itself, its low-speed performance is not good, and its application in aircraft is limited. It is only used for missile-rocket auxiliary engines, unmanned aerial vehicles, auxiliary standby power systems of large aircraft and air-launched target bombs. The advantage of ramjet engine is its high speed (up to Mach 6 at the earliest), but the disadvantage is that it needs external energy to start (usually rocket boost) because of ram air intake. Not suitable for recycling.
Air China B747-400 aircraft is equipped with turbofan engines [edit this paragraph] 1 and CFM56-3 series engines. These typical engines were jointly developed by Snecma Company of France and General Electric Company of the United States, and were put into use in 1979. Up to now, more than 15300 engines have been delivered, accounting for 100 seats in the world. It belongs to Gao Han Dobby, a twin-rotor engine. China began to prepare to install this engine on Yun-10, and later planned to dismount for various reasons. Mainly used for medium-range passenger aircraft (Boeing 737-300/400/500 CL series).
2.PW4000 series engines: produced by Pratt & Whitney Company, with airworthiness certificates of 1986 July thrust of 24909daN (i.e. PW4052 and PW4 152) and 1988 April thrust of 26690daN (i.e. PW4 158). 1987 was delivered for the first time in July and equipped on B767-200 and A3 10 aircraft. Mainly used for large and medium-sized passenger aircraft engines (Boeing 747, 767, Airbus A300, A330 and other models).
3. Turboprop 6: 1969 In order to improve the transportation and combat capability of the troops, the government of China requires the development of medium-sized transport aircraft and its power. China Southern Power Machinery Co., Ltd. began to develop turboprop for Y-8 aircraft in August 1969. First flight in September 1970, first flight in April 1973. 1976 was designed and equipped for military use. Mainly used for domestic Yun -8 series aircraft engines.
The Y-8 aircraft with turboprop 6 and Taihang engine (turbofan 10) was developed by China Aviation Research Institute 606. Facing the grim situation of China's aviation industry, the country decided to develop a new generation of large thrust turbofan engines in the mid-1980s. The turbofan 10A is being tested and finalized with the pre-production of J 10. It can be formally produced in 2004 and finalized with J 10, and put into mass production randomly in 2005. Mainly used in J 10 aircraft.
The above is my partial summary based on my understanding after work. Please correct me if there are any shortcomings. My purpose is just to hope that you can have a preliminary understanding of aircraft engines. The content is wide but not deep, and many places will stop. For more professional guidance, please consult professional knowledge or relevant professional books. You can also send me a message if you have any questions. Thank you.