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Types of Chinese Aeroengines

The piston engine is an internal combustion engine using gas to push the piston for the reciprocating movement and then through the linkage and crankshaft to turn it into the rotating movement of the shaft for driving the aircraft propeller or helicopter rotor. The piston engine was adopted for the aircraft industry at the beginning of the 20th century and went to its peak in the 1940s, with its power increasing from several dozens of kW to about 3,000 kW (4,000 hp). After World War II the piston engines were gradually substituted by gas turbine engines in military and large civil aeroplanes. The small piston engine, however, is more economical than the gas turbine engine, and therefore is still widely used in light and low speed transport aeroplanes, trainers, and, in particular, aircraft with specialized functions such as animal husbandry, agriculture, forestry, geographical survey, mapping and sports.

In the early 1950s, all of China' s trainers, transports and bombers were powered by piston engines. Therefore, the production, modification and development of China's aeroengines started with the piston engines and in the 1960s a series of piston engines was formed.

The development from piston engines to the jet engines was a revolution in aeroengine history. Due to its light weight, compactness, smooth running, high power and good altitude characteristics, the turbojet engine is much more superior over the piston engine at high speed and high altitude, particularly at the flight speed approaching the sound speed, when there is a tremendous shock wave drag called the "Sonic Barrier" . Due to the power limit and dramatic reduction in propeller efficiency at high speed, the propeller aircraft powered by the piston engine could not overcome this barrier. The jet engine, however, can smoothly pass it because of the advantages mentioned above. Thus, the jet engines gradually replaced the piston engines for application in military and large civil aeroplanes.

The turbojet engine is formed by use of the core engine and a pipe. The core engine consists of the compressor, combustor and gas turbine. The high velocity gas from the core engine rushes out through the jet pipe creating the reaction force and pushes the aeroplane forward. The installation of the afterburner in the jet pipe forms the afterburning jet engine which can produce additional thrust for short periods. This type of engine is suitable for high speed aircraft. From the mid 1950s, China' s aircraft industry started the trial production of turbojet engines. Firstly it completed the transition from the piston engines to the jet engines and then, in the configuration of the turbojet engine, completed the transition from the centrifugal flow compressor to the axial one and from one shaft to two shafts. It also successfully made large turbojet engines.

The turbofan engine is developed from the turbojet engine by adding a fan and a bypass duct. The fan is driven by the gas turbine thus creating the bypass flow. Both the bypass flow and the hot gas expelled from the core engine create reaction thrust. The turbofan engine can be also equipped with an afterburner. This type of engine has better propulsive efficiency, low s.f.c., low noise and low gas pollution. It is suitable for large passenger aeroplanes and can be also used for long distance supersonic fighters, bombers and attack aircraft with a wide range of speeds. China's aviation industry started to develop turbofan engines in 1962. Over the next twenty years, it has developed the WS5, WS6, WS6A, No 4 lift-fan, WS8 and WS9 engines. Although many of them were halted midway due to task adjustment, many valuable experiences were gained.

The turboprop engine is a type of aero gas turbine engine which uses the gas turbines to drive the propellers. The power consists of the pull force from the propeller and the thrust generated by the exhaust gas. Compared with the piston engines, it has higher power, a lighter weight and lower vibration. Compared with the turbojet engine, it has lower s.f.c. and higher take-off thrust. Due to the restriction of the propeller, the turboprop aeroplane normally can fly at 550 to 750 km / h. In structure, the turboprop engine is the turbojet engine plus more stages of turbines, the reduction gear box and propeller. This type of engine is widely used in commuter aeroplanes, long range transport aeroplanes and multi-role aeroplanes.

China set up a turboprop engine design office in HEF in 1958 and the office then endeavored to design a turboprop engine. As the need for piston engines decreased, HEF and ZEF, under the leadership of their Directors Tang Qinxun and Guo Gubang, actively turned to producing and developing gas turbine engines. In 1968, Zhuzhou Aeroengine Research Institute (ZARI) was established. In the past twenty or so years, China has developed and produced several kinds of turboprop engines for application on transport and water-based bombers. The turboshaft engine is derived from the turboprop engine and used as the powerplant for helicopters. Its work concept and structure are basically the same as that of the turboprop engine. The power turbine drives the helicopter's main rotor and tail rotor through the transmission systems. As the speeds of the main and tail rotors should not be too high, it is necessary to have several reduction gears between them and the engine main shaft.

The turboshaft engine has higher power to weight ratio and longer life, and its s.f.c. is equivalent to that of superior piston engines. It can use the cheaper kerosene rather than gasoline. Therefore, from the 1950s, it has gradually replaced piston engines on helicopters. The use of turboshaft engines makes the design and manufacture of large helicopters become feasible. China's aviation industry started to develop turboshaft engines from the mid 1960s. It has developed and produced WZ5, WZ6 and WZ8 engines.

The helicopter power transmission system is a gear train transmission unit which reduces the speed of the output shaft of the turboshaft engine or piston engine to the speeds required by the main rotor and the tail rotor. The system consists of the main reduction gear box, the intermediate reduction gear box, the tail reduction gear box and driving shafts. The main reduction gear reduces the speed of the engine output shaft from several tens of thousands r.p.m. to a few hundred r.p.m. through multi-reduction. Therefore, it requires compact structured, light weight reduction gears, which can reliably operate for long periods of time at high speed and high load conditions. Also they need to be smooth working, with low noise and even engagement and good matching. Therefore, the design and manufacture of the power transmission system is also an important subject in the aeroengine field.

China's aviation industry set up the production of the power transmission system for piston engine helicopters in HEF at the end of the 1950s. They produced the P-5 reduction gear box for the Z-5 helicopter in batches. Later they designed and developed the reduction gear box for the Z-6. Towards the beginning of the 1980s, the development and manufacture capabilities of the helicopter power transmission system were set up in South China, which included ZEF, ZARI and the Hunan Aero-Gear Factory. They developed the power transmission system for the Z-7 helicopter and carried out the development and production of the power transmission system for the Z-8 helicopter. The Z-9 helicopter's power transmission system was developed and produced by HEF and the Hunan Aero-Gear Factory.

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