An engine that provides power for the flight of an airplane. The characteristics of engine research and development are technical difficulty, high cost and long cycle. Engine has a decisive influence on the performance of aircraft and the success or failure and progress of aircraft development. Moreover, engine technology has good dual-purpose characteristics and is of great significance to national defense and national economy.
The characteristics of engine research and development are technical difficulty, high cost and long cycle. Engine has a decisive influence on the performance of aircraft and the success or failure and progress of aircraft development. Moreover, engine technology has good dual-purpose characteristics and is of great significance to national defense and national economy. Therefore, several countries in the world that can independently develop advanced aero-engines regard the development of aero-engines as a national policy, list engine technology as the key technology of the country and national defense, give a lot of investment, ensure the relatively independent leading development of engines, and strictly prohibit the export of key technologies. Some aero-engine post-industrial countries have also made major technological development plans, trying to establish the ability to independently develop or participate in international cooperation in the development of advanced aero-engines.
There are two main types of modern aero-engines: piston engines and jet engines. Low-speed, small and short-haul aircraft often use "piston engine"; Jet engines are usually used in high-speed, large (medium) and long-range (medium) aircraft. No matter which type, when used as an aero-engine, its basic requirements can be summarized as follows:
First of all, the power-to-weight ratio is very large.
Any part of an aircraft should be as light as possible on the premise of meeting the requirements of use. For the engine, it is necessary to ensure enough power and light weight. The standard for measuring engine power and weight is "power-to-weight ratio". That is, the ratio of the power generated by the engine to the weight of the engine. The greater the "power-to-weight ratio", the lighter the engine is at the same power.
The unit of power-to-weight ratio of piston engine is "horsepower/kg"; For jet engines, it is thrust (Newton)/weight (Newton), and there is no unit.
Second, the fuel consumption is small.
Whether the engine saves fuel or not is an important economic index for aircraft use. To evaluate the economy of an engine, the "fuel consumption rate" is often used as the standard. "Fuel consumption rate" refers to the weight of fuel consumed per unit power (one Newton or one horsepower) in one hour. The smaller the fuel consumption rate, the more fuel-efficient the engine is.
Third, the windward area is small.
Aero-engines should strive to be smaller under the premise of ensuring power reduction. Small size can make the engine occupy less space, which is beneficial to aircraft loading personnel, goods and equipment. In terms of volume, efforts should be made to reduce the "windward area" to reduce air resistance.
Fourth, the work is safe and reliable, and the service life is long
The safety of aircraft flying in the air is ensured by the reliable work of all components. To maintain flight, the engine must always be in a reliable state. Therefore, the reliability of the engine is very important. In order to ensure the safe and reliable operation of the engine, it is necessary to carefully design, select suitable materials and strictly standardize the process. After the engine assembly is completed, the engine is "tested" and various altitude conditions are simulated on the "test bench". There will be a trial run after being loaded on the plane. Only when it is determined that all the specified indicators meet the requirements can the aircraft fly. In order to ensure that the aircraft is in a reliable state at any time, the engine should be inspected and maintained regularly during the whole use process.
Under the premise of ensuring the reliability of the engine, the "long life" of the engine is required. This is another indicator of engine economy. Long service life, can reduce the use cost and save raw materials.
Engine life can be divided into "renovation life" and "service life". "Refurbishment life" refers to the service (actual work) time between two refurbishments or between the start of new engine use and the first refurbishment, and the unit is "hours". "Service life" refers to the service (actual work) time of a brand-new engine from the beginning of use to scrapping, and the unit is also "hours". Due to the differences in design, materials, technology and service conditions, the "life" of each engine is also different.
Five, convenient maintenance
Maintenance and repair are collectively called maintenance. This is an important work to ensure the reliability of the engine. Whether the engine can be in a reliable state at any time largely determines the "maintenance" quality. Maintenance quality affects the life of the engine.
One of the purposes of maintenance is to find and eliminate faults, and to detect, clean and replace lubricating oil in necessary parts. According to the length of engine working hours, maintenance work will generally be carried out regularly according to different projects. "Repair" is only carried out when the parts are damaged. Because of the heavy workload of "maintenance", it accounts for a large proportion in the cost of aircraft use. The convenience of disassembly, inspection and maintenance should be considered in the design to reduce the workload and cost of maintenance.