Military aerospace engine is the pinnacle of human Industrial Science and technology. In addition to the safety and reliability of civil aircraft parts and engine component, it has higher requirements for thrust and flexibility. Its production and processing difficulties have reached the peak, from design, processing, assembly to maintenance, are rich in high-tech content. At present, only a few countries have such technologies, and they also keep these technologies strictly confidential. Even if they export engines, they only export finished products, and the internal structure will never be easily revealed. Next, we will discuss the difficulties of military aerospace engine production.
Difficulty 1: difficult to reverse copy
As long as the finished products are imported from other countries, it is easy to disassemble and research the finished products and realize reverse replication. Even if the researchers don’t have drawings in hand, it’s not hard to do that. This is particularly common in the cycling industry. But for aerospace engines, it is almost impossible to replicate in reverse.
For example, the cfm-56 series, the mainstream engine used on Boeing 737 airliners, was produced by GE since 1974. Up to now, more than 20000 sets have been produced. Almost all single channel airliners dominated by Boeing and Airbus are in use. For more than 40 years, no company has been able to successfully replicate this product, because after dismantling, it will be found that the nail size area on the engine blade is covered with numerous small pores, which play an important role in cooling the engine. Once the air hole position of the replica is slightly deviated, it will seriously affect the cooling effect of the engine, which often leads to disastrous consequences. There are still many such designs. GE has developed engines for various models based on cfm-56’s technical foundation, and has launched fierce competition with Pratt & Whitney.
Difficulty 2: difficult to make materials
The structure of aero-engine may not be complicated, but consists of high and low pressure compressor, high and low pressure turbine and annular combustion chamber. But the working environment of these parts is different, the temperature and pressure they need to bear are also different. In order to ensure the performance of the engine and reduce the production cost as much as possible, there are extremely strict requirements for the materials used in various parts.
For example, turbine blades, working at thousands of degrees Celsius and tens of thousands of revolutions per minute, are made of a mixture of various metals in different proportions. The blade near the combustion chamber is subjected to higher temperature, and the materials used are required to have stronger high temperature resistance, and the proportion of rare metal elements added in the materials will also be different.
Like the turbine blade, the materials used for each component of the engine are also different. For example, the cfm-56 engine turbine is made of superalloy, and other parts are made of composite materials. The manufacture of these materials is not easy. In many materials, the proportion of various components is strictly confidential.
Difficulty 3: difficult to process and manufacture
Even with advanced drawings and materials, it is not possible to produce high-quality military aerospace engines. Because the production and processing technology of each part is also a difficult problem to solve. For example, the diameter of cfm-56 engine fan is only 1.55 meters, and the length is only 2.5 meters. It is difficult to imagine the complexity of the process to generate 86kn thrust in such a small space. Moreover, the precision of military aero-engine parts is very high. At present, the main precision casting process of single crystal turbine blade requires the error within 0.1 mm, so as to ensure that each blade can work normally.
Due to the use of a variety of metal alloy materials, the processing and welding process of superalloy is also essential technology. There are also some soft parts, such as the outer end of the engine blade, which is used to realize the seamless connection with the outer ring structure. The software made of special materials often has higher requirements on the processing technology than the hard materials.
Generally speaking, the design and manufacture of military aeroengine is so difficult that it becomes an important standard to distinguish the industrial strength of various countries. At present, no one can shake the status of the United States and Russia, but China is still in the catching up stage. With the development of a new generation of cj1000a turbofan engine superior to cfm-56, a new breakthrough has been brought to China’s aeroengine industry.