Chinese Aero Engine information thread
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From Superalloy To Single Crystal Alloy + Compound Cooling, Look At The Development Of Aero-Engine Blades.
As we all know, the aero engine is the core of the entire aircraft, and its performance directly determines the overall performance of the aircraft, so the aero engine is also known as the "jewel in the crown of industry". In aero gas turbine engines, the worst working environment and the most complex stress are the turbine blades. At the same time, the turbine blades are also the key to achieving high performance under the condition of small size and light weight. Therefore, if the aero engine is the core of the entire aircraft, then the turbine blades are the "core in the core" of the entire aircraft!
F-20 engine tail nozzle.
For aero engines, an increase in temperature will bring about an increase in thermal efficiency. Relevant studies have shown that the temperature in front of the aero engine turbine will be 55℃ every time it is prompted, and other conditions will remain unchanged. Under the circumstances, the thrust of the engine can be increased by about 10%. Therefore, as high-performance aeroengines continue to pursue large thrust and high thrust-to-weight ratio, increasing the temperature of the front wheel of the turbo has naturally become the direction of vigorous development of aeroengines, and the increase in the temperature of the front of the turbine is based on the performance of the turbine blade material at high temperature ( Based on the improvement of endurance strength, creep strength, toughness, thermal fatigue resistance, etc.).
Anatomy of a turbofan engine with a large bypass ratio.
However, in the process of continuous development of aero engines, the temperature of the front wheel of the turbine develops much faster than the bearing temperature of the turbine blade material. In terms of technical level, the bearing temperature of a “bare” turbine blade in an aero engine is only about 1100°C at most, while the operating temperature of the blade has reached 1700°C. The difference between the two can be such a big difference. The development of various cooling technologies for turbine blades.
The application of superalloy ushered in the first revolution in turbine blades
The first revolution of aero-engine turbine blades began with the emergence of superalloys. The first superalloy was developed in the 1940s. Afterwards, the superalloy replaced the previous high-temperature stainless steel with its excellent high-temperature performance. It was applied to the first generation of aviation gas turbine engine in the 1950s,At this time, the operating temperature of the superalloy turbine blades has reached 800°C. Since the bearing temperature is not much different from the operating temperature, this blade has not yet used cooling technology.
Directional alloy greatly increases the blade bearing temperature
By the 1960s, The application of vacuum casting technology can be said to be one of the most significant events in the history of the development of superalloys. Vacuum casting greatly reduces the content of impurities that are harmful to the performance of superalloys and improves the purity of the alloys. Later, in order to solve the "plastic trough" problem in the alloy, directional solidification alloy technology was also invented. Because directional solidification makes the crystalline direction of the alloy parallel to the direction of the main stress axis of the blade, and basically eliminates the transverse crystal perpendicular to the stress axis. It can improve the plasticity and thermal fatigue properties of the alloy.
Turbine blade performance comparison under different processes.
At this time, the bearing temperature of turbine blades made of directional casting superalloy has reached 1000℃ (approximately 1273K). With an increase of about 200°C, combined with simple blade air cooling technology, the temperature in front of the turbine of the second-generation aero gas turbine engine has reached 1300K-1500K, and the performance of the aero engine has been further improved.
The first generation of single crystal alloy + film cooling technology
in the 1970s , The alloying theory and heat treatment process have been breakthroughs. The process at this time can completely eliminate the grain boundary on the basis of the directionally solidified alloy. The single crystal alloy turbine blade manufacturing technology was born, and it also set off a second revolution in the materials used for turbine blades. , The thermal performance of alloy blades has been further improved (about 30℃), and the bearing temperature of turbine blades has reached 1050℃ (about 1323K).
However, the requirements of the third-generation aero gas turbine engine also further increase the working temperature and load-bearing temperature of the turbine blades.Since then, the cooling technology of turbine blades has been paid more attention. By designing cooling channels and cooling holes on the blades, the "low temperature gas" of several hundred degrees Celsius in the compressor is introduced into the turbine blades, and then sprayed from the cooling holes on the blade surface to form a gas film, which has a relatively high temperature isolation. The low turbine blades and the high temperature gas in the working environment are called film cooling technology.
Close-up of the cooling holes on the engine blade.
The application of film cooling technology enables the working temperature of the turbine blade to be much higher than the bearing temperature of the blade material itself. Therefore, under the comprehensive application of the first-generation single-crystal alloy + single-channel film cooling technology, the third-generation aeroengine's temperature in front of the turbine reached 1680K-1750K, and turbofan engines with a thrust-to-weight ratio of 8 began to appear (currently turbofan-10 Just be in this generation).
Second-generation single crystal alloy + composite cooling technology
By the end of the last century, the fifth The generation fighter has put forward the requirement of "supersonic cruise", and the thrust-to-weight ratio and thrust of the engine need to be further improved. The second-generation single crystal alloy further improves the microstructure stability of turbine blade alloys by increasing muscle rhenium, cobalt, molybdenum and other elements, and achieves a good balance between endurance strength and oxidation and corrosion resistance, so that its bearing temperature is once again It has increased by about 30°C, reaching a level of 1100°C (about 1370K).
The development path of materials used in turbine blades.
At this time, it has become difficult to increase the working temperature of turbine blades by improving material performance, and single-channel film cooling technology has begun to be insufficient. A composite cooling technology with simultaneous application of a variety of cooling technologies (convection, impingement, film structure, divergent cooling, etc.) has been developed. At present, through compound cooling of the turbine blades, the working temperature of the blades (temperature before the turbine) can be about 400K higher than the bearing temperature, reaching 1850K-1980K.
The development of blade cooling technology.
The second-generation single crystal alloy combined with compound cooling technology for turbine blades,It has been applied to the current mainstream fourth-generation aero engine (mainly represented by F-119 and EJ-200 engines).
Third-generation single crystal alloy/ceramic matrix composite material + multi-channel double-layer hollow wall cooling technology
_!--H2--21!-- H2--H2--
At present, the research and development of the sixth-generation fighter has been put on the agenda, but there is still relatively little information about the fifth-generation gas turbine engine. According to the breakthroughs made in related technologies in recent years, further optimization of alloy elements The third-generation single crystal alloys and new ceramic-based composite materials derived from the composition will become the first choice materials for the fifth-generation gas turbine engine blades. Among them, the improvement of ceramic-based composite materials is more obvious (the bearing temperature can reach 1200℃, and the weight is only It is 1/3 of the nickel-based single crystal alloy), but the technology is not yet mature.
The development of turbine blades of each generation of engines.
In the next generation of turbine blade cooling technology, the cooling channels inside the turbine blades will be further increased to make the scattering of the blades more uniform; adopt double-layer hollow wall cooling technology , Adding a hollow structure to the double-layer splint of the turbine blade can further improve the cooling efficiency. As the research on multi-channel double-layer hollow wall cooling technology is relatively complicated, there are relatively few domestic researches in this area at present.
Summary and prospects for the development of aero-engine turbine blades.
In general, the manufacturing and optimization of aero-engine turbine blade materials is an extremely complex process that requires a lot of experimentation to find the optimal or near optimal The optimization of the turbine blade cooling scheme is based on the design and manufacturing. Every time the cooling technology optimization of the turbine blade is also a huge test for the blade design and manufacturing. Therefore, it is no exaggeration to say that the price of a single crystal blade exceeds the same weight of gold.
Ceramic-based composite turbine blades exhibited by GE
From the perspective of the development of aero-engine turbine blades, the development of more high-temperature-resistant turbine blades is the key to improving engine performance. And after decades of development,The potential of single crystal alloy blades seems to have been tapped out. If you want to further improve the performance of aero-engines, looking for new directions has become a choice that has to be faced in the development of turbine blades; although there is still a lot of optimization in the cooling technology of aero-engine turbine blades Space, but it will undoubtedly further increase the difficulty of blade processing and manufacturing.
Figaro
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Are there any updates on when Y-20s will be produced with WS-20s? It doesn't make sense to me that J-20, J-10, Chinese flankers have all switched to the WS-10 in mass production but the Y-20 is still relying on the old low bypass WS-18s. Especially with the WS-15 and WS-10 progress, it doesn't make sense why this hasn't occurred yet.
Iron Shrappenel
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Polestar 2
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Need to keep close following of J-35 project. It is using WS-13IPE.
Open source information. Can not say how to find it because this information may be hidden in future if it is known all around the web
Polestar 2
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How do you know WS-18 is low by pass? It looks like DKP30 engine, doesnt mean it performs like it. With new metallurgy, WS-18 spec is definitely better than old Russian engine. Plus, PLAAF seems very satisfy for WS-18 that they continue using this engine with very slow induction phase of WS-20.
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