Aeroengine blisks & Material (marketing department of Shanghai HY Industry Co., Ltd)
Aeroengine is the “heart” of an aircraft, and is also known as the “Pearl in the Crown of Industry”. Its manufacturing integrates many cutting-edge technologies in modern industry, involving materials, machining, thermodynamics and other fields. However, as various countries have higher and higher requirements for engine performance, new structures, new technologies, and new processes in the process of research and development and application are still challenging the peak of modern industry. And one of them plays an important role in improving the thrust-to-weight ratio of aeroengines, which is the overall blisk.
01 Advantages of Aeroengine blisks & Material
Before the appearance of the blisk, the rotor blades of the engine needed to be connected to the wheel disk through tenons, tenons and locking devices, but this structure gradually failed to meet the needs of high-performance aeroengines. The integral blisk of the engine rotor blade and the disc was designed accordingly, and it has become a necessary structure for high thrust-to-weight ratio engines. It has been widely used in military and civil aeroengines, and has the following advantages.
1. Lose weight：Since the rim of the wheel disc does not need to be machined with a tongue and groove for installing blades, the radial dimension of the rim can be greatly reduced, thereby significantly reducing the mass of the rotor.
2. Reduce the number of parts：In addition to the fact that the wheel disc and the blade are integrated, the reduction of locking devices is also an important reason. Aero-engines have extremely strict requirements on reliability, and the simplified rotor structure has a great effect on improving reliability.
3. Reduce airflow loss：The escape loss caused by the gap in the traditional connection method is eliminated, the working efficiency of the engine is improved, and the thrust is increased.
It not only reduces the weight but also improves the thrust, so the overall blisk that is conducive to improving the thrust-to-weight ratio is naturally not an easy “pearl”. On the one hand, the overall blisks mostly use difficult-to-machine materials such as titanium alloys and high-temperature alloys; on the other hand, the blades are thin and have complex blade shapes, which place extremely high requirements on manufacturing technology. In addition, when the rotor blades are damaged, they cannot be replaced individually, which may lead to the scrapping of the entire blisk, and repair technology is another problem.
02 Manufacture of Aeroengine blisks & Material
At present, there are three main technologies for the manufacture of blisks.
1. Five-axis simultaneous CNC milling
Five-axis linkage CNC milling is widely used in the field of blisk manufacturing due to its advantages of fast response, high reliability, good processing flexibility and short production preparation period, mainly including side milling, plunge milling and trochoidal milling and other milling methods. The key factors to ensure the success of blisk machining include:
1) A five-axis linkage machine tool with good dynamic characteristics;
2) Optimized professional CAM software;
3) Tools and application knowledge dedicated to titanium alloy/superalloy machining.
2. Electrochemical machining
The electrochemical machining method is an excellent machining method for the blisk channel of the aeroengine. In the electrochemical machining, there are mainly several machining technologies such as electrolytic nesting, profiling electrolytic machining and numerical control electrolytic machining.
Since electrochemical machining mainly utilizes the characteristics of metal anodic dissolution in electrolyte, when electrochemical machining technology is applied, the cathode part will not be lost, and the workpiece will not be affected by cutting force, machining heat, etc. during machining. The residual stress after machining of the overall blisk channel of the aero-engine is reduced.
In addition, compared with five-axis milling, the working hours of electrochemical machining are greatly reduced, and it can be used in rough machining, semi-finishing and finishing stages, and there is no need for manual polishing after machining. One of the important development directions of channel processing.
3. Welding process
The blades are processed separately, and the blades processed in the previous stage are welded to the blisks by welding technologies such as electron beam welding, linear friction welding, or vacuum solid-state diffusion bonding. Its advantage is that it can be used in the manufacture of blisks where the blade and disk materials are not consistent.
When the welding process is adopted, the welding quality of the blade is required to be high, which directly affects the performance and reliability of the overall blisk of the aero-engine. Moreover, due to the fact that the actual shape of the blades used in the welded blisks is not the same, the position of each blade after welding is not the same due to the limitation of welding precision. It is necessary to use adaptive processing technology to carry out personalized precision CNC milling for each blade.
In addition, welding is a very important technology in the repair of the overall blisk. Among them, linear friction welding is a solid-phase welding technology with high quality and good reproducibility of the welded joints. One of the reliable and trustworthy welding techniques.
03 Application of blisks
EJ200 aero-engine: EJ200 aero-engine has 3-stage fans and 5-stage high-pressure compressors. Individual blades are electron beam welded to the disc to form an integral blisk, which is used in the third-stage fan and the first-stage high-pressure compressor. The blisk and other rotors are not welded together to form a multi-stage integral rotor, but are connected by short bolts. Generally speaking, the blisk is in the initial stage of application.
F414 turbofan engine: In the F414 turbofan engine, the second and third stages of the 3-stage fan and the first three stages of the seventh-stage high-pressure compressor adopt integral blisks, which are processed by electrochemical methods. And GE has also developed a set of feasible repair methods. On this basis, the overall blisks of the second and third stages of the fan are welded together to form an integral rotor, and the first and second stages of the compressor are also welded together to further reduce Reduce the weight of the rotor and improve the durability of the engine. Compared with EJ200, F414 has taken a big step forward in the application of blisks.
F119-PW-100 engine: The third-stage fan and the sixth-stage high-pressure compressor all use integral blisks, and the blades of the first-stage fan are hollow, and the hollow blades are welded to the wheel disc by linear friction welding to form an integral blade. Disc, so that the rotor weight of this stage is reduced by 32kg.
BR715 engine: In the civil large engine, the blisk has also been applied. The BR715 engine uses five-axis linkage CNC milling technology to process the overall blisk, which is used on the two-stage booster compressor behind the fan, and the front and rear two-stage blisks are welded together to form an integral rotor. It is used on Boeing 717.