Proč letecké motory používají integrální lopatky? Jsou klíčem k létání! Česká republika

The aircraft engine is the "heart" of the aircraft and is also known as the "crown jewel of industry". Its manufacturing integrates many cutting-edge technologies in modern industry, involving materials, mechanical processing, thermodynamics and other fields. As countries have higher and higher requirements for engine performance, new structures, new technologies and new processes in research and development and application are still constantly challenging the peak of modern industry. One of the important factors in improving the thrust-to-weight ratio of aircraft engines is the integral blade disk.

Advantages of blisks

Before the emergence of the integral blade disk, the rotor blades of the engine needed to be connected to the wheel disk through tenons, mortise and tenon grooves and locking devices, but this structure gradually failed to meet the needs of high-performance aircraft engines. The integral blade disk that integrates the engine rotor blades and the wheel disk was designed, and has now become a must-have structure for high thrust-to-weight ratio engines. It has been widely used in military and civil aircraft engines and has the following advantages.

1.Úbytek hmotnosti:Since the rim of the wheel disc does not need to be machined to install the tongue and groove for installing the blades, the radial size 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 blades are integrated, the reduction of locking devices is also an important reason. Aircraft engines have extremely strict requirements on reliability, and a simplified rotor structure plays a big role in improving reliability.

3.Reduce airflow loss:The escape loss caused by the gap in the traditional connection method is eliminated, the engine efficiency is improved, and the thrust is increased.

The blisk, which reduces weight and increases thrust, is not an easy "pearl" to obtain. On the one hand, the blisk is mostly made of difficult-to-process materials such as titanium alloy and high-temperature alloy; on the other hand, its blades are thin and the blade shape is complex, which puts extremely high demands on manufacturing technology. In addition, when the rotor blades are damaged, they cannot be replaced individually, which may cause the blisk to be scrapped, and the repair technology is another problem.

Manufacturing of blisks

At present, there are three main technologies for manufacturing integral blades.

• Five-axis CNC milling

Five-axis CNC milling is widely used in the manufacturing of blisks due to its advantages of rapid response, high reliability, good processing flexibility and short production preparation cycle. The main milling methods include side milling, plunge milling and cycloidal milling. The key factors to ensure the success of blisks include:

Five-axis machine tools with good dynamic characteristics

Optimized professional CAM software

Tools and application knowledge dedicated to titanium alloy/high-temperature alloy processing

• Electrochemical machining

Electrochemical machining is an excellent method for machining the channels of integral blade disks of aircraft engines. There are several machining technologies in electrochemical machining, including electrolytic sleeve machining, contour electrolytic machining and CNC electrolytic machining.

Since electrochemical machining mainly utilizes the property of metal dissolution at the anode in the electrolyte, the cathode part will not be damaged when the electrochemical machining technology is applied, and the workpiece will not be affected by cutting force, machining heat, etc. during machining, thereby reducing the residual stress of the integral blade channel of the aircraft engine after machining.

In addition, compared with five-axis milling, the working hours of electrochemical machining are greatly reduced, and it can be used in the rough machining, semi-finishing and finishing stages. There is no need for manual polishing after machining. Therefore, it is one of the important development directions of aircraft engine integral blade channel processing.

• Svařování

The blades are processed separately, and then welded to the blade disk by electron beam welding, linear friction welding or vacuum solid-state diffusion bonding. The advantage is that it can be used for the manufacture of integral blade disks with inconsistent blade and disk materials.

The welding process has high requirements on the quality of blade welding, which directly affects the performance and reliability of the overall blade disk of the aircraft engine. In addition, since the actual shapes of the blades used in the welded blade disk are not consistent, the positions of the blades after welding are not consistent due to the limitation of welding accuracy, and adaptive processing technology is required to perform personalized precision CNC milling for each blade.

In addition, welding is a very important technology in the repair of integral blades. Among them, linear friction welding, as a solid phase welding technology, has high welding joint quality and good reproducibility. It is one of the more reliable and trustworthy welding technologies for welding high thrust-to-weight ratio aircraft engine rotor components.

Application of blisk

1. EJ200 aircraft engine

The EJ200 aircraft engine has a total of 3-stage fans and 5-stage high-pressure compressors. Single blades are welded to the wheel disc by electron beam to form an integral blade disk, which is used in the 3rd-stage fan and the 1st-stage high-pressure compressor. The integral blade disk is not welded together with the rotors of other stages to form a multi-stage integral rotor, but is connected with short bolts. Generally speaking, it is in the early stage of the application of integral blade disks.

2. F414 turbofan engine

In the F414 turbofan engine, the 2nd and 3rd stages of the 3-stage fan and the first 3 stages of the 7th stage high-pressure compressor use integral blades, which are processed by electrochemical methods. GE has also developed a feasible repair method. On this basis, the integral blades of the 2nd and 3rd stages of the fan are welded together to form an integral rotor, and the 1st and 2nd stages of the compressor are also welded together, further reducing the weight of the rotor and improving the durability of the engine.

Compared with the EJ200, the F414 has taken a big step forward in the application of integral blades.

3. F119-PW-100 engine

The 3-stage fan and 6-stage high-pressure compressor all use integral blades, and the 1st-stage fan blades are hollow. The hollow blades are welded to the wheel disc through linear friction welding to form an integral blade, which reduces the weight of the rotor of this stage by 32kg.

4. BR715 engine

In large civilian engines, the integral blade disk has also been used. The BR715 engine uses five-axis CNC milling technology to process the integral blade disk, which is used on the second-stage supercharger compressor after the fan, and the front and rear integral blade disks are welded together to form an integral rotor. It is used on the Boeing 717.