Thrust-to-weight ratio and power-to-weight ratio are the most important technical indexes to measure and evaluate the advanced nature of aero-engines. In order to pursue the thrust-weight ratio of the engine to more than 10, the aero-engine continuously uses new materials and introduces new structures to reduce the weight of aero-engine components while greatly increasing the engine turbine front temperature. This puts forward higher technical requirements for engine manufacturing, and promotes the continuous emergence and development of new technologies in aero engine manufacturing. A series of key manufacturing technologies developed for the development of high-performance aero engines will become or have become the direction of advanced manufacturing technology development. This paper introduces the key manufacturing technology of aero engine from three aspects: key technology, hot technology and basic technology. The key manufacturing technology is the necessary technology to develop advanced aero engine. Manufacturing hotspot technology is a technology that must be studied to improve the manufacturing efficiency and manufacturing quality of engine. Basic manufacturing technology is the technology that should be gradually accumulated and developed in engine development and mass production, and represents the soft power of engine manufacturing technology level and production capacity.
Key technology of aero engine manufacturing
Manufacturing technology of single crystal turbine blade
- The turbine front temperature of modern aero engine is greatly increased, and the turbine front temperature of F119 engine is as high as 1900~2050K, and the turbine blades cast by traditional process simply cannot withstand such a high temperature, and even will be melted and cannot work effectively. Single crystal turbine blades successfully solve the problem of high temperature resistance of turbine blades of engines with a thrust-to-weight ratio of 10 stages. The excellent high temperature resistance of single crystal turbine blades mainly depends on the fact that there is only one crystal in the whole blade, thus eliminating the defects in high temperature performance between grain boundaries caused by the polycrystal structure of equiaaxial and directional crystal blades.
- The single crystal turbine blade is the engine part with the most manufacturing process, the longest cycle, the lowest qualification rate, and the most strict foreign blockade and monopoly. The process of manufacturing single crystal turbine blades includes core pressing, core repair, core sintering, core inspection, matching of core and mold, wax mold injection, wax mold X Light inspection, wax mold wall thickness detection, wax mold dressing, wax mold combination, crystal extraction system and pouring gate combination, paint sand removal, shell drying, shell dewaxing, shell roasting, leaf pouring, single crystal solidification, shell blowing, initial inspection, fluorescence inspection, core-removal, grinding, chord width measurement, blade X-ray inspection, X-ray film inspection, profile inspection, refined blade, blade wall thickness detection, and final Check the manufacturing process. In addition, it is necessary to complete the design and manufacturing of turbine blade investment casting mold.
- At present, only a few countries in the world such as the United States, Russia, the United Kingdom, France, and China can manufacture single crystal turbine blades. In recent years, great progress has been made in the manufacture of single crystal turbine blades in China. The single crystal turbine blades of thrust-to-weight ratio 10 stage engines have been developed and the single crystal turbine blades of high-power-to-weight turboshaft engines have been mass-produced.
High efficiency, high precision and low cost machining technology of integral blade disc
- The application of integral blade disk technology promotes the innovation of aero engine structure design and the leap of manufacturing process, realizes the purpose of engine weight reduction and efficiency increase, and improves the reliability of engine operation. At the same time, the thin thickness of the blade, large bending and high efficiency pneumatic design, resulting in poor blade rigidity, easy deformation and difficult to control problems; The narrow and deep airflow channel between the blades makes the realization of the blade disk processing technology poor. High strength materials such as titanium alloy and superalloy are difficult to cut and have low efficiency. The United States and Britain in the 1980s began to apply the new engine monolithic disk technology, China’s monolithic disk technology started around 1996.
- The application of integral blade-disk technology has promoted the development of engine component structure integration technology. The tandem integral blade-disk with drum, blade disk with shaft, disc drum shaft combination, closed blade disk with hoop, rectifier stator ring blade disk and two-stage or multistage blade disk combination have been applied successively in the development of new aero engines. On the basis of the axial flow disk and the centrifugal impeller, the large and small blade structure disk and the oblique flow cotyledon disk are developed.
- Since the monolithic blade disk was applied in high-performance aero engines, the monolithic blade disk manufacturing technology has been developing and improving. At present, the monolithic blade disk processing process mainly includes the following 5 kinds of process methods: the lost wax precision casting monolithic blade disk, the electron beam welding monolithic blade disk, the electrochemical machining monolithic blade disk, the linear friction welding monolithic blade disk and the five-coordinate CNC machine tool machining monolithic blade disk.
- The five-coordinate CNC machine tool machining integral leaf disk manufacturing process is the earliest, widest engineering application and high technical maturity in domestic aero engine integral leaf disk manufacturing process. Among them, the key to the development and application of this technology is the slotting and slotting technology, the symmetrical spiral milling blade profile finishing technology, the blade front and back edge machining error compensation technology and the whole blade disc profile adaptive machining technology [1]. Foreign T700 engine, BR715 engine booster stage, EJ200 engine integral blade disk using this processing method processing and manufacturing, China CJ1000A, WS500 and other aircraft engine integral blade disk is also using five coordinate CNC machining technology manufacturing. FIG. 1 shows the first stage integral blade disc of commercial aero-engine high-pressure compressor manufactured in China.
Hollow blade manufacturing technology
- The fan of the turbofan engine is far away from the combustion chamber, and the heat load is low, but the requirements of the advanced aeroengine for its aerodynamic efficiency and the ability to prevent foreign object damage are constantly improving. The high performance aero engine fan adopts wide chord, no shoulder and hollow fan blade.
- The hollow fan blade of the triangular truss structure developed by Luo Luo Company is an improvement of the original honeycomb sandwich blade. Luo Luo Company calls it the second generation hollow fan blade. The process is to use the superplastic forming/diffusion connection (SPF/DB) combination process method to make the 3-layer titanium alloy plate into a wide chord hollow fan blade. The hollow part of the blade is a triangular truss structure, which is already used on the Trent engines of Boeing 777 and A330 aircraft. The hollow fan blade manufacturing technology of triangular truss structure in China has also made a breakthrough (Figure 2 shows the hollow fan blade and the internal triangular structure), but in order to meet the engineering application, a lot of strength, vibration, fatigue test and process optimization research work need to be carried out.
- The manufacturing process of hollow blade is as follows: First of all, 3 titanium alloy plates need to be prepared and placed in the upper, middle and lower layers, the middle layer is the core plate, the upper and lower layers are the leaf basin and the leaf back plate, respectively. Then, the fan hollow blades are formed by three titanium alloy plates after oil removal and pickling, intermediate layer coating with flux check, titanium plate welding, mold heating, argon purification, diffusion connection, superplastic forming, cooling with furnace, surface washing, blade root and inlet and exhaust edge processing, blade inspection and other procedures [2] superplastic forming/diffusion connection (SPF/DB).
High-end bearing manufacturing technology
- Bearing is one of the key components of aero engine, bearing in the high-speed tens of thousands of RPM running for a long time, but also to withstand the engine rotor high-speed rotation of the huge centrifugal force and various forms of extrusion stress, friction and ultra-high temperature effect. The quality and performance of bearings directly affect engine performance, life, reliability and flight safety. The development and production of high-end bearings is closely related to the interdisciplinary research of contact mechanics, lubrication theory, tribology, fatigue and damage, heat treatment and material organization, etc., and must also solve a large number of technical problems in design, materials, manufacturing, manufacturing equipment, testing and testing, grease and lubrication.
- At present, the research and development, manufacturing and sales of high-end bearings are basically monopolized by bearing manufacturing enterprises in Western countries such as Timken, NSK, SKF, and FAG. China’s aircraft engine manufacturing technology is backward, and the production capacity and development level of domestic bearing manufacturing enterprises cannot provide high-end bearings suitable for advanced aircraft engines in the short term. Bearing has become the “Mount Everest” that is difficult to cross in China’s aero engine research and development, which greatly restricts the development of high-performance aero engines in China.
Manufacturing technology of powder turbine disc
- Aeroengine turbine disk is subjected to superposition of high temperature and high stress, harsh working conditions, complex preparation process, and technical difficulty, which has become one of the difficulties in engine development in China. Powder superalloys are widely used in high performance aero engines in foreign countries because of their excellent mechanical properties and good thermal and cold process performance. The manufacture of powder turbine disk includes a series of key manufacturing technologies such as material development, master alloy melting, powder preparation and treatment, hot isostatic pressing, isothermal forging, heat treatment, and high-precision detection and evaluation, etc. It carries the key manufacturing technology indispensable for advanced aero engine manufacturing. The trend of foreign research on powder turbine disk is to develop from high-strength turbine disk to damage resistant turbine disk in terms of service performance, and the pulverization process to ultra-pure fine powder. Besides hot isostatic pressing, extrusion molding and isothermal forging forming processes are also developed. In China, Beijing Institute of Aeronautical Materials has developed a variety of aero-engine powder turbine disks, which has solved the key manufacturing technical problems of advanced aero-engine powder turbine disks, but the engineering manufacturing problem of powder turbine disks has not been completely solved.
Composite material manufacturing technology
Composite material technology has been widely used in high performance aero engines. To meet the needs of LEAP engine development, Sniema adopts 3D woven resin transfer molding (RTM) technology to manufacture composite fan casings and composite fan blades. LEAP engine parts manufactured by RTM technology have high strength, And the mass is only half the mass of titanium alloy parts of the same structure. In the process of developing the F119 engine, Pratt & Whitney developed continuous SiC fiber reinforced titanium matrix composite wide chord fan blades. This kind of composite blade has the properties of high stiffness, light weight and impact resistance, and is called the third generation wide chord fan blade. F119 turbofan engine 3 stage fan rotors are all made of this material. In China, composite material manufacturing technology has also been applied in the manufacturing of aviation engine parts, and the melt autogenous TiB2 particle reinforced aluminum matrix composite fan blades have made great progress. But TiB2 particle reinforced aluminum matrix composite fan blade efficient processing, processing surface strengthening, anti-fatigue performance and anti-foreign object damage technology are the key and difficult to realize the application of this material fan blade engineering research.