The main components of aero-engines are as follows: compressors, fan blades, turbine blades and other components.
Aero-engine is a highly complex and precise thermal machinery. As the heart of an airplane, it is not only the driving force for the flight of the airplane, but also an important driving force for the development of the aviation industry. Every important change in the history of human aviation is inseparable from the technical progress of aero-engine. This paper focuses on introducing the main component structures of aero-engine.
1. Compressor and fan blades
Cold end core components. During the working process of the engine, the blades are affected by centrifugal force, aerodynamic force generated by air and gas, thermal stress, alternating force and random load, which accounts for more than 3% of the whole engine manufacturing workload. Under the action of various loads, blades are prone to high cycle fatigue and thermal fatigue. In order to ensure the working quality and efficiency, the material selection and production technology of blades have extremely high requirements.
according to their positions and functions, engine blades can be divided into fan blades, compressor blades and turbine blades, in which fan blades and compressor blades are cold-end components and turbine blades are hot-end components.
compressor blades can be divided into compressor rotor blades (working blades) and compressor stator blades (rectifying blades), and turbine blades can be divided into turbine working blades and turbine guide blades. The fan blades preliminarily compress the air entering the engine, and the compressed air is divided into two paths, one of which enters the inner duct for further compression, and the other enters the outer duct for direct high-speed discharge to generate thrust.
the compressor blades further compress the air entering the inner duct, and the pressure and temperature of the air flow increase obviously to meet the requirements of the combustion chamber. Turbine blades have the effect of expansion and decompression, which can transform the chemical energy of gas into the mechanical energy of turbine.
The blades are made of aluminum alloy, stainless steel, titanium alloy, superalloy and composite blades. Fans and compressor blades are cold-end components, and their working temperature is relatively low. Generally, titanium alloy, high-temperature alloy and other materials are used. Among them, titanium alloy is widely used in the production of compressor blades because of its low specific gravity, high specific strength and corrosion resistance.
From the manufacturing technology, the compressor blade profile is thin and easy to deform. Precise control of its forming accuracy and efficient and high-quality machining are the core difficulties in the blade manufacturing process. Among all kinds of blades, compressor blade is one of the parts with the most complicated midsurface structure and the harshest working environment in aero-engine.
in order to reduce the dynamic loss of air flow, the most important characteristics of compressor blades compared with other blades are their complex profile twist and their own thin thickness. The complex twist of the profile is embodied in the different bending and twisting angles of the profile from the blade root to the blade tip. On the other hand, the thickness of the leading and trailing edges of the blade is only .1-.2mm, and the profile is required to be high.
2. Turbine blades
Hot-end parts. Turbine blades belong to the hot-end parts in aero-engines and need to work in high temperature and high pressure environment, which is the most difficult blade to manufacture in turbofan engines. The high-temperature and high-pressure gas expands in the turbine to drive the turbine to rotate at high speed to drive the compressor. The gas flow enters the tail nozzle through the turbine outlet, the pressure is reduced, the speed is increased, and finally it is discharged from the engine to generate power.
the structure and materials of turbine blades are constantly upgraded. In the mid-2th century, the second generation engine was mainly used, and the typical model was Spey MK22, which mainly used solid turbine blades. After that, more advanced hollow turbine blades were gradually used. The fifth generation engine F135 has adopted double-wall ultra-cold/cast-cold turbine blades.
turbine blades are generally made of high-temperature alloy or titanium-aluminum alloy, and the blade blanks with small allowance and high quality are made by precision casting. With the improvement of engine performance, high-pressure turbine blades have gradually developed into directional crystallization and single crystal material blades.
directional crystallization is a casting process in which molten alloy is crystallized and solidified in the direction opposite to the heat flow in investment casting shell. The turbine blades formed by this process have high thermal fatigue resistance and thermal shock resistance.
3. Other parts
1. Disc parts
mainly include turbine disc, compressor disc and integral bladed disc. Integral bladed disk structure is a new type of integrated disk structure developed on the basis of conventional disk separation structure, which has the advantages of weight reduction, degradation, efficiency improvement and reliability improvement. Titanium alloy and superalloy are generally used as materials.
Turbine disk and compressor disk are both rotor parts of aero-engine. Turbine disk is a part of aero-engine used to install and fix turbine blades to transmit power, and bears complex loads in high temperature, high pressure and high speed working environment.
2. Casing
The main load-bearing component on an aero-engine is the key component for bearing load and containing the engine, and it is a typical thin-walled structural part.
its main functions are: to protect the engine core machine and provide support for externally installed engine components such as fuel pump, lubricating oil pump, generator, gear box and pipelines; The stator and combustion chamber are mainly installed inside, which together with the rotor assembly form an air circulation channel.
casings can be classified into fan casings, bypass casings, intermediate casings, compressor casings, combustion chamber casings, etc. The casing materials are mostly titanium alloy and high temperature alloy, so it is necessary to control the high-precision form and position tolerance and thin-wall deformation during machining.