| Since 1960 s, military ships’ power systems have started to put gas turbines into use. Gas turbines are gradually used in various power generation assemblies because of high economical efficiency. Gas turbines also take most part in power systems of aviation field. Key technologies of design, process and manufacture and detection of gas turbines are monopolized by western developed countries for the long time. Our country started to do research about gas turbines much more later and has a weak technology fundation.In gas turbines’ power systems, the compressor precompresses air and increases air total pressure(stagnation pressure) before air getting into the turbine and expanding to work. Thus, air and fuel are well mixed and burned to become high temperaure and high pressure gas.The compressor requires to be small-sized, light-weighted, big pressure ratio and high efficiency, which means that compressor has to have smaller windward area and fewer stages. Besides, under these requirements, shock waves easily appear in the impeller cascade passages. What’s more, airflow usually has flow separation in the position of the back of blades. From the above, compressor blades work in a harsh environment and are difficult to design. Compressor blades are core function components. To ensure compressor work with safety and high efficiency, it is pretty necessary to ensure the working ability of key components such as compressor blades.In the thesis, firstly, compressor third stage rotor blade was studied. A model based on that blade was set up based on beam elements. According to the 3D model of the blade, the shape of the blade was obtained. Parameters of the blade profiles such as area, core, inertia moment and main inertia axis as well as section modulus were calculated. Blade torsion was also taken into account based on displacement method and stress method in theory of elastic mechanics. Balance equations, geometric equations, physics equations and boudary conditons were established, too.Secondly, elasticity modulus, shearing modulus of elasticity, density, fitted value and blade height were chosen to be the variables. Each time, a variable were changed 100 times and blade strength were calculated. Centrifugal forces, centrifugal moments, aerodynamic forces and aerodynamic moments of each section were calculated to get inlet, outlet and back of blade total stresses along the blade height. Based on the energy method, single blade A0 vibration frequence were obtained. According to Alembert principle, the calculation of frequences were translated into the calculation of eigenvalues. By using beam elements to calculate blade vibration, the first six dynamic frequences were obtained. Fatigue ultimate strength of blade material were obtained after the calculation of frequences.Then, blade’s strength, vibration and fatigue reliabilities were calculated based on Monte-Carlo method. Compared with stress-strength interference method results. Monte-Carlo method used in this example were easily shown to be benificial in some way.Last, commercial finite element software was applied to calculate the blade with cracks. The results included crack propagation stress and crack propagation analysis. Blade breakage reliabilty analysis were carried out finally. |
