Investigation On Pre-twist Zigzag Shroud Of Turbine Blade For Aero-engine

Turbine blades, as the critical parts of aero-engine, often work in the bad environment with high speed, high temperature and high pressure. In order to improve the turbine efficiency and enhance the blade stiffness and vibration damping effectiveness, the pre-twist zigzag shroud was usually designed and applied into the advanced turbine blade with high aspect ratio. The pre-twist zigzag shroud has series of structure design parameters, and the selection of these parameters have a directly influence on the safety of aero-engine and even aircraft. Therefore, this paper will mainly focus on the following several studies:(1). The basic methods for designing the structure of the pre-twist zigzag shroud and the basic theory for analyzing the strength and vibration were described with including the basic principle of finite element analysis, general process and displacement principle. In addition, the contact analysis theory of the pre-twist zigzag shroud were introduced with including two sorts of friction force model and coulomb friction model and the hysteretic spring friction model and getting the formula for solving the equivalent stiffness and the equivalent damping.(2). The theoretical analysis of the tightness of the shrouds reached a significant conclusion that the preliminary assembly tightness of the shrouds would became bigger when the pre-twist angle increase. For a finite element model with three blades, the contact analysis of the pre-twist zigzag shroud was done to study the influence of the pre-twist angle and the deflection angle on the contact and the structural strength of the pre-twist zigzag shroud.(3). The first10natural frequency and modes of the turbine blade with the pre-twist shroud were given through the modes analysis at a speed of0rpm, taking into the influence of the centrifugal force at different speed on the natural frequency of blade consideration. Also, based on the harmonic balance method, the nonlinear vibration response analysis is conducted by using the hysteretic spring friction model. The element MATRIX27is also applied to simulate the equivalent stiffness and damping, and to carry on the dynamic response analysis.(4). The parametric3D model of the pre-twist zigzag shroud was established by means of the second development of UG software, which takes the main structure characteristic parameters of the pre-twist zigzag shroud into consideration. The parametric model provides convenience for further design analysis and parameter adjustment of the shroud structure.