Vibration Reliability Analysis of Turbine Blade Based on Response Surface Method

Abstract

Many stochastic parameters have an effect on the reliability of a steam turbine blade during practical operation. To improve the dynamic strength reliability design of blade, it is necessary to take these stochastic parameters into account. In this paper, a variable-section torsion blade is investigated and a new method which is the combination of finite element method (FEM), response surface method (RSM) and Monte Carlo simulation method (MCS) is put forward to solve the vibration reliability analysis in the case of geometrical parameters, material parameters, installation parameters and rotation speed are considered as input random variables while the dynamic frequencies are output random variables. Based on the finite element parametrical model of torsion blade and reasonable experiment design, analysis file of the blade is complied by deterministic finite element method and applied to be loop life to create sample points. A quadratic polynomial with cross terms is chosen to fitting these samples by step-forward regression method and employed as a surrogate of numerical solver to drastically reduce the number of solvers call. Then Monte Carlo method is used to obtain the statistical characteristics and cumulative distribution function of dynamic frequencies. Aiming to the blade's dangerous mode of vibration, performance function is created and the vibration reliability analysis is carried out. Moreover, the proposed method (FEM-RSM-MCS) in this paper is compared with the Latin Hypercube samples Mont Carlo simulation method (LH-MCS) which is acted as relative precision method. The comparison result show that FEM-RSMMCS is an optional approach for the dynamic strength reliability analysis of the blade as it has less and fast calculations and high regression accuracy.