Numerical analysis of blade flutter in low-pressure turbine

In this paper the flutter phenomenon in turbomachinary is introduced. The importance and characteristics of the flutter as a dynamic aeroelastic instability is presented. Conventional methods for the blade flutter test and different approaches in flutter analysis of blade are described. Among the existing analysis methods, one approach which only examines the stabilizing effect of fluid is used in order to analyze the flutter in this paper. Firstly, its equations are described and a criterion for the determination of the stability based on the analysis results is presented. According to the criterion the local and global stability can be concluded. Numerical analysis has been performed by ANSYS CFX. Mesh independence and two different turbulence models have been examined and results have been validated by test results. Numerical analysis has been carried out for two steady and unsteady states. In unsteady state the response of fluid to blade vibration in three modes has been calculated. In order to assess the total response two methods have been used and the results have been compared. Eventually local instability has been calculated and the results presented in figures which illustrate the contribution of adjacent blades in instability of specific blade. The evaluation of global instability for three modes has been presented and the obtained results are in excellent agreement with experiment.