59147 - Forced Response Excitation of a Compressor Stator Owing to Shock Wave Induced by Adjacent Rotor Blade 

Accurate prediction of High Cycle Fatigue (HCF) is becoming one of the key technologies in the design process of state-of-art axial compressors these days. If they are not properly designed, both rotor blades and stator vanes can be damaged. There are two main factors to cause HCF. One is Low Engine Order (LEO) and the other is High Engine Order (HEO) excitation fluid force associated with adjacent rotor-stator interaction. Concerning the front stages of axial compressors for power generations and aero engines, inlet mach number of rotor tip typically exceed the speed of sound and strong shock waves tend to be induced. This can be the source of HEO excitation fluid force and adjacent stator vanes sometimes are damaged severely. Thus, the aim of this study is to establish an efficient method to predict the vibration response of this kind of problem with high accuracy. To achieve this, numerical investigations are carried out by means of 1-way Fluid Structure Interaction (FSI) simulation. To validate the accuracy of FSI simulation, measurement tests are also conducted using a gas turbine engine for power generation. In the experiment, vibration level is measured utilizing strain gauges mounted on the surface of stator vanes and the data are compared with the predicted results

In the first part of the study, efficient prediction methods of excitation fluid force on the stator vane is investigated using Time Transformation (TT) and Harmonic Balance (HB) methods. The accuracy of them is validated by comparing the results with those calculated by direct Transient Rotor Stator (TRS) simulation. It is found that TT method can accurately predict the excitation fluid force with lower computation load even when there are pitch differences between rotor and stator regions.

In the second part of the study, forced response analyses are carried out by mapping the excitation fluid force obtained in the unsteady flow simulation. To obtain total damping, both hammering test and flutter simulations are carried out. Computed results are validated with experimental data and it is found that predicted vibration level is in good agreement with experimental results.

Through this study, an effectiveness of 1-way FSI simulation is confirmed for this kind of forced response prediction. By utilizing the combination of efficient unsteady CFD methods and harmonic response analysis, vibration amplitude can be predicted accurately and efficiently.