Blade Vibration Analysis for Radial Turbine Featuring a Multi-Channel Casing Design

Multi-channel casing (MC) shows promising results in controlling the performance of the radial turbines. It has neither movable parts nor complicated control mechanisms therefore it withstands higher thermal loads compared to the commonly used control systems such as the Variable Geometry Turbine (VGT). This advantage makes the MC applicable for a wider range of applications which is difficult to be covered with the common control systems. Replacing the traditional spiral casing with the MC affects the blade's vibration behavior. First, a 3D unsteady computational fluid dynamic (CFD) simulation is performed to investigate the influence of using MC on the turbine flow field for both full and partial admission operation. Second, a forced response analysis is performed based on the CFD result to calculate the blade vibration amplitude at different resonance crossings. Finally, an MC is manufactured and tested experimentally to validate the numerical study. The results show that ignoring the casing replacement effect on the blade vibration during the MC design phase led to a high vibration amplitude and consequently causes high cycle fatigue.