Session: 19-08 Turbine Design

Paper Number: 129628

129628 - Blade Excitation Alleviation of a Nozzleless Radial Turbine by Casing Treatment Based on Reduced Order Model 

High cycle fatigue (HCF) is the most common form of blade failure in nozzleless radial turbines. Current efforts on blade vibration reduction mainly focus on the optimization of geometries of turbine blade and volute, following guidelines of the reduction of excitation force or the enhancement of the strength. However, these methods usually have drawbacks of long time-consuming, performance sacrifice and poor universality. This paper investigates a novel flow control method for blade vibration reduction via a reduced order model which is established on the mechanism of blade excitation. Firstly, the mechanism of the blade excitation is studied by the numerical method validated by the experimental measurement. It is confirmed that the blade excitation is triggered by different mechanism at low pressure ratios from that at high pressure ratios. Specifically, the excitation at 4^th excitation order is mainly influenced by the tongue wake propagation at low-pressure ratio while by the potential field of the volute at high-pressure ratio. An equivalent excitation pressure is proposed to evaluate the vibration behaviors of the turbine blade. Based on the mechanism, a reduced order model is developed to predict the equivalent excitation pressure at high-pressure ratio. The model is then validated at different pressure-ratios. Based on the reduced order model and excitation mechanism, the method of blade vibration alleviation with external excitation is proposed to offset the equivalent excitation pressure of the tongue. Finally, the casing treatment with slots is designed to attenuate the blade vibration based on the reduced order model. The experimental results show that the displacement of the vibration is reduce by 48% by this new method.

Presenting Author: Mingyan Yang Shanghai Jiao Tong University

Presenting Author Biography: Associate professor In MechEng School, Shanghai Jiao Tong University. Major in aerodynamics of radial turbomachinery, SCO2 turbomachinery and waste heat recovery.

Authors:

Mingyan Yang Shanghai Jiao Tong University
Zhaokai Lu Shanghai Jiao Tong University
Wataru Sato IHI co. Ltd
Teppei Kuwata IHI Co. Ltd