Abstract
Turbine blade fracture, resulting from high-cycle fatigue (HCF), is the most commonly observed failure mode of turbochargers. In a vaneless turbine, the radial turbine blade is susceptible to HCF under excessive aerodynamic excitation due to the flow field distortion caused by the volute tongue. The present study explores a technique to mitigate blade excitation by reducing pressure disturbance in the volute tongue area. The gas with higher pressure in the inlet section of the volute is transferred to the low-static pressure area upstream of the volute tongue through a throat jet hole. The usage of high-pressure gas improved the homogeneity of the flow field near the volute tongue. The study investigates the mitigation of high-pressure gas jet on turbine blade excitation, the impact of jet hole geometry on the suppression effect of the blade vibration, and the effect of high-pressure jet on turbine performance using numerical simulation of unsteady flow fields. The results indicate that the jet flow has a substantial impact on dampening the blade vibrations. The harmonic pressure amplitude at the monitor point located within the high blade vibration amplitude region is reduced by up to 56%. Generalized pressure analysis reveals that the aerodynamic excitation of the turbine blades is significantly reduced. Experimental evidence verifies the effectiveness of the jet hole scheme in reducing blade vibration. Moreover, the jet hole has a negligible effect on turbine efficiency. However, there is a degree of increased stress in the volute tongue with a jet hole which needs to be evaluated in engineering applications.
