Study on influence of admissions on loss generation in a twin-entry nozzleless radial turbine

Abstract

Twin-entry radial turbine has an evident advantage of enhancing the output power in internal combustion engine, while it is confronted by complex inlet conditions because of the interval flow feeding into two limbs. Although the performance of twin-entry turbine is notably influenced by admission conditions, detailed flow mechanism is yet fully revealed in previous researches. This paper investigates the mechanism of the influence by different admissions on a nozzleless twin-entry turbine via experimentally validated numerical methods. Turbine performance is studied under different admission conditions and the results demonstrate that twin-entry turbine performance is notably different between two partial admission conditions, although the volute passage is symmetrically divided. Rotor decomposition methods are employed for the analysis of loss distributions to understand this performance difference. Flow separation and tornado vortex generated near the rotor inlet is confirmed as the key source for the flow loss in the rotor. The off-design incidence angle near the hub rather than the shroud is the reason for the vortex initiation in the twin-entry turbine. Moreover, the volute flow features demonstrate that volute leakage flow is the reason for the lower incidence angle near the blocked limb. Consequently, the mechanism of the asymmetric performance of the symmetric twin-entry turbine under partial admission conditions is revealed.