Michiteru Yamaguchi

Effects of Tip Clearance of Nozzle Vanes on Performance of Radial Turbine Rotor

In radial turbines with variable nozzles, the flow downstream of the nozzles could be distorted by the leakage flow through the tip-clearance of the upstream nozzle vanes. To investigate the effects of flow distortion on the performance of turbine rotors, two rotors with different number of blades were tested for three types of distorted velocity distributions at the rotor inlet. In the case of the 20 blade rotor with moderate blade loading, the flow distortion at the rotor inlet had negligible effect on the rotor characteristics, and the measured data on the turbine performances agreed well with a prediction. Predictions were made with a conventional one-dimensional flow model applied to the rotor flow while a two-layer flow model was applied to the flow in the nozzle with clearance. In the case of the 10 blade rotor with heavy blade loading, however, the rotor performance was found to be sensitive to the inlet flow distortion and was considerably lower than the prediction.Copyright

Effects of inlet flow distribution on performance of radial turbine rotor. Comparison of a 10 blade rotor with a 20 blade rotor.

In radial turbines with variable nozzles, the downstream flow of the nozzles is distorted by the leakage flow through the tip-clearance of the upstream nozzle vanes. To investigate the effects of flow distortion on the performance of turbine rotors, two rotors with different numbers of blades were tested for three types of distorted velocity distributions at the rotor inlet. In the case of the 20 blade rotor with moderate blade loading, the flow distortion at the rotor inlet had negligible effect on the rotor characteristics, and the measured data on the turbine performances agreed well with the prediction. In the case of the 10 blade rotor with heavy blade loading, however, the rotor performance was found to be sensitive to the inlet flow distortion and was considerably lower than the prediction.