Study on the Interaction of Clearance Flow and Shock Wave in a Turbine Nozzle

Paper #:
  • 2017-01-1039

Published:
  • 2017-03-28
Abstract:
Radial flow Variable Nozzle Turbine (VNT) enables better matching between the turbocharger and engine, and can improve the engine performance as well as decrease the engine emissions, especially when the engine works at low-end operation points. With the increased nozzle loading, stronger shock wave and clearance leakage flow are generated and consequently introduces stronger rotor-stator interaction between turbine nozzle and impeller, which is also the key factor of the impeller high cycle fatigue or failure. In present paper, flow visualization experiment is carried out on a linear turbine nozzle. The turbine nozzle is designed to have single-sided clearance and the Schlieren visualization method is used to describe the formation and developing process of clearance leakage flow and shock wave under different t clearance and expansion ratio configurations. Numerical simulations are also performed to investigate the flow structure and the interaction behavior between shock wave and clearance flow in details. Results indicate that for the investigated turbine nozzle, the flow region influences by the clearance leakage flow reaches up to 20% span and the shock wave is squeezed and bent in the opposite direction of meanflow in the interaction region. In the location close to the endwall, the shock wave is truncated by the clearance leakage flow and mixed downstream-wise with a distorted shock wave structure. Results also show that with the increase of clearance size, the shock wave structure near the endwall is further distorted while the shock wave intensity near midspan is increased. In addition, under the disturbance of the shock wave, the clearance leakage vortex is weakened when it transports downstream the shock wave.
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