Numerical Investigations into the Origin of Tip Unsteadiness in a Transonic Compressor

Three-dimensional numerical simulations are conducted to investigate the origin of flow unsteadiness and its associated unsteady flow phenomena in a transonic compressor rotor. The predicted results are compared with the available experimental data and a good agreement is achieved. The numerical monitoring results and further analyses of the flow field indicate that flow unsteadiness is detected in the passage with the operating condition approaching the stability limit, and the highest oscillating region is at the leading edge of the blade pressure surface; the tip leakage vortex breakdown is not a decisive factor for the flow unsteadiness, and the shock oscillation is a unsteady flow phenomenon resulted from the vibration of the recirculation region; a U-type vortex emerges in the tip leakage vortex breakdown region, and its periodic impingement on the pressure surface of the adjacent blade is treated as a trigger that leads to the flow unsteadiness.

Keywords:

Transonic compressor rotor , Flow unsteadiness , Vortex breakdown , Shock wave oscillation