Inter-row traveling shock in a transonic turbine

Stator vanes especially vane suction sides of transonic turbines are subjected to high frequency excitation forces under many circumstances, and thus are exposed to the risk of high cycle fatigue. Therefore, it is necessary to reveal the flow mechanism of this kind of excitations for potential prevention measures. In this paper, the traveling shock phenomenon in the transonic turbine stator/rotor gap is observed and the concept of ‘Inter-Row Traveling Shock (IRTS)’ is proposed through the unsteady Reynolds-Averaged Navier–Stokes (RANS) simulation of a typical highly-loaded transonic turbine stage. The characteristics of an IRTS were described and summarized in aspects of unsteady shock wave system, aerodynamic characteristics and motion. The probable forming mechanism of an IRTS was explained through a theoretical model and it was validated through correct prediction of the flow state parameter change across the IRTS. Since IRTSs would strike onto vane suction sides, the pressure oscillation dynamic modes on vane suction side corresponding to the characteristic frequencies associated with IRTS were extracted through Dynamic Mode Decomposition (DMD), from which the way and extent of the IRTS influences on vane aerodynamic excitation were revealed and evaluated. Over 82% pressure oscillation energy on vane suction side could be brought by the IRTS sweeping along with blade rotation.