Vortex interactions and loss mechanisms in the tip region of axial turbine rotors with cutback squealer tip

The vortex interactions in the rotor tip region and the resulting loss significantly reduce energy utilization efficiency of gas turbines. The vortex interactions and loss generation mechanisms in the tip region, under the effects of suction side cutback rim, are investigated numerically in this paper. The results show that a large notch could cause intruding gas to disrupt the scraping vortex, increasing the internal gap loss. More importantly, the rim notch causes a dramatic increase in leakage near the notch, leading to the formation of the leading-edge tip leakage vortex (LTLV). The interaction between the LTLV and the upper passage vortex (UPV) causes significant local loss and leads to the rapid dissipation of the UPV. This is beneficial for suppressing the interaction and mixing losses between the UPV and the tip leakage vortex (TLV) downstream. These two opposing effects mean that there may be an optimal rim notch configuration where the strength of the LTLV is just right to balance these two types of losses, potentially improving turbine aerodynamic performance. The effect mechanisms of the LTLV on the TLV and the UPV could provide guidance for flow control technologies based on the introduction of novel vortices.