Cooling effectiveness and aerodynamic performance in a 2D-Contoured endwall passage with different mass flow ratios

Endwall 2D-contouring is a presently-employed design feature for reducing the strength of secondary flows within gas turbine passages. Such contouring can lead to significant changes of passage flow, making the flow field different from that of the widely-studied flat-endwall passage. Also, there is an interface, or leakage slot, on the endwall between the combustor and the turbine affecting the passage flow. Though introduced for eliminating ingression of passage gas into the cavity, leakage flow through it, which has bypassed the combustor, can be used to cool the endwall and vane surfaces. Moreover, this leakage flow interacts with the main flow resulting in a change of aerodynamic losses. In this study, a 3D RANS method using an SST gamma-theta transition model was employed to investigate endwall adiabatic cooling effectiveness values, eta , and passage total pressure loss coefficients, TPLC, in a nozzle guide vane passage with a 2D-contoured endwall. Cases of differing mass flow ratios, MFRS, for flow through the slot were evaluated and compared. The numerical method employed was validated by comparing its computed results with experimental data. The results show how cooling effectiveness, aerodynamic performance and vortex structures near the endwall are significantly affected by passage flows of various MFR values. An appropriate range of MFR was found for gaining high adiabatic cooling effectiveness values and low aerodynamic losses while avoiding hot gas ingression into the slot.