Using contoured endwalls to achieve proper scaling for a gas turbine vane model using a low speed testing facility
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The testing of gas turbine vane and blade models is often performed in low speed, large scale infinite cascade facilities to allow for more precise machining of parts and more accurately measured data. However, flow in engine scale turbines reaches well into the compressible gas range while low speed facilities run in the incompressible fluid range, and engines have three dimensional flow effects due to having contoured endwall while traditional cascade testing has not accounted for three dimensional effects. This means that matching pressure distributions cannot be achieved between engine scale and experimental scale through simple geometric scaling of the model. In the past, these differences in pressure distributions were often overcome by changing the geometry of the test model. An alternate to this is to use contoured enwalls inside the test facility to allow the decreased area to correct for the differences in pressure distributions. In this work, the concept of using contoured endwalls in the test facility to achieve a matching pressure distribution on a vane was tested. Three dimensional computation fluid dynamics (CFD) simulations were used to find the correct geometry for the contoured endwalls. The proposed endwalls and vanes were then built and tested in a low speed simulated infinite cascade testing facility. The pressure distribution was measured at low turbulence levels and Re = 1.1×10⁶. It was shown that the pressure distribution in the test model with contoured endwalls did match within uncertainty the pressure distribution predicted for the engine scale using CFD. Thus, contoured endwalls can be said to be a viable option to force the matching of pressure distribution of a model test vane to that of engine conditions. Additionally, a vane model with a constant heat flux surface was tested at the same conditions, and the heat transfer coefficient distribution for the vane was determined. It was shown that the endwalls had minimal effects on the spanwise uniformity of the heat transfer coefficient distribution.