Study of Secondary Cooling Effect on the Endwall Region With Various Trailing Edge Cutback Configurations

Designing the cooling schemes for the endwall region of 1st stage vanes is a challenging task due to the requirement of low NOx emissions and the presence of strong secondary flows. Considering the adequate use of coolant, the coolant injections from the trailing edge cutback not only cool the vane surface but also protect the downstream endwall region. This is called the secondary effect of cooling and is worth studying. In the present paper, distributions of cooling effectiveness on the endwall surface are measured using the PSP technique. Discrete slots are implemented near the airfoil trailing edge to provide the coolant with three compound angles (β = 15°, 30°, and 45°). Two positions of cutback slots are studied: trailing edge pressure side cutback (PC) and central cutback (CC). Experiments are conducted in a five-passage linear cascade in a suction-type wind tunnel with the inlet Reynolds number of 1 × 105 based on the axial chord length. Effects of mass flow ratio (MFR = 1%–4%) are also considered. Aerodynamic losses are obtained by solving the Reynolds-averaged Navier-Stokes equations to assess the interaction of coolant and mainstream. Results show that, with the increase of MFR, the cooling performance on the endwall surface is improved greatly. At a higher MFR, as the compound angle increases, the coolant coverage is expanded significantly and the high cooling effectiveness region gradually shrinks towards the trailing edge. In addition, the influence of cutback slot position behaves differently.