The Cooling Effect of Combustor Exit Louver Scheme on a Transonic Nozzle Guide Vane Endwall

The ever-increasing combustor exit temperature in modern turbine engine designs raises challenges for the nozzle guide vane cooling. Due to the challenges of NGV cooling design, the cooling effect from the combustor cooling features can prove valuable. This study investigates, experimentally and numerically, the cooling effect of a louver cooling scheme near the combustor exit on the NGV endwall. The wind tunnel testing and CFD simulation are carried out with engine-representative conditions of Maexit = 0.85, Reexit = 1.5 × 106, Tu = 16%, and DR = 2.1. Various coolant mass flow rates from 1% to 4% are tested to demonstrate the effect of the coolant rate. For the geometry studied, the results found a critical MFR between 1%∼2%. By exceeding this value, the coolant forms a uniform film which provides good coverage upstream of the NGV passage inlet. As for the cooling of the NGV passage, the MFR of the range investigated is not sufficient for desirable cooling performance. The pressure side endwall proves most difficult for the coolant to reach. In addition, the fishmouth cavity at the combustor-NGV passage causes a three-dimensional cavity vortex that transports the coolant in the pitch-wise direction. The coolant transport pattern is dependent on the coolant MFR. Based on the results, it is proposed to combine this louver scheme with the upstream jump cooling scheme for a desirable NGV cooling system.