Abstract
One of the new cooling concepts of turbine nozzle and blade endwall for next generation 1700℃ class industrial gas turbines is an impingement cooling technology in a closed cavity. As the turbine inlet temperature increases the turbine aerodynamic load becomes high and the secondary flow generated by pressure difference between pressure side and suction side of a vane becomes strong. Thereby, passage vortex glows strong and rolls up the film cooling air blowing through the endwall to cool the endwall. An impingement cooling is used to attain higher heat transfer coefficient on stagnation region and to control the heat transfer coefficient and film cooling air blowing ratio. Especially, not to penetrate the film cooling air into the passage vortex, film cooling air must remain in the boundary layer under the passage vortex. New concept of impingement cooling in a closed cavity will solve these problems. In this paper heat transfer coefficients of impingement cooling in closed cavities were studied by using naphthalene sublimation method.
