Abstract: A theoretical analytical method is presented to investigate the characteristics of the turbine with different mixtures of cooling air. The improved Ito’s loss model is used to calculate the flow loss caused by film cooling, and the flow loss generated by the coolant ejection at trailing is computed with the Schoberi’s loss model. Suppose that the flow losses are caused by different types independently and the total flow loss is the sum of their flow losses. The effects of different cooling air parameters and geometry parameters on the loss and performance for a high-pressure turbine are presented. The results show that the total pressure loss varies greatly with the coolant eject angle, the blow ratio and the thickness of mixing layer. It is supposed that the minimum flow loss is obtained by optimum design.

Key words: mixing layer, total pressure loss, film cooling, blow ratio