Discharge coefficients of the film cooling holes were investigated using a large-scale low speed turbine cascade.Discharge coefficients with coolant injection were determined at different density ratio

blowing ratio and Reynolds number.The results show that the influence of density ratio of secondary flow to mainstream flow on discharge coefficients of the film cooling holes is different at different hole array position.The effect of density ratio on suction surface and leading edge is more evident.The data of turbine blade surface film holes discharge coefficients obtained from experiments with small difference in temperature of the secondary and mainstream airflow should be corrected when it was attempted to apply to practice.