HEAT TRANSFER COEFFICIENTS OF FILM COOLING ON A ROTATING TURBINE BLADE MODEL: PART II.EFFECTS OF REYNOLDS NUMBER AND ROTATION NUMBER

摘要

An experimental study was conducted to investigate the heat transfer characteristics of film cooling on a rotating turbine blade model with a single cylindrical injection hole. As an important supplement to the study of Tao et al. [Z. Tao, Z.M. Zhao, S.T. Ding, GQ. Xu, B. Yang and H.W. Wu, Experimental investigation of film cooling on a rotating turbine blade model: Part I. Effect of blowing ratio on heat transfer coefficients], the effects of Reynolds number Re_D and rotation number Rt on local heat transfer coefficient distributions are presented in this paper. A steady-state thermochromic liquid crystal technique was employed to measure the temperature distribution of test surface on the blade model, and a telemetering data acquisition system was used to collect the signals from the rotating blade model by wireless approach. During the experiments, the Reynolds number based on the mainstream velocity and film hole diameter varies from 1841 to 4296, and the rotation number ranges from 0 to 0.0249. Both the air and CO_2 are used as coolant, yielding the averaged density ratio of DR=1.02 and 1.53, respectively. Experimental results show that the rotational effect has a significant influence on the heat transfer coefficient distributions. The profiles of h/h_0, which is the ratio of heat transfer coefficient with film cooling to that without film cooling, will deflect towards the high-radius locations due to the strong centrifugal effect as Rt increases, and the deflective tendency of h/h_0 is more apparent on the suction surface. The h/h_0 values augment with the incremental Re_D on the pressure surface, but decline firstly and then increase again on the suction surface. Furthermore, the averaged values of h/h_0 for CO_2 injection presents lower magnitudes as compared to the air injection.