Research On Heat Transfer Characteristics And Discharge Coefficient Of Impingement/effusion Cooling System

The experimental investigations on heat transfer characteristics and discharge coefficient of impingement/effusion cooling are conducted to reveal the features of this cooling configuration. There are two types of hole arrangements both in impingement wall and effusion wall, such as aligned rows and staggered rows. The effusion walls are made of copper or bakelite board, and the angles of effusion holes include 35°and 90°. In experiment, the infrared camera is used to measure the temperature distribution of the effusion wall surface, and the non-dimensional formulas for film cooling effectiveness and complex cooling effectiveness are obtained, which are better fit to the experimental results.The results of experiment show that:(1) For 35°holes, the film cooling effectiveness of impingement/effusion cooling changes slightly with the increase of blowing ratios, and for 90°holes, in the foreside of the holes, the effectiveness also changes slightly, but in the rearward, the effectiveness increases with the increase of blowing ratios.(2) For the same blowing ratios, both the film cooling effectiveness and the complex cooling effectiveness of impingement/effusion cooling are increased with the increase of the distance between adjacent holes. Besides, the effusion cooling effectiveness also follows this rule.(3) For 35°holes, the film cooling effectiveness of impingement/effusion cooling is decreased with the increase of the distance between impingement wall and effusion wall, while for 90°holes, the effectiveness changes lightly. Besides, the complex cooling effectiveness of impingement/effusion cooling is higher in the case of higher blowing ratios and lower distance between impingement wall and effusion or lower distance and higher blowing ratios.(4) All the cooling effectiveness of 35°effusion holes is higher that that of 90°effusion holes.(5) For both the effusion cooling and impingement/effusion cooling, the Nu number goes up with the increase of the blowing ratios.(6) The discharge coefficients of impingement/effusion wall or effusion wall alone are increased with the increase of the coolant flow Reynolds number. (7) The discharge coefficient of impingement/effusion wall goes up with the increase of the distance between adjacent holes, which is higher in the case of staggered rows than that of aligned rows.