Research On Mist/Air Film Cooling Enhancement Techniques Of Plate

To improve the overall thermal efficiency, the inlet temperature and compressorpressure ratio are increasing for the next generation of gas turbine systems. The safeoperating range of the turbine blade materials improves slowly, so effective blade coolingtechnology is very important. Now the film cooling techniques are one of the most commoncooling structures. Change the cooling working fluid would significantly improve the coolingeffect. Although the application of steam cooling can improve the cooling efficiency, itrequires the external steam system. As a result, the study of the two-phase cooling whichcontains mist and air has a great significance. The principle of the water droplets and aircooling heat transfer enhancement is the latent heat of vaporization to absorb a lot of heat inthe process of water droplets to evaporate; and the heat capacity of the water vapor and waterdroplets is much higher than air. The research using based on tablet film cooling model, forits structure is simple and convenient to study various geometric parameters and aerodynamicparameters on the flow characteristics and heat transfer enhancement.This paper bases on the flat film cooling model. The physical mechanism on mist/air film coolingenhancement of converging slot hole film cooling and Cylindrical film cooling are investigated:1.Cylindrical film cooling model is studied, and analysis the relationship of vorticity andtemperature. Differences between the air film cooling and the mist/air film cooling. Thecooling enhancement influenced by different blowing ratio hair. Jet angle influent the coolingcharacteristics. The quality of humidifing influent the cooling enhancement.2. Improve thestructure of the film cooling, the character of converging slot hole film cooling is that filmcooling holes along the flow direction is gradually shrink and in the spanwise direction isoutward expansion and the entire channel cross-sectional area is gradually reduced. Thesegeometric characteristics make the jet flow from converging slot hole film cooling holesand the cylindrical film cooling holes having different characteristics. In a wide range ofblowing ratio, converging slot hole film cooling jet penetrating to mainstream can getsuppression. In spanwise direction, the film coverage is wider and the convective heattransfer capacity is high. Comparison of different geometric parameters (export slit width,aspect ratio and film hole angle) impact the film cooling characteristics great, especially in the big blowing ratio conditions.