Investigation Of The Influence Of Density Ratios On Film Cooling On Turbine Blade Surface

Experimental investigation to film hole discharge coefficients, heat transfer coefficients and film cooling effectiveness on turbine blade surface were carried out by using large scale low speed wind tunnel in Northwestern Poly-technical University. The influences of mainstream Reynolds number, blowing ratio and density ratio were researched. The geometry of turbine blade is provided by Gas Turbine Establishment of China.A three-blade liner cascade was used in the experiment. There were two test blades, One blade with smooth surface is used for measuring surface static pressure, and another blade with 6 rows cylindrical film cooling holes on the surface is used for measuring film hole discharge coefficients, heat transfer coefficients and film cooling effectiveness.Firstly, the pressure coefficients and the velocity ratios distribution on the turbine blade surface were measured in cases of Reynolds number changed from 100000 to 450000. The influence of mainstream Reynolds numbers on the pressure coefficients and the velocity ratios were described.Secondly, the film holes discharge coefficients were obtained in the condition of Re_∞ = 100,000 ~ 450,000, BR = 0.5 ~ 2.0 , DR = 1.0,1.52 . The influences of Reynolds numbers, blowing ratios and Density ratios and Momentum ratios on discharge coefficients were investigated. The results show that the Momentum ratios are the main influence factor to the discharge coefficients of film holes.Lastly, the local heat transfer coefficients and the film cooling effectiveness at different locations on blade surface were detailed measured in cases of mainstream Reynolds number changing from 20000 to 400000 and blowing ratio changing from 0.5 to 2.0 by using air and carbon dioxide as the secondary flow. The influence of Reynolds numbers and blowing ratios and density ratios on local heat transfer coefficients and the film cooling effectiveness on blade surface were investigated.The results show that the data of turbine blade surface film holes Discharge coefficients and local heat transfer coefficients and the film cooling effectiveness were measured at low difference in temperature with air as secondary and mainstream fluid should be corrected when it beapplied into the practice.