Optical Measurements For Flow Field Of Transonic Gasturbine Linear Cascade

In practical engineering applications,linear cascade wind tunnel experiment is still a significant method to obtain aerodynamic performance of the blade to modify its profile.One can obtain pressure data of flow field and meanwhile capture typical instantaneous flow structures,which mainly depend on traditional pressure measuring methods and optical measurements developing continuously.This article mainly aimed at linear cascade consist of transonic high-pressure gasturbine stator blades,apart from pressure measurements on wall surfaces and cascade exits,background oriented schlieren and particle image velocimetry were also used to measure the density and velocity fields respectively to realize instantaneous non-contact quantitative measurements of aerodynamic parameters.Firstly,numerical simulation combined with experiment were used to verify the improvement of tailboard for periodicity of cascade flow field.This article studied on the effect of tailboard with different void ratios,pitch angles and slot widths on periodicity of flow field in detail,meanwhile ensured the optimal combination of these parameters via orthogonal experiment of numerical results and confirmed it by experiment.The results show that the periodicity of cascade flow field could be improved apparently with a tailboard of appropriate parameters,the optimal parameters for the cascade referred in this article were s=50%?a=70°?w=2mm.Secondly,quantitative measurements of density field of cascade flow field were conducted on transonic linear cascade wind tunnel by background oriented schlieren,then density vector distribution was used to reconstruct density field by line integration and Poisson equation respectively.Besides density values were extracted on special positions to make a direct comparison between reconstruction results obtained by different reconstructing methods.The results show that background oriented schlieren was feasible to obtain density field of transonic cascade flow field,typical flow structures such as wakes and trailing edge shocks were captured successfully,furthermore the experimental and numerical results agreed well with each other.Finally,quantitative measurements of velocity field of cascade flow field were conducted on transonic linear cascade wind tunnel by particle image velocimetry,then experimental results were processed and compared with numerical results,besides detailed analysis on typical flow structures were conducted.The results show that particle image velocimetry was feasible to obtain velocity field of transonic cascade flow field,furthermore the experimental and numerical results agreed well with each other.