| In the study of gas turbine compressor flow field,it is necessary to use plane cascade test to verify the theoretical research of blade design and performance improvement.Cascade test can obtain the pneumatic performance of blade shape at different intake angles and incoming Mach numbers,and accumulate database,which is of great significance to improve the overall performance of turbine and compressor.Therefore,it is very important to obtain the detailed information of the flow field in the plane cascade.Optical testing technology is an effective means to obtain flow field information.In this paper,according to the requirements of cascade test,the design of planar cascade test-bed,the fluency test based on laser Doppler velocimeter(LDV),the flow field test based on light field particle image velocimeter(LF-PIV)and the comparative analysis of flow field simulation and test data are completed.The main research results of this paper are as follows:The main contents are as follows: 1)according to the research demand of non-contact optical testing technology of flow field,a plane cascade test-bed is built;the fan selection,stable section and shrinkage section,plane cascade test section are designed,and the test-bed is built and debugged;combined with the specific structure of the test-bed,the technical scheme of flow field test with LDV and LF-PIV is designed,and the layout scheme of visual window is modified and installed.2)under the conditions of 0 °angle of attack and 10 °angle of attack,the flow field of plane cascade with Mach number of 0.047 is measured by LDV technique for 50%,70% and 90%blade height positions.The two-dimensional velocity and turbulence information of each measuring point are obtained,and the distribution law of the average velocity field in the wall boundary layer and cascade channel is analyzed.In the process of research,the influence of laser incident angle and optical window thickness on the offset of measuring point is determined by means of theoretical analysis and experimental verification,and the correction calculation program of optical path distortion is compiled.The influence of tracer particle size on following time and lag distance is studied,and the influence of tracer particle size and outlet pressure of tracer particle generator on the test results is analyzed.The results show that the single point flow field information and boundary layer velocity gradient of cascade channel can be effectively obtained by using LDV,and the time-averaged velocity field of cascade can be obtained by scanning analysis.3)according to the demand of three-dimensional measurement of plane cascade flow field,the LF-PIV measurement technology based on single camera is carried out,and the test results of cascade flow field with the center of focusing plane are 90% H,80% H and 70% H,respectively.By comparing with the LDV measurement results,it is found that the overall trend of the time-averaged flow field obtained by the two methods is the same,and the measurement error of the typical measurement surface is less than 5%.The research shows that the LF-PIV measurement technology can use a single camera to obtain the spatial three-dimensional velocity information of the cascade flow field,and the combination of LDV and LDV can realize the same field calibration of the test accuracy,which is an effective means to measure the cascade flow field.4)according to the test condition,CFX is used to simulate the cascade flow field,and the LDV test results are used to modify the boundary conditions of the simulation entrance.The modified numerical simulation results are highly consistent with the test results,which shows that the flow field test technology based on optical diagnosis and the test results have a good supporting effect on the model verification of numerical simulation and the improvement of calculation accuracy. |
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