Experimental Study On Vibration Characteristics Of Axial Compressor Blade

The axial flow blade is the most important part in the structure of compressor,turbine,fan,etc.The vibration characteristics of the blade have always been a problem that researchers can't avoid.The finite element analysis or modal test is generally used in engineering to obtain the vibration characteristics of the blade.The modal test of the blade has always been an indispensable part of the R&D design process.In the modal test of the blade,carrying out the resonance method need to design a reliable vibration fixture to connect the vibration table and the blade.The design of the blade vibration fixture is related to the accuracy and reliability of the blade modal test result.Therefore,it must be carefully designed so that the vibration characteristics of the blade can be accurately characterized in the resonance test.In this paper,a short blade of aero-engine compressor is taken as the research object.Based on the electric vibration table,the special vibration fixture of the short blade is designed.According to the actual situation,different test methods are adopted,and finally more accurate results are obtained including natural frequency,vibration mode,and strain distribution.The main contents are as follows:(1)According to the relevant theory of the vibration fixture,the special fixture for the aero-engine compressor blade is designed,include determining the material and connection method of the vibration fixture,designing the structure and size of the vibration fixture by the structure and test requirements of the blade.Based on the Tosca optimization software,the topology of the vibration fixture model is optimized to improve the first-order natural frequency of the vibration fixture.The first-order natural frequency of the final vibrating fixture reached 7346.4 Hz,much higher than the experimental frequency(5000 Hz),and the fixture was used to measure the first four modes of the blade.(2)Based on the Abaqus,considering the influence of bolt preload and contact friction on the vibration characteristics of the assembly,static analysis and modal analysis were carried out on the assembly model of the vibration fixture and the blade.The analysis results show that the design of the vibration fixture can accurately test the various modes of the blade and provide the necessary guidance for subsequent experiments.(3)The vibration fixture and blade simplified model designed was manufactured,and based on the electric vibration test system,the modal test of the blade was carried out.In the test,the first three natural frequencies of the blade were accurately measured by the laser displacement sensor;the first four modes of the blade were measured by the sand method;the relative distribution of the strain of the blade under the resonance state was measured by the strain electric measurement method.Comparing the test results with the results of the finite element analysis,it can be concluded that the vibration fixture and test method can basically accurately test the modal frequency,vibration mode and strain distribution of the blade,which can provide a reference for the vibration characteristics batch test(static frequency)of the axial flow blade.