Development And Research On Middle-High Frequency Modal Characteristics Test System Of Axial-Flow Rotor Blade

For the traditional hammering method of modal test method,its incentive way is impact excitation,attenuation signal of blade vibration response is used,so there are some shortcomings of low energy and Frequency leakage phenomenon as well as low accuracy and recognization at middle and high frequency in hammering method because decay signals generated by impact excitation are used in this approach.In order to test out the modal characteristics of blade at middle and high frequency accurately and effectively,a testing system that aiming at measuring the modal characteristic of blade is developed basing on Lab View and time-domain resonance method,by which Determination of each order of natural frequencies of the rotor blades is realized,Modal damping ratio at any natural frequency as well as vibration mode is recognized and the estimated value of the proportional damping coefficient ??? is also given.In this paper,we derive the identification method of natural frequency and modal damping ratio and the ratio of damping coefficient.Identification of modal parameters for a test system in a modal analysis diagram generated after processing the response signal.The filtering principle of various digital filters is introduced,and the feasibility of the method of data processing in the system is verified through the comparative study of the effect of various kinds of filters.And the construction of the experimental platform for the modal characteristics of the axial flow rotor blades are described in detail.The test system can be used to complete the acquisition of vibration signals,which shows that the analysis of time domain and frequency domain,and the identification of modal characteristics of blade can be used in a series of functions.The main functions of the test software of the axial flow blade modal characteristics are that,(1)The function of the manual mode test.The manual adjustment function generator sends out the excitation signal,which causes the blade to generate the synchronous response,and the natural frequency of the blade is found through the resonance search.(2)The automatic modal testing function.The blade was automatic frequency scanning test disposable blade modal characteristics;(3)The modal test results of data storage and playback function to generate a report.The test software can be used to complete the acquisition of vibration signals,which shows that the analysis of time domain and frequency domain,and the identification of modal characteristics of blade can be used in a series of functions.Test platform is set up,and the test system is used to test the modal characteristics of a certain type of axial flow compressor.Through comparing the test results with each other and their comparative analysis the accuracy and reliability of the test system can be verified.The comparison results show that the measurement range of the test system is large and the precision is high.It can overcome the shortcomings of the traditional hammering method,which has good stability and accuracy.And the test system has a good human-computer interaction interface,the test process is more automated,its modal information is more abundant.