Vibration Modal Analysis And Experimental Study Of Impeller Blades

Modal analysis an experimental and analytic technique to analyze the dynamic performance of machines, establish the dynamic models and optimize the parameters. It's very powerful in the research fields of space and aviation,now, in the vibration performance research of turbine parts it's also very useful.Modal analysis is a very effective method for the study of vibration characteristic of impeller blade. Natural frequencies and vibration mode can be obtained by modal analysis. If we make the working speed of impeller far away from the resonance speed, the severe fatigue damage because of external frequency can avoid. On the other hand, when the leaf structure failure, such as cracks, loose parts damage, etc., the structure of physical parameters will change, and the characteristic parameters, such as natural frequencies, modal damping, mode shapes, and frequency response function, coherence function will also change. We can judge the fault type by the changes in these parameters, and sometimes judge the fault location. For example, we can judge the emergence of crack by the change of natural frequencies, and we also can judge the location of the crack according to mode shapes.Based on the vibration theory of impeller blade, this paper analyzes the leaf structure, vibration mode and natural frequency in theory. It analyzes the vibration mode of an experimental impeller by ANSYS finite element software. This paper analyzes the vibration strain in a variety of speeds strain By ANSYS simulation and strain gauge measurement experiments. It lays a foundation for the system of monitoring the state of stress and strain of impeller and fault diagnosis. The detailed content of this paper shows as follows:(1) This paper introduces the structure of the impeller blade, analyzes the blade vibration modes and deduces the formula of natural frequency of impeller blades. According to vibration theory, the differential equation of motion of vibration of impeller blades has been established.(2) Using the ANSYS software of finite element, modal analysis of impeller blades is executed. The five steps natural frequency and vibration mode of impeller blades are obtained. The detailed analysis of vibration mode, deformation and Von Mises stress of impeller blades is presented. This paper analysis the resonance characteristics of impeller blades and figure out the resonance speed based on the five steps natural frequency form modal analysis.(3) The vibration strain of impeller blades at a variety of speeds has been researched by calculation of ANSYS software of finite element and experiment measurement of two position on the blades. Vibration response of the experimental results and finite element results has been compared.