Study On Dynamic Characteristics Of Squeeze Film Damper Based On Two Phase Flow Theory

Squeeze film damper(SFD)is a passive vibration damping device.Its main function is to reduce the resonance amplitude and the external force of the rotor when passing through the critical speed.Considering the simple structure and obvious vibration reduction effect,The SFD has been widely used in a series of engineering fields,such as aero-engine and marine gas turbine.The focus of research on SFD is to study the dynamic characteristics of it.The early theoretical researches on the dynamic characteristic coefficient of SFD is mostly devoted to solving the distribution law of oil film pressure in Reynolds equation,and then to identify the dynamic characteristic coefficient of SFD.But this method has a narrow application scope and low accuracy.Based on the CFD two-phase flow theory,a numerical study is carried out for the actual structure of a squeeze film damper in a dynamic characteristic test.The main contents are as follows:Firstly,the physical model is established according to the actual structure of the squeeze film damper tester.Based on the Mixture model and the Z-G-B cavitation model,the motion trajectory of the grid boundary is preset by the built-in UDF of the FLUENT software,and the three-dimensional unsteady flow field model of the squeeze film damper is established by using the dynamic grid technique.The oil film force at every moment of the squeeze film damper is obtained by FLUENT software,and the dynamic characteristics of the SFD oil film force are studied using time domain and frequency domain method.Then,taking the test results as reference,the damping coefficient of the squeezed oil film damper is identified by the short bearing assumption recognition method based on Reynolds equation,the same amplitude frequency method based on CFD technology and the positive and negative circular precession excitation method,and the difference in the recognition results is analyzed.The results show that for the direct damping coefficient Cxx and Cyy,the error of the recognition results of short bearings is large.While for the cross damping coefficient Cxy and Cyx,the recognition results of the positive and negative circular precession excitation method are not accurate enough.The identification of the damping coefficient of SFD with the same amplitude frequency method is less than the test result,and it is more reliable.Finally,on this basis,the physical model of the squeeze film damper with different lubricating oil viscosity,oil inlet pressure and radius gap is established,and the influence of the above parameters on the oil film force characteristics and damping coefficient of the squeeze film damper is compared and analyzed.The results show that reducing the radius gap and increasing the dynamic viscosity of the lubricating oil can effectively improve the film force and damping coefficient of the SFD extrusion oil,and the oil pressure has little effect on the performance of the damper.