The Multi-channel Power Flow Characteristics Testing Analysis Of Typical Floating Raft Isolation System

In the floating raft isolation system of the ship,on the one hand,the vibration energy of the equipment is transmitted to the hull base through the floating raft and vibration isolator of the supporting channel,and on the other hand,it is also transmitted to the hull through the connecting pipeline and pipeline supports and hangers of the non-supporting channel.With the adoption of various active and passive control methods to effectively control the vibration transmitted from the supporting channel to the hull,the problem of vibration transmitted through the non-supporting pipeline channel becomes prominent.Therefore,it is necessary to carry out relevant research work on the energy transmission and distribution characteristics of the floating raft isolation system including the non-supporting pipeline channel.First,the power flow characteristics of a typical multi-channel floating raft isolation system are numerically calculated and studied.Based on the finite element method,the modeling method and power flow calculation method of floating raft isolation system with non-supporting pipeline channels are given.The finite element model of floating raft isolation system of the test bed is established by ANSYS software.The dynamic stiffness and damping parameters of vibration isolator and flexible pipe varying with frequency are obtained by using the parameters of impedance test.The vibration response and dynamic force of the floating raft isolation system are obtained by harmonic response analysis,and the power flow of the supporting channel and nonsupporting pipeline channels are calculated and analyzed.The modeling and calculation methods proposed in this chapter can provide reference for the study of vibration power flow of complex vibration isolation systems,and the simulation analysis results can be compared with the power flow test results in the following chapters of this paper to verify the reliability of the modeling and calculation methods and test results.Then,the power flow testing approaches of a typical multi-channel floating raft isolation system is studied.Each isolator of floating raft isolation system is simplified as a four-terminal parameter system,and the principles of direct measurement method and indirect measurement method are introduced to test the power flow at the supporting channel and non-supporting pipeline channel of floating raft isolation system respectively.The comparison results between the power flow obtained by direct and indirect methods show the accuracy of the indirect method and the feasibility of replacing the direct method in engineering.The power flow calculation results based on finite element method in chapter 2 are compared with the power flow measurement results by indirect method,which further shows the reliability of measuring vibration power flow by indirect method,and also verifies the rationality of the power flow numerical calculation method for floating raft isolation system proposed in this paper.Next,the power flow transmission and distribution characteristics of a typical multi-channel floating raft isolation system are studied.The typical vibration transmission path of floating raft isolation system is analyzed,and then the power flow transmission and distribution characteristics tests are carried out under hammer excitation and pump operation.The main energy transfer paths and distribution characteristics of floating raft isolation system in this test bed are identified by analyzing the power flow of different transfer paths.The power flow of different transmission paths is calculated by finite element simulation and compared with the power flow distribution result obtained by hammering method.Finally,the power flow testing of floating raft isolation system with different installing process parameters is analyzed.The typical installing process parameters of floating raft isolation system in the stage of berth building are summarized,including the bolt tightening torque of vibration isolator,the parallelism,roughness and thickness of the mounting plate of the base vibration isolator,etc.Based on the principle of measuring power flow by indirect method,the influences of the installing process parameters on the vibrational power flow of floating raft isolation system are analyzed through series of tests.The results show that the bolt tightening torque has little influence on the power flow when the bolts of the vibration isolators are not loose.And the power flow will increase obviously when the bolts of the vibration isolators are fully loose.The changes of parallelism and roughness of the mounting plate of the base vibration isolator within the given parameters have little influence on the power flow.However,the power flow will increase with the reduction of the thickness of the mounting plate.The power flow calculation method of multi-channel floating raft isolation system and the power flow test method based on indirect method proposed in this paper have good engineering feasibility and reliability,which can provide support for the design optimization of floating raft isolation system in engineering and the measurement of power flow characteristics of floating raft isolation system with non-supporting channels.The research conclusion on the influence of process parameters on power flow can also provide reference for low noise installation of floating raft isolation system.