Multi-loaded operation is always a feature of marine equipment. Experiments were done on marine centrifugal pumps to study the influence of the shifting-load. Variation of parameters related to rotation speed and flow rate was analyzed. Results of experiments confirmed the empirical formula of the rotation speed against vibration. It was concluded that the vibration level of the centrifugal pump is proportional to the forth to ninth power of the rotation speed. Changing of flow rate has a greater influence on low and high frequency vibration than that on intermediate frequency vibration. The influence even becomes much larger at the characteristic frequency of blades of the centrifugal pump. The general conclusion is that when low flow rate operation condition is required, the rotation speed of the pump should be lowered to reduce the operation noise instead of adjusting the valve of the pump.

Abstract : Transfer path analysis (TPA) is an effective method for structure vibration performance optimization, evaluation and fault diagnosis. The basic theory and characteristic of TPA method is mainly described in the paper. The experiment system is established for TPA method to verify the TPA method. Comparison of simulation calculation value with experiment value shows that simulation result and experiment result are basically consistent. TPA method is used in four improved structures separately and reasonable structure is confirmed. The analytical results showed that the TPA method is a good way to find the vibration transmission path which provides the evidences to control the vibration transmission effectively.

Different component parts of equipment have different vibration causes, so the methods of their vibration source identifications are also different. Based on the measurement data and the signal processing, some methods of vibration source identification, including time-domain analysis, frequency domain analysis, self-correlation, cross-correlation, envelope analysis etc., of rotational machinery and their engineering applications were studied. This work provides a help for handling different methods of vibration source identification.

Based on modal control method, the vibration modes in an object test are directly controlled. The aim of the experiment is to reduce the vibration of the base of the object. The experiment result shows that the modal vibration shape can be controlled using this method, and the bases vibration can be reduced.

Using the statistical energy analyzing method (SEA), a model for analyzing the marine floating raft isolation system is established. The vibration isolating effect of the raft isolation system is measured and analyzed by means of the Vibration Level Difference method. Comparing experiment result with theoretically estimated value is civen out. It shows that this method can meet general need of engineering design.

The paper intends to analyze quantitatively the correlation between the NASTRAN finite element (FE) model and a testing model for a middle raft frame of a floatingraft isolation system. The first five vibration modes of the raft frame are estimated by finite element method (FEM) and measured by testing. The modal assurance criterion (MAC) matrix is established in LMS virtual lab for relativity analysis between the FE model and the testing model. The MAC estimated by LMS virtual lab shows that the modal computed by FEM is basically correct and the method can be used for dynamic esponse analysis of the structure.