Vibration Analysis Of A Three Screw Pump Unit

With the rapid development of the marine industry, the low-noise ship is the future trend.Since various types of mechanical and electrical equipments are the main vibration source of ships, it is of crucial significance to perform the investigation on the control of vibration and noise of mechanical and electrical equipments. In this thesis a certain type of three screw pump unit was studied, which was a typical type of mechanical and electrical equipments.The vibration characteristic of the three screw pump was analyzed from vibration source and transfer path.The vibration source of the three screw pump was calculated at first. The equations of spatial curved surfaces of screw rotors were developed by using vector algebraic, then the dynamic force on the rotors was calculated by surface integration. The contact model of rotors was contracted in the ADAMS software based on multi-body dynamics theory and Hertz theory. And the contact force during meshing process was calculated. Then how the assembly clearance of rotors influenced the contact force below 100Hz was concluded. The force calculating result was verified by the response error. After constructed the FE model of the screw pump unit, the vibration responses caused by the fluid force and the contact force were predicted, and the similarity of the calculating response and the testing response verified the correctly of the force.Then the vibration transfer path of the pump was analyzed. The internal force of the screw pump was equivalent to a concentrated load near the bearing, and the testing points participated in load identification were chosen by the average condition number. Then the load identification was done through singular value decomposition method, with testing responses input. The result of load identification was verified by response error. After analyzing the vibration response, it was found that the main vibration source of the screw pump was caused by its working characteristic. And the main vibration was caused by resonance. The vibration was reduced by improving the transfer path, and the future work direction that to improve the vibration source was given.