The Research On Characteristics Of Vibration And Underwater Radiated Noise Of Shaft-stern Coupled System

Concealment is of great significance to warships. It has big inflence in both combateffectiveness and survivability. Genarally, there are three main sourses of noise: mechanicalnoise,propellpr noise and fluid noise.When warship is in low-speed, the mechanical noise couldhold over40percents of all noises. As a consequence,controling and reducing the mechanicalnoise is very important for ships’ quiet sail.In last few years, different kinds of controllingmethods of vibration are used and the vibration and radieted noise of engine and gear box havewent down.However,no efficient measure has ever been taken to control the vibration andradieted noise caused by shaft.Therefore the stern and shaft are modeled as a whole system andthe transmission path of the coupled model is analyzed,taking the coupling effect of ship hulland shaft system.After finding the main transmission path, the control measure based on it wouldbe proposed and verified.Main researches completed in this dissertation are as follows:1. A large amount of litrature on stern vibration,shaft vibration,stern-shaft coupled vibrationhas been reviewed.The background,significance,current state of research have been introduced,aswell as the main technical approches used in the dissertation.2. Based on FEA method, a shaft-stern coupled system is modeled.the natural frequence ofshaft system is computed, a dynamic test on shaft system is done, the vibration reponses ofcouples system are obtained by nastran.The transmission paths of the coupled model areinvestagted using power flow analysis.3. The functions of damper and stiffness in vibration control have been summerised andanalyzed. The inflence of changes of damper and stiffness has been investagted which are basedon coupled model and shaft system model.Optium proposes are given according to thecalculation.4. Based on FEA/BEA method,the characteristics of under water radieted noise arecalculated,which covering the pressure of surface, the presssue of field points and the radietedpower of noise.The coupled model with optimized parameter has been analyzed and evaluated.