Study On Vibration And Underwater Acoustic Radiation Of Propeller-shaft-hull Coupled System Under Control Of The Longitudinal Vibration Of Shafting

In order to effectively control the vibration and acoustic radiation of the hull,especially for the low frequency part of vibration,the transmission and coupled effects of vibration energy of propeller-shaft-hull coupled system must be considered.The longitudinal vibration of the propulsion shafting is one of the most important channels of the acoustic radiation of the hull,so the most direct and effective way to reduce the acoustic radiation of the hull is to reduce the longitudinal vibration of the shafting to the hull.Some achievements have been made about the effect of the longitudinal vibration of shafting on the vibration and acoustic radiation of the hull,so this thesis establishes the finite element model of propeller-shafting-hull coupled system,and analyzes its vibration and transmission characteristic.On this basis,control the vibration of propeller-shafting-hull coupled system by means of passive dynamic absorbers,active electromagnetic actuators and active-passive combined,and verify the inhibitory effect of longitudinal vibration controller on the longitudinal vibration of shafting by experiments,which is very important to improve the stealth performance of the submarine.Chapter 1 mainly introduces the research background and significance of this thesis,and then systematically reviews domestic and international research results from three aspects,namely,research status of propulsion shafting,structure vibration and acoustic radiation and vibration control.Chapter 2 establishes propeller-shafting subsystem,and carries on modal analysis so as to obtain natural vibration characteristics and typical modes of the propeller-shaft subsystem.Then couple propeller-shafting subsystem with hull to form the finite element model of propeller-shafting-hull coupled system.Study on natural vibration and transmission characteristics of propeller-shafting-hull coupled system induced by the propeller’s oscillatory forces transferred from the propulsion shafting to hull.Chapter 3 indicates that the most direct way to reduce acoustic radiation of hull is to reduce the longitudinal vibration of propulsion shafting to hull.On this basis,control the vibration of propeller-shafting-hull coupled system by means of passive dynamic absorbers,active electromagnetic actuators and active-passive combined.For the passive,a feasible way is to install dynamic vibration absorbers.Design parameters of dynamic vibration absorbers according to the optimal coherent and optimal damping conditions and then install it on propeller-shafting-hull coupled system to control specific frequencies of the propulsion shafting,namely,the first order longitudinal resonant frequency and the second order longitudinal resonance frequency to reduce the longitudinal vibration of the hull effectively.For the active,install electromagnetic actuators to control the vibration.As electromagnetic coefficient of the existing electromagnetic actuator is small,heat and magnetic leakage is large and activation force is small and so on.Design a new symmetric electromagnetic actuator and conduct the magnetic analysis.Then install it on propeller-shafting-hull coupled system in two different ways of active damping to control the low frequency part of the longitudinal vibration.For the active-passive combined,the dynamic vibration absorber is combined with active vibration isolator,which can effectively reduce the amplitude of the low frequency part.Then install it on propeller-shafting-hull coupled system,and find it is better than active control by comparing acceleration response characteristics of the thrust bearing pedestal.Chapter 4 carries on research on vibration and acoustic field of the coupled system.Structural vibration and acoustic field characteristics are closely related,on the one hand,structural vibration will form acoustic field in the fluid,on the other hand,acoustic field will react to structure vibration in turn,which makes acoustic field characteristics very complex.Study on the infinite fluid acoustic radiation characteristics through coupled system.Chapter 5 carries on research on vibration characteristics of bearing pedestal,frequency response of longitudinal vibration controller and inhibitory effect of longitudinal vibration controller on the longitudinal vibration of shafting by experiments,which provide references for vibration control.Obtain the longitudinal vibration and frequency response characteristics of bearing pedestal in rotation condition of shafting through vibration characteristics test of shafting,and evaluate the effect of longitudinal vibration controller on characteristics of the base;Obtain the external characteristics of the controller,namely,output force and harmonic suppression ratio;Obtain inhibitory effect of the longitudinal vibration controller on the longitudinal vibration of shafting by experiments so as to evaluate vibration control performance of the controller and algorithm.Chapter 6 summarizes conclusions of this thesis,the innovation and problems for further study are presented as well.