Research On Dynamic Modeling And Vibration Noise Characteristics Of Submarine-stern Shaft

Submarines are known as ocean ghosts,because their stealth performance is often able to attack in the war and achieve unintended effects.The stealth performance of the submarine is closely related to the acoustic radiation which is generated by the vibration of the hull.The submarine’s own radiated noise also directly affects the concealment of the submarine.Therefore,improving the submarine’s ability requires improving its ability to reduce vibration and noise.With the advancement of technology,submarines have greatly improved in terms of design methods and stealth performance.Countries have also actively adapted to the developmental need of submarines and vigorously developed submarine-related science and technology.In this paper,the vibration and acoustic radiation characteristics of submarine models with five-bladed propellers,boring shafts,bearings and hulls are studied from the perspective of simulation and experiment.The dynamics of the whole system under different excitation forces are discussed.The main research contents include:Firstly,the submarine-stern system is modeled by the dynamic equilibrium equation.The effects of the lateral excitation force and the vertical excitation force generated by the propeller in the actual work are considered.The dynamics of the Newmark-β method is used to solve the equilibrium equation,and the solved data is processed by Matlab software.The vibration response of the node at the propeller in the submarine-stern shaft system is analyzed by means of spectrogram,three-dimensional waterfall,axis trajectory and Poincare section.The response of the submarine-shaft system at different speeds is analyzed.It is found that the lateral excitation force can cause more complex frequency components than the vertical excitation force.The frequency components of the blade frequency doubling and the blade leaf frequency in the spectrogram are mainly caused by the lateral excitation force.Secondly,in order to analyze the acoustic characteristics of the submarine-stern shaft system,the acoustic model of the submarine-shaft system is established.The modeling process is as follows:(1)The finite element model of the submarine-stern shaft is established in ANSYS.The stern shaft and the hull are connected by a spring unit,and the specific modeling parameters of the propeller,shaft and submarine shell are given and the model is modally analyzed.(2)Apply lateral excitation and vertical excitation at the propeller to solve the node vibration velocity.(3)Import the node vibration velocity as a boundary condition into the acoustic software virtual.lab,and import the mesh model into the software.(4)The surface mesh of the whole model is extracted by acoustic software and,and the acoustic response of the system is solved by the acoustic boundary element method.The sound of the lateral excitation force and the vertical excitation force on the submarine-shaft system is obtained.Finally,in order to verify the accuracy of dynamics and acoustic simulation,a submarine-spindle vibration and noise test bench was built by simplifying the design of the submarine-stern shaft.The experiment starts from two directions of dynamics and acoustics.In the dynamic experiment,the vibration response data measured in the experiment is compared with the simulation results of the dynamics.The results show that both the experiment and the simulation have good similarity.The three main frequency components of blade fundamental frequency,blade frequency doubling and blade leaf frequency are characterized,which explains the correctness of the simulation to some extent.The acoustic pressure level curve measured by the experiment is compared with the simulation result by performing an acoustic test on the submarine-shaft test bench.Considering the influence of machining error,assembly error,deformation of welding parts and background noise,there is a certain error between the experimental results and the simulation results.However,the overall trend of the curves in the experiment is similar to the simulation,and the frequency at the peak of the experiment is similar to the simulation.The experimental results verify the accuracy of the simulation model.