Vibration Analysis And Noise Control Of Piping System On The Ship

With the increasing demand for high navigational speed,high-power propulsion systems are widely used on ships.The application of high-power propulsion systems causes more and more vibration problems.Piping system is widely used on many different kinds of ships,the vibration of which affect the safety of the ship.The damage of pipes caused by vibration may lead to leak of oil and gas.The dynamics of pipes conveying fluid has an obvious difference from that of empty pipes,the vibration of which belongs to fluid-structure interaction.In this thesis,the dynamics of piping system on the ship is investigated,especially pipes conveying fluid,and blocked mass is used to reduce the vibration of pipes.Theoretical,numerical and experimental methods are used to investigate the dynamics of piping system in this thesis.At first,the full derivation of the equation governing the motion of a simply supported pipe conveying fluid without the damping is presented.And the equation is solved by using Galerkin's method after discretion.Then structure damping of pipes and viscosity of fluid are taken into consideration.Correction equations of natural frequency of pipes conveying fluid are derived.After that,fluid-structure interaction model is set up to simulate the vibration of pipes conveying fluid and empty pipes by using ANSYS software.The modal of pipes is calculated taking different fluid velocity and different structure damping into consideration.Modal identifications are based on strain gauge test carried out on both empty pipes and pipes conveying fluid.After the investigation of dynamics of pipes,blocked mass is used to reduce the vibration of pipes.Experimental results show that as the increase of incident wave frequency,the transmission loss increases.At last,the important noise source of piping system—the centrifugal fan is investigated.The volute tongue is modified and the noise of the centrifugal fan decreases.In this thesis,more accurate equations governing the motion of a simply supported pipe conveying fluid are presented.Blocked mass is used to reduce the vibration of pipes,and the transmission loss is investigated.The noise of a centrifugal fan decreases after its volute tongue improved.The results in this research would provide a reference for piping system design on the ship.