| It is of great significance to improve the acoustic stealth performance of submarine to improve its combat ability.The vibration of the pipeline system composed of many pumps,valves and pipes has become one of the main sources of radiation noise of submarine in quiet sailing conditions.Fluid-induced vibration is one of the difficulties in vibration analysis of pipeline system.The multi-factor coupling mechanism of complex fluid-induced vibration is not clear,and there is no unified analysis method for fluid-induced vibration of pipeline system.Therefore,it is urgent to establish an accurate,efficient and feasible method for fluid-induced vibration analysis of pipeline system.In the past,piping systems were usually designed with low vibration and noise for a single flow-through component under constant conditions,and the dynamic coupling effect of multiple flow-through components under transient conditions such as pump start-stop and valve on-off was ignored,which resulted in the instability of selfexcited oscillation in off-working conditions.In order to solve this problem,this paper takes the circulating water pipeline system composed of centrifugal pump and ball valve as the research object,and carries out the multi-source,multi-field and multi-dimensional coupling modeling calculation method of pipeline system.The fluid-induced vibration characteristics of pipeline system under transient conditions were explored,and the coupling mechanism of fluidinduced multi-factors was revealed,which provided theoretical basis and technical support for low vibration and noise design and stable operation of pipeline system.The main research work of this paper is as follows:Aiming at the problem of unclear multi-field coupling mechanism caused by internal rotorstator interference in centrifugal pump under constant working condition,the fluid-induced vibration characteristics of a certain type of centrifugal pump under constant working condition were analyzed.The unsteady flow characteristics in centrifugal pump were studied based on computational fluid dynamics(CFD)method.The whole flow field numerical model of centrifugal pump was established,and the pulsating pressure characteristics in centrifugal pump were analyzed.On this basis,the way of flow excitation transfer to the pump body was analyzed,and the excitation characteristics of blades in the impeller-shaft-support transfer path were studied in depth.The dynamic model and boundary conditions of centrifugal pump were further modified by vibration characteristics test.Finally,based on the structural finite element method considering the rotor dynamics,the fluid-induced vibration characteristics of the whole centrifugal pump including the rotor system were analyzed.Aiming at the problem that it is difficult to accurately predict the fluid-induced vibration caused by internal transient flow during centrifugal pump starting,the calculation method of fluid-induced vibration under centrifugal pump starting condition is studied.The load extraction strategy of unidirectional decomposition and coupling is adopted to calculate and analyze the fluid-induced vibration of centrifugal pump under starting condition by using finite volume method and time-domain finite element method based on dynamic mesh method.The applicability of the dynamic grid method to deal with the transient flow caused by boundary motion is discussed.A multi-field coupled fluid-induced vibration model of centrifugal pump was established under the condition of sharp boundary change at start-up.A method based on regional dynamic slip coupling to calculate the flow induced vibration of centrifugal pump is proposed.The problem of accurate capture of fluid excitation load under transient conditions is solved.The accurate prediction and analysis of transient characteristics of fluid-induced vibration under transient conditions are realized.Aiming at the problem that it is difficult to accurately predict the transient flow-induced vibration of pipeline in the instantaneous opening and closing process of ball valve,the flowinduced vibration characteristics of ball valve under constant working condition and the calculation method of flow-induced vibration during closing process were studied.The internal flow characteristics of ball valve under constant opening were analyzed based on computational fluid dynamics method,and the influence of valve opening and flow rate on the flow field characteristics of ball valve was explored.Furthermore,the pulsating pressure on the ball valve core and inner surface is applied to the structure model to analyze the dynamic characteristics.Finally,the calculation method of flow-induced vibration in the pipeline during valve closing process was studied.The flow characteristics in the pipeline during valve closing process were calculated based on the sliding mesh method,and the flow-induced vibration phenomenon caused by pressure fluctuation in the pipeline caused by valve closing process was analyzed by using the time-domain finite element method.Aiming at the difficulty of system-level flow-induced vibration calculation for complex pipeline system,a multi-source multi-field multi-dimensional flow-induced vibration calculation method for complex pipeline system was studied.In view of the complexity and systematicness of the pipeline system,the one-dimensional and three-dimensional coupled flow field calculation scheme was determined,and the coupling algorithm and coupling principle suitable for the pipeline system were explored according to the flow characteristics of the centrifugal pump and the pipeline.A multi-source,multi-dimensional and multi-field coupled fluid-induced vibration model of pipeline system was established,and a calculation method of fluid-induced vibration of pipeline system level based on one-dimensional and threedimensional coupling was proposed,which solved the problems of uncontrollable calculation amount and insufficient correlation of pipeline system components,and realized the global systematic analysis of fluid-induced vibration of pipeline system.Aiming at the unclear mechanism of flow induced vibration in pipeline system under transient conditions,the characteristics of flow induced vibration in pipeline system under transient conditions were studied.The calculation model of transient operating condition of pipeline system is established.The transient characteristics of valve closing process of single pump circulation pipeline system,single pump start-up process and single pump shutdown process of parallel pumping system are studied successively.The dynamic coupling effect between the components of the pipeline system under variable operating conditions is explored,and the fluid-induced vibration mechanism of the pipeline system under transient conditions is revealed,which provides theoretical support and technical support for the design of low vibration and noise and stable operation of the pipeline system. |
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