Study On The Acoustic Simulation System Of Marine Engine Exhaust Silencers

In order to achieve the purpose of rapid design and optimization for silencers,the traditional transfer matrix method,which can calculate quickly,and the meshless method,which can be pretreatment simpler are chose for related research.According to the acoustic–electric analogy,in this paper,we begin with the analysis of the basic anechoic units and their acoustic characteristics.Then,the acoustic design and optimization system for marine engine exhaust silencers is completed,which is based on the one–dimensional transfer matrix method and the series or parallel relations characteristics between the basic acoustic units.The overall mentality,the platform of simulation system running environment,the design of interface,the simulation system framework and functional module is introduced in detail.Meshless method,springing up in this decennium,is introduced to the numerical simulation of acoustic cavity.Some familiar treatments for boundary conditions in the numerical simulation of meshless method are expounded.The characteristics of direct match point type meshless method and Hermite type meshless method are analyzed.An acoustic numerical simulation example is studied to analyze the treatments of boundary conditions containing derivative boundary.The factors inflecting the calculation precision of acoustic meshless method is deeply analyzed,including wave number,type of boundary condition,type of distribution points,number of distribution points and the magnitude of shape parameter.By comparing with analytical solution or referential solution,the affection principles of these factors are analyzed.As some of these affection principles is still in a lack of rigorous mathematical theory to deduce,the analysis of the acoustic instance summary is particularly important,which leads a sound foundation for the meshless method to better apply to acoustic design and numerical calculation.For the familiar acoustic dispersion problem,often appearancing in acoustic numerical simulation,the reproducing kernel hierarchical partition of unity method is introduced.By combining with the weak variational principle of numerical calculation and applying the reproducing kernel hierarchical partition of unity method with different number order,theacoustic dispersion problem is improved.To examine the treatment effect of meshless method for acoustic impedance boundary,multiple acoustic impedance boundary are defined in a L acoustic cavity,compared with the referential solution,excellent capacity of numerical calculation of meshless method is proved.By setting the inlet as pressure boundary condition,the outlet as the boundary condition with no sound reflection,other boundary as absolute hard boundary,the meshless method is applied to silencer's acoustic numerical calculation.In this calculation case,a certain extent accurate result is achieved with less number of nodes.Through comparing with finite element method with nodes of high density and experiment,the correctness of the meshless method numerical calculation expanding d to the3–dimension muffler acoustic meshless method is verified.Meshless method can obtain accordance solutions with finite element method(fem)and experiment results,which needing too much number of nodes.And compared with the experimental method,the result in high frequency is obviously better than finite element method's solution.In addition,the meshless method need not cells information requiring in finite element method in the prophase.The meshless method can complete the silencer acoustic numerical calculation just requiring for the domain nodes spreading in the solving region.It offers a possibility to improve the design efficiency and reduce the consumption of computing resources.The development of the meshless method is just beginning.