双级膨胀腔消声器声学与阻力特性的CFD仿真分析

使用二维轴对称时域CFD法计算双级膨胀腔消声器在无流和有流条件下的声衰减性能,并与实测结果进行比较。由于时域方法在计算中可以考虑复杂气流流动和介质粘性的影响,因而可以比较准确地预测双级膨胀腔消声器的传递损失。基于定常流动模型,使用Fluent软件预测双级膨胀腔消声器的压力损失,CFD计算结果与实验测量结果吻合良好。     

汽车排气消声器性能分析及改进

针对某汽车排气消声器插入损失不达标的问题,利用GT-Power软件建立了发动机与进排气系统耦合的仿真模型,对排气消声器的声学性能和空气动力性能进行数值计算,分析了发动机转速1 000~2 500(r·min~(-1))范围内的插入损失和压力损失。根据分析结果,基于试验设计(Design of Experiment,DOE)方法,对消声器结构进行多工况、多参数、多目标优化。优化结果表明,改进后的消声器的插入损失有了明显提升,空气动力性能良好,其综合性能得到显著提升。     

排气消声器声学及阻力特性数值仿真研究

对某一轻型卡车所装配的消声器,利用声学软件SYSNOISE对消声器声学性能进行数值仿真计算;利用计算流体动力学软件FLUENT对消声器的阻力特性进行数值仿真计算。模拟结果清楚地反映了消声器内的流场和声场的情况,结果表明数值方法能准确的模拟排气消声器的性能。通过仿真模拟,综合考虑消声器内部的声学性能和空气动力性能,表明运用数值方法预测排气消声器的阻力及声学性能在工程中是有效的,为消声器的改进设计和优化设计提供了依据。     

基于CFD和声学有限元法的抗性消声器性能研究

空气动力学性能和声学性能是用来评价抗性消声器优劣的主要指标。针对管道消声中常用的抗性消声器,利用计算流体动力学(CFD)方法模拟三种不同结构抗性消声器内部流场的压强分布特性,获得抗性消声器的压力损失,并与半经验公式的计算结果进行对比,分析不同结构抗性消声器的空气动力学性能以及半经验公式法的适用性;利用声学有限元方法对三种结构抗性消声器的传递损失进行计算,定性地分析和验证三种抗性消声器的声学性能。研究结果可为抗性消声器的结构优化设计和综合性能的提高提供参考。     

汽车排气系统噪声数值仿真分析与结构优化

针对某型车排气尾管噪声过高问题,利用三维有限元方法对排气消声器声学性能进行分析;再应用计算流体动力学方法对消声器内部流场进行模拟计算,分析产生气流再生噪声的原因。根据分析结果对排气消声器结构进行优化。使用优化后的排气消声器进行整车排气尾管噪声测试,结果表明尾管噪声明显降低,达到设计目标值。     

混合膨胀腔消声器声学性能时域CFD分析

将三维时域CFD法应用于计算混合膨胀腔消声器声学性能。首先介绍了三维时域CFD法的计算原理与过程。接着使用该方法预测了混合膨胀腔消声器传递损失,时域法计算结果与实验测量结果、有限元法计算结果吻合良好。计算结果表明,流阻率对混合膨胀腔消声器消声性能有显著影响。     

内燃机排气消声器试验系统

针对消声器性能测试需在发动机或台架上进行,不方便且成本大的情况,研制一种内燃机排气消声器试验系统。首先阐述该系统的工作原理和系统各组成部分,对试验系统进行声学特性和振动特性分析,然后以分流气体对冲消声单元为对象,采用CFD方法对其计算5种不同入口速度下对应的出口速度,并与用本试验系统实测的数据进行对比验证。结果表明:试验系统的噪声源、气流源均可满足试验需求;试验系统隔声罩隔声效果明显;试验系统音箱隔声罩在噪声和气流同时开启的工况下z轴方向的振动最大,峰值为0.44 g,试验时不会引起试验台共振,也不会对试验设备造成明显的影响。CFD方法计算结果与实测结果基本一致,证明了试验系统设计的正确性,可以满足消声器的测试需求,而且该系统制作成本低、结构简单紧凑。     

正交实验法在消声器设计中的应用研究

将正交实验法用于消声器的设计，通过试验证明，应用该方法所设计的消声器具有良好的消声性能和空气动力性能。     

非均匀流条件下穿孔管消声器传递损失计算方法与特性分析

实际应用中的消声器通常具有比较复杂的内部结构,其内部流体速度分布不均匀,而且消声器内部的回流管路和穿孔元件使得消声器内部的流体流动更加复杂,其消声性能不可避免地受到流体流动的影响。为了计算非均匀流条件下穿孔管消声器的传递损失,应用计算流体力学(Computational Fluid Dynamics, CFD)软件FLUENT计算消声器内部的流场,然后将流体属性通过网格映射的方式转移到LMS Virtual Lab声学有限元模型中,并且选用不同的穿孔阻抗模型计算消声器的传递损失,计算结果与实验测量结果进行了比较。文章对消声器内部流场的流动特征也做了仔细地分析,并研究了气体流速对消声器传递损失的影响,随着气体流速的增加,消声器的传递损失会增大,共振峰的峰值会减小。     

燃气轮机进气系统性能仿真分析

进气系统噪声是燃气轮机主要噪声源之一。应用计算流体动力学和声学有限元法分别对燃气轮机进气空气滤清器和进气消声器的流动阻力和消声特性进行计算和分析。研究不同结构参数对进气系统空气动力性能和消声性能的影响,用于指导燃气轮机进气系统的优化设计。     

Uncertainty‐based robust aerodynamic optimization of rotor blades

The aerodynamic performance of a compressor is highly sensitive to uncertain working conditions. This paper presents an efficient robust aerodynamic optimization method on the basis of nondeterministic computational fluid dynamic (CFD) simulation and multi‐objective genetic algorithm (MOGA). A nonintrusive polynomial chaos method is used in conjunction with an existing well‐verified CFD module to quantify the uncertainty propagation in the flow field. This method is validated by comparing with a Monte Carlo method through full 3D CFD simulations on an axial compressor (National Aeronautics and Space Administration rotor 37). On the basis of the validation, the nondeterministic CFD is coupled with a surrogate‐based MOGA to search for the Pareto front. A practical engineering application is implemented to the robust aerodynamic optimization of rotor 37 under random outlet static pressure. Two curve angles and two sweep angles at tip and hub are used as design variables. Convergence analysis shows that the surrogate‐based MOGA can obtain the Pareto front properly. Significant improvements of both mean and variance of the efficiency are achieved by the robust optimization. The comparison of the robust optimization results with that of the initial design, and a deterministic optimization demonstrate that the proposed method can be applied to turbomachinery successfully. Copyright © 2012 John Wiley & Sons, Ltd.     

泡沫铝消声器的优化与仿真分析

基于多目标优化软件ISIGHT,运用多岛遗传算法对泡沫铝消声器进行优化设计。在不改变泡沫铝消声器整体结构的基础上,对消声器的进口管、出口管以及中间管的长度和直径尺寸进行修改,并分别在FLUENT和SYSNOISE中对优化前后的消声器进行仿真分析。结果表明：优化后的泡沫铝消声器的传声损失比优化前平均提高了5 dB左右,压力损失降低了11 %左右,优化后的泡沫铝消声器具有更好的声学性能和空气动力学性能。     

汽车排气消声器三维声场分析

采用三维有限元法对某车型排气消声器进行优化设计,根据传递导纳理论对消声器穿孔管和穿孔板进行处理,建立数值模型并进行三维声场仿真分析,获得主副消声器总成的传递损失;运用双负载四传声器法测试消声器传递损失,测试结果表明三维有限元法预测消声器声学性能有较高的精度,根据仿真结果和消声器设计原理,对主消声器进行优化,可提高排气系统声学性能,满足汽车噪声排放法规的要求。     

Aerodynamic Characteristics of Popcorn Ash Particles

Popcorn ash particles are fragments of sintered coal fly ash masses that resemble popcorn in low apparent density. They can travel with the flow in the furnace and settle on key places such as catalyst surfaces. Computational fluid dynamics (CFD) models are often used in the design process to prevent the carryover and settling of these particles on catalysts. Particle size, density, and drag coefficient are the most important aerodynamic parameters needed in CFD modeling of particle flow. The objective of this study was to experimentally determine particle size, shape, apparent density, and drag characteristics for popcorn ash particles from a coal-fired power plant. Particle size and shape were characterized by digital photography in three orthogonal directions and by computer image analysis. Particle apparent density was determined by volume and mass measurements. Particle terminal velocities in three directions were measured in water and each particle was also weighed in air and in water. The experimental data were analyzed and models were developed for equivalent sphere and equivalent ellipsoid with apparent density and drag coefficient distributions. The method developed in this study can be used to characterize the aerodynamic properties of popcorn-like particles.     

穿孔管串并联耦合消声结构研究

涡轮增压器进气管道的气动噪声严重影响着汽车的安全性和舒适度,由于穿孔管对中高频率宽频噪声具有良好的消声性能,因而得到广泛应用.该文设计一种模块化穿孔管串并联耦合的消声器结构,在分析消声器在常温无流与气固耦合状态下的模态频率与振型的基础上,研究气流流速对消声器模态频率和振型的影响规律以及消声器内部的气流再生噪声,气流的存...     

进气系统微穿孔管消声器设计与优化

针对某车型进气系统在高转速时的宽频带进气噪声问题,提出了一种多腔微穿孔管消声器结构。根据传递矩阵法,建立了有流条件下多腔微穿孔管消声器传递损失计算模型;针对研究车型进气口噪声的频谱特性,采用多种群遗传算法对多腔微穿孔管消声器的结构参数进行优化设计,通过阻抗管台架和实车测试验证了消声器消声效果。结果表明,优化的多腔微穿孔管消声器能够有效拓宽降噪频带,消声器传递损失预测结果与实验测试结果一致,验证了所提出的传递损失计算模型的准确性及优化算法的有效性;在实车进气系统中采用该微穿孔管消声器后,进气噪声在600~1800 Hz中高宽频段以及200~400 Hz低频段均有明显降低,证实了所提出的多腔微穿孔管消声器的实际宽频消声特性。     

CFD-based optimization of hovering rotors using radial basis functions for shape parameterization and mesh deformation

Aerodynamic shape optimization of a helicopter rotor in hover is presented, using compressible CFD as the aerodynamic model. An efficient domain element shape parameterization method is used as the surface control and deformation method, and is linked to a radial basis function global interpolation, to provide direct transfer of domain element movements into deformations of the design surface and the CFD volume mesh, and so both the geometry control and volume mesh deformation problems are solved simultaneously. This method is independent of mesh type (structured or unstructured) or size, and optimization independence from the flow solver is achieved by obtaining sensitivity information for an advanced parallel gradient-based algorithm by finite-difference, resulting in a flexible method of ‘wrap-around’ optimization. This paper presents results of the method applied to hovering rotors using local and global design parameters, allowing a large geometric design space. Results are presented for two transonic tip Mach numbers, with minimum torque as the objective, and strict constraints applied on thrust, internal volume and root moments. This is believed to be the first free form design optimization of a rotor blade using compressible CFD as the aerodynamic model, and large geometric deformations are demonstrated, resulting in significant torque reductions, with off-design performance also improved.     

Topology design of reactive mufflers for enhancing their acoustic attenuation performance and flow characteristics simultaneously

When seeking to enhance the acoustic attenuation performance of a reactive muffler, it is necessary to ensure that the flow resistance does not increase significantly. To date, there have been very few attempts to simultaneously optimize the transmission loss and pressure drop of a muffler. In this study, a multiobjective topology optimization problem is formulated to maximize the transmission loss at a target frequency and minimize the pressure drop simultaneously. The objective function in the formulation is given as the sum of weighted transmission loss and weighted pressure drop. The effect of the weighting factors on the optimal topologies of a muffler is investigated. Furthermore, the physical interpretation of partition layouts of optimized mufflers is discussed. The proposed muffler design method involving multiobjective topology optimization is compared with the previous muffler design method that involves single‐objective topology optimization to maximize only the transmission loss. The most important advantage of this study is shown by considering numerical results; the proposed muffler design method is applicable to nonconcentric expansion chamber mufflers, unlike the previous muffler design method. Copyright © 2012 John Wiley & Sons, Ltd.     

一体式排气净化消声器消声性能分析

为了达到船用柴油机排气净化和降噪的双重功能,对设计的一体式排气净化消声器,建立有限元模型,运用声场仿真分析软件Virtual Lab 对其消声特性进行分析,分别研究排气流速,温度,出口管反射,内插管及蜂窝载体对消声器消声性能的影响,得到了各个因素的影响机理,从而验证了一体式排气净化消声器设计的合理性。