高速动车组气动噪声试验与仿真分析

通过风洞试验对某高速动车组整车、受电弓及转向架远场气动噪声特性进行分析.试验结果表明,高速动车组远场气动噪声是一宽频噪声,总声能随速度的6.6次方增加;由受电弓引起的远场气动噪声主要集中在中高频,噪声峰值频率随速度变化线性增加;由转向架引起的远场气动噪声主要集中在中低频,噪声峰值频率与速度无关.在此基础上,通过大涡模拟...     

汽车涡轮增压器同步谐波噪声仿真与优化

针对增压发动机急加速急减速时产生的增压器同步谐波噪声问题,该文通过噪声仿真技术进行分析与优化.首先,分析该噪声的特征与传播路径;其次,建立流场仿真模型.利用剪切应力输运湍流模型与分离涡流模拟湍流模型对增压器进行稳态与非稳态瞬态流场分析,提取非稳态流场的叶轮与压气机流道表面的偶极子声源;最后,建立噪声传播模型,计算该增压...     

快速随机粒子网格法的气动噪声预测方法

耦合随机湍流速度生成模型与线化欧拉方程技术,形成了一套具备模拟噪声在非均匀流场中传播能力的气动噪声混合预测方法。该混合方法的随机湍流速度生成模型采用了快速随机粒子网格法,为声传播模拟提供了可靠的源项。而噪声的传播计算选用线化欧拉方程,其空间离散采用9点5阶的色散保持关系格式,时间推进选用了高精度大时间步长的6级4阶龙格库塔格式,远场边界应用了无分裂形式的理想匹配层边界条件。首先,选用高斯脉冲传播算例对线化欧拉方程的时空离散格式、远场无反射边界条件进行了验证分析。然后,计算分析各向同性湍流的空间相关性验证湍流速度生成模型的可靠性。最后,基于已搭建的气动噪声混合预测方法进行了30P30N三段翼缝翼噪声的计算分析。计算分析可知:监测点处功率谱密度曲线、噪声指向性等计算结果与参考文献结果取得了较好的一致性。数值计算结果表明所建立的气动噪声混合预测方法能有效预测二维复杂构型的气动噪声问题。     

开式轴流风扇气动噪声预测

本文采用LES/FW-H的匹配方法,研究了开式轴流风扇内部旋涡流动特征及其与叶片表面干涉引起的气动噪声之间的联系,同时进行了远场噪声预测,探讨了叶轮不同表面辐射噪声时的频谱分布特征.研究结果表明,开式轴流风扇吸力面附近形成的叶尖涡和前缘分离涡在吸力面叶片表面相应位置形成大压力波动,形成主要噪声源;叶片吸力面的辐射噪声可以通过改善吸力面附近的旋涡流动来降低;低速轴流叶轮由叶轮壁面辐射的噪声以宽频成分为主.     

轴流通风机气动噪声的实验与预测

１引言轴流风机的气动噪声基本可分为紊流噪声及离散噪声。在中、低压头范围,尤其是单转子风机情况下,离散噪声经过管道声阻抗的衰减作用,在远离风机声场中可降到很低水平,此时紊流噪声成为主要成分。紊流噪声可有多种声源［１］,包括来流攻角引起升力变动相应的紊流噪声,叶片表面紊流边界层直接幅射的素流噪声,边界层分离的噪声,及叶片尾涡引起升力变化诱发的噪声。这些噪声都具有宽频带的特性。在来流无冲击进口,无边界层分离的正常运行条件下,从边界层中小尺寸旋涡直接幅射的声能是不大的。对有限叶片弦长,因叶片两表面大尺寸…     

基于涡声理论的低速轴流风机气动噪声研究

采用PIV和CFD对不同安装角低速轴流风机流场进行对比研究,结合低速等熵流动的涡声理论分析风机内部流场与噪声辐射关联,在此基础上计算风机气动噪声.研究表明,低速等熵流动的气动噪声主要源于流场中涡系的拉伸与破裂.均匀进气情况下低速轴流风机的主要气动噪声源为叶片尾缘涡脱落噪声和叶尖涡噪声,其中前者强度明显大于后者.在此基础上,应用基于CFD的涡脱落噪声预测模型对风机气动噪声预测结果与实验吻合较好.     

环境风对高速列车气动噪声特性的影响分析

气动噪声随着列车运行速度的提高急剧增加,是高速列车噪声的重要组成部分。本文使用缩比为1:20的三车编组模型,通过三维瞬态延迟分离涡模型求解高速列车的外流场,分析了环境风对流场结构与声源特性的影响;之后使用FW-H方程进行噪声传播计算,分析了不同速度的环境风对高速列车气动声学行为特性的影响。结果表明：高速列车主要的噪声源分布在转向架附近,在环境风的影响下,列车背风侧声源强度高于迎风侧,列车底部声源强度增幅较大。10 m/s以内的环境风会改变高速列车在尾流区域的声学指向性,并使气动噪声增加2.1~8.7 dB。相关结论可以为高速列车气动声学设计等研究提供参考。     

车辆天窗气动噪声的数值分析与实验研究

本文从汽车天窗气动噪声的机理入手,利用与实车几何尺寸为1:5的简化模型进行了空腔绕流的数值计算,分析了其流场结构及气动噪声产生的原因.在低速静音风洞中进行了不同流速下的流场和声场实验研究,研究了天窗不同位置的速度剪切层变化,以及不同流速下的声压级变化,发现了除了特征频率下的风振噪声,还存在较大频率范围的气动噪声,其随着...     

阀门气动噪声的振声转化计算方法

采用振动与噪声转化的方法计算气体流经阀门产生的管内气动噪声。通过推导管壁振动与管内噪声的计算公式,建立了管壁振动加速度级与管内噪声级之间的转换损失数理模型,并在低频区域,通过修正的频率因子,扩展了转换损失适用的频率范围,实现了通过阀门管内气动噪声的无损伤预测。利用实验对计算模型和方法进行了验证,结果表明,预测总声级的最大误差为0.98%,在整个频域内大约有69.3%⁷8.3%的数据预测误差在±5 dB以内,因而具有较高的精度,为阀门气动噪声的计算和分析提供了新的方法。     

应用随机模型方法预测汽车风噪声

采用随机模型方法,对简化汽车头部外形进行风噪声数值模拟.将计算区域分为声源区域和传播区域,在声源区域采用随机模型构造湍流脉动速度场,传播区域通过求解带源项的线化欧拉方程实现声波向外传播得到声场解.同直接模拟方法相比,该方法具有计算量小、计算所需内存少等优点.数值模拟结果与实验数据吻合较好,验证了该方法预测汽车风噪声的可行性,为研究实际汽车外形的风噪声问题打下基础.     

On measurements of aerodynamic noise generated by a high-speed electric train

Noise measured above a high-speed railway train indicates that aerodynamically generated noise may be quite significant at high vehicle speeds. A comparison of experimental and predicted noise levels demonstrates the similarity between the levels of aerodynamic noise produced by aircraft (airframe noise) and railway vehicles.     

Prediction of aerodynamic noise reduction by using open-cell metal foam

As the speed of high-speed train (HST) increases continuously, aerodynamic noise has become more remarkable compared with the wheel/rail noise, which affects the inhabited environment along the railway and the riding comfort. This paper preliminarily investigates the feasibility of using open-cell metal foam covering layer to reduce the low Mach number aerodynamic noise generated by the flow around a circular cylinder which is the typical section of pantographs. The aerodynamic noises radiated from the circular cylinder with and without metal foam are calculated. The hybrid method combining two-dimensional large eddy simulation (LES) with Ffowcs Williams–Hawkings (FW–H) equation is employed. The calculated Strouhal number, time-averaged drag coefficient, base pressure and overall sound pressure level agree well with some available experimental data. Then, the influences of metal foam porosity, pore density, thickness of covering layer and the speed of train on the aerodynamic noise and the aerodynamic forces are investigated, and some detailed comparisons of flow field are made. The numerical results indicate that as a passive scheme, the open-cell metal foam with high porosity can modify the flow, adjust the vortex shedding frequency and regularize the wake, leading to a significant reduction of aerodynamic noise. The results are expected to provide useful information for the control of aerodynamic noise using this new material.     

Experimental and numerical analysis of automotive gearbox rattle noise

The aim of this work is to characterize the rattle noise of automotive gearboxes, resulting from impacts between toothed wheels of unselected gear ratios. These stereo-mechanical impacts are modeled by a coefficient of restitution which describes damping during the squeezing of the lubricant film for approaching surfaces, and the elastic deformation of impacting bodies. The dynamic response of the loose gear first depends on the design parameters and the engine operating conditions. The unknown parameters are the drag torque and the coefficient of restitution. They are identified experimentally through implementation of two optical encoders in an actual automotive gearbox and the operation of a specific test bench which replicates the automotive power train. Models of the different drag torque sources are validated from analysis of the free damped response of the driveline. The coefficient of restitution and its probability density function are measured from experiments under stationary operating conditions. A nonlinear model is built. The dynamic response of the loose gear depends on the dimensionless backlash, the coefficient of restitution and a dimensionless parameter proposed to describe the rattle excitation level. Experiments under controlled excitation are performed to validate the assumptions, to confirm the ability of the parameter proposed to describe the rattle noise threshold, and to characterize the dynamic response. The nonlinear model predictions are fitted with the drag torque and coefficient of restitution previously identified. They are compared with measurements to demonstrate the ability of the model to predict gear rattle for any loose gear, any gearbox and any operating condition.     

柜式空调器室内机风道优化与降噪研究进展

空调器噪声问题一直饱受广大用户诟病,就柜式空调器而言,其室内机风道系统的内流及声学特性对降噪研究尤为重要。本文综述了国内外风道优化与降噪技术的研究进展,对柜式空调用多翼离心风机、换热器和进出风口在结构、材料等方面的优化改进进行了总结,分析了目前研究的不足之处。最后提出未来研究应向多态多目标集成优化方向发展,对多个结构和部件进行整体优化,以提高空调器性能。     

家用空调冷凝器的仿真与实验研究

为了缩短对家用空调冷凝器的性能研究时间和开发新产品的周期,开发了冷凝器仿真程序。利用分布参数模型对家用空调冷凝器进行仿真计算,并设计建立了冷凝器实验装置,对仿真结果进行实验验证。对冷凝器进行了在不同风速,不同冷凝温度下的实验,进行分析得到实验结果。并将其与仿真程序的计算结果进行了比较。通过比较证明了仿真结果和实验结果总体变化趋势一致;在相同工况下,模拟换热量的数值比实验换热量要低7.7%~12%;由此验证了仿真程序的可行性。     

汽车空调平行流冷凝器的仿真研究

分析并选取汽车空调平行流冷凝器传热和压降的数值计算模型,基于平行流冷凝器中的过热段、饱和段和过冷段的数模形态,分别进行压降和传热的仿真计算程序编制。该程序基于给定的冷凝热负荷,可计算出过热、饱和、过冷段各段扁管长度和压降值,对某大型客车平行流冷凝器模拟仿真结果显示,冷凝器扁管总长度模拟值与实测值误差为6.2%,说明仿真模型切合实际。该仿真程序可用于类似新型平行流冷凝器的开发研究,以达到提高开发效率、节省研究成本的目的。     

Prediction of flow-generated noise produced by acoustic and aerodynamic interactions of multiple in-duct elements

Flow-generated noise problem caused by in-duct elements is due to the complicated acoustic and turbulent interactions of multiple in-duct flow noise sources. The approach of partially coherent sound fields used previously by Mak and Yang [C.M. Mak, J. Yang, Flow-generated noise radiated by the interaction of two strip spoilers in a low speed flow ducts, Acta Acust united with Acustica 88 (2002) 861–868] and Mak [C.M. Mak, A prediction method for aerodynamic sound produced by multiple elements in air ducts, J Sound Vib 287 (2005) 395–403] is adopted to formulate the sound powers produced by interactions of multiple elements at frequencies below and above the cut-on frequency of the lowest transverse duct mode. The study indicates that the level and spectral distribution of the additional acoustic energy produced by the interactions of multiple elements can be predicted based on the measured data with respect to the interactions. The proposed method can form a basis of a generalized prediction method for flow-generated noise produced by multiple elements. The application of the proposed method is supported by two engineering examples.