地铁车轮振动声辐射特性和车轮降噪

为降低地铁车轮振动噪声,建立车轮三维有限元模型实体网格,利用有限元法计算车轮的固有频率和模态振型;将径向单位力激励下的车轮表面振动速度作为边界条件,采用直接边界元法分析车轮振动声辐射特性;利用阻尼措施降低车轮辐射噪声.结果表明：轮辐和踏面是产生高频噪声的主要部位,在3 731.3 Hz的声功率级最高为69.2 dB(A),此频率下轮辐对总声压贡献最大;采用阻尼措施后声功率级最高值下降4.7 dB(A).数值仿真结果可以为低噪声车轮的研究提供参考.     

基于有限元法的齿轮箱辐射噪声预测与分析

利用有限元分析软件ANSYS对齿轮箱系统在齿轮啮合激励力作用下的动态响应进行计算,提取齿轮箱表面选定区域网格节点的法向振动速度.利用节点法向振动速度的均方根值对选定区域以及箱体各表面的辐射噪声进行预测,得到辐射噪声的声压级与声功率级.通过与实测数据进行对比,证明预测结果与实测结果基本吻合.     

高速列车受电弓气动噪声分析与降噪研究

随着列车速度的大幅提升,气动噪声问题愈发凸显。受电弓噪声在整车噪声中占较高位置,为研究高速列车受电弓气动噪声特性,通过Lighthill声学理论的宽频噪声模型对高速列车气动噪声源进行识别,利用定常SST k-w湍流方法分析高速列车受电弓的流场特性;基于大涡模拟与FW-H声学比拟理论计算高速列车受电弓远场气动噪声。数值算例结果表明,受电弓部位的碳滑板、弓头为受电弓主要噪声源;以轨道中心线为对称线,远场气动噪声监测点的声压级及频谱特性表现出较高的对称性;在同一列车运行速度下,监测点声压级随离轨道中心线距离增大而减小,列车以不同速度运行时,其声压级降低的幅值相差较小;高速列车远场气动噪声为宽频噪声,主要能量集中在500Hz~5000Hz。提出一种射流降噪方法,在350km/h速度下,监测点总声压级值降低了15.2dB。     

大型车辆发动机冷却风扇流场的数值仿真方法

给出了发动机冷却风扇的数值仿真的建模方法和求解技术。以大型车辆发动机冷却风扇为研究对象,采用分区域划分网格的方法,运用滑移网格技术,对大型车辆冷却风扇三维流场进行了数值模拟和气动性能、气动噪声的研究。流场稳态模拟采用了基于雷诺平均的RNGκ-ε湍流模型,流场瞬态模拟采用了大涡模拟方法。给出了风扇流场的压力分析和速度分析,讨论了对风扇流量和气动噪声的影响因素。     

航空发动机试车台噪声声功率谱技术研究

由于航空发动机转速高，空气流量大，排气温度高，试车时产生的强烈噪声形成大范围的环境污染；通过讨论航空发动机试车台噪声的声功率谱分析技术，对某型涡轮螺旋桨发动机试车噪声的声功率谱进行分析，讨论该型发动机的噪声级、主要噪声源及其特征；试验结果表明其方法可行，与理论经验一致；此次试验为借助噪声进行故障研究提供了经验。     

有源电光调制式高功率瞬态电场传感器的研制

瞬态电场防护及应用技术的研究离不开瞬态电场测试系统;文中基于有源电光调制法,研制了一种高功率瞬态电场传感器;通过建立该传感器的等效电路模型,并借助CST仿真建模,分别从频域和时域角度分析了传感器的接收特性,并得到了一致的结果;最后利用脉冲噪声模拟器和吉赫兹横电磁波小室对研制的传感器性能进行了测试;结果表明:接收天线为单极子天线,天线负载采用高阻时响应电压与被测电场场强成正比;研制的传感器带宽为10kHz～314MHz,可用于纳秒级高功率瞬态电场的时域测试。     

消声器薄壳辐射噪声优化

针对消声器薄壳辐射噪声声能虽小但仍不可忽略的问题,运用CAE方法对某消声器进行分析,计算得到由内部声场引起的辐射声功率和消声器的传声损失．结果表明,增加消声器薄壳的厚度可以有效减少薄壳的辐射声功率且不削弱消声器的消声性能．通过格林分析法可得到消声器薄壳表面对外部观测点的噪声贡献量,为优化薄壳辐射噪声提供参考．     

基于仿真与实测的列车远场气动噪声分析

随着高速列车气动噪声诱发的铁路沿线噪声污染问题变得日益明显,需对高速铁路诱发的远场噪声特性进行研究。基于Lighthill声学理论,应用LES大涡模拟和FW-H声学模型对高速列车整车的气动噪声进行数值模拟,实测高速列车以300 km/h运行时的通过噪声,将仿真与实测进行对比分析。高速列车诱发的远场气动噪声是宽频带噪声,能量主要集中在200~1500 Hz的中低频带范围内。实测与仿真的噪声声压级频谱分析具有相似的变化趋势,但声压级数值不同;由于实测噪声数据不仅包括气动噪声,还包括轮轨、集电系统噪声等,所以实测数据普遍大于仿真结果。通过对比分析验证了仿真结果的科学性,为数值模拟方法研究高速列车气动噪声问题提供了科学依据。     

一种新型SOI高声压噪声传感器研制

简介了一种新型绝缘体上硅(SOI)高声压噪声传感器.主要对提升噪声传感器关键指标的感声膜结构的设计过程进行了仿真和计算,利用ANSYS软件对设计尺寸进行了模拟仿真.对设计的噪声传感器进行了频响以及线性度测试:在高声压级135～200 dB动态范围内的线性度小于1％,频率响应为20～100000 Hz;工作温度范围在-40～260℃,传感器的输出为标准电压信号,可组成被动式声测量阵列,用于测量高声压级的噪声信号.     

轨道车辆车轮辐板阻尼层对其降噪效果的影响分析*

采用模态叠加法求得阻尼车轮导纳特性,利用已建立的轮轨滚动噪声预测模型,以轮轨表面粗糙度为激励,分析了辐板阻尼层与其厚度对阻尼车轮振动与声辐射特性的影响规律.首先,建立了阻尼车轮三维实体有限元模型,采用Block Lanczos方法计算车轮模态特征;其次,利用模态叠加法求得车轮在单位荷载激励下的频响函数;然后,利用虚拟激励法求得车轮在粗糙度谱激励下的频域振动特性;最后,依据车轮动态响应通过解析的方法求得车轮声辐射频域特性.计算结果表明:(1)车轮辐板敷设阻尼层对车轮1000Hz以下频率的振动与噪声的抑制作用不明显,而对车轮1600Hz以上的高频振动具有良好的抑制作用;(2)车轮辐板双侧敷设阻尼的降噪效果优于单侧阻尼;(3)阻尼层可以有效抑制车轮振动,且车轮辐板敷设阻尼层厚度越厚效果越明显.     

Noise exposed of the operators of combine harvesters with and without a cab

A considerable number of the combine harvesters in Turkey are rather old and used without cabs resulting in unhealthy working conditions for their operators. Noise is one of the detrimental factors. This study deals with determining and comparing the noise exposed on the operators of the combines with and without a cab used for wheat harvesting in Turkey. The sound pressure levels (dB) at octave band center frequencies (31.5–8000 Hz) and the sound levels (dBA) at the ear level of the operators were measured on 37 different combine harvesters with four different makes and different years from 1976 to 2001. Fifteen of the combines were without a cab, another 15 had original cabs while remaining seven combines had cabs mounted on them after manufacturing.

The sound pressure levels were in a decreasing trend from the lower frequencies to higher frequencies. This trend was more noticeable for the combines with original cab and with the cab mounted after manufacturing compared to the ones without cab. The use of a cab was more effective in the insulation of the noise at the medium and higher frequencies, which have more bothersome effect compared to the lower frequencies. The sound pressure levels were 75–102 dB and 46–89 dB at low (31.5–500 Hz) and high (500–8000 Hz) frequencies for all combines, respectively. The sound pressure levels at the frequency of 4000 Hz at which the human ear is most sensitive were 6–17 dB lower for the combines with the cabs mounted after manufacturing and 9–28 dB lower for the ones with the original cabs compared to the combines without cab. The sound levels were 85–90, 81–83, and 76–81 dBA for the combines without cab, with cab mounted after manufacturing, and with original cab, respectively.

The study showed that the use of a cab was useful in the insulation of the noise, particularly at higher frequencies. In addition, it protects the operator from the factors having detrimental effects on the working efficiency such as high temperature and dusty environment. The authors strongly recommend mounting of a cab on to the combines currently being used without a cab in rental system in Turkey to provide healthy working conditions for their operators.     

Exploration on relationship between flow rate and sound pressure level of piezoelectric pump

This study presents the relationship between flow rate and sound pressure level of piezoelectric pump. It also presents the analysis and theoretical calculation for umbrella valve piezoelectric pump on the sound pressure level. Sound pressure level of umbrella valve piezoelectric pump in composite field (medium are air and water) was simulated by software Actran. Simulation results reveal that: The sound pressure level of Piezoelectric actuator in air field is bigger than that in water field. This result means that pump chamber with air and water has a higher sound pressure level than pump chamber with water. The flow rate and sound pressure level characteristics of umbrella valve piezoelectric pump with different pump chamber depths (d = 0.5 mm, 1.0 mm, 1.5 mm, 2.0 mm) is obtained by experiments in a voltage range of 160–220 V and a frequency range of 160–340 Hz. Experimental results show that: At different pump chamber depth (d), the range of flow rate is from 173.4 to 271.0 mL/min at 0.5 mm chamber depth, 75.0 to 149.0 mL/min at 1.0 mm chamber depth, 3.4 to 57.0 mL/min at 1.5 mm chamber depth, 2.8 to 32.8 mL/min at 2.0 mm chamber depth, the sound pressure level is from 57.52 to 65.14 dB, 54.54 to 60.05 dB, 55.26 to 69.24 dB, 53.39 to 61.19 dB. For piezoelectric pump with different pump chamber depths (d), flow rate and sound pressure level of piezoelectric pump increase as voltage increases. It is a great method to monitoring flow rate by monitoring the sound pressure level.

     

动车组明线运行速度提高对空调工作的影响

为研究列车运行速度提高对空调工作的影响,采用三维定常不可压缩k-ε湍流模型,对不同运行速度下4辆编组的某新型动车组明线运行的空气动力学特性进行仿真,分析在不同运行速度下客室和司机室的空调冷凝器进、出口表面压力变化规律,预测冷凝风机通风量随列车运行速度提高的变化规律。计算结果表明:随着运行速度的提高,动车组车体表面和冷凝器进出口表面压力逐渐降低,冷凝器进、出口压差基本呈降低趋势,头车司机室和客室的前通风机通风量逐渐降低,尾车司机室和客室的后通风机压差为负且绝对值逐渐增大,说明通风机通风量逐渐提高。     

Helmholtz共振腔气动噪声数值仿真

为探究出一套完整、准确的气动噪声仿真方法,用FLUENT和Actran仿真Helmholtz共振腔旁接管道系统模型.针对流场仿真,采用六面体网格建模,分析选择合适的网格密度,明确网格及边界条件的影响,以获得准确的声源信息;运用Lighthill声类比方法对声场进行仿真,采用数值计算、传声损失仿真和气动噪声仿真计算等3种方法提取管道内部场点声压级频谱曲线,分析曲线峰值频率特征,包括共振频率分析和声模态分析等.采用CFD软件与声学仿真软件相结合的方法,可以有效进行流场和声场的仿真.     

Sound field analysis and simulation for fluid machines

Fluid machines, such as pumps, fans, and internal combustion engines, are widely used in duct systems for air-conditioning, cooling, ventilating, heat releasing, and dust collecting. Vibration and noise will be created when the fluid machine works with fans at various rotating speeds. Noise problems associated with fan installation are a concern in fluid machines. Methods to analyze the sound field and simulation of fan installation are, therefore, important for the design to reduce the noise output from fluid machines. The sound field is simulated by using the boundary element method (BEM), which is a numerical technique to reduce the boundary integral equations using the fundamental solution and Green’s transfer functions, for sound field analysis in this paper. For the sound field analysis, the geometry of the fluid machines (the axial fan and centrifugal fan) and the acoustic properties are modeled in Beasy software based on the boundary element method technology. The 1/1 octave frequency band from 63 Hz to 8 kHz ranges are selected on sound field analysis. The sound pressure of the fan and the motor in each octave band are calculated by the parameters of rotating speed, flow volume, horse power and number of blades used. The results show that there is a high level sound pressure inside the housing of the axial fan due to the sound source located there. The higher sound pressure level is observed on both the inlet and outlet. The results for the centrifugal fan are the higher the frequency, the heavier energy that is found to radiate around the sound source.     

高速列车车内低频气动噪声预测

为研究气动载荷下高速列车的车内低频噪声,建立高速列车空气动力学模型,采用大涡模拟(Large Eddy Simulation,LES)法计算中间车的表面脉动压力.将脉动压力加载到高速列车的有限元模型上,通过瞬态分析得到车体的振动位移响应;将位移响应作为边界条件,采用边界元法(Boundary Element Method,BEM)分析车内噪声.结果表明：车窗振动位移最大,车顶和车底次之;中间车车厢的两端声压比中部大;在低频范围内,车厢内声压呈强弱交替分布,声场强弱界限较明显,且随着频率的增大,沿车体纵向和横向干涉条纹增多;车内低频气动噪声随速度二次方的增大而增加.     

Passenger comfort on high-speed trains: effect of tunnel noise on the subjective assessment of pressure variations

When passing through a tunnel, aerodynamic effects on high-speed trains may impair passenger comfort. These variations in atmospheric pressure are accompanied by transient increases in sound pressure level. To date, it is unclear whether the latter influences the perceived discomfort associated with the variations in atmospheric pressure. In a pressure chamber of the DLR-Institute of Aerospace Medicine, 71 participants (M = 28.3 years ± 8.1 SD) rated randomised pressure changes during two conditions according to a crossover design. The pressure changes were presented together with tunnel noise such that the sound pressure level was transiently elevated by either +6 dB (low noise condition) or +12 dB (high noise condition) above background noise level (65 dB(A)). Data were combined with those of a recent study, in which identical pressure changes were presented without tunnel noise (Schwanitz et al., 2013, ‘Pressure Variations on a Train – Where is the Threshold to Railway Passenger Discomfort?’ Applied Ergonomics 44 (2): 200-209). Exposure-response relationships for the combined data set comprising all three noise conditions show that pressure discomfort increases with the magnitude and speed of the pressure changes but decreases with increasing tunnel noise.

Practitioner Summary: In a pressure chamber, we systematically examined how pressure discomfort, as it may be experienced by railway passengers, is affected by the presence of tunnel noise during pressure changes. It is shown that across three conditions (no noise, low noise (+6 dB), high noise (+12 dB)) pressure discomfort decreases with increasing tunnel noise.     

火箭发动机喷流噪声数值模拟及声振分析

为给火箭系统结构振动响应分析提供有效载荷,采用雷诺平均N S（Reynolds averaged N S,RANS）方程求解喷流流场与用非线性声学求解器（Non linear Acoustics Solver,NLAS）求解喷流声场相结合的方法,对某高超声速火箭液体发动机喷流噪声进行数值模拟.用有限元法和统计能量分析相结合的方法,求解发动机模型在噪声作用下的全频段振动响应.计算结果表明：发动机喷流噪声声压级大小与喷流流场的湍流动能密切相关,湍流强度大的位置喷流噪声声压大;喷流流场初始段混合层内产生的噪声在高频段大于过渡区内产生的噪声,但中低频段却相反.