4100QBZ发动机排气消声系统匹配研究及其声学特性分析

首先将不同容积大小的汽车排气消声器和各种不同参数尺寸的排气总管匹配成的若干组排气消声系统,并建立仿真模型.然后运用SYSNOISE软件得到其各频率下的传递损失和声压级分布,通过比较分析消声性能优劣得到了该系统的最佳匹配方案.并讨论了排气管对消声量的影响和消声器容积变化对消声量的影响.     

Experimental and numerical analysis of an air cleaner's acoustic performance

To improve acoustic performance of an air cleaner system,both experimental and theoretical studies were carried out.The air cleaner' s acoustic numerical model was built by finite element methods (FEM)...     

基于声模态的抗性消声器的声学性能分析

利用声学有限元软件Sysnoise对进出口偏置的扩张式消声器进行了分析,并得到传递损失与声学模态.结果表明：通过消声器进口插入管的设置,能改变扩张腔内部的声学模态,从而达到改变传递损失曲线的目的;特种模态的激发和传递损失峰值的出现是相对应的.     

基于小波包分析的模拟天然气管道泄漏声发射定位

开展了模拟天然气管道泄漏检测与定位研究,研究利用小波包分析技术,首先对声发射信号进行分解,再对衰减的信号在不同频率段内进行有效的补偿,然后对分解的信号进行小波包重构,利用互相关技术计算两个声发射传感器接收到的声发射信号的时差,进而进行声发射源定位。对模拟天然气管道泄漏的声发射信号的处理结果表明该方法能够有效实现管道泄漏检测与泄漏源定位,并且泄漏源的定位精度高,误差〈8%。如能将这一技术改进并实现长距离管道泄漏检测与定位,将具有广阔的应用前景。     

Modeling and finite element analysis of transduction process of electromagnetic acoustic transducers for nonferromagnetic metal material testing

Facing the problems lack of considering the non-uniform distribution of the static bias magnetic field and computing the particle displacements in the simulation model of electromagnetic acoustic transducer (EMAT),a multi-field coupled model was established and the finite element method (FEM) was presented to calculate the entire transduction process.The multi-field coupled model included the static magnetic field,pulsed eddy current field and mechanical field.The FEM equations of the three fields were deri...     

轿车车身NVH特性研究分析

车身结构与车室声腔模态分析是车身NVH特性研究的重要内容,识别车身系统模态对避免车身结构与声腔共振、降低车内噪声有着重要的意义。以某轿车车身为例,利用有限元法建立车身结构模型和车室声腔模型,分别进行模态分析计算,获得车身结构的模态频率和变形部位、空腔声学系统的声学模态频率和声压分布情况,为车身系统结构与声学优化设计提供依据。     

能量高效的水声传感器网络路由协议

为了解决水下声信道对网络性能的影响,在综合考虑了节点的剩余能量和信道传输质量的基础上,提出了一个基于链路质量估计的能量高效路由协议。该协议根据节点的可用能量、位置以及信道传输质量估计等因素确定转发节点,能减少信息的盲目转发,提高能量的利用率,均衡网络的能量消耗,从而实现了网络能量的平稳下降,有效地延长网络的生存时间。仿真结果表明,该协议具有能量利用率高,信道利用合理等特点,比无信道传输质量估计的协议能量利用率提高9%左右。     

Dynamic destabilization analysis based on AE experiment of deep-seated, steep-inclined and extra-thick coal seam

No. 5 coal seam in Huating Coal Mine is a deep-seated, steep-inclined extra-thick coal seam where excavation disturbance is quite frequent. The maximum and minimum principal stresses differ widely. During mining, dynamical destabilization happens frequently and induce tragedies. Based on the comparison between the acoustic emission （AE） experiment on dynamical destabilization of coal rock and the related in situ testing results, this article provides comprehensive analysis on the regular quantificational AE patterns （energy rate, total events） of coal rock destabilization in complex-variable environment. The comparison parameters include dynamic tension energy rate, deformation resistance to compression, and shear stress.     

Study of electromagnetic and acoustic emission in creep experiments of water-containing rock samples

Based on biaxial shear creep tests conducted on rock samples with different water contents, we present the results of our study on the regularities of electromagnetic and acoustic emission during the process of creep experiments in which we have ana-lyzed the contribution of water to the occurrence of electromagnetic radiation. The result shows that in the creep-fracturing course of rock samples, when the water content increases, the initial frequency and amplitude of electromagnetic and acoustic emission also increases, but at a decreasing growth rate caused by loading stress. This can be used as a criterion for the long-term stability of rock masses under conditions of repeated inundation and discharge of water.     

楔形海域声矢量场分析

海洋环境中的声传播是水声学研究领域的一个经典问题.在传统的研究中,关心的主要是声压场.随着矢量水听器的出现,不仅是声压场,介质质点振速场也受到极大关注.应用虚源法分析了ASA基准楔形模型中谐和点源的三维质点振速场.基于Deane和Buckingham给出的声场声压表达式,文中推导了三维质点振速的积分公式,并应用数值积分的方法计算了声场声压与质点振速,分析了它们的传播损失和相位差以及不同方向声强的衰减过程.结果表明,即使在远距离上,声压与质点振速的相位差并不为零.