控制排气管道低频噪声的半主动消声装置研究

为了控制排气管道中的低频噪声,提出一种基于HQ管的新型半主动消声装置,设计并试制了半主动消声装置及实验台架系统,开展了半主动消声装置的有限元仿真与实验研究以及被动消声器的实验研究。结果表明,仿真和实验结果基本吻合,半主动消声装置在低频段具有良好的消声效果,尤其是对于50Hz-150Hz的频段,平均消声量在35d B左右,其性能明显优于被动消声器;在150Hz-350Hz的频段,半主动消声器整体消声性能在抗性消声器之上;在350Hz以上的频段,半主动消声器的消声性能相比于抗性消声器则较差。     

TCM叉车消声器的试验研究

地ＴＣＭ叉车消声器的消声量测试,得知其对中高频段噪声声效果不好。对该消声器进行结构参数分析,并在改进设计中增大了消声器容积比和改进排气尾管结构形式,改进后的消声器经装车试验,表明改进是成功的。     

摩托车排气净化消声器性能分析

研究了催化器结构对消声器性能的影响,在催化器内加入细插入管建立新催化器模型来模拟催化器的内噪声传递及损失,分析并对比了安装与未安装催化器的消声器的噪声传递损失,运用GT-Power软件建立摩托车发动机工作过程与带催化器的消声器的耦合仿真模型,得到消声器在发动机各转速下的插入损失和压力损失。分析结果显示,消声器在中低频段消声效果较好,在中高频段消声效果较差。根据仿真和试验结果对消声器结构进行改进,改进后的消声器在发动机各转速下消声效果得到改善,插入损失增加3~5dB,仿真结果与试验结果吻合良好。     

汽车排气消声器性能仿真分析与结构改进

传递损失属于消声器本身的消声性能,通过理论建模并使用声学软件Sysnoise对一款汽车排气消声器的传递损失性能进行了仿真分析,发现该款消声器存在基频和高频消声能力不足;运用现代消声器设计理论对原消声器进行了结构改进,通过仿真分析发现改进后消声器消声效果明显;采用两负载实验法测出原消声器和改进后消声器的传递损失,与仿真预测值吻合良好。     

排气消声器的设计及性能仿真分析

利用基于三维声波波动方程的有限元软件ANSYS对设计的某型重型卡车排气消声器进行声学仿真分析,计算得到其在(0~2000)Hz各频率上的声压等值线图,并计算得到传递损失曲线。将消声器性能测试所得结果与仿真结果相比较,发现在分析频段内消声量能较好的吻合,证明该方法是高效可行的,能较准确地预测消声器性能。相对传统的经验类比法和传递矩阵法,在设计理论和计算方法上都有很大提高,能够有效减少消声器基于一维平面波理论设计所带来的误差,对企业实际生产具有重要意义。     

双层串联微穿孔板消声器的设计与试验

针对某抽气泵排气噪声从高于80dB(A)降低到72dB(A)以下的要求,应用微穿孔板吸声体理论,设计双层串联微穿孔板消声器,并制作样件进行试验。结果表明安装消声器后,最大噪声值不超过67dB(A)。且在1000Hz～2500Hz频段,噪声下降尤为明显,消声量达到了10dB(A)～20dB(A),满足了设计的目标,验证了理论与实际的一致性。     

基于GT-Power和CFD的某发动机消声器结构优化与分析

针对某四缸发动机消声性能在某些工况下不理想的状况,本文通过在GT-Power中建立发动机及消声器耦合模型,同时联合使用CFD仿真,在不增大压力损失的前提下,对其消声器进行了优化。通过对消声器消声扩张比,扩张腔个数及长度,内插管长度的优化改进,提高了消声性能。结果表明:优化后的消声器在260-690Hz范围内,消声量平均提高了7dB,全频率范围内消声量减小了4dB,消声效果明显。     

小排量发动机系统模型的消声器的改进方法研究

为降低单缸汽油机的排气噪声水平,有效提升其声学性能,通过建立发动机和消声器的系统耦合仿真模型,对消声器进行设计与改进.通过分析其阶次噪声及排气频谱图,着重优化消声器中低频段的消声性能,综合动力性和经济性选出最佳方案,从插入管孔径和有无套筒两个角度对其进行进一步优化.最终在确保消声性能明显提升的同时,1.0、1.5和2....     

客车排气消声器的数值仿真计算方法

采用有限元法建立一6m轻型客车的消声器模型,并用边界元方法计算了该排气消声器的声学特性.经与试验测试结果比较,在分析频段内能较好的吻合,表明该设计方法是有效可行的.并对比了改进后消声器的消声性能,结果显示消声性能得到了提高.证明这种消声器的设计和数值计算方法,在解决企业实际问题中可以缩短设计周期,更好的降低排气噪声.     

基于声品质提升的汽车消声器结构研究

研究的目的在于通过利用多孔管,膨胀腔的消声特性解决在满足基本消声性能前提下声品质不佳的问题,提升消声器的主观感受声品质,其对整车的乘员舒适性改进有较明显的效果,对消声手段的应用有现实的指导意义.通过具体的实例来说明消声元件的消声结构和能达到的消声效果之间的主客观数据对应关系,在解决排气噪声问题的同时能够尽量提升声品质并...     

Minimal Realization of Linear Graph Models for Multi-physics Systems

An engineering system may consist of several different types of components,belonging to such physical"domains"as mechanical,electrical,fluid,and thermal.It is t...     

INTEGRAL EQUATION METHOD＇S APPLICATION IN HOLE-EDGE STRESS OF COMPOSITE MATERIAL PLATE WITH DIFFERENT SHAPED HOLES

The strength of composite plate with different hole-shapes is always one of the most important but complicated issues in the application of the composite material. The holes will lead to mutations and discontinuity to the structure. So the hole-edge stress concentration is always a serious phenomenon. And the phenomenon makes the structure strength decrease very quickly to form dangerous weak points. Most partial damage begins from these weak points. According to the complex variable functions theory, the accurate boundary condition of composite plate with different hole-shapes is founded by conformal mapping method to settle the boundary condition problem of complex hole-shapes. Composite plate with commonly hole-shapes in engineering is studied by several complex variable stress fimction. The boundary integral equations are founded based on exact boundary conditions. Then the exact hole-edge stress analytic solution of composite plate with rectangle holes and wing manholes is resolved. Both of offset axis loadings and its influences on the stress concentration coefficient of the hole-edge are discussed. And comparisons of different loads along various offset axis on the hole-edge stress distribution of orthotropic plate with rectangle hole or wing manhole are made. It can be concluded that hole-edge with continuous variable curvatures might help to decrease the stress concentration coefficient; and smaller angle of outer load and fiber can decrease the stress peak value.     

Non-monotonic material contrast in scanning ion and scanning electron images

30 keV Ga⁺ focused ion beam induced secondary electron (iSE) imaging was used to determine the relative contrast between several materials. The iSE signal compared from C, Si, Al, Ti, Cr, Ni, Cu, Mo, Ag, and W metal layers does not decrease with an increase in target atomic number Z₂, and shows a non-monotonic relationship between contrast and Z₂. The non-monotonic relationship is attributed to periodic fluctuations of the stopping power and sputter yield inherent to the ion–solid interactions. In addition, material contrast from electron-induced secondary electron (eSE) and backscattered electron (BSE) images using scanning electron microscopy (SEM) also shows non-monotonic contrast as a function of Z₂, following the periodic behavior of the stopping power for electron–solid interactions. A comparison of the iSE and eSE results shows similar relative contrast between the metal layers, and not complementary contrast as conventionally understood. These similarities in the contrast behavior can be attributed to similarities in the periodic and non-monotonic function defined by incident particle–solid interaction theory.     

Application of Feature Extraction through Convolution Neural Networks and SVM Classifier for Robust Grading of Apples

This paper proposes a novel grading method of apples,in an automated grading device that uses convolutional neural networks to extract the size,color,texture,an...     

分布动态载荷识别的抗噪处理

针对正交多项式频域法在用多种响应对矩形薄板进行载荷识别中抗噪性较差的问题,综合运用平均法、矩阵预处理和奇异值截断法等方法对之进行改善,并引入空间映射的思想,将该方法的应用范围拓展为复杂的模型.利用仿真算例,证实了该方法具有较好的抗噪性.     

基于MELTAC-N平台的核电厂安全级DCS环网研究与测试

针对工程实践中环网通讯相关问题的处理缺乏理论基础及国产化安全级DCS平台的开发缺乏成熟经验借鉴问题,对基于MELTAC-N平台核电厂安全级DCS环网的软硬件实现进行了研究。提出了安全级DCS环网双环网冗余设计、光切换开关设计等硬件设计方法,以及以RPR协议为基础,采用全数据收发策略的软件设计方法。在CPR1000安全级DCS平台上对安全级DCS环网的可靠性及实时性进行了评价,并进行了容错能力、响应时间及响应时间稳定性测试验证实验。结果表明,基于MELTAC-N平台安全级DCS环网软硬件设计具有较好的容错能力及响应时间稳定性。     

Short-Term Relay Quality Prediction Algorithm Based on Long and Short-Term Memory

The fraction defective of semi-finished products is predicted to optimize the process of relay production lines, by which production quality and productivity ar...     

End-to-End Multiview Gesture Recognition for Autonomous Car Parking System

The use of hand gestures can be the most intuitive human-machine interaction medium.The early approaches for hand gesture recognition used device-based methods....     

The laboratory simulation of abrasive wear

Abrasive wear has long been recognised as one of the most potentially serious tribological problems facing the operators of many types of plant and machinery; several industrial surveys have indicated that wear by abrasion can be responsible for more than 50% of unscheduled machine and plant stoppages. Locating the operating point of a tribological contact in an appropriate operational ‚map’︁ can provide a useful guide to the likely nature and origins of the surface degradation experienced in use, though care must be exercised in choosing the most suitable parameters for the axes of the plot. Laboratory testing of materials and simulations of machine contacts are carried out for a number of purposes; at one level for the very practical aims of ranking candidate materials or surface hardening treatments in order of their wear resistance, or in an attempt to predict wear lives under field conditions. More fundamentally, tests may be aimed at elucidating the essential physical mechanisms of surface damage and loss, with the longer term aim of building an analytical and predictive model of the wear process itself. In many cases, component surface damage is brought about by the ingress of hard, particulate matter into machine bearing or sealing clearances. These may be running dry although, more usually, a lubricant or service fluid is present at the interface. A number of standardised wear test geometries and procedures have been established for both two- and three-body wear situations, and these are briefly described. Although abrasive wear is often modelled as following an ‚Archard’︁ equation (i.e. a linear increase in material loss with both load and time, and an inverse dependence on specimen hardness) both industrial experience and laboratory tests of particularly lubricated contacts show that this is not always the case: increasing the hardness differential in an abrasively contaminated lubricated pair may not always reduce the rate of damage to the harder surface.     

Limits of topographic measurement by the scanning tunnelling and atomic force microscopes

Parameters describing the topographic character of a surface (height, surface wavelength, slope and curvature) can be derived from equivalent sinusoidal profiles. The response of a surface-measuring instrument may be modelled in terms of instrument parameters such as stylus radius, and scanning range and resolution. The performance of the instrument may then be mapped as a zone in amplitude-wavelength (AW) space to show the sinusoidal profiles it is capable of measuring. In a first-order analysis the STM and AFM are considered as equivalent to contact-stylus instruments with a notional stylus radius equal to the tip radius plus the gap. Comparisons between different instruments and types of instrument are readily made by mapping in AW space. The error arising from convolution of the sinusoidal profile with that of the finite tip may be quantified and plotted as contours in AW space.