离心风机蜗舌过渡半径的数值优化研究

对离心风机的多级蜗舌进行了研究,着重探讨了离心风机多级蜗舌过渡半径的求解方法。利用ANSYS/Fluent软件对风机进行二维数值模拟,采用变参数的方法,找出过渡半径与风机性能参数的关系,从而确定最佳半径取值。对比改进前后风机的数值模拟结果发现,改进风机在降低噪声的同时兼顾了其他的性能指标,同时验证了理论的可靠性。     

离心风机蜗舌气动噪声D－最优声学模型的研究

阐述了Ｄ－最优化建模理论，根据影响离心风机蜗舌噪声的结构参数，研究了离心风机蜗舌引起的噪声辐射增量的Ｄ－最优数学模型的建模方法，并通过试验建立了鼠笼式离心叶轮蜗舌气动噪声辐射增量的数学模型，取得了理论计算与实验结果的良好拟合。     

面向降噪的汽车空调用多翼离心风机性能研究及改进

为获得流动性能和噪声性能的优化,对多翼离心风机叶片、进口集流器和蜗舌进行了改进,并采用CFD数值模拟软件FLUENT对这些机型进行了模拟计算,通过对其流场进行对比分析得到了两台流动和噪声性能均比原风机显著提高的机型。     

离心风机蜗舌气动噪声D—最优声学模型的研究

阐述了Ｄ－最优化建模理论，根据影响离心风机蜗舌噪声的结构参数，研究了离心风机蜗舌引起的噪声辐射增量的Ｄ－最优数学模型的建模方法，并通过试验建立了鼠笼式离心叶轮蜗舌气动噪声辐射增量的数学模型，取得了理论计算与实验结果的良好拟合。     

汽车空调鼓风机倾斜蜗舌流场及噪声研究分析

针对一款应用在汽车空调上的多翼离心风机的噪音问题进行分析。利用Strar CCM+软件对常规直蜗舌和加斜蜗舌后的多翼离心风机进行数值模拟研究。计算结果表明：斜蜗舌对蜗舌附近及蜗舌后的流场都有较大的影响，好的倾斜蜗舌设计可以改善蜗舌处的流场，减小蜗舌区域的旋涡强度。对多翼离心风机加装倾斜蜗舌前后风量和噪音变化进行试验，结果表明：在相同转速下，风量基本没有变化，斜蜗舌对总噪声值改善较小，但可以明显改善叶轮阶次噪声，叶轮阶次频率处噪声降低了7dB左右。     

基于仿生蜗舌的离心风机降噪研究

以某型离心风机为研究对象，针对风机运行时的噪声问题，运用仿生学原理对蜗舌进行改型设计，在贝壳类生物中得到启发，设计出交错阶梯型的蜗舌结构。采用雷诺时均方程和声类比相结合的方法对离心风机进行流场以及声场的数值模拟，分析了仿生蜗舌对风机性能、流动特征及气动噪声的影响。结果表明：仿生蜗舌对风机性能影响不大；额定工况下，仿生蜗舌结构风机出口附近的噪声降低了2.8dB，风机整体辐射噪声降低了3.3dB；对离心风机内部的流动特征以及噪声特性进行分析，发现仿生蜗舌处的速度分布更加均匀，抑制了蜗舌处的流动分离现象，在低频段内蜗舌处的压力脉动有所下降，表明风机在运行时的噪声得到了一定的控制。     

阶梯蜗舌蜗壳的降噪分析和实验

介绍了阶梯蜗舌技术，并将其应用于一种排油烟的离心风机运用CFD软件Fluent6．0对常规蜗舌和阶梯蜗舌蜗壳进行了二维流场的数值模拟并作了对比，从而探讨了阶梯蜗舌降噪的机理。最后分别对两种蜗壳的风机进行了噪声和其他性能参数的测量。结果：表明采用阶梯蜗舌蜗壳对于降噪是有效的。     

蜗舌深度对离心风机气动性能和噪声影响研究

针对新风空调离心风机功率高、噪声大的问题,基于CFD仿真与试验研究了不同蜗舌深度对离心风机气动性能和噪声的影响,并着重对A10,A30,A40共3种方案蜗壳在25～60 m³/h流量范围内风机性能和噪声水平进行了分析。结果表明,蜗舌深度优化后,在额定流量45 m³/h工况下,仿真全压值提高5 Pa,全压效率提高17.28%,试验测试功率降低7.8 W,噪声降低1.7 dB;合理选择蜗舌深度能够改善蜗壳扩压段处流动,提高风机气动性能,同时降低风机噪声。研究结果可为离心风机设计提供指导。     

阶梯蜗舌蜗壳降噪的分析和实现

介绍了阶梯蜗舌技术，并将其应用于一种排油烟离心风机，运用CFD软件Fluent6．0对常规蜗舌和阶梯蜗舌蜗壳进行了二维流场的数值模拟，并作了对比，从而探讨了阶梯蜗舌降噪的机理。最后分别对两种蜗壳的风机进行了噪声和其它性能参数的测量。结果表明，阶梯蜗舌蜗壳是一种有效的降噪措施。     

基于Fluent的多翼式离心风机性能分析

使用Fluent软件对不同工况下的多翼式离心风机进行三维数值模拟,研究风机的典型几何参数对其流噪声和风量的影响规律;采用Coupled耦合算法结合MUSCL离散格式、定常RANS方程组求解风机内流场;采用FW-H声学模型结合大涡模拟计算风机流噪声。结果表明:变工况计算结果与试验值吻合,风机的蜗舌半径、叶片数、叶片进口安放角对风机的风量和流噪声均有一定的影响。本文的研究成果可以为多翼式离心风机的优化设计提供参考。     

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...     

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。     

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.     

Fractional order nonsingular terminal sliding mode control for flexible spacecraft attitude tracking

This paper investigates a fractional terminal sliding mode control for flexible spacecraft attitude tracking in the presence of inertia uncertainties and extern...     

奥氏体不锈钢表面双辉等离子渗锆的动力学

利用双辉等离子渗金属技术在0Cr18Ni9Ti奥氏体不锈钢表面制备了一层均匀、致密、呈良好冶金结合的渗锆合金层,并对1 060℃下的渗锆动力学进行了研究。结果表明:随着距锆合金层表面距离的增加,锆元素的含量呈梯度递减,扩散系数逐渐减小,而扩散激活能逐步增大;在1 060℃采用双辉等离子技术渗锆时,渗锆合金层表层的空位密度为2.945×(1012~1013)cm-2,与相同温度下采用常规渗金属工艺相比,提高了1~2个数量级。     

气化炉三维扫描测量与数据处理

以德士古气化炉耐火砖的内壁蚀损检测设备为基础,对采集到的点云数据做了进一步处理.通过对数据的筛选和剔除,实现了数据点的平滑降噪细化和精简.然后利用点云对整、网格划分和分色显示等方法,最终完成了内壁腐蚀情况的三维建模.重点讨论了点云数据的预处理及后处理的方法,并根据内壁耐火砖的腐蚀阈值,提出了一种气化炉内壁腐蚀区域的识别与分割方法.对耐火砖的腐蚀分析、气化炉的生产与维修提供了可靠依据,并在工程应用中获得了一致认可.