蜗壳宽度对风机性能影响的数值分析

离心风机蜗壳的最佳宽度问题,目前工程中还没有得到完全解决。本文利用数值分析的方法,通过选择不同的蜗壳宽度参数,对4-72、5-48、6-30等三种常用后弯叶片离心风机进行空气动力学计算分析。计算结果表明,合理选择蜗壳宽度参数可以改善蜗壳内部流动特性,提高通风机空气动力性能。     

低噪声离心通风机最佳蜗壳结构的确定

提供了一种确定低噪声离心通风机蜗壳结构的方法。通过对现有的一台离心通风机的改造——对进风口以叶轮进口速度分布均匀性为优化目标进行优化设计；采用改变蜗壳宽度的办法，对其进行回归正交设计，得出Ａ声压级与蜗壳相对宽度的函数关系式。并用求极值方法得出噪声最小的蜗壳宽度。计算结果与试验结果吻合较好，与原蜗壳相比降低噪声３．５ｄＢ（Ａ）。     

低噪声离心通用机最佳蜗壳结构的确定

提供了一种确定低噪声离心通风机蜗壳结构的方法。通过对现有的一台离心通风机的改造－对进风口以叶轮进口速度分布均匀性为优化目标进行优化设计；采用改变蜗壳宽度的办法，对其进行回归正交设计，得出Ａ声压级与蜗壳相对宽度的函数关系式。并用求极值方法得出噪声最小的蜗壳宽度。计算结果与试验结果吻合较好，与原蜗壳相比降低噪声３．５ｄＢ（Ａ）。     

基于CFD的离心风机蜗壳优化研究

为研究离心风机蜗壳出口宽度对风机性能的影响,用solidworks建立了风机模型,并通过测试验证了模型选取的合理性。在原风机模型基础上,改变蜗壳出口宽度,对两种不同出口宽度的风机进行气动优化计算分析,优化后的模型效率提高了4.5%。研究表明:蜗壳出口宽度偏小,其流量小,压力大,效率低;蜗壳出口宽度偏大,流量大,压力小。     

蜗壳宽度与粗糙度对小型高速离心风机性能特性的影响北大核心CSCD

针对小型高速离心风机内部毫米级流道尺度和相对粗糙度大幅增加带来的性能衰退问题,采用整机数值模拟结合试验测试的方法,分析了蜗壳粗糙度和蜗壳宽度对风机性能的影响,并对其内部流动进行探究。研究发现:蜗壳宽度的增加,会使其内部流动更加紊乱,导致性能下降,当蜗壳宽度为4.4 mm时,其性能最优;而壁面粗糙度的增加会使主流区集中于流道中部,壁面速度梯度增加导致风机的性能下降。随着粗糙度的增加其性能逐渐降低,当粗糙度达到30μm时,其压升相对降低了12.5%。通过性能随蜗壳粗糙度的变化曲线以及宽度的影响分析,可以为高速小型离心风机的研发与改型设计提供参考。     

蜗壳与叶轮相对位置对多翼离心风机性能的影响

为探索蜗壳与叶轮轴向相对位置对多翼离心风机气动性能的影响,在保持其它参数不变的情况下,分别对仅改变蜗壳前端面与叶轮前盘间距、仅改变蜗壳后端面与叶轮后盘间距的改造风机进行数值计算,然后选取2个阶段中性能较好的方案进行组合从而确定最佳的蜗壳与叶轮轴向相对位置。研究结果表明:当叶轮出口宽度和蜗壳总宽度的相对值为0.81时其气动性能最佳,与原风机相比,效率提高了2.34%,静压提高了3.61%,噪声下降0.75 dB。     

离心风机蜗壳型线设计方法的分析研究

蜗壳是离心式通风机的一个重要部件,其结构是复杂的空间曲面体。蜗壳设计较明显的影响参数是蜗壳的型线、蜗壳截面形状和布置方式,如何绘制蜗壳型线将直接影响蜗壳内的流动损失。本文对现有文献介绍的通风机蜗壳的工程设计方法进行了分析,总结了各设计方法的特点及其适用范围,并就对离心风机性能影响较明显的蜗壳型线和截面形状等因素进行总结分析,对离心风机蜗壳型线设计方法的改进提供了一定的工程设计借鉴价值和学术价值。     

基于正交试验设计的离心风机多因素优化研究

以G4-73№8D型离心风机为研究对象,在蜗壳型线优化的基础上,采用正交试验设计方法耦合蜗壳宽度、蜗舌间隙及叶轮轴向相对位置三因素,通过正交表确定试验方案。利用Fluent数值模拟软件,对部分试验方案的风机内部三维流场进行数值模拟和对比分析。计算结果表明:A1B3C1(型线优化风机)和A3B3C3(耦合风机)较原风机,全压和效率都有较大提高;正交试验设计方法为风机的多因素优化提供借鉴意义。     

新型高效5-29离心通风机模型开发

基于风机行业多年前联合设计开发的5-29离心风机气动参数,设计出新型5-29离心通风机。通过Solidworks软件建模,CFX软件进行气动计算分析,调整了b_1/D_1值、叶片出口角、蜗壳宽度等参数。优化后的最终风机模型,流场中边界层分离和环流损失均较小。具有效率高、高效运行区宽广、性能曲线平坦等特点。CFD计算值和实测值基本吻合,实测最高效率高达85.2%,高出国家一级能效等级标准6.2%。     

蜗壳及叶片外形对双吸式多翼离心风机性能影响的试验研究

以某款效率低、全压低的双吸式多翼离心风机为实验对象,通过试验研究蜗壳型线,叶片外形以及增加叶片数对风机性能的影响。试验结果表明:蜗壳型线的变化趋势对双吸式多翼离心风机的性能有着很大的影响,良好的蜗壳型线不仅提高了风机效率以及全压,还改变了流量-压力曲线的变化趋势;相比原风机,采用改型蜗壳及改型叶轮的方案2风机能够大幅提升风机性能,使效率提升幅度达到10.93%,风机全压提升近40Pa;当叶片数从46片增加至56片,风机在大流量工况下提升了风机静压,但风机效率会略有下降。     

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.     

ANGULAR DISTORTION ALLOWABLE VALUE AND ASSESS METHOD OF WELD ON COKE TOWER

A graph as the new engineering method for estimate the safety of bulging deformation of coke tower is proposed. Through stresses analysis of circumferential weld of coke tower and comparing the stresses produced by pressure with heat stress of steady state, residual stress, bending stress produced by both itself weight and wind loads, it showed that the stresses produced by pressure on the angle distortion are the main factor of equivalent stress of the combined stress. After comparing four kinds of stress controlling conditions, the relation to stress with depth of angular distortion, grade of curvature of angular distortion and half of region of angular distortion has been inferred. Graph of deformation allowable value of coke tower for different condition by angular distortion and half of region of angular distortion has been plotted. The five steps for its engineering use have been explained. The lighter the grade of curvature is, the larger of bulge allowance, may be, and the bigger of depth of angular distortion may pose too. For the coke tower with a popular structure of Dg 5 400 mm×28 mm, the result by graph is nearly more than the result of two formulas formed by other research, the error is less than 7.0%. But, the graph can be easily applied to different size of angular distortion.