卷边吸尘口流场特性研究

真空吸尘式清扫车是一种利用负压工作的新型清扫车辆。吸尘口是其气路系统的关键部件,对整台清扫车的吸尘能力、吸尘效率以及工作可靠性等各方面有着决定重要的影响。以吸尘口为研究对象,采用UG软件建立吸尘口的三维模型,使用Gambit软件进行网格离散,运用Fluent软件进行流场分析,对不同的卷边吸尘口进行吸尘效果的对比研究,设计出了一种前曲面挡板的吸尘口,并进行了气固两相流的运动仿真验证。研究表明:前宽后窄、带有前曲面挡板的吸尘口具有良好的吸尘效果。     

小型清扫车吸嘴的优化设计与试验

为进一步提高小型清扫车的吸尘效率,基于对国内外反吹式吸嘴研究的基础,设计了一种适用于小型清扫车的吸嘴。运用计算流体力学(CFD)方法对吸嘴进行流场仿真分析,采用二次正交旋转组合设计试验方法,研究了排气管倾斜角、径长比、宽长比、反吹口的反吹量等参数对吸嘴吸尘率的影响。试验表明:影响吸嘴吸尘率性能的大小依次为径长比反吹量排气管倾斜角宽长比。在排气管倾斜角为108.35°,长径比为0.22,长宽比为0.49,反吹量为1 400 m~3/h时,吸嘴吸尘率达93.28%,满足实际工程需要,研究为小型清扫车吸嘴的优化设计与性能进一步提高提供参依据。     

基于流场仿真的真空清扫车吸尘口的参数化分析

吸尘口是真空清扫车气路系统的关键部件,对清扫车吸尘能力起着决定性的作用.传统吸尘口往往是基于经验类比进行设计的.为了更加合理地设计吸尘口,文中借助于计算流体动力学(Computational Fluid Dynamics,CFD)软件分析了吸尘口结构参数对吸尘能力的影响.结果表明:侧板水平倾角与吸管直径的增加,侧板铅垂倾角的减小,以及后挡板高度的降低,均有利于从速度与压强方面整体改善吸尘效果;后板倾角将主要影响吸管入口压强的变化;前板圆弧半径的增大将降低进口速度与吸管入口的压强.该研究对真空清扫车吸尘口的设计具有实际的指导意义.     

槽型轨道清扫车吸尘口参数优化研究

槽型轨道清扫车是利用负压空气动力技术工作的新型车辆,用于现代有轨电车轨道槽的清扫。为了合理优化吸尘口结构,采用DPM气固两相流的方法,对离散相污染物颗粒在吸尘口内的运动过程以及连续相流场进行了仿真分析,确定出影响吸尘口出口颗粒质量流量Q_m的三个主要因子:前板长度W_1、后板长度W_2、顶板高度W_3。同时运用CFD和DOE仿真技术,进一步优化吸尘口的结构参数,提高吸尘效果。结果表明:适当缩小前板和后板长度差,其大小组合比例控制在4:6至6:4之间,顶板高度控制在(10~20)mm之间,约为侧板高度的(1~2)倍,均有利于改善吸尘效果;前板长度相比后板长度、顶板高度对吸尘效果影响更为显著,前板、后板和顶板三者之间的交互作用对出口颗粒质量流量也有重要影响。为槽型轨道吸尘口结构的进一步优化设计,提供了合理的依据。     

某型公铁两用清扫车吸尘系统仿真分析与优化

针对清扫对象的特点,对公铁两用清扫车吸尘系统的风机风量、吸尘口最小风速等参数进行了理论计算。利用CFD方法分析和优化了吸尘系统,并对清扫车的吸扫性能进行了实车测试。     

吸扫式清扫车工作参数匹配研究

吸扫式清扫车的工作参数对其清扫效率和清扫能力有决定作用。开展了清扫车工作参数与清扫性能试验,获取了清扫车速度、风机工作流量、盘刷转速和垃圾分布密度与清扫效率的作用规律,开展了清扫车工作参数正交变量试验。试验结果表明:工作参数对清扫效率的主次顺序为风机流量、清扫速度、盘刷转速、垃圾分布密度。进行了不同参数组合下吸扫式清扫车清扫效率试验研究。采用线性拟合的方法建立了清扫车清扫效率计算公式。采用求解极值的方法获取了清扫车的最大清扫效率。提出了清扫车工作参数匹配规律:当风机流量为760 m3/h,清扫速度为5.5 km/h,盘刷转速为120 r/min时,清扫车具有最佳工作性能。     

纯扫式街道垃圾清扫小车的设计

为了改进纯扫式垃圾清扫车的工作性能,在分析传统纯扫式清扫车清扫部件结构和原理的基础上,设计了一种新型纯扫式街道垃圾清扫小车.小车改进了传统纯扫式清扫车撮土板的设计.试验表明清扫小车克服了传统纯扫式清扫车的不足,提高了工作性能,清扫效果好.     

spICP-MS准确定量多分散金纳米颗粒的颗粒数量浓度

建立了基于单颗粒电感耦合等离子体质谱（spICP-MS）法准确定量分析多分散金纳米颗粒（AuNPs）的颗粒数量浓度。以包含30 nm和60 nm AuNPs的多分散样品为研究对象,考察载气流速和采样深度对尺寸分辨率,以及采集时间和驻留时间对颗粒数量浓度测定结果的影响。研究表明：优化载气流速能显著改善尺寸分辨率,而采样深度的影响相对较小,在载气流速0.8 L/min、采样深度9 mm时,获得了最佳的尺寸分辨率;延长采集时间能有效降低测定结果的相对标准偏差（RSD）,当采集时间增加至180 s时,多分散样品中30 nm和60 nm AuNPs颗粒数量浓度测定值的相对标准偏差降至5%以下（n=3）;选取驻留时间为0.1 ms时,测定结果与配制值相符,且颗粒信号与离子信号的区分更加明显。在优化的条件下,粒径和颗粒数量浓度检出限分别为10 nm和49 NPs/g。采用本方法对不同混合比例的多分散样品进行定量分析,其测定结果与标准值相符,证明了方法的可靠性。将该方法应用于自来水、泉水和湖水中多分散纳米颗粒的定量测定,3种水样的加标回收率在80%~120%之间。本方法具有尺寸分辨率高、测量精密度好、离子干扰小等优点,可为环境基体中多分散纳米颗粒的定量测定提供方法参考。     

基于MATLAB的清扫车滚筒装置设计和参数优化

为解决清扫车清扫性能低、二次扬尘大、能耗高的问题,设计了一种新型滚筒式吸尘口的清扫装置模型,并借助现代接触动力学和MATLAB求出滚筒装置的最优参数解,同时也为吸尘口设计提供设计约束。优化结果表明:滚筒装置前档板与水平夹角β=30°、滚筒临界点与水平夹角α=60°为滚筒装置的最优参数解。     

特征分区的不确定性及模糊熵评判研究

分析了影响有效监控的各因素，阐述了刀具破损监测中存在的特征分区问题。以各个信号特征区间为模糊子集，以模糊熵值为参数来评判各种分区方法，结果表明，采用模糊熵值小的分区法能更准确识别刀具状态。     

Fluid dynamic mechanisms of particle flow causing ductile and brittle erosion

Traditional prediction of erosion focuses on the use of velocity and impact angle of particles as independent variables in analytically derived models. This approach is most suitable for numerical predictions of erosion in disperse flow fields where particle trajectories may easily be followed prior to impact. For dense particle flows, the prediction of individual particle or particle cluster movement is nearly never attempted by following trajectories. Instead, two-fluid Eulerian–Eulerian approaches are used in which a continuous particle fluid phase is considered.The present study shows that the impact velocity and angle of attack of particles at the eroding surface are difficult to obtain for dense flows, thus being difficult to consider as parameters for predicting erosion. Instead, it is proposed that the normal and the shearing components of the viscous dissipation of the particulate phase are more suitable as independent flow variables governing the erosion process. These variables describe deformation and cutting wear processes, respectively, and are readily derived from the flow field.Eulerian erosion models are proposed, based on these independent variables. It is possible to implement previous results and theories concerning the material–mechanical interaction between the abrasive and an eroding surface to achieve model improvements. In this work, only a simple model taking into account a threshold elastic strain limit is proposed, to more correctly model the deformation wear.The particle-flow boundary condition — a partial-slip condition — significantly influences the erosion process, particularly the cutting erosion. The boundary condition depends on parameters such as the local particle phase flow, the mean diameter and the sharpness of the abrasive as well as the surface roughness.A simple 2D test application — a jet stream of particles impinging a tilted plate — is presented, and the qualitative angular behaviour of ductile and brittle erosion is reproduced at the target position. A scheme is presented for determination of material constants and suitable boundary conditions to be used in the proposed erosion models.     

Control and evaluation of particle impact conditions in a sand erosion test facility

For the prediction of actual damage to plant component materials and for making the erosion mechanisms clear, it is important to control and to evaluate the particle impact conditions in a testing facility. A sand blast type erosion test rig, which can achieve the particle impact velocities up to 135 m s⁻¹ and a wide range of impact angles has been constructed. The key factors in particle impact conditions of particle flux, impact velocity and impact angle were examined. The relative distance between particles and particle size was discussed, as the particle flux affected erosion rate of material. A new method was proposed to determine particle velocities in this facility. The theoretical velocity of the particle calculated by the equations of particle motion was compared with the experimental results. The divergence of particles from a geometrical angle was evaluated by measuring surface roughness of the specimens. Although some spread of the particles were observed surrounding the central damage area of the specimen surface, the greatest amount of damage was concentrated in the center. As a result, it was found that particle impact conditions were well controlled in this testing unit.     

[供应链调度]基于信息熵的物料配送时间节点预测方法

针对不确定性干扰因素影响复杂产品装配车间物料配送时间准确性的问题,提出了一种基于信息熵评价的物料配送时间节点预测方法。分析了复杂产品装配车间不确定性干扰因素的种类,采用综合时间需求因子量化不确定性干扰因素,定义装配工位状态,并建立工位状态转移概率矩阵。基于工位状态变化的马尔可夫链特性,建立复杂产品装配车间物料配送时间节点预测模型。提出平均预测误差的动态误差补偿方法修正预测值,并选取最大配送可行性时限和配送准确度为评价指标,构建基于信息熵的物料配送系统评价体系,对物料配送时间节点预测方法的有效性进行评价。最后,以某公司磨床主轴装配工位的物料配送历史数据为例,对提出的预测方法进行验证。结果表明,所提出的预测方法有助于增大物料配送系统的最大配送可行性时限、提升物料配送时间节点的准确性。     

Effect of swirling flow by normal injection of secondary air on the gas residence time and mixing characteristics in a lab-scale cold model combustor

The present study investigates gas residence time and mixing characteristics for various swirl numbers generated by injection of secondary air into a lab-scale cylindrical combustor. Fine dust particles and butane gas were injected into the test chamber to study the gas residence time and mixing characteristics, respectively. The mixing characteristics were evaluated by standard deviation value of trace gas concentration at different measurement points. The measurement points were located 25 mm above the secondary air injection position. The trace gas concentration was detected by a gas analyzer. The gas residence time was estimated by measuring the temporal pressure difference across a filter media where the particles were captured. The swirl number of 20 for secondary air injection angle of 5° gave the best condition: long gas residence time and good mixing performance. Numerical calculations were also carried out to study the physical meanings of the experimental results, which showed good agreement with numerical results.     

信息熵与优化LS-SVM的轴承性能退化模糊粒化预测

为了提高滚动轴承性能退化指标的预测精度,得到性能退化指标的一个预测范围,本文提出信息熵与优化最小二乘支持向量机(LS-SVM)的轴承性能退化趋势模糊粒化预测。首先利用信息熵理论提取轴承信号的性能退化指标序列,再利用模糊信息粒化理论对该性能退化指标序列进行模糊信息粒化;然后将粒化后的数据输入给LS-SVM进行回归预测,并采用粒子群算法(PSO)优化LS-SVM的惩罚参数和核函数参数;最后根据实测值和预测值的对比分析评估预测模型的优良性。实验结果表明,对于每个时间段内的轴承性能退化指标,该方法均能获得准确的预测结果,具备较强的实用性和工程应用价值。     

离心泵叶轮内水流相对速度的实验研究

该研究应用PIV系统(粒子成像测速仪)这种先进的流场测试技术在不干扰流场的情况下,进行高精度的测量,即利用撒在流体中的粒子对光的散射作用,用光学的方法记录下粒子在不同时刻的位置,从而得到粒子的位移,基于粒子对流场的跟随性,测出水流在离心泵叶片流道内的绝对速度分布,并利用软件进行数据处理,得到离心叶轮内部从吸力边到压力边相对速度的分布,为离心泵的设计提供了更为可靠的理论依据。     

Application of scanning electron microscopy for pollution particle source determination in residential dust and soil

Many tons of electric furnace flue dust accumulated in an industrial area in Tifton, Georgia. Vehicles transporting the flue dust, classified as K061 hazardous waste because it contained lead and cadmium, initially dumped the material in a warehouse. Once the warehouse was full, the flue dust was dumped in uncovered piles. Run-off from the piles and wind-driven particles had the opportunity to contaminate nearby industries, residential buildings, and neighborhood soils over a period of many years. Scanning electron microscopy-energy dispersive x-ray spectrometry (SEM-EDS) was used to compare the morphology and chemical composition of fly ash dust from the suspect pile with samples collected from the surrounding buildings and soil. Adhesive samplers were used to collect dust that had accumulated in buildings surrounding the fly ash dump site. Suspect dust particles were analyzed by SEM-EDS and compared with known dust particles from the fly ash pile. Soil samples were dried, sieved, and the “fines” analyzed by SEM-EDS for comparison with samples from the fly ash pile. Fly ash particles similar in morphology and chemical composition to the fly ash in the suspect pile were identified in most of the buildings sampled surrounding the fly ash dump site and in all of the soil samples analyzed surrounding the dumpsite. This case study illustrates the usefulness of applying morphology and chemistry information acquired by SEM-EDS for pollution particle source determination.     

积灰对光伏组件输出特性影响建模与分析

灰尘沉积在光伏组件上严重影响光伏系统输出的稳定性,导致发电量降低的同时缩短了组件的使用寿命。准确地评估光伏现场积灰浓度,将有助提升光伏发电功率预测模型的精度。本文以光伏电站现场采集的灰尘颗粒为研究对象,首先分析了灰尘颗粒的元素组成、含量、形貌特征和粒径分布,根据光伏组件实际的发电效率和环境参数,建立了积灰浓度软测量模型,用于快速定量评估光伏电站积灰程度;其次,为了准确地获取模型的相关参数,开展了多组积灰浓度影响发电性能实验,得到了组件输出功率和辐照度、积灰浓度、组件温度的关系;最后,在自然条件下,验证了模型的准确性和可靠性。对比其他传统方法,结果表明:本文提出的模型具有更好的预测性能,准确率可达89.6%。     

曲波域铁谱磨粒图像特征提取方法研究

曲波变换具有多尺度分析能力,与小波变换相比可更好地表达图像的曲线特征.为有效描述铁谱磨粒的形貌特征,提出一种曲波域图像特征提取方法.利用曲波变换将磨粒图像进行分解,得到不同尺度的曲波系数;根据曲波系数统计分布特点,采用广义高斯分布模型对细尺度和精细尺度曲波系数分布进行建模;提取粗尺度曲波系数的均值、标准差、能量和熵等统计特征,以及细尺度和精细尺度曲波系数的广义高斯分布模型参数描述磨粒特征.将提取的特征用于发动机典型磨粒识别,识别成功率达到了88.9%,表明该方法所提特征能很好地表达铁谱磨粒的形貌特征.     

Explosion characteristics of combustible wood dust in confined system: Analysis using oxygen consumption energy

The explosion characteristics, such as maximum explosion pressure, rate of explosion pressure rise, explosion efficiency, were investigated to determine the roll and significance of oxygen consumption energy in dust explosion. Dust explosion experiments were conducted in a Siwek 20L spherical explosion apparatus for three wood dust samples from a wood-based panel production factory. Unlike gas explosions having maximum explosion pressure at near chemical stoichiometric concentration, both the maximum explosion pressure and the maximum rate of explosion pressure of wood dusts appeared at three times or much higher equivalence ratio. Although there were differences in particle size among tested dusts, in the case of dust of which the mean particle size was not larger than 100 µm, P_max appeared at lower equivalent ratios when mean particle sizes were smaller and at higher equivalent ratios when mean particle sizes were relatively larger. Explosion efficiency for all dusts are around 10 %, of which the value is relatively lower than most of other normal combustion, which signifies dust explosion remains 90 % of unburned dust with high fire risks after explosion. In a dust explosion, it is difficult to estimate the weight of suspended dust participating in explosions, especially in fuel rich conditions, so a method for estimating explosion overpressure by applying oxygen consumption energy based on unit volume (1 m³, SAPT condition) was newly proposed and verified from the result of explosion efficiency. To practically apply these results to dust treating industry, the assessment procedure for dust explosion influence has been provided by introducing TNT equivalent model and its scaled distance.