气力输送吸嘴的自转和公转

吸嘴是吸送式气力输送装置的关键部件。转动吸嘴的研制成功对提高吸煤机的生产能力起到了突破性的作用。转动吸嘴公转是在吸煤实验中发现的,转动吸嘴的公转,不仅扩大了它的工作范围,还能给它提供更加充足的可吸送物料,文中阐述了转动吸嘴公转现象产生的机理,推导出了转动吸嘴公转的数学公式。并据此提出了转动吸嘴公转时的扒煤松料条件。     

双出口旋风除尘器压损和分离效率的模拟研究

通过对新型双出口旋风除尘器在不同风量、不同粒径大小等条件下进行数值模拟分析,研究结果表明：双出口旋风除尘器进口风量越大,系统的流速越大,旋风除尘器的压差也越大,压力损失主要集中在旋风除尘器的入口至蜗壳处、除尘器上部以及旋切叶片与出风口连接处,当入口风速为13.21m/s时旋风除尘器压损为375Pa,当入口风速增加至26.42m/s时旋风除尘器压损为1 572Pa,即入口的风速增加一倍,旋风筒的压损增加三倍左右;双出口旋风筒入口流速与收尘效率呈正相关,入口流速越大,内部分离效率越高,收尘效率也越高,但阻力也随之增大,因此入口流速的选择应平衡效率和阻力的关系;粉尘颗粒粒径越大,越容易被捕集,当粉尘粒径<5μm时,很难被双出口旋风除尘器完全捕集下来。     

外循环式分解炉压力损失的冷模试验研究

外循环式分解炉是西安建筑科技大学开发的新型碳酸盐分解反应炉,在工程应用中取得了很好的效果,为进一步优化反应炉的结构,试验测试了分解炉截面风速为5～8 m/s,三次风入口风速为24 m/s、26 m/s和28 m/s,固气比Z=0.5的条件下,外循环式分解炉系统主体段压力损失和粗分离器压力损失.结果表明:系统空载运行时,随分解炉截面风速的增大,分解炉主体段和粗分离器的压力损失增大;分解炉截面风速不变,随三次风入口风速的增大,分解炉主体段压力损失减小.系统投料运行时,随分解炉截面风速的增大,分解炉主体段和粗分离器的压力损失增大;三次风入口风速对其压力损失的影响不大.相比空载运行,投料运行时分解炉主体段压力损失增加约1～1.2倍,粗分离器压力损失增加约10％ ～ 50％.适当降低分解炉截面风速,是降低分解炉压力损失的有效手段.     

支管流量对T型管内流体速度场的影响

为弄清支管入口流量(直径及流速)对T型管内流体速度场的影响规律,采用计算流体力学方法,对T型管进行了数值模拟,得到了其内部流体速度分云图及矢量图,结果表明,入口管流速超过0.4 m/s出现明显涡流,管径比在0.7812时开发区截止至z=130 mm。     

新型热电制冷装置的实验开发

旨在开发一种热电制冷装置(TEC), 实现微电子设备芯片低于环境温度的冷却, 解决芯片超频运行后的散热问题。为了研究该装置的制冷效果, 将其串联在传统液冷散热系统中。通过搭建实验测试平台, 对该装置在不同环境温度、芯片不同热流密度、不同工况和不同制冷效率下的制冷性能进行了实验研究。研究表明, 维持热源表面温度与环境温度相等、TEC工作电压48V、风速3~5m/s的条件下, 散热能力可达7W/cm²。散热器工作在高环境温度(35℃)下, TEC能有效降低散热阻力, 提升最大散热量。当热流密度为23.78W/cm²、风速为5m/s时, TEC工作在16~48V电压值下, 热源表面温度最大降低5.4℃。实验研究同时显示, 传统液体散热系统对提升TEC能效比(COP)有较积极的作用。维持热源表面温度比环境温度高10℃、TEC输入电压4~48V、风速3~5m/s情况下, 最大能效比达3.5, 最大热流密度达到15W/cm²。     

蓝山至临武220kV输电线路工程抗风及抗冰设计

利用蓝山和临武国家地面气象观测站自建站以来至2015年的逐日最大风速资料,逐日雨凇、雾凇等与电线积冰关联的天气现象资料和逐日平均相对湿度资料,引入湖南电线覆冰厚度估算模型,构建电线积冰厚度的历史序列,确定不同重现期最大风速及年最大积冰厚度,从而得出蓝山和临武两县220KV输电线路工程的抗风及抗冰设计标准,其中送电线工程的基本风速设计重现期为30年,对应的蓝山和临武的风速分别为19.1m/s和20.8m/s,可以23.5m/s为输电线路设计风速;架空输电线路设计冰厚重现期为30年,对应的蓝山和临武海拔600m以下地区最大标准积冰厚度均小于8.9mm,输电线路可按轻冰区10mm设计,海拔600~700m地区30年一遇最大标准积冰厚度在15.9~26.4mm之间,可按重冰区30mm设计。     

超音速气流粉碎机喷嘴的模拟与实验研究

采用Matlab软件,利用工程热力学的知识设计实验室气流粉碎装置的喷嘴结构和参数,用Fluent流体模拟软件对所设计喷嘴进行流场模拟,并以此对所设计喷嘴的效果进行检验.讨论了顶锥角对超音速喷嘴的影响.通过模拟比较得到,入口压力3.5MPa、入口直径为6mm的喷嘴为设计的最佳喷嘴.对于设计出的超音速喷嘴,顶锥角在8°～12°之间变化时,对喷嘴的性能影响不大.用所设计的喷嘴对重质碳酸钙进行粉碎实验的研究,证明了所设计的喷嘴的粉碎能力,同时得到了其粉碎重质碳酸钙的最佳工艺参数:即在入口压力为3.8MPa,靶距为25mm,管距为1 mm的工艺条件下,可将平均粒径为300μm的重质碳酸钙粉碎至20μm以下.     

聚酯切片皮的形成及防治

聚酯切片气送过程中切片皮形成的原因是风速高、温度高和有静电。防治方法是确保输送风速小于 5m/s ,静电接地线要与大地导通。     

垂直安装丝网除雾器的表面速度

通过文献分析及试验表明:垂直安装的高空隙率丝网除雾器应用于空气-水系统的气液分离时确定3.68m/s为最大允许表面速度是可行的:确定2.77m/s为设计表面速度是合适的;在1.71m/s至3.53m/s的入口表面速度范围内,具有98—99％以上的除雾(或净化)效率,且压降与表面速度线性相关。     

垂直轴5叶片阻力型风力机的动态特性

采用CFD对风轮直径为4 m的垂直轴5叶片阻力型风力机的瞬态流场进行数值模拟. 通过对不同入口风速和风力机转速条件下风力机流场和力矩系数随时间的变化情况的计算模拟,分析了垂直轴5叶片阻力型风力机的动态特性. 结果表明,流场和力矩系数的变化具有周期性,随转速增加,力矩系数的均值和周期均减小,振荡幅度增大;随风速增加,力矩系数均值和振荡幅度均大幅上涨. 力矩系数呈调制波形式,风速对曲线形态有较大影响. 随风速增大,风力机的最佳转速和风能利用率逐渐增加. 当入口风速从7.5 m/s增加到9 m/s时,风力机的最佳转速和风力机的风能利用率最大值分别从13 r/min和23.2%增加到19 r/min和25.8%.     

新型吸送式气力输送原理与实验

为了提高气力输送重要技术指标之一的固气混合比 ,近年来洛阳工学院研制了新型吸送式气力输送实验装置。在该实验装置的供料器内 ,经喷嘴引入压缩空气 ,提高了供料器内的真空度 ,使物料能更加充足、均匀地进入供料器。着重从理论上论述了压缩空气喷嘴的流动参数计算方法和喷嘴射流抽引现象产生机理 ,分析了新型吸送式气力输送的原理与可行性 ,并对其进行了实验。实验结果证明 ,不但新型吸送式气力输送原理正确 ,而且比传统的吸送式气力输送固气混合比大幅度提高     

An experimental study of energy-saving pneumatic conveying system in a horizontal pipeline with dune model

In order to reduce power consumption and conveying velocity, a pneumatic conveying system where a dune model is mounted in a pipeline is proposed in this paper. The experimental study focuses on the effect of the mounted dune model in the horizontal pneumatic conveying system in terms of pressure drop, power consumption and conveying velocity. The test pipeline consisted of a horizontal smooth acrylic tube with an inside diameter of 80 mm and a length of about 5 m. Polyethylene spherical particles with a density of 952 kg/m³ and diameters of 2.3 and 3.3 mm are used as conveying materials. The mean air velocity is varied from 9 to 16 m/s, and the solid mass flow rate is from 0.25 to 0.45 kg/s. Firstly, the effect of the dune model location on pneumatic conveying is experimentally studied. It is found that in the lower air velocity range, the pressure drop of the pneumatic conveying with a mounted dune model is lower than that of a conventional pneumatic conveying system. A lower conveying velocity and energy-saving conveying can be realized by installing a dune model in the conveying pipe. Especially the case of fixing the dune model on the bottom of the pipe at the inlet of particle feed is more effective. The particle flow patterns also show that the dune model reduces the deposition of particles. Then, the effect of different surface materials of the dune model is examined. By using a surface material of the dune model with a large coefficient of restitution, the pressure drop of conveying large particles is the lowest. When conveying relatively small particles, however, the pressure drop becomes the lowest by a small coefficient of restitution. The maximum reduction rates of the minimum velocity and power consumption by the dune model are about 19% and 34%, respectively.     

Application of high-speed PIV and image processing to measuring particle velocity and concentration in a horizontal pneumatic conveying with dune model

The purpose of this study focuses on analyzing the particle velocity and concentration characteristics in a horizontal pneumatic conveying with dune model, so as to reveal the mechanism of the low conveying velocity and saving-energy conveying. The test pipeline consisted of a horizontal smooth acrylic tube with an inside diameter of 80 mm and a length of about 5 m. The polyethylene particles of density 978 kg/m³ and 952 kg/m³ with diameters of 2.3 and 3.3 mm are used as conveying materials. High-speed PIV was first applied to measure the time-averaged particle velocity and was proven to be an efficient measurement technique in the pneumatic conveying. Then the particle velocity and concentration distributions of three locations were measured at mean air velocities of 12 m/s and 13 m/s and the solid mass flow rates of 0.45 kg/s and 0.43 kg/s. A comparison of the particle velocity and concentration profiles between dune model and non-dune model was performed. It is found that the particle concentration of using dune model becomes higher in the upper part of pipeline and becomes lower near the bottom of pipeline in the acceleration region. The particle velocities of using dune model are clearly higher than that of the conventional pneumatic conveying along pipeline and display a uniform profile at the downstream. It is also clear that the particles can be effectively accelerated by increasing air velocity and impacting the surface of dune model. The effect of dune model on the velocity profile of relatively small particles is larger than that of the larger particles and maintains to the downstream.     

Coupled DEM‐CFD Simulation of Pneumatically Conveyed Granular Media

A DEM‐CFD coupling for the simulation of gas‐solid flows was successfully implemented and simulations were performed for the application to industrial‐scale pneumatic conveying. Therefore, all particle collisions and phase interactions were considered and porosity determination was optimized. The aim of this work is to show the applicability of the presented simulation model to the different regimes of pneumatic conveying systems. As a first test case a dense vertical pneumatic conveying system was chosen and an individual plug was investigated in detail. Variations of the conveying air velocity were also considered. As a second test case dilute conveying in a horizontal‐to‐vertical pipe bend was simulated. The occurrence of roping and the reduction of particle velocity is of high interest for the design of specific pneumatic systems. It is shown that both regimes can be captured reasonably well and the results are rich in details.     

气固两相流在水平管道中的数值模拟

在水平T型分支管道中,利用压缩空气作为输送介质,平均粒径为0.9 mm的小米为输送对象,进行气力输送实验。在实验基础上,利用Fluent软件就三维水平圆柱管中气力输送过程进行了数值分析。对某一流速和压力下管道内部轴向压强、径向速度和单相浓度进行了模拟与监测,幵将模拟结果与实验结果对比,发现模拟结果与实验结果趋势基本相同,相对误差较小,有较好的一致性。     

不同粉料在双套管气力输送系统中的输送特性

选择粉煤灰、萤石粉与白灰3种典型粉料,在长100 m、管径100 mm的双套管气力输送系统实验台上进行了输送特性的研究,考察了粉料密度与粒径对其在双套管输送系统内输送效果的影响. 研究范围内,粉煤灰、萤石粉、白灰在本实验系统内的最小输送耗气量依次约为200, 300, 800 m3/h,最低输送压力梯度依次为0.8, 1.2, 1.1 kPa/m;物料输送质量流率最高点对应的输送耗气量依次约为500, 620, 820 m3/h. 根据物料在管道中的输送状态及压力梯度沿管线的变化特点,可将整体管道分为起始、过渡与充分发展3段.     

宁东灵武矿区煤粉密相输送管道压降研究

采用Barth气力输送理论,通过实验在质量流率1 550—1 700 kg/h的输送范围内,研究了宁东灵武矿区煤粉密相输送的压降和表观气速的关系。结果表明:随着表观气速的增加,水平管道和竖直管道的压降都是先降低后升高,但竖直段的压降变化速度比水平段变化快,水平段的经济气速(4 m/s)小于竖直段的经济气速(7 m/s)。通过计算值与实验值比较,发现理论计算值与实验值偏差在30%以内,说明基于Barth附加压降法对宁东灵武矿区煤粉密相气力输送管阻力特性的计算具有较好的适应性。     

Experimental investigation on blockage boundary for pneumatic conveying of powders in narrow bifurcation slits

To investigate the blockage characteristics for dense-phase pneumatic conveying in narrow bifurcation slits, a study on the blockage boundary conditions of powders was undertaken. The results show that the solid mass flow rate for blockage increases with superficial air velocity, and the variation trend can be divided into three typical stages. Besides the relationship between the solid loading ratio and superficial air velocity for blockage in the bifurcation slit displays a “S” shape with the increase of air velocity, the solid loading ratio increases, then decreases, finally increases, and in each stage above, the relationship between the two approximately meets power function, respectively. According to the “S” shape relationship, the formula used for blockage boundary [Setia, Mallick, Wypych, and Pan (2013). Validated scale-up procedure to predict blockage condition for fluidized dense-phase pneumatic conveying systems, Particuology, 11, 657–663] was modified into piecewise function for bifurcation slits. In addition, with the increase of the bifurcation angle and conveying pressure, the superficial air velocity decreases, while the solid mass flow rate and the critical solid loading ratio increase. The research work could help understand the blockage theory of the dense-phase pneumatic conveying.     

烧结灰在双套管气力输送系统中输送特性的实验研究

在长200 m、管径100 mm双套管气力输送系统实验台上进行了烧结除尘灰输送实验,考察了其输送特性. 根据所得输送压力梯度特点可将管道分为起始段、过渡段与充分发展段. 在研究范围内,烧结灰输送压力梯度最低值为1.071 kPa/m,最高值为1.616 kPa/m,质量流率最高值为33 t/h,物料流率/气流流率最高值约为36,能耗最低值约为2.6 kW×h/(t×km).     

水平分支管路气力输送阻力特性的预测

在水平T型分支管道中,用压缩空气作为输送气体,对平均粒径为0.25 mm和0.5 mm的砂石进行气力输送试验。通过试验和GRNN神经网络对输送表观气速和两分支管路流量控制阀开度发生变化时,各分支管路中的阻力特性进行了研究。结果表明:随着表观气速的逐渐减小和两分支管路流量控制阀开度差值的增加,各分支管路中的阻力特性相应地发生了变化。通过试验值和GRNN网络模拟值的对比,发现试验值和模拟值间相互吻合得较好,说明采用GRNN网络来模拟两分支管路中各自的阻力特性适应性较好。