The role of flow characteristics in corrosion-erosion of tube inlets in the inlet channel of shell and tube heat exchangers

Hydrodynamic aspects of the corrosion—erosion of tube inlets in the inlet channel of a typical shell and tube heat exchanger handling solutions with some solid content were investigated. A cross flow pattern near the tube inlets was identified by flow visualization. This is considered to be the main factor contributing to the corrosion—erosion of tube inlets. A computer model simulating the cross flow and tracing the trajectories of particles in the flow was developed to help identify the range of particle sizes likely to result in tube inlet corrosion—erosion.     

特定条件下气-液喷射器结构合理性分析

为找出喷射器气液混合效果不理想的原因,创建了喷射器流场模型,采用CFX软件对喷射器流场进行了稳态和瞬态的数值模拟计算。得到了模型在不同工况下的气液混合效果、两进口的压差和两进口流量和压力的波动情况。计算结果表明此喷射器气-液混合效果受两进口压差的影响较大,只有在两进口压差较小的情况下才能完成气液混合。     

A Membrane Inlet for a Portable Mass Spectrometer

A system of membrane injection of a sample into a portable mass spectrometer which is used for determining the concentration of organic components in complex mixtures is described. Spectra of samples containing alkanes from methane to hexane have been measured. The data obtained using the membrane and diaphragm inlets to are compared. The potentialities of membrane inlets for portable mass spectrometers intended for environmental and process monitoring are shown.     

运行过程中转速变化时可倾瓦推力轴承油膜温度瞬态变化规律的实验研究

本文实验研究了可倾瓦推力轴承在运行过程中的不同载荷下、不同升速时间下从起始转速８００ｒ／ｍｉｎ升到截止转速５０００ｒ／ｍｉｎ时油腊温度和油膜厚度变化值的瞬态变化规律。实验时,在瓦块进油、出油边及油腊与瓦块接触面上布置了若干根铜－康铜热电偶和电涡流传感器。实验表明大运行过程中。转速升高时,不同的升速时间对油膜温度、进油边温度、出油边温度以及油腊厚度变化的影响基本相同;不同载荷对油膜温度、进油边温度以     

Numerical study on performance of supersonic inlets with various three-dimensional bumps

Numerical investigations were performed with a supersonic inlet system installed with a three-dimensional bump which was substituted for a diverter or conventional ramp-type compression systems at Mach 2. The modified inlets were designed to have two oblique shocks and a terminal normal shock followed by a subsonic diffuser, with a circular cross-section throughout. A numerical analysis was conducted to understand the three-dimensional flow field including shock/boundary layer interactions that occur around a three-dimensional bump and to evaluate the performance of the supersonic inlets. The current numerical simulations showed a bump-type inlet based on a conventional ramp-type inlet can provide an improvement in total pressure recovery downstream of the shock/boundary-layer interaction over a ramp-type inlet.     

Operational efficiency of spindles in metal-cutting machines with partially porous gas-static bearings

The operational efficiency of spindles with partially porous gas-static bearings is experimentally studied. The output characteristics of gas-static bearings with porous inserts are compared with those of traditional gas-static bearings that contain delivery inlets.     

A numerical study on the effect of the flow control using bleeding systems in a bump-type inlet

In many supersonic inlets, several oblique shock waves are followed by a terminal normal shock wave. The normal shock-wave/turbulent boundary-layer interaction is critical with respect to its influence on the development of boundary layer throughout the subsonic diffuser and the total pressure recovery at the engine face. In the current study, the bump-type inlet was designed for two oblique shock waves and a normal shock wave. In addition, a porous surface was installed underneath the root of the normal shock wave. The effect of flow control on the interaction between the normal shock wave and turbulent boundary layer in supersonic inlets by using the bleeding system was investigated numerically and was evaluated with respect to the inlet performance parameters.

     

离心泵偏置短叶片叶轮内部流动的粒子图像速度测量

对三副短叶片不同偏置的低比转数复合叶轮离心泵,应用粒子图像速度仪分别测试大流量、设计流量和小流量三种工况下长短叶片叶轮同一叶槽内的瞬时流场.分析叶槽内相对速度矢量、速度等值线的特征,揭示短叶片不同偏置时的速度分布规律.研究三副长短叶片复合叶轮出口处径向速度、切向速度、相对速度和相对液流角沿圆周的分布,测得与三副叶轮相对应的泵外特性曲线.测量结果表明,分流短叶片不同偏置对叶槽内流场的影响差异明显,当短叶片进口相对出口向压力面偏转时,叶轮出口相对速度分布很不均匀,短叶片工作面出口存在较大的低速区;与之相反,当短叶片进口相对出口向吸力面偏转时,叶轮出口速度分布较均匀,并且泵的扬程与流量曲线明显右移,大流量时,效率显著提高.     

户内变电站通风换热的数值模拟与优化分析

为了解决户内变电站夏季通风换热引起温度过高导致的设备安全问题,基于CFD数值模拟技术,利用专业流体仿真分析软件Fluent对户内变电站主变压器室的通风换热效果进行了数值模拟,优化分析了变电站进出风口尺寸、方位、流速以及户内变电站内部流场的分布,提出了加装导流片改善变电站通风换热效果的方法,并对导流片参数进行了优化计算,实现了户内变电站通风换热的优化设计,不仅保证了户内变电站夏季高温时期的设备安全,而且也有利于降低户内变电站噪声对环境的影响     

双排多辊冷轧管机轧制钢管的轴向力研究

考虑双排辊轧制时两段变形区之间金属的相互作用,以及两排轧辊对应的变形区金属的入口速度不同等特点,提出了双排多辊冷轧管机轧制钢管时,轧辊和芯棒作用于管料上的轴向力的计算方法,并对其影响因素进行了分析。     

Experimental and numerical analysis on the effect of inlet distortion on the performance of a centrifugal fan with a mixing chamber

Inlet flow distortions, which are caused by fluid mixing, cause a significant deterioration in fan performance. An experimental test rig for an industrial fan with dual inlets and a mixing chamber was constructed. The flow fields in the mixing chamber of the fan were numerically investigated. Consequently, impact parameters, including the length of the mixing chamber (100, 200, and 300 mm) and the mass flow rate ratio (1 to 10), as well as their effects on fan performance, were discussed. A generalized formula considering the Reynolds number, hydraulic diameter, and mixing length was proposed to predict the pressure drop in dual inlets. Results show that the efficiency of and pressure in the fan decreased by 6.5% and 203 Pa, respectively, under mixing inlet condition. Optimum fan performance is achieved at a flow rate ratio of 5 under the same mass flow rate. The increase in the flow rate ratio kept the fan performance almost constant. At the design stage, fan performance and pressure decrease by an average of 2% and 70 Pa in increments of 100 mm mixing length, respectively. The results presented in this paper provide a basis in the design optimization of mixing structures.     

10万t/a甲醇（焦炉合成气）离心压缩机性能方案的修改

根据技术协议要求机组出厂前需在厂内进行机械运转和性能试验。在审查试车性能试验方案时,发现该性能试验方案存在选择不完善的问题,对此提出了机组性能试验的改进方案,即：对机组的三进二出风口全部采用开式接管路、电动阀门形式试车,结果证明该方案正确可行。     

Comparison between externally pressurized gas thrust bearings with different orifice and porous feeding systems

This paper analyzes the influence of feeding system type on the performance of externally pressurized gas bearings. It compares the optimum characteristics regarding load capacity, stiffness and flow rate of an air thrust bearing which can be obtained by using different kinds of multiple inlets specifically designed with orifices or porous compensation. The investigations have shown that optimum performance may be achieved for each of these different feeding systems, which depend on an optimum number of inlets, position of orifices, or permeability coefficient of the porous material.     

Numerical and experimental studies on the mixing characteristics of two jets with inclined angles in a rectangular chamber

Mixing characteristics in a rectangular chamber are investigated using experimental and numerical methods. A mixing chamber with an axial inlet (representing fuel inlet) and a side inlet (representing air inlet) is designed. Two jets with different momentum ratios through the two inlets are mixed in the chamber. Computational fluid dynamic simulation is validated by experimental data of particle image velocimetry that measures flow velocity distribution. The momentum ratios of the two jets and the height of the axial inlet significantly influence the penetration depth of axial jet into the mixing chamber and the pressure drops at recirculation zones.     

微波引导下的滚筒杀青机内电磁场分布研究

基 于 电 磁 场Ｍ ａｘ ｗｅｌｌ 方 程 理 论 及 微 波 的 热 效 应 理 论 ，利 用 有 限 元 软 件 对 谐 振 腔 内 的 电 磁 场 分布 模 态 进 行 了 仿 真 计 算 ，并 讨 论 了 微 波 馈 入 口 位 置 、数 量 、方 向 等 对 滚 筒 内 电 磁 场 均 匀 性 的 影 响 。 结 果 表明 ，电 磁 波 谐 振 模 式 严 重 影 响 电 磁 场 在 谐 振 腔 内 的 分 布 ，通 过 对 模 态 的 选 择 可 实 现 温 度 场 的 均 匀 分 布 ，最 终形 成 对 茶 叶 的 均 匀 杀 青 效 果 。     

The design of single particle laser mass spectrometers

This review explores some of the design choices made with single particle mass spectrometers. Different instruments have used various configurations of inlets, particle sizing techniques, ionization lasers, mass spectrometers, and other components. Systematic bias against non-spherical particles probably exceeds a factor of 2 for all instruments. An ionization laser tradeoff is the relatively poor beam quality and reliability of an excimer laser versus the longer wavelengths and slower response time of an Nd-YAG laser. Single particle instruments can make special demands on the speed and dynamic range of the mass spectrometers. This review explains some of the choices made for instruments that were developed for different types of measurements in the atmosphere. Some practical design notes are also given from the author's experience with each section of the instrument.     

双锥对置锥螺杆海水液压泵流场数值模拟分析

为了深入分析泵压对双锥对置锥螺杆海水液压泵特性的影响,建立了该液压泵系统的三维模型及其流体动力学分析模型,运用CFD软件对液压泵的内部流场进行仿真分析,分别得出了不同进出口压差条件下和不同转子位置时的腔室液体压力分布以及转子受到的液压力。分析表明：新型海水液压泵腔室压力分布以啮合线为界限,由入口处到出口处交叉分布,且压力值逐级递增;左右转子受到的轴向液压力大小相等,方向相反;转子受到的液压力的方向沿转子自转的相反方向转动,而液压力大小基本不变。     

三入口单级分形微流控浓度梯度芯片的设计与性能分析

 传统浓度梯度生成方法具有效率低、梯度不够精确、稳定性差等不足，微流控芯片因其特征尺寸小、反应快、精度高和易操控等优点，被广泛用于微流体浓度梯度生成。微流控芯片的通道结构与进样条件对浓度梯度的生成具有重要影响。基于自相似分形理论，开发了三入口单级分形微流控浓度梯度芯片。建立基于有限元的多物理场耦合模型，通过归一化流量矩阵与浓度矩阵的耦合设置，得到呈偏态分布与正态分布的浓度梯度分布规律。以红色染料与去离子水为样本进行实验，结果与数值模拟吻合较好，验证了芯片设计的科学性与有效性。     

圆形出液口悬浮阴极平面电化学加工间隙建模及实验研究

提出利用极间电解液液膜支撑阴极悬浮形成加工间隙,通过调节流量和电流实现极间间隙的调节和控制的新方法。以圆形出液口悬浮阴极平面电化学加工为例,基于流体力学和电极过程动力学理论建立加工间隙的数学模型,得到间隙与流量、压差及电流之间的关系。利用Fluent软件对间隙模型流场特性进行分析,得到间隙中电解液的压力场和速度场的分布情况,进而得到进出口压差和出口流速;实验获得不同流量、电流条件下的加工间隙。理论模型计算结果和实验数据结果相近,变化规律基本一致。     

非磁性微粒的负磁泳-惯性组合分选研究

为了分选颗粒直径十分接近的非磁性颗粒,数值计算了负磁泳耦合的惯性分选器在不同磁场强度、微通道结构参数、入口速度和速度比情况下3μm、4μm、5μm的三种颗粒的侧向偏移,结果表明：颗粒的侧向迁移随磁场强度和颗粒尺寸的增大而增大;颗粒的分离效率随着入口流速的减小和入口流速比的增大而提高;越小的微通道结构参数Ha/Hb和越大的扩张区扩张比,都有利于颗粒分离。计算结果部分得到了激光诱导荧光图像实验的验证,证明了数值模型的有效性。