基于流量分配均匀性的集箱设计探究

集箱是热轧带钢冷却系统的重要装置,其流量分配均匀性是影响钢板性能的重要因素。为了提高集箱支管流量分布均匀性,本文结合理论分析对集箱内的阻力系数、压力分布规律、支管流量分布均匀性系数进行了研究,采用分段设计方式对不同段支管内的节流孔板进行了设计,并通过数值模拟对各支管分配流量进行了分析。结果表明,采用不等直径节流孔板能更好的提高集箱分配流量均匀性,有利于提高轧线冷却系统性能。     

基于Icepak 的水冷板散热器性能研究

文中采用Icepak 数值模拟的方法,研究不同结构形式的水冷板散热器的换热性能与压力损失,分析了并联流道截面积、流道布局对换热性能与压力损失的影响。结果表明:并联形式的水冷板散热器3的换热性能最好,且压力损失适中。当分流道截面积逐渐增大时,水冷板散热器3 的换热性能及压力损失逐渐降低。而当分流支路当量直径较大时,主管路的压力损失占主导,各分流支路流量受主管路压力损失控制,则此时各分流支路的流量分配不均匀,越远离入口处的分流支路流量越小。     

单板干燥室配风管速度均匀性的优化研究

喷气式单板干燥室的气流分配不均是影响单板干燥质量的主要因素。通过对配风管气流分配特性的实验和仿真研究,提出了一种导流板设计方案。通过对导流板中心孔间距、板厚、安装位置和孔径对配风管气流均匀性的影响进行分析,优化了导流板的设计参数。结果表明:相对于无导流板的配风管,导流板中心孔间距为45mm时,配风管的气流分配效果提升了41%;板厚为8mm,安装位置在分配管的2/5处时,配风均匀度分别提高了66%和67%;孔径为12mm时,气流分配效果提升了87%。     

一种梗条自动分配器的设计和应用

为解决卷烟厂制梗丝线上多台切梗丝机同时均匀供料的问题,设计一种梗条自动分配器。该梗条自动分配器主要由分配器主体、导流板、出料管、分配板、伺服气缸等部分组成,利用PLC程序控制伺服气缸的行程,控制分配板的摆动角度,实现分配器内不同入口面积的自动调节,从而自动调节出料管的物料流量,满足生产的需要。结果表明,梗条自动分配器能较好地满足配备四台切梗丝机的卷烟厂开二台备二台,或开三台备一台的生产需要。该技术为类似物料输送的按比例分流调节提供一种方法。     

铜硬钎焊炉均风孔板优化设计

为保证铜硬钎焊过程中的工艺温度,改进了连续式铜硬钎焊炉的结构设计,通过增设热风搅拌装置及均风孔板来提高温度均匀性。利用计算流体力学仿真技术分析了钎焊室孔板性能,研究了孔板开孔率及开孔方式对温度分布的影响规律。研究结果表明:采用50%开孔率的均风孔板时,工件部位温度均匀性要好于其他开孔率的孔板;同一开孔率时不同开孔方式也会影响工作位置的温差,50%开孔率时两端大中间小的开孔方式可有效控制温差。研究过程中采用多孔介质对孔板结构进行简化,有效降低了建模难度,减少了分析时间,为类似结构分析及优化设计提供了依据。     

基于CFD数值模拟的板式换热器分配器性能研究

基于计算流体动力学(Computational fluid dynamics, CFD)数值模拟方法,对板式换热器分配器在单相流动和两相流动时的分配性能分别进行研究.把板式换热器在有、无分配器作用时的数值模拟结果作对比,定量分析分配器对板式换热器并联流道间流体流量均匀分配的作用;进一步分析换热器并联流道数、工作流体流量和进口干度(两相流动时)变化对分配器流动分配性能的影响.结果发现,分配器显著提高换热器流道间流体分配的均匀性;无论是单相流动还是两相流动,并联流道数对换热器流道间流动分配均匀性的影响要大于工作流体流量变化的影响;与单相流相比,两相流动时分配器的分配性能较差,在制冷系统中当板式换热器作蒸发器使用时,这将会降低换热器的换热性能.研究结果为进一步改进分配器结构,改善板式换热器流道间流动分配的均匀性提供必要的理论依据.     

蒸发器内置毛细管开孔系统强化换热的试验研究

基于场协同强化理论,结合射流冲击的换热特点对常规毛细节流制冷系统进行优化,设计出一种新型的换热器装置。该换热器装置是将开孔毛细管内置到蒸发管中,使得制冷剂在节流后直接从毛细管沿轴向的不同孔口处冲击到蒸发管的内壁上蒸发换热,该冲击过程中由于速度场与温度梯度方向的协同性最大而具有显著的强化换热效果。首先,理论分析了毛细管进口速度(2m/s和0.5m/s)和开孔直径(1mm和0.5mm)的速度场与温度梯度方向的协同性,其次,在0MPa的回气压力下对该新型换热器装置进行性能试验,并以常规毛细节流系统作对比试验。试验结果表明,开孔试验中蒸发管表面的温度场比较稳定,而常规毛细试验中各测点由于毛细管节流的流量调节能力差而存在较大的波动。在蒸发压力和换热面积相同条件下,毛细试验的排气压力要比开孔试验高出13.6%,所以开孔试验的性能系数、制冷剂充注量比毛细试验更优;同时,毛细试验的压缩机功耗要比开孔试验高出9.1%,可见开孔试验系统的制冷效率比常规毛细试验的更高。开孔试验因为在多处射流冲击供液,并且射流冲击在冲击区中射流工质的流场和温度梯度场具有极好的协同度而能显著强化换热,使得蒸发管表面形成的温度场相对更均匀。     

喷射式绞纱染色机分流器均匀性的研究与优化

针对现有的大容量喷射式绞纱染色机存在的出口流量分配不均匀的问题,利用Fluent软件对分流器内部流场进行模拟,结合多孔管流量分配理论对出口流量分配不均匀的原因进行分析,指出选择合适的斜面个数和斜率是提高分流器出口流量均匀性的有效措施,改进后的分流器分流均匀性得到显著提高,并且所做的改进不会对染色机其它结构产生影响,达到了预期的优化目的.     

适用于孔板送风的孔板阻力特性研究

为了提高孔板送风房间流场预测的准确性,采用数值模拟结合试验验证的方法,以局部阻力系数为评价指标,分别对不同开孔形状、孔板厚度、孔口直径、开孔率的孔板的阻力特性展开了研究。结果表明：开孔形状对局部阻力系数影响较小,随着当量直径的增大,局部阻力系数略微增加,5种常见开孔形状下的平均局部阻力系数最大值与最小值偏差为4.5%;随着孔板厚度的增大,局部阻力系数减小,孔板厚度在1～3 mm范围内,平均局部阻力系数最大值与最小值偏差为17.8%;随着孔口直径的增大,局部阻力系数增加,直径在4～10 mm范围内,平均局部阻力系数最大值与最小值偏差为15.1%;随着开孔率的降低,局部阻力系数显著提高,且两者之间存在幂函数的变化关系。通过对数据进行分析,得到了适用于开孔率范围为0.01～0.05的孔板局部阻力系数近似计算式,该式为孔板送风房间流场预测提供了一定的数据基础。     

增益发生器中多孔管分流均匀性的数值计算

通过数值计算的方法,分析了反应气体流量等级提高对增益发生器中多孔管分流均匀性的影响,计算证明经典设计中流量等级达到500%,多孔管分流均匀性变差;确定了小孔入口静压为流量分布均匀性的关键影响因素,并提出了两种优化方案,计算结果验证了两种优化方案均能改善高流量时多孔管分流均匀性。     

气体涡轮流量计后导流体结构优化设计

通过数值模拟和实验测试相结合的方法,研究了LWQ80气体涡轮流量计后导流体的结构优化及其计量性能的变化规律。基于流量计内部流场特征及其流动机理的探究,分析得出造成后导流体压损的主要原因是后导流体区域的壁面边界层分离和流体流向偏转。由此提出了缩小分离区和提升导流片导流效果的优化思路,通过延长后导流体的长度和延后导流片的位置,设计了一种改进型的后导流体结构。研究结果表明：后导流体结构经过改进后,气体涡轮流量计的计量性能得到了明显提升。在流量为250 m~3/h时流量计的压损降低了20.5%左右,仪表系数的恒定性显著提高,最大示值误差降低了近2.5倍,且能有效延长流量计的使用寿命。研究结果有助于为气体涡轮流量计的结构与性能优化提供理论指导和技术支持。     

圆盘止推静压气体轴承亚音速流场的简化计算

雷诺气体润滑方程仅涉及轴承气膜内的静压分布,对静压气体轴承流道特性的准确刻画还需要研究轴承流道内的气流速度场。将忽略惯性力的纯粘性等温气膜和等熵流动的供气孔拼接,建立了单供气孔环面节流圆盘止推轴承的流道简化模型,给出流道各部分气流马赫数、雷诺数和压力分布的计算公式。结果表明,气膜中气流速度随矢径变化的性质,取决于速度梯度为零的矢径位置;气膜中的气流雷诺数随矢径的增加不断减小。实际的计算结果表明,只要气膜入口截面上的气流马赫数小于临界声速,整个轴承流道将工作在亚音速,供气压力或气膜高度的变化对气膜起始区域边界层发展段长度的影响很小,供气孔始末端截面上压力和温度的变化也很小,忽略惯性力的纯粘性等温雷诺模型基本能够适用轴承的整个亚音速工况。气膜起始区域边界层发展段的长度,可以用气膜中雷诺数大于临界雷诺数的区域长度来近似。     

Measurement of the sunroof buffeting noise with an automatic deflector-traversing device

A wind deflector that is properly installed near the leading edge of the sunroof opening of a vehicle is known to effectively suppress the sunroof buffeting noise. However, the efficiency of wind noise reduction is very sensitive to the position and angle of the deflector. An automatic deflector-traversing device was devised to automate the sunroof deflector test procedure. It can automatically place a deflector at any desired position and angle with high accuracy. The deflector-traversing device was tested in a SUV vehicle at various wind speeds in an acoustically treated wind tunnel. In the test reported in the present work, the investigation area within which the position of the deflector could be varied was approximately 12mm × 20mm. Hundreds of deflector positions and angles were tested in the investigation area in a relatively short time period. A post-processing program was then used to process the abundant data obtained from the automatic measurements. For a narrow region of investigation, the post-processing program yielded color maps with high resolution for the high-frequency wind rush noise levels as well as the low-frequency sunroof buffeting noise levels as functions of the positions and angles of the deflector. It is concluded that the deflector-traversing device can be used together with an analytical model for the prediction of the buffeting noise for optimizing the deflector position to effectively suppress both the buffeting noise and the wind rush noise.     

Analysis of the Internal Characteristics of a De ector Jet Servo Valve

In current research on deflector jet servo valves, the receiver pressure estimated using traditional two-dimensional simulation and theoretical calculation is always lower than the experimental data; therefore, credible information about the flow field in the prestage part of the valve can hardly be obtained. To investigate this issue and understand the internal characteristics of the deflector jet valve, a realistic numerical model is constructed and a three-dimensional simulation carried out that displays a complex flow pattern in the deflector jet structure. Then six phases of the flow pattern are presented, and the defects of the two-dimensional simulation are revealed. Based on the simulation results, it is found that the jet in the deflector has a longer core area and the fluid near the shunt wedge cannot resist the impact of the high-speed fluid. Therefore, two assumptions about the flow distribution are presented by which to construct a more complete theoretical model. The receiver pressure and prestage pressure gain are significantly enhanced in the calculations. Finally, special experiments on the prestage of the servo valve are performed, and the pressure performance of the numerical simulation and the theoretical calculation agree well with the experimental data. Finally, the internal mechanism described by the theoretical and numerical models is verified. From this research,more accurate numerical and theoretical models are proposed by which to figure out the internal characteristics of the deflector jet valve.     

A "tabletop" electrostatic ion storage ring: Mini-Ring

We report on the design, construction, and commissioning of a novel electrostatic ion storage ring of small dimensions--in the following referred to as "Mini-Ring." Mini-Ring consists of four horizontal parallel-plate deflectors and two conical electrostatic mirrors. Ions are injected through the two deflectors on the injection side and off axis with respect to the conical mirrors which face each other. The first injection deflector, originally at zero voltage, is switched to its set value such that the ions after one turn follow stable trajectories of lengths of roughly 30 cm. This design reduces the number of electrodes necessary to guide the ion beam through the ring in stable orbits. The six elements (deflectors and mirrors) are placed on a common grounded plate--the tabletop. Here, we present the design, ion trajectory simulations, and results of the first test experiments demonstrating the successful room-temperature operation of Mini-Ring at background pressures of 10(-6) - 10(-7) mbar.     

100-ps framing-camera tube

The optoelectronic framing-camera tube described is capable of recording two-dimensional image frames with high spatial resolution in the <100-ps range. Framing is performed by streaking a two-dimensional electron image across narrow slits. The resulting dissected electron line images from the slits are restored into framed images by a restorer deflector operating synchronously with the dissector deflector. The number of framed images on the tube's viewing screen equals the number of dissecting slits in the tube. Performance has been demonstrated in a prototype tube by recording 135-ps-duration framed images of 2.5-mm patterns at the cathode. The limitation in the framing speed is in the external drivers for the deflectors and not in the tube design characteristics. Faster frame speeds in the <100-ps range can be obtained by use of faster deflection drivers.     

基于FLUENT的滑阀液动力补偿的研究

液动力是滑阀和阀腔的结构设计中考虑的关键因素之一。提出了一种在阀套上开圆弧型进出口流道的方法,对进出口处的油液进行导流,以达到减小液动力的目的。同时利用FLUENT软件分析该阀内流场,并与传统的直流道滑阀相比较,然后对改进后滑阀的液动力特性和阀口流量特性分析计算。该研究对滑阀的结构优化设计有一定的参考意义。     

一种新型无阀微泵的原理和模拟

提出了一种新型无阀微泵的设计概念及相应的模型 ,它利用合成喷流动的基本原理实现对流体流动方向的控制 ,结构简单 ,工作频率高。对这种泵的工作状况进行了数值模拟和整体分析 ,结果表明这种泵流量大 ,在驱动器工作频率为 1 0 0 0 Hz,喷口雷诺数为 2 5 0 0时泵送空气流量达 6L/min     

Stage-discharge relationship for slide gates installed in partially full pipes

Sluice/slide gates are widely used for flow depth control and flow discharge measurements in open channels. The hydraulic behavior of the sluice gates located in the rectangular open channels is well documented in the literature. This study reports the results of an investigation conducted to establish the stage-discharge relationship for the sluice gates located in horizontal, circular open channels/pipes under free outflow conditions. Different stage-discharge models were proposed based on the Buckingham's theorem of dimensional analysis and orifice theory. A comprehensive series of laboratory experiments (729 runs) were performed to study the sluice gates located at the middle, and at the end of two circular pipes. Using the data collected from two circular open channels of nominal diameters 20 and 30 cm, the proposed models were calibrated. For the middle slide gates, the experimental results showed that the discharge prediction can be improved by introducing the Reynolds number. For the slide gates located at the middle of the channel, the best proposed model has an average error of 1.40% with a maximum error of 7.12%. For the slide gates located at the end of the channel, the Reynolds number has no significant effect and best proposed model has an average error of 2.47% with a maximum error of 6.59%. The results also showed that the flow discharge of the end slide gate (with unconfined free jet under gravity) is higher than the flow discharge of the middle slide gate for the same gate opening areas and upstream flow depths. The proposed sluice/slide gate for circular open channels offers a simple and reliable discharge measurement approach with acceptable accuracy.     

椭圆形丁胞数目及分布对传热管内流动和传热特性的影响

通过建立含不同参数椭圆形丁胞的传热管有限元模型,仿真研究雷诺数Re在5000~40000范围内椭圆形丁胞数目、轴向间距及交叉分布对传热管内流体介质流动及传热特性的影响规律。仿真研究结果表明,相比于光滑传热管,椭圆形丁胞的存在将增强对流传热的效果,且雷诺数Re越大越明显,但同时也会增加流体通过传热管时的流动阻力。此外,在雷诺数Re=40000时,椭圆形丁胞圆周分布数目N=6、轴向间距P=14 mm以及交叉分布角度为0°对传热管内流体的流动和传热综合特性影响最大,相比于光滑传热管,PEC分别达到1.156,1.15和1.13。