渐扩管内气液环状流附壁特性研究

利用Fluent软件模拟了油气两相流在渐扩管内的液相的附壁情况,得到了渐扩管扩张段的速度场和压力的分布规律,并分析了改变渐扩管的扩张角对扩张段环状流液膜附壁的影响。结果表明,渐扩管扩张段的锥角对环状流液膜的附壁有很大的影响,扩张段横截面的速度差值和压降随扩张角增大而增大,但是轴向梯度力却随之减小。这些结论对油气润滑系统中的输运有指导意义。     

粮食稀相气力输送弯管段防磨减压的研究

针对粮食颗粒稀相管道输送弯管处存在的压降及磨损问题,采用管径渐扩张多级分段法对小曲径比弯管进行结构调整。应用FLUENT(软件)在双欧拉模型下对弯管内的气固两相流场进行数值仿真,并分析其流动特性。结果表明:渐扩张弯管在其内部的压强场、速度场、颗粒分布场等气固两相流态与普通弯管相似,其最大压强下降了26%,压损减小了76%,弯管口处的颗粒速度降低了11.5%,且弯管段的滞留颗粒体积降低。说明调整后的弯管具有较高防磨减压能力和稳定的输送性能。     

基于ANSYS Workbench的天然气渐扩管冲蚀磨损仿真模拟

为了研究含砂天然气集输管道渐扩管的冲蚀磨损现象。运用ANSYS软件建立渐扩管流场的Euler多相流、流固耦合及冲蚀模型,分析渐扩管的应力分布、流动特性及冲蚀效果,并与突扩管进行比较;通过改变管道入口流速、颗粒粒径、颗粒质量流率等参数,对渐扩管流场特性及冲蚀规律进行分析。结果表明,渐扩管应力集中在喉部及出口管段内壁面,冲蚀区域集中在出口管段下表面及出口处,出口管段冲蚀区域呈“椭圆形”,出口处冲蚀区域呈“U”形;突扩管应力集中在进口管段与出口管段交界处的上壁面,冲蚀区域位于进口管段;渐扩管冲蚀速率随入口流速增加先增大后减小再增大,随颗粒粒径的增加先增大后减小最终趋于稳定,随颗粒质量流率增加呈线性增长;相同条件下,突扩管最大等效应力是渐扩管的1.73倍,变形位移是渐扩管的1.77倍,而渐扩管冲蚀较为严重,最大冲蚀速率是突扩管的1.7倍。     

负压钻进水平钻孔浓相气力输送特性的研究

叙述了气体输送特性参数的理论分析,根据一些基本原理导出输送特性参数的计算公式。为了给输送特性参数的试验研究提供基础,通过试验分别研究了影响输送特性的因素,再根据试验数据,考察了输送压力、管径、钻杆角度和输送距离对输送特性的影响。研究与计算表明:输送能力与输送压力之间是近线性关系;较小的角度变化范围下,随着角度的增大,固体颗粒速度减小;发现固气比越大,滑移速度越小;最后通过试验得出:只需要在较小的输送压力下以较低的速度输送煤屑就可以实现高固气比输送,这样不仅能减少系统所需要的动力,而且煤屑输送速度的降低也可以减少对输送管道的磨损。该研究成果对工程应用具有一定的指导意义。     

水平渐缩管道浓相气力输送流动阻力特性研究

在水平渐缩管内浓相气力输送试验台上,以压缩空气作为输送动力,脱硫石膏粉体为输送物料进行了气固两相输送试验,在试验的基础上得出了不同输送条件下气固两相通过水平渐缩管时压力降的变化规律及影响因素。研究表明,管径比、固气质量比和扩散角度对管道压力降影响显著。同时,利用相似第二定律和量纲分析法建立了水平渐缩管的阻力特性关联式。通过将压力降试验值与计算值进行对比,发现该阻力特性关联式具有较好的精确度。     

基于CFD柴油机进气系统防爆栅栏结构优化设计

进气系统防爆栅栏作为防爆柴油机重要的组成设备,可有效防止发动机进气系统带来的爆炸危险发生。根据防爆要求,对柴油机进气防爆栅栏进行设计。基于CFD仿真分析柴油机进气系统的压力云图和温度云图;对圆柱形进气栅栏进行结构分析和流场分析;根据压力和温度云图,将进出口圆管分别加大一倍,再改为渐扩管阻火器的结构和性能研究,分别对120°、127°、134°、141°渐扩角进行分析;获得压力损失、出口流量与渐扩角之间关系;基于防爆柴油机试验台,对不同的优化方案下柴油机功率进行对比分析,以获取最优设计。结果可知:进气阻火器占整个进气系统压力损失的94.2%;当渐扩角134°时,压力损失随着渐扩角的增加而降低,流量随之增加;当渐扩角≥134°时,压力损失随着渐扩角的增加而上升,流量随之减小;在试验所测的转速范围内,渐扩角进气防爆栅栏的柴油机功率随损失最小,比原方案高15%,这说明改进方案是有效的,所以改进进气防爆栅栏的结构来减少进气阻力对于改善柴油机的经济性动力性是十分必要的。     

渐扩管内流动特性的理论分析与试验研究

通过对渐扩管流动特性的理论分析与试验研究，其结果发现：渐扩管元件对管道和系统的作用不仅和全身尺寸有关，而且也和安装位置有关。设计不合理的渐扩管使管道系统产生再生气流噪声，同时使管道系统气流引起更大脉动，造成整个系统振动。本文为渐扩管的合理设计提供了可的参考资料，具有重要的工程应用价值。     

密相气固两相管道输送粉体的特性研究

在1:1的试验台上采用粉煤灰、水泥两种不同粉体作为输送物料,压缩空气作为输送动力进行了气固输送试验,在试验基础上得出了密相气固两相流动特性及阻力特性的变化规律.试验结果表明,在发送压力基本保持不变的情况下,随气体表观速度的增大,固体质量流率、固体速度增大,而阻力损失减小;同时考察了物料特性对输送性能的影响.利用根据力平衡原理建立的料栓平衡方程式并结合试验数据得出了预测栓流运动压力损失的公式.误差分析表明,该公式具有良好的精度.     

双沟球轴承外圈冷辗扩数值模拟与试验研究

毛坯尺寸和芯辊进给速度是环件冷辗扩工艺参数研究的重要内容,通过对一组毛坯和芯辊进给速度进行模拟优化,分析比较了不同宽径比和进给速度对辗扩力及辗扩力矩的影响,得出了最优参数,并采用优化参数进行试验,得到了合格的双沟球轴承外圈产品。     

基于ADAMS的辊子式小规格瓷砖直角输送机构参数优化

探讨了辊子式直角输送机构的输送参数对小规格瓷砖输送质量的影响,通过仿真优化得到最优输送参数。首先基于多刚体动力学理论,在ADAMS中建立了辊子式小规格瓷砖直角输送多体模型;接着根据小规格瓷砖输送要求给出了瓷砖稳定输送约束条件;然后采用全因子设计试验方法对辊子式小规格瓷砖直角输送模型进行了运动仿真分析;最后根据仿真结果对输送机构的输送参数进行了优化,利用优化的输送参数进行了多块小规格瓷砖的仿真试验与样机试验。仿真结果表明,辊子式小规格瓷砖直角输送机构的输送参数严重影响了小规格瓷砖的直角输送。在相同输送速度比下,安装高度差的减小会提高小规格瓷砖的直角输送质量;输送速度比的减小会使小规格瓷砖转动角度增大,使小规格瓷砖更易于实现直角输送。得到了安装高度差为2.5mm、速度比i=0.3时,辊子式小规格瓷砖直角输送机构具有满足输送要求的最佳输送质量。     

Simulation of the fluidic features for diffuser/nozzle involved in a PZT-based valveless micropump

PZT-based valveless micropump is a microactuator that can be used for controlling and delivering tiny amounts of fluids, and diffuser/nozzle plays an important role when this type of micropump drives the fluid flowing along a specific direction. In this paper, a numerical model of micropump has been proposed, and the fluidic properties of diffuser/nozzle have been simulated with ANSYS. With the method of finite-element analysis, the increased pressure drop between inlet and outlet of diffuser/nozzle induces the increment of flow rate in both diffuser and nozzle simultaneously, but the increasing rate of diffuser is faster than that of nozzle. The L/R, ratio of L（length of cone pipe） and R （radius of minimal cross section of cone pipe） plays an important role in fluidic performance of diffuser and nozzle as well, and the mean flow rate will decrease with increment of L/R. The mean flow rate reaches its peak value when L/R with the value of 10 regardless the divergence angle of diffuser or nozzle. The simulation results in-dicate that the fluidic properties of diffuser/nozzle can be defined by its geometric structure, and accordingly determine the efficiency of micropump.     

A novel clocking effect between inlet bend and volute in an automotive turbocharging system

Numerical methods were carried out on a turbocharger compressor with inlet bent pipe to research a novel clocking effect between the inlet bend and the volute. It was found that the clocking effect with 3.4 percent of variations (1.9 percentage points) in compressor efficiency positively exists at the research point near chock. The reason for the changed efficiency loss is that the inlet bend induces a serious distortion of approaching flow to impeller inlet on one hand, and the downstream volute causes a circumferentially non-uniform distribution of pressure in vaneless diffuser. By adjusting the clocking positions between inlet bend and volute, not only is the unsteadiness of the flow rate through single impeller channel changed, but the uniformity of the incoming flow at the vaneless diffuser inlet is modulated as well. It is the dominant reason for the novel clocking effect that the bad uniformity causes more flow loss in both diffuser and volute.

     

加强型微型热声制冷机谐振管的设计

设计一种高效率的热声制冷机谐振管，采用Fluent流体软件对比渐扩管、直管、渐缩管中的压力，发现渐缩管具有增压作用。设计了1／4波长的谐振管，并调节其声腔使其达到纵向谐振频率状态，以便提高热声制冷机的效率。     

基于阻抗法的悬挂器试压波动抑制技术

以水击方程为基础,借鉴电路的阻抗分析方法,研究连续波动在管道中的传递特性。分析了外接管道对波动传递的影响,设计了用于滤除管道内特定频率波动的滤波器,推导出管道长度和滤波器尺寸与波动传递之间关系。通过实际应用发现,以阻抗理论为基础设计的滤波器能够很好地抑制泵压波动,提高试压过程的准确性和效率。     

基于Fluent的新型布水器的设计与分析

针对传统多孔布水器布水不均匀、布水口易堵塞的现象,提出了双臂单孔的新型布水器的设计.该结构包括中央旋转水管和可调控的布水横管,中央旋转水管带动端部的布水横管实现圆周运动,使圆形水池内污水均匀覆盖.建立了布水器的数学与运动学模型,利用Fluent对不同扩散角的喷嘴内外流场进行数值模拟,优化喷嘴参数,使新型布水器达到预期的布水均匀效果.     

基于热-结构耦合的干气压缩机出口输气管道应力分析

结合高温高压管道在生产中的重要性,利用大型有限元分析软件ANSYS对输气管道的温度场和应力应变场的变化进行分析研究。采用具备符合高温高压管道受力特点的ANSYS单元,对管道进行热结构耦合的应力分析,掌握了管道在内压恒定、不同温度载荷下的应力分布规律。计算结果表明,当管道温差过大时,外壁所受应力较大,应进行必要的保温措施,从而防止管道泄漏或破裂等恶性事故的发生。     

The pressure distribution in and flow characteristics of wide-angle diffusers using perforated plates for flow control with application to electrostatic precipitators

To perform effectively, electrostatic precipitators require a highly uniform velocity distribution in the treatment zone. This requirement places particular demands on the design of the wide-angle diffuser upstream of the treatment zone. To generate satisfactory diffuser exit velocity profiles, perforated plates are installed within the diffuser. This paper provides a report of an experimental investigation of the nature of the flow generated by installing two perforated plates in the diffuser. Detailed measurements of the static pressure distribution and flow patterns are reported. The effects of altering the porosity and locations of the perforated plates on the flow and pressure loss characteristics are considered.     

基于FLUENT的直管气体输送参数的研究

对气体通过水平直管进行研究,计算管道中的压力损失、速度等参数,采用分段思想对长直水平管进行分段计算压力损失,得到较为精确、实用的压力损失计算方法。利用FLUENT软件进行模拟仿真计算,比较分段计算的结果和软件仿真计算结果的差异,并分析产生误差的原因,为以后气体输送的管道设计提供理论依据。     

The study on pressure oscillation and heat transfer characteristics of oscillating capillary tube heat pipe

In the present study, the characteristics of pressure oscillation and heat transfer performance in an oscillating capillary tube heat pipe were experimentally investigated with respect to the heat flux, the charging ratio of working fluid, and the inclination angle to the horizontal orientation. The experimental results showed that the frequency of pressure oscillation was between 0.1 Hz and 1.5 Hz at the charging ratio of 40 vol.%. The saturation pressure of working fluid in the oscillating capillary tube heat pipe increased as the heat flux was increased. Also, as the charging ratio of working fluid was increased, the amplitude of pressure oscillation increased. When the pressure waves were symmetric sinusoidal waves at the charging ratios of 40 vol.% and 60 vol.%, the heat transfer performance was improved. At the charging ratios of 20 vol.% and 80 vol.%, the waveforms of pressure oscillation were more complicated, and the heat transfer performance reduced. At the charging ratio of 40 vol.%, the heat transfer performance of the OCHP was at the best when the inclination angle was 90°. the pressure wave was a sinusoidal waveform, the pressure difference was at the least, the oscillation amplitude was at the least, and the frequency of pressure oscillation was the highest.     

风洞大开角段法兰载荷分析

大开角扩散段在风洞回路中有着非常广泛的应用,其在跨超声速风洞中具有重要作用。以风洞大开角扩散段法兰联接为背景,根据压力容器国家标准中有关法兰设计的理论,结合风洞大开角扩散段法兰结构的特点,对该类法兰的载荷进行了分析,给出了载荷及其作用位置的计算公式。