车用压缩机管道内部流场分析与优化设计

针对某电动客车的往复式压缩机组振动明显,本文就其中一段管路进行气流脉动研究,而孔板是抑制气流脉动最简单有效的方法,虽然在相关行业中已被广泛应用,但是目前孔板的各个设计所需参数还处于靠经验取值阶段.针对这种情况,根据计算流体动力学(CFD)方法建立了管道系统的流体力学模型,选择了合理的边界条件,通过数值模拟,分析了不同孔径比、孔板厚度、孔板位置对管道系统气流脉动的影响,并与无孔板的情况进行了比较,表明添加适当尺寸参数的孔板确实对管道系统的气流脉动具有良好的抑制效果.     

孔板消减气流脉动的机理、计算与试验研究

许多事实已经证明,在往复式压缩机管道的适当部位安置孔板是消减现场管道振动的有效措施之一,而实施起来又并不麻烦,故已日益受到国内各压缩机用户的注意。 本文着重阐述孔板消减气流脉动的机理,并同时介绍计算结果、试验以及现场使用的一些情况,为孔板消振问题提供了一个较为全面的论述。     

基于Fluent的均流孔板阻力特性数值模拟研究

均流孔板作为空气净化设备送风系统的气流均布元件,在增大腔体气流均匀性,提升设备净化效果方面具有明显优势。为了研究均流孔板结构及相关参数对其阻力特性的影响,基于流体力学理论,以空气为介质,在入口风速为0.5～8 m/s范围内,对开孔率为0.07～0.48、孔数为286～3185、相对厚度为0.17～0.75的均流孔板进行了阻力特性数值模拟分析。分析结果表明:开孔率对均流板的阻力特性影响显著,相对厚度次之,在高开孔率条件下入口风速对孔板阻力特性影响较小,并且开孔间距与开孔孔径对湍流强度有着重要影响。     

往复压缩机管道气流脉动分析及控制

管路振动是往复压缩机应用时的重要安全隐患,主要阐述了往复压缩机管道气流脉动引起管路振动的原因;基于平面波动理论,对某一往复压缩机的排气管路进行气流脉动计算与分析,并根据API618中气流脉动的相关要求进行校核,采用增设孔板的方法来消减压力脉动幅值,通过在排气缓冲器出口安装合适的孔板,最终将管道压力脉动幅值控制在标准规定的范围内。     

孔板在往复压缩机管道减振中的应用

针对往复压缩机管道振动超标的问题,通过测试关键测点的振动数据,结合管道结构的模态分析与气柱的声学分析,得出气流脉动是引起管道振动的主要原因。为了消减振动,在管道的适当位置安装恰当尺寸的孔板。完成整改后,再次对关键测点的振动水平进行测试,通过对比分析,数据显示,安装孔板后管道的振动情况明显改善,达到安全生产的要求。     

基于CFD的罗茨机械增压器减小气流脉动方法仿真研究

针对罗茨机械增压器工作时排气口高压气体向基元容积回流所引起的气流脉动现象,通过FLUENT动网格技术分别并对传统、逆流冷却和渐扩缝隙三种不同壳体结构的机械增压器进行数值模拟分析,描述机械增压器内部湍流流动的流场分布和气流脉动特征规律,计算结果表明:不同壳体结构影响增压器内部气流漩涡尺度大小,且逆流冷却和渐扩缝隙壳体结构能有效地消减排气时的气流脉动。本文数值分析结果,可为研究机械增压器气流脉动和壳体结构设计优化提供依据。     

空气冷却塔的设计改造

测定空气冷却塔筛板的孔径、孔数、开孔率、板间距、压降以及漏液速度等流体力学性能参数,并对试验数据进行理论分析及模拟研究,摸索出对大孔径（φ10mm）、大开孔率（〉20％）的无溢流筛板,给定塔径、空气、水量及流速,选择塔板筛板塔的结构（孔径为d0、孔心距为t、开孔率和板间距）进行迭代计算的设计计算方法。     

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。     

缓冲器的内部流场分析和优化设计

工业生产中常采用设置缓冲器来消减压缩机管道系统内的气流脉动和减小管道振动。但是工厂投入使用的缓冲器,缓冲容积普遍偏小,或者安装位置离压缩机气缸进出口太远,导致缓冲效果不理想。针对上述问题,利用流体仿真软件FLUENT建立了管道内气体的三维非稳定流动模型,计算了缓冲器和孔板对管道内气体压力脉动的影响;并在大量仿真实验的基础上,利用MATLAB软件拟合出缓冲器进出口压力变化和体积的关系曲线,从而实现对缓冲器体积的优化设计。     

亥姆霍兹脉动衰减装置设计与数值模拟

亥姆霍兹共鸣器是一种常见的声学元件,可应用于衰减管道内气流脉动。根据API618标准推荐的亥姆霍兹共鸣器设计方法,针对往复压缩机排气管路设计气流脉动衰减装置;搭建三维压缩机气流脉动数值分析模型,计算发现管路内存在频率高达120 Hz的气流压力脉动;根据亥姆霍兹共鸣器的低通滤波特性,使用截止频率为110 Hz的亥姆霍兹共鸣器可削弱频率为120 Hz的气流脉动;在三维压缩机气流脉动分析模型中添加截止频率为110 Hz的亥姆霍兹共鸣器,发现频率为120 Hz的气流压力脉动幅度被削弱了76%。     

环形多孔节流空气静压轴承气膜流场分析

为提高空气静压轴承工作的稳定性,设计一种环形多孔节流空气静压轴承,建立其物理模型,并采用大涡模拟方法对轴承节流孔出口处附近计算区域的气膜流场进行分析。结果表明：空气静压轴承气膜压力在节流孔的出口附近气膜间隙上出现分离,但在远离节流孔的出口气膜压力曲线是重合的;节流孔数为9时轴承节流孔出口处的最大压降幅度为节流孔数为1时的26%左右,最大速度突升幅度为节流孔数为1时的43%左右,表明增加节流孔的孔数可以显著减小节流孔的出口附近压力的突降、速度的突升,提高轴承工作稳定性;在空气静压轴承工作过程中,节流孔出口处附近压力和速度的突变会产生微振动现象,而采用环形多孔节流可显著降低微振动现象。     

Analytical and experimental study of flow through elliptical side orifices

Discharge estimation is important for water management. Side orifices are commonly used in irrigation and drainage networks for distributing the water. Despite the vast amount of theoretical and experimental studies published, no generally applicable discharge equations are available for elliptical sharp-crested side orifices. When the length (diameter) of the circular side orifice is not sufficient to divert the water, an elliptical side orifice is a good alternative. In this paper, the elliptical sharp-crested side orifices were studied theoretically and experimentally. Several models were developed to predict the discharge coefficient of elliptical side orifices based on the Buckingham's theorem of dimensional analysis. A series of laboratory runs (588 runs) were conducted for different values of orifice geometry. The main channel discharge used in the tests ranged from 13.8 to 39.6 l/s and the side orifice discharge ranged from 3.66 to 21.4 l/s and upstream Froude number ranged from 0.22 to 0.77. Using measurements obtained by laboratory runs carried out in this investigation the proposed models of elliptical side orifices were calibrated under free outflow conditions. The model that includes the approach Froude number had an average error of 1.74%, while other model that does not include the approach Froude number had an average error about 2.43%. Moreover, suitable models were proposed for design procedure when measurement data for flow depths above the centroid of the orifice are not available. In this case, the model that includes the approach Froude number had an average error of 1.92%, while other model that does not include the approach Froude number had an average error of 2.24%. It was found that the proposed stage-discharge relationships were in an excellent agreement with the experimental results.     

A CFD study of low pressure wet gas metering using slotted orifice meters

Wet gas metering is becoming an increasingly important problem to many industries, in particular the oil and gas industry. Extensive studies have been done in the past on Venturi and standard orifice differential pressure (DP) flow meters to tackle wet gas flow problems. However in recent years, the slotted orifice flow meter has been developed in the attempt to improve the performance of the standard orifice meter. The novel flow meter is shown to be insensitive to the upstream flow profile with lower head loss and faster pressure recovery. This paper describes the numerical studies to establish the effect of different geometrical perforations on the performance of the slotted orifice. Three sets of slotted orifices with varying aspect ratios (1.5≤l/w≤3.0), of rectangular perforations and one slotted orifice with a circular perforation and a β ratio of 0.40 are simulated in a 1.6 m horizontal pipe using the k-ε turbulence model over a range of parameters, i.e. gas volume fraction (GVF) and gas mass flow rate. The commercial CFD code, FLUENT 6.3 was used to model the wet gas flow. Simulation results revealed that the shape of the perforation has no effect on the differential pressure, However, a marginally better pressure recovery was observed with rectangular perforations of l/w=3.0. The relatively higher over-reading values obtained in this work are consistent with the results of Geng et al. (2006) [1] that for a slotted orifice, a low β ratio is more sensitive to the liquid presence in the stream and hence is preferable for wet gas metering. Mass flow prediction by wet gas correlations showed that the homogeneous model, Steven’s and De Leeuw’s correlations had the best performance, with a calculated mean error of 4%-5%.     

小孔节流静压气体轴承承载力分析

以小孔节流静压气体轴承为研究对象,从节流孔内的流动出发,通过工程假设实现气体轴承的建模与分析,并借助MATLAB编程,采用有限差分法、牛顿迭代法实现对气膜流场二维设计计算,得到轴承的压力分布和承载力,并分析讨论对轴承承载力可能产生影响的因素,包括偏心率、轴承间隙、供气孔直径、环境温度、节流孔个数、供气压力。结果表明:不同参数对承载力影响不同,偏心率、轴承间隙及供气压力对承载力影响较大,增大偏心率、增大供气压力、减小轴承间隙、减小节流孔直径及增加节流孔个数,均会使轴承承载力变大;节流孔直径及每圈节流孔个数因为实际工程限制存在较佳值。     

Discharge coefficients of orifice-type restrictor for aerostatic bearings

The paper describes an experimental study conducted in order to determine the supply hole discharge coefficients of externally pressurized gas bearings. Tests were carried out on annular orifices and simple orifices with feed pocket. Air consumption and pressure distributions were measured as a function of supply pressure and air gap height for several different orifice and pocket sizes. Discharge coefficients were approximated by an experimental formula based on the Reynolds number and feeding systems geometry.     

环形多孔气体静压止推轴承静态性能研究

为提升气体静压止推轴承的静态性能,设计一种新型环形多孔气体静压止推轴承。依据气体润滑原理、采用有限体积法对环形多孔气体静压止推轴承的三维物理模型进行数值模拟,研究节流器上节流孔数量、直径、分布方式和供气压力对气体静压止推轴承静态性能的影响。结果表明：节流孔数量对环形气体静压止推轴承的承载力影响显著,但孔数增加到一定程度后承载力增速放缓;节流孔直径对承载刚度影响较大,随着节流孔直径逐渐减小最佳刚度逐渐增大;节流孔排布方式和供气压力对气体静压止推轴承的静态性能均有明显影响。     

基于正交试验的静压径向气体轴承数值分析*

以气动涡轮支承结构静压径向气体轴承为研究对象,建立静压径向气体轴承的微分模型,利用工程数值方法计算轴承承载力、刚度和气体质量流量,运用正交试验法研究节流器参数对轴承性能的影响,以及不同优化方向下轴承的综合性能。结果表明：不同的优化方向节流器参数的敏感性不同,以气体质量流量为优化方向明显不符合设计需要,以承载力为优化方向得到的轴承综合性能最好;平均气膜厚度、节流孔直径和数量是影响轴承承载特性的主要因素,节流孔直径越小承载性能越好。     

基于数值模拟的小孔节流空气静压轴承静动态特性研究

为了提高小孔节流空气静压轴承的静动态性能,基于流体力学和固体力学的基本控制方程,建立小孔节流空气静压轴承双向流固耦合数值模拟模型;采用静态数值模拟方法获取了设计参数对承载力和刚度的影响规律,进一步对微气膜间隙内三维流场特性进行了分析,有效降低了微气膜间隙内气体冗余现象对空气静压轴承动态稳定性的影响,并在数值计算的基础上对空气静压轴承结构和工作参数进行优化设计;在气体静压试验平台上对自行研制的空气静压轴承进行静动态特性测试。试验结果表明:所提出的数值模拟方法具有很好的预测效果;所采用的优化设计方法能够显著提升空气静压主轴的静动态特性。     

Discharge characteristics of sharp-crested circular side orifices in open channels

A side orifice is a flow diversion structure provided in one or both side walls of a channel to spill/divert water from the main channel. It is widely used in irrigation and environmental engineering. Analytical and experimental studies related to the discharge characteristics of sharp-crested circular side orifices in open channels under free flow conditions have been presented in this paper. Considering the side orifice as large, the discharge equation for the side orifice is derived analytically. Experiments were performed to estimate the coefficient of discharge which depends on the approach flow Froude number and ratio of the diameter of the orifice and bed width of the channel. Relationships for the coefficient of discharge, considering the orifice as large and small were developed. Such relationships were used to compute the discharge through the orifice for data not used for proposing such relationships for the coefficient of discharge. The computed discharges were within ±5% of the observed ones. The average percentage error in computation of discharge through the orifice considering it as large and small are, respectively, 1.59% and 1.66% which are practically the same. Therefore, it is recommended that the discharge through the side orifice can be computed considering it as a small orifice within the range of data used in the present study.     

负载口独立控制系统的节能边界

为了找寻负载口独立控制系统的极限节能边界,并明晰其节能机理,建立传统阀控系统和负载口独立控制系统的静态效率与静态能耗模型,利用归一化处理使模型转化为无量纲形式.选取与传统阀控系统可比拟的2种工况,即同泵源压力和同阀口开度,在负载口独立控制系统处于节能极限时(出油阀口全开)进行对比.仿真分析不同工况下2种系统的静态效率与...