前、后置定子泵喷推进器的水力性能对比

为探究前置定子泵喷和后置定子泵喷水力性能上的不同,采用计算流体力学方法,基于经验证的数值计算模型,从敞水性能、空化性能和脉动特性三个方面对两类泵喷的水动力性能差异进行研究。结果表明:消耗功率相同、几何尺寸近似前提下,后置定子泵喷推进性能、平衡性优于前置定子泵喷,在较宽进速范围其推力效率高出后者2个百分点;前置定子泵喷抗空化性能比后置定子泵喷差,空化数越小推力效率降低幅值越大;前置定子泵喷转子叶片引起的旋转部件流场脉动压力幅值大于后置定子泵喷,而定子、导管等静止部件的流场脉动压力与之相反,后置定子泵喷脉动压力幅值大于前置定子泵喷。     

前、后置定子泵喷推进器的水力性能对比

为探究前置定子泵喷和后置定子泵喷水力性能上的不同,采用计算流体力学方法,基于经验证的数值计算模型,从敞水性能、空化性能和脉动特性三个方面对两类泵喷的水动力性能差异进行研究。结果表明:消耗功率相同、几何尺寸近似前提下,后置定子泵喷推进性能、平衡性优于前置定子泵喷,在较宽进速范围其推力效率高出后者2个百分点;前置定子泵喷抗空化性能比后置定子泵喷差,空化数越小推力效率降低幅值越大;前置定子泵喷转子叶片引起的旋转部件流场脉动压力幅值大于后置定子泵喷,而定子、导管等静止部件的流场脉动压力与之相反,后置定子泵喷脉动压力幅值大于前置定子泵喷。     

前、后置定子泵喷推进器的水力性能对比

为探究前置定子泵喷和后置定子泵喷水力性能上的不同,采用计算流体力学方法,基于经验证的数值计算模型,从敞水性能、空化性能和脉动特性三个方面对两类泵喷的水动力性能差异进行研究。结果表明:消耗功率相同、几何尺寸近似前提下,后置定子泵喷推进性能、平衡性优于前置定子泵喷,在较宽进速范围其推力效率高出后者2个百分点;前置定子泵喷抗空化性能比后置定子泵喷差,空化数越小推力效率降低幅值越大;前置定子泵喷转子叶片引起的旋转部件流场脉动压力幅值大于后置定子泵喷,而定子、导管等静止部件的流场脉动压力与之相反,后置定子泵喷脉动压力幅值大于前置定子泵喷。     

前置与后置定子泵喷推进器的水动力性能对比

为探究前置和后置定子泵喷水动力性能上的不同,本文采用计算流体力学方法,基于物理试验数据验证的数值计算模型,从敞水性能、空化性能和脉动特性3个方面对两类泵喷的水动力性能差异进行研究。结果表明:在消耗功率相同、几何尺寸近似的前提下,后置定子泵喷推进性能、平衡性优于前置定子泵喷,在较宽进速范围其推力效率比后者高2%;前置定子泵喷抗空化性能比后置定子泵喷差,空化数越小,推力效率降低幅值越大;前置定子泵喷转子叶片引起的旋转部件流场脉动压力幅值大于后置定子泵喷,而定子、导管等静止部件的流场脉动压力与之相反,后置定子泵喷脉动压力幅值大于前置定子泵喷。     

双定子液压马达差动连接转矩脉动分析

随着液压技术的不断发展,液压传动在各行业得到了广泛应用,同时也对液压马达输出转矩脉动特性提出了更高的要求。目前广泛使用的液压马达均是一个转子对应一个定子,无法实现液压马达的差动连接来满足复杂工况的需求。双定子液压马达因其特殊的结构形式,可在一个壳体内形成内外两组液压马达,可实现液压马达的差动连接。作者基于双定子液压马达结构形式及其差动连接原理,分析得到双定子液压马达差动连接时内、外马达之间的具体关系,即双定子液压马达差动连接时内马达由外马达驱动旋转,实现了泵的工作原理,并将其排出的油液输入到外马达中。在此基础上,深入分析了内、外马达的理论流量和理论转矩,并通过分析内、外马达的瞬时流量,得出马达瞬时转矩的变化情况,进而利用波动系数分析出在内马达输出脉动油液影响的前提下,双定子液压马达输出转矩波动性的一般规律,利用Matlab软件仿真得出不同滞后角φ₀所对应的双定子液压马达差动连接时输出转矩曲线。并搭建了双定子液压马达差动连接试验平台进行试验。结果表明：滞后角对双定子液压马达差动连接时输出的转矩脉动具有很大影响,可以通过合理调整滞后角使双定子液压马达差动连接时输出的转矩更平稳。研究结果可为双定子液压马达差动连接的设计与应用提供参考。     

水压轴向柱塞泵配流盘预升压角

为了调查流量特性,以水压轴向柱塞泵为研究对象,在考虑预升压角的作用和关键摩擦副泄漏的前提下,建立了泵实际输出流量的数学模型,对配流盘的结构参数进行了设计计算.运用PumpLinx软件对不同预升压角下泵的流场进行了数值模拟,对泵的流量特性进行了分析.研究结果表明:水压轴向柱塞泵在排水过程中,会产生流量倒灌现象,使得单个柱塞腔内的压力和流量以及泵的输出流量产生脉动.增大预升压角可以增长柱塞腔内部流体的预压缩时间,减小柱塞腔内部和泵出口的压力差,从而减少柱塞腔的流量倒灌量,降低柱塞腔内的压力和流量脉动.适当增大预升压角有利于提高泵的流量特性,预升压角取20°时,泵的流量特性最佳.但预升压角超过20°时,预升压区和预卸压区流量倒灌的叠加会导致泵出口的流量脉动增大.     

矩形断面迎风面脉动压力特性试验研究

当紊流流经矩形钝体时,由于漩涡的拉伸和旋转运动,其顺流向脉动压力具有明显的非定常性和空间三维性,且主要依赖于紊流积分尺度与结构特征尺寸之比。为了深入研究紊流尺度效应作用机理,以4:1矩形断面为研究对象,基于三维谱张量理论和刚性节段模型测压试验,系统研究矩形断面顺流向脉动压力的非定常气动力特性。结果表明：在紊流从矩形断面驻点至分离点运动过程中,脉动压力的谱能量从低频向高频转移,且该现象随着L_u/D（L_u为脉动风的纵向积分尺度,D为迎风面高度）的减小更明显。与之相比,紊流三维效应和畸变效应随L_u/D的增大而减弱,在此过程中脉动压力的能量由于阻塞效应只在低频发生了明显的衰减,在高频无明显变化。并通过引入三维压力导纳来揭示紊流作用下矩形断面迎风侧脉动压力的非定常效应机理,对于驻点压力,L_u/D越大,压力导纳越接近准定常理论;对于非驻点压力,其距驻点位置越远,阻塞效应对于低频能量的减弱作用越明显,紊流三维效应越弱,而高频的畸变效应则只由L_u/D控制。     

粘性流场中吊舱推进器性能的数值模拟

针对粘性流场中吊舱推进器的水动力性能问题,采用FLUENT软件进行了相关计算,计算中利用湍流模型封闭方程,采用滑移网格技术模拟螺旋桨的旋转.计算了吊舱推进器各部分的轴向力、侧向力、垂向力变化及主桨叶的受力变化,分析了偏转角和安装角对推进器性能的影响.计算结果表明,舱体和支架上的力为阻力,吊舱推进器会受到一定的侧向力和垂向力,二者大小相近,其影响不能忽略.螺旋桨尾流的影响使得桨盘面处的伴流不均匀桨叶受力产生脉动.当存在偏转角时,推力变大,轴向力变小,运行角会使推力减小,扭矩增加,效率降低.     

间隙流动模型对泵喷推进器水动力性能的影响

泵喷作为一种带定子的导管类组合推进器,其内部存在强烈的间隙流动,为了更加准确地预报泵喷推进器水动力性能,本文根据已有的梢部泄露涡模型,考虑泵喷间隙处流动的真实流动情况,考虑间隙区域流体粘性的影响,构建了适用于泵喷的间隙流动模型.通过对比分析泵喷转子、定子以及导管的水动力性能以及压力、环量分布发现:当考虑间隙流动模型的影...     

旋喷泵叶轮及内部流场的数值研究

对由矩形流道叶轮、复合式叶轮与大包角后弯叶轮组成的旋喷泵进行全流道数值模拟。研究发现,矩形流道叶轮的压力、速度分布都较均匀,泵的扬程、效率均能达到要求;后两种形式的叶轮的压力梯度分布不均匀,出口处压力分布不理想,速度分布也不均匀。速度分布的不均匀反映出内部流动的不平稳,有回流和大旋涡产生,效率很低。因此,旋喷泵的叶轮选择矩形流道的叶轮较好。     

Numerical study on the separation and superposition of the influences from up- and downstream rotors

A three-dimensional Navier-Stokes solver is used to investigate the separation and superposition of the influences from upstream and downstream rotors in an axial-radial combined compressor for unsteady design applications. The data from rotor/stator and stator/rotor configurations show that the unsteady flow response in axial stator passage is caused only by one rotor. The results from the rotor/stator/rotor configuration revealed the superimposed characteristic of influences from upstream and downstream the rotor. The impact of the superimposed characteristic was studied by analyzing the virtual relative flow angle at the stator exit. The results show that the axial velocity in the passage of axial stator can be influenced by wake from upstream axial rotor and potential field of downstream radial rotor. While they are coupled to have an effect on the unsteady flow in axial statot passage, the excitation or suppression phenomena appear and lead to different levels of deterministic fluctuation kinetic energy. Their locations are determined by the frequencies of the involved influences. In addition, the variability of superimposed characteristic （ excitation and suppression） at the stator exit modulates the inlet flow angle for downstream rotor.     

EMS型磁浮列车驱动力和悬浮力的计算新方法

针对电磁悬浮(EMS)型磁浮列车用凸极直线同步电机定子和转子齿槽不连续分布的特点，提出一种基于解析的驱动力和悬浮力计算新方法.该方法在分析列车运行时所在位置处的定子和转子几何分布和载荷分布基础上，根据列车所在位置处的定子电流磁动势分布和磁场强度的分布，计算出所有驱动力的大小.通过研究列车所在位置处的定子与转子总的磁导率函数分布和励磁曲线分布，得出列车运行过程中所有悬浮力的大小.计算结果表明，驱动力和悬浮力的波动频率是定子电流变化频率的6倍.当转子极距大于定子极距时，可以获得较大的悬浮力和驱动力，驱动力和悬浮力的波动也相对较小.     

Investigation of influencing factors of hot streaks migration in high pressure stage of a vaneless counter-rotating turbine

Three-dimensional, viscous, and unsteady CFD simulations have been performed in order to reveal the influencing factors of hot streaks migration in high pressure stage of a vaneless counter-rotating turbine. Based on the numerical results, the comparison between the case with inlet hot streaks and case without inlet hot streaks is carried out, which shows that the effect of inlet hot streaks on the load distributions of high pressure turbine airfoils is not notable and the airfoil load distributions are directly related to the inlet pressure distributions. The predicted results also indicate that the circumferential and radial movements of the hot streaks were not observed in the high pressure turbine stator. This means that the combined effects of secondary flow and buoyancy are very weak in the high pressure turbine stator. The numerical results also prove that the circumferential flow angle effect at the inlet of the high pressure turbine rotor, secondary flow effect and buoyancy effect are the mainly influencing factors to directly affect the migration characteristics of the hot streaks in the high pressure turbine rotor.     

Improving the accuracy of vertical angle observations

The influences of instrumental errors, measurement errors, and the fluctuation of refraction angles,etc., on the observation accuracy of vertical angles are analysed. A new target used to observe the vertical angle was designed. Some measures are suggested to reduce the errors in observing vertical angles. They are proved to be effective by experiments. Project supported by the National Natural Science Foundation of China Synopsis of the first author Xiao Fuhe, professor, born in Mar., 1924. Speciality: geodesy or control surveying, electromagnetic distance measurements. Research area: Theory of atmospheric refraction and its influence on surveying.     

Effects of operating condition on fish behavior and fish injury in an axial pump

In this study, fish behavior and fish injury at different operating conditions are investigated via numerical simulation to evaluate the fish-friendliness of an axial pump that comprises an inlet pipe, a rotor with six blades, a stator with eight vanes, and an outlet pipe. To precisely obtain the flow field when the fish passes through the axial pump, a hybrid large eddy simulation and immersed boundary method is adopted with the full consideration of the fluid-structure interaction comprehensively. The results indicate that the collision between the fish and the wall of flow components in the axial pump is concentrated near the inlet of the rotor, which results in the complexity of the fish trajectory, especially under the large flow rate condition. It is noted that the fish is likely to move in the reverse direction of the main flow after the impact with the rotor blade if the flow rate coefficient is too large, which increases the possibility of collision between the fish and the rotor blade. It is also indicated that the primary factor affecting the strike injury on the fish when it passes through the axial pump is the strike between the fish and the leading edge of the rotor blade. In addition, the strike injury becomes more significant as the flow rate coefficient increases. Furthermore, the results demonstrate that the fish may simultaneously suffer from strike, pressure, and shear stress injuries, once the collision between the fish and the wall of flow components occurs in the axial pump, thus aggravating the combined damage on the fish. Based on these results, it is recommended that hydraulic machinery should not be operated at large flow rates during fish migration from the view of fish-friendliness.

     

异步电动机转子故障对定子故障检测的影响与对策

定子绕组匝间短路是异步电动机常见故障之一,因此研究其检测方法具有重要意义。首先,完成了异步电动机定子绕组匝间短路与转子断条故障仿真并对仿真结果做了分析,指出异步电动机转子故障对定子绕组匝间短路故障检测存在不利影响,甚至导致故障误判。进而明确揭示出该影响之原因,即转子故障将导致定子电流中出现边频分量。之后,提出了计及转子故障时的异步电动机定子绕组匝间短路故障检测策略,其关键在于预先采用频谱校正与自适应滤波技术滤除定子电流中由转子故障所导致的边频分量。     

超临界二氧化碳高压涡轮气动设计及性能

为建立高性能超临界二氧化碳(SCO2)布雷顿循环系统,基于西安热工研究院的5 MW等级SCO2火力发电试验平台的高压涡轮设计参数,采用基于Denton损失模型的自编一维涡轮设计程序、AXIAL软件及AXCENT软件设计了2级轴流超临界二氧化碳涡轮,采用CFX软件RANS方程与NIST的真实超临界二氧化碳工质物性数据相结合的数值方法,研究了超临界二氧化碳高压涡轮设计工况和变工况气动特性.结果表明:综合考虑高设计参数下的超临界二氧化碳涡轮辅助系统的可实现性,选择两级轴流直叶栅涡轮设计方案,经叶型优化后可实现两列涡轮静叶的总压损失约为0.042,第1/第2列动叶栅相对总压损失为0.050和0.064,叶片的根部、中部和顶部流场的马赫数分布合理.考虑动静叶泄漏掺混损失的高压涡轮的等熵效率可达到84.88%,轴功率3 251 k W,涡轮变工况性能良好.     

Earth pressure coefficient at rest during secondary compression

In order to obtain the earth pressure coefficient at rest (K ₀) at higher consolidation pressures during secondary compression, a series of K ₀ tests for saturated reconstituted clay were conducted. The results indicate that the measured K ₀ in secondary compression can be described by equations related to internal friction angle, secondary compression coefficient, compression index, recompression index, and sediment time. Effects of consolidation pressures and sediment time on K ₀ during secondary compression can be attributed to cementation (part of cohesion) increase and internal friction angle decrease. Cementation increase leads to nonlinear variation for K ₀ and internal friction angle decrease results in increase of K ₀. K ₀ computed by equations associated with internal friction angle is overestimated at apparent lower consolidation pressures with different sediment time, which agrees with the measured values well at apparent higher consolidation pressures.     

湍流强度对桥梁断面气动力特性的影响

桥梁结构处于大气边界层中,由于断面外形复杂、折点较多,其绕流常呈现复杂的流动分离和再附着状态,应评估来流湍流对桥梁断面气动特性的影响。基于节段模型测压风洞试验,获取了均匀流场和3种格栅湍流场下模型表面平均和脉动压力分布,评估了桥梁断面气动力特性的改变,分析了不同风场下断面流动分离再附着的变化。研究发现:湍流显著改变桥梁断面前缘（特别是零度和正攻角时上表面和负攻角时下表面）的分离和再附着特性,进而影响桥梁整体断面的气动力特性;随着湍流强度增加,前缘分离点的平均压力系数的幅值增大,而再附着点向上游移动;湍流强度对分离和再附着的影响程度随着风攻角的增大而变得显著;三分力系数在小风攻角时受湍流强度影响较小,在大风攻角下湍流强度的影响较大,变化的主要原因是断面前缘的压力分布变化。