结合数值计算与模型试验研究阻抗

通过带调压室水电站的模型试验和数值仿真计算，分析了阻抗式调压室在各种水力过渡过程下的水力工作特性。研究得出阻抗式调压室阻抗损失系数在不同工况下的变化规律，以及在确定阻抗式调压室阻抗损失系数时，需结合模型试验结果最终确定流进与流出的阻抗损失系数。     

液压盘式制动器模型试验

设计了通过测量制动臂所受的弯矩间接获得制动力矩的实车制动试验,采用系统辨识法获得制动力矩系数,得到盘式制动器试验模型.首先对应变电压-制动力矩的关系进行标定,然后实车测试不同制动工况下的制动力矩.根据实车试验得到制动压力,采用系统辨识的方法获得车辆制动压力-制动力矩的传递函数.试验结果表明,前、后轮的液压-制动力矩关系式可适用于不同工况下的制动力矩计算;制动器理论模型和试验模型的增益系数基本相符,但试验模型具有一阶惯性环节,更能准确地反映实际车辆的制动压力-制动力矩之间的关系.     

Mathematical modeling of open-channel velocity profiles for float method calibration

A computational method based on mathematical modeling of steady-state hydraulics is described for improving the accuracy of the float method for estimating open-channel discharge. Both two-dimensional (2-D) and three-dimensional (3-D) velocity distribution model versions were developed for steady-state uniform flow in open channels with rectangular cross-sections. The normal depth of flow was obtained by solving the Chézy equation for uniform flow conditions. Cross-sectional velocity distributions were calculated by solving the Reynolds-averaged Navier-Stokes (RANS) equations and an algebraic model for turbulent stresses, without the use of wall proximity corrections to the pressure strain term. The calculated 3-D velocity coefficients were found to be in the same range as previously published United States Bureau of Reclamation (USBR) coefficients, but the results also indicate that the USBR coefficients, which are based solely on average water depth, can be improved by taking into account other hydraulic parameters such as longitudinal bed slope, channel base width, and wall roughness. The mathematical model exhibited considerable sensitivity to initial conditions, boundary condition parameters, and numerical convergence criteria, also manifesting spikes in the calculated surface velocity coefficients for discrete changes in hydraulic parameters. Finally, it was found that the 2-D version of the model is not appropriate for calculating surface velocity coefficients because it does not account for secondary flow in the channel cross-section, and the calculated surface velocity in the center of the cross-section is overestimated.     

Velocity profile modeling in rectangular and compound open-channel cross sections

A 3-D hydraulic model was developed for computing velocity profiles, surface velocity coefficients, and discharge under steady, uniform flow conditions for rectangular and compound open-channel cross sections. Reynolds-averaged Navier–Stokes equations, Reynolds stress equations, and kinetic energy and dissipation equations were applied in the model using the finite-volume method with the k–ε turbulence model. Many previously unpublished approaches to solving the numerical details of this type of hydraulic model are presented herein. Four different sets of Reynolds stress equations (one using the Boussinesq hypothesis and three algebraic stress models of varying complexity) were tested. Only one of the four stress models was successful in predicting the depression of the maximum stream-wise velocity below the water surface. The model was verified using data collected at the Utah Water Research Laboratory. A companion paper (Marjang and Merkley in Irrig Sci, 2009, in press) describes the application of this model to the calculation of surface velocity coefficients for the float method to estimate discharge in rectangular and compound irrigation canals.     

离心泵多工况水力性能优化设计方法

基于全局优化算法和各项损失计算的离心泵能量性能计算模型,提出一种离心泵多工况水力性能优化设计方法.该方法以原始设计的关键几何参数值为初始条件、设计工况的扬程为约束条件、多个工况的加权平均功率最小为目标,同时采用自适应模拟退火算法对离心泵能量性能计算模型进行求解,采用超传递近似法来确定各目标函数的权重因子,并采用该方法对一比转数为129.3的离心泵进行了多工况优化,最后分别对原设计和多工况优化设计进行了数值计算,计算结果表明：0.6Qd和1.2Qd工况下,多工况优化得到的功率低于原始设计,而设计工况下,多工况优化得到的功率比原始设计略高;多工况优化得到的3工况点加权平均功率比原始设计低0.06%;多工况优化的3点加权平均效率则比原始设计高0.46%.研究结果对于离心泵的节能设计具有比较重要的参考价值.     

喷灌压力管网系统水力特性的模拟模型研究

本文从系统的观点出发，首先分析了水泵直接加压式喷灌压力管网系统的组成，继而运用图示模拟技术，着重研究探讨了计算各类水力单元直至全系统水力特性的模拟模型，并针对一个规模较大，地形较为复杂的坡地喷灌工程，具体介绍了运用该模型进行图示模拟计算的方法和步骤。计算结果表明，该模型能如实地反映喷灌压力管网系统的运行客观规律，从而为了解把握喷灌压力管网系统的水力特性提供了一种行之有效的实用计算方法。     

水力瞬变中动态摩阻的改进加权类模型

有压输水管道系统中,由于阀门的启闭或水力元件的不当操作等因素常会发生水锤现象,从而可能会影响水力系统的正常运行甚至发生危险事故.因此,针对上述管道水锤现象进行有效的数值模拟预测具有重要意义.在管道水力瞬变过程模拟计算中,Zielke提出的加权动态摩阻模型可以较好地模拟压力波动过程,是一维水锤模拟中计算结果最接近试验值的数学模型.由于加权函数与历史流速及历史加速度相关,模型计算时需保存每一时步的流速值,占用计算机内存大,故计算效率较低.为提高模型计算效率,尝试利用Matlab 的LSQNONLIN函数模块对Zielke加权函数进行3个指数函数之和型式的近似拟合,得到新的近似加权函数的各系数值,并通过与Zielke加权函数曲线及已有的改进加权函数曲线对比验证新函数的优越性,以及利用试验数据验证新模型的准确性和高效性.结果表明,模型在一定程度上提高了加权类动态摩阻模型的计算效率.     

Numerical Analysis to Solve the Hydraulics of Trickle Irrigation Units

A model to solve the hydraulics of trickleirrigation units is developed in thisstudy. This model is based on utilizingNewton Raphson technique. The modelconverts laterals into equivalent outletsthrough utilizing a simple power relationbetween inlet lateral discharge andhydraulic head. This relation is obtainedthrough least squares analysis betweeninlet lateral discharge and hydraulic head. This study showed that this relation withonly two coefficients is sufficient todescribe the relation between inlet lateraldischarge and hydraulic head. Based onthis relation, the model converts manifoldlines into equivalent laterals and solvestheir hydraulics by Newton Raphsontechnique. After that solution, the modelevaluates trickle irrigation units byestimating statistical uniformity andChristiansen uniformity coefficients andchecks the solution obtained throughforward step method for each lateral. Several numerical examples for utilizingthe model are presented in this paper.Palestine Authority     

Surface velocity coefficients for application of the float method in rectangular and compound open channels

A three-dimensional mathematical hydraulic model was applied to calculate velocity profiles and discharge under steady, uniform flow conditions in rectangular and compound open-channel cross sections. The velocity profiles were used to calculate surface velocity coefficients for use with the float method for discharge estimation in the field. Surface velocity coefficients were calculated at increments of one-eighth of the base width from the vertical walls to the center of the cross section, and submergence of the float object from 0 to 30 cm, with a 5-cm depth increment. Model results were summarized to show the relationship between surface velocity coefficient and channel characteristics compared to values published by the US Bureau of Reclamation (USBR). For rectangular cross sections, the coefficients from the model are generally higher than the published USBR values. But the coefficients from the model and USBR are in very close agreement for the tested compound cross sections. The published coefficients by the USBR are a function of only average water depth. However, the model results show that the coefficient is also related to channel size, cross-sectional aspect ratio, surface roughness height, float submergence and lateral location of the float object. These factors should be included in the determination of the surface velocity coefficient to improve the discharge estimations from the application of the float method.     

EPC总承包模式在水利工程中的应用

针对水利工程的施工特点,EPC总承包模式在水利工程中的应用进行了分析探讨,对于进一步提高EPC总承包模式在水利工程中的应用具有一定借鉴意义。     

基于卷积神经网络的水电机组轴心轨迹类型识别

针对常规水力机组故障类型识别需要人工参与、识别效率低下的问题,借助轴心轨迹图片蕴含的丰富信息,在引入细粒度模型对故障严重程度进行区分的基础上,提出了一种基于卷积神经网络的水力机组轴心轨迹类型的智能识别方法.该方法先建立了4种故障严重程度的评判标准和对应的2种水电机组轴心轨迹细粒度数据库;利用改进过卷积层与池化层参数的卷...     

考虑压力效应的液压缸摩擦模型研究

应用经典摩擦模型描述液压缸摩擦力时,由于未考虑油液压力效应对摩擦力的影响,模型预测效果欠佳。为了克服该问题,引入压力影响系数和动态摩擦时间常数,基于Stribeck和广义Maxwell滑动模型（GMS）提出了改进的稳态摩擦模型（P-Stribeck）和动态摩擦模型（P-GMS）。搭建了伺服阀控液压缸系统摩擦特性测试实验台,在不同密封形式、不同缸径、不同负载、不同加速度及频率下进行了液压缸往复运动摩擦特性测试。采用智能遗传算法,利用液压缸测试实验台采集的进出口压力、位移、速度、摩擦力等数据,分别采用改进的稳态摩擦模型和动态摩擦模型进行参数辨识和模型检验。对不同复杂工况下实验数据与经典摩擦模型以及所提出的改进模型的预测结果进行对比和误差分析,结果表明：P-Stribeck模型预测液压缸稳态摩擦力的精度明显优于Stribeck模型,P-GMS模型预测液压缸动态摩擦力的精度优于GMS摩擦模型,从而验证了所提出摩擦模型的有效性。     

不同形状阻抗孔口的阻抗系数研究

结合云南漫湾水电站，利用最新的CFD（Computational Fluid Dynamics）技术分析了阻抗式调压室阻抗孔口的形式对阻抗系数的影响。计算结果表明阻抗损失系数不是常数，它随着分（汇）流比的变化而变化，当分（汇）流比增加时，通过孔口的流量增加相应的水头损失的值也增加。在各流态下3种阻抗孔的阻抗系数与分流比的二次曲线图几乎重合在一起，这说明了阻抗孔口的形式对相应阻抗系数大小的影响不大。分流情况下的水头损失比汇流情况下的水头损失要大。     

平原河网一维水流计算模型在洪水期和枯水期的应用

平原河网在洪水期注重行洪要求,在枯水期要提供一定的用水功能,不同时期的水流变化具有不同的特点,需要了解水流的变化规律以调控河网水位。河网一维水动力模型作为水流模拟的基础,在洪水期和枯水期的边界条件及过流工程的运行方式差异明显,应该综合加以考虑,在洪水水流模型的基础上,对枯水水流模型进行相应局部调整,以适应边界条件的变化状况。通过建立的河网水动力计算模型,结合不同水文时期河网与概化湖泊的水量交换以及边界条件的变化,对研究区实际发生的洪水和枯水水流进行模拟验证。计算分析表明,模型能够适应不同时期的水动力计算要求,且精度相对较高,为平原河网在急流和缓流不同状态下的稳健交替模拟以及普适性研究提供了基础。     

考虑水头损失的管道灌溉分水口轮灌分组优化模型

[目的]优化灌溉系统中分水口轮灌分组的灌溉制度,在满足流量要求的条件下节约电能.[方法]提出了在考虑水头损失时不同分水口状态与管道进口压力的关系模型,该模型利用分水口开关0,1状态作为自变量,从管道末端起利用推导的递推公式求出管道进水口的等效水头损失系数.依据该模型,在定流量分组轮灌优化中得到为使分组轮灌功率最小的目标...     

液压支腿机械液压联合仿真分析——基于ADAMS与AMESim

以机械平衡用的果园多功能移动作业平台液压支腿为研究对象,分别建立了实体模型与液压回路模型,通过机构简化与分析构建了支腿运动方程;分析了双作用单活塞杆在液压缸内速度以及缸内液体压力的变化规律,利用ADAMS和AMESim软件进行了参数化设计及联合仿真,并对仿真结果进行了分析。其结果证明了液压支腿机械液压联合仿真控制闭环模型的可行性,为液压支腿设计与优化提供了捷径,使结构设计与仿真模型更符合工程实际,有助于提高系统性能。     

弹性水击下非线性水轮机的哈密顿模型

为了将水轮机及水力系统纳入广义哈密顿框架下研究其运行控制的动力学机制,对非线性水轮机的哈密顿建模问题进行了研究.将增量形式的传递函数所描述的弹性水击水力动态,改写为相对值形式的一阶微分方程组,并与导叶开度微分方程一起构成扩展的水轮机仿射非线性系统.构造水轮机的哈密顿函数,应用哈密顿正交分解实现方法将其转化为哈密顿系统形式,进而通过结构矩阵分解和反馈耗散设计转化为耗散哈密顿模型.对所建立的水轮机哈密顿中耗散结构的变化、反馈等价以及能量流等问题进行了分析,所获得的哈密顿系统的广义能量流的物理概念与实际系统是一致的.结合实例的仿真表明,所选择的哈密顿函数包含了水轮机暂态中能量变化的主要信息,是合适的.     

核电站冷却水循环泵模型试验

介绍了按照核电站冷却水循环泵的技术要求开发的核电站冷却水循环泵模型,给出了其结构方案;运用CFD方法设计开发了优秀的水力模型,并通过模型泵进行了验证测试;简要介绍了用于测试水力损失和观测流态的冷却水循环泵进水流道设计试验装置．验证测试的结果表明,该泵额定点效率达92％且高效区范围宽;泵运行噪声小,运行平稳;在额定工况点,设计的肘型进水流道水力损失小,仅为0．273m．该水力模型的综合指标达到了同类泵的先进水平,因此,我国核电站冷却水循环泵可实现国产化．     

竖井对低扬程贯流泵装置性能影响的数值模拟

为研究竖井贯流泵中竖井部分对贯流泵装置的水力性能的影响,采用计算流体动力学方法对包含进出水延长段、进出水流道、叶轮和导叶在内的整体泵装置进行数值模拟,分析竖井长度、竖井头部型线以及竖井尾部型线对进水流道水力损失、出口断面轴向速度分布均匀度、出口断面速度加权平均角以及泵装置能量特性的影响.结果表明:竖井长度、竖井头部和尾...     

低比转速离心泵加大流量设计法研

建立了求解低比转速离心泵加大流量设计时计算两个放大系数的约束方程组，数值计算得到了能够在运行点得到最高效率的比转速放大系数和流量放大系数的系列曲线图。进而得到了比转速放大系数与流量放大系数的关系，以及建立在这一关系基础上的叶轮出口宽度计算公式。现有的采用加大流量设计法得到优秀的水力模型大都满足计算得到的结果，一般设计采用的叶轮出口宽度计算的经验公式也与计算结果相吻合。然后以实例对低比转速离心泵加大流量法设计的关键几何参数的选取进行了分析并进行了实验研究。