Analytical study on water hammer pressure in pressurized conduits with a throttled surge chamber for slow closure

This paper presents an analytical investigation of water hammer in a hydraulic pressurized pipe system with a throttled surge chamber located at the junction between a tunnel and a penstock, and a valve positioned at the downstream end of the penstock. Analytical formulas of maximum water hammer pressures at the downstream end of the tunnel and the valve were derived for a system subjected to linear and slow valve closure. The analytical results were then compared with numerical ones obtained using the method of characteristics. There is agreement between them. The formulas can be applied to estimating water hammer pressure at the valve and transmission of water hammer pressure through the surge chamber at the junction for a hydraulic pipe system with a surge chamber.

兼顾调节特性和经济成本的调压室体型优化策略

过渡过程动态特性和调压室建设成本是调压室体型设计中需要关注的两个主要方面。如何选取调压室体型参数使两者均达到最优对水电站建设和运行具有重要意义。针对这一问题,基于第三代非支配排序遗传算法(NSGA-Ⅲ)和优劣解距离评价方法(TOPSIS),提出了一种兼顾大小波动调节特性和工程投资最优的调压室体型优化策略。首先,基于特征线法,建立水力发电系统精细化模型。其次,以调压室断面直径、阻抗孔直径和安装位置为决策变量,分别建立以大波动动态特性(机组最大水头+机组转速最大上升率)与调压室体积为目标的大波动优化模型和以转速超调量与ITAE为目标的小波动优化模型,并引入NSGA-Ⅲ算法,得到调压室在两种优化模型下的Pareto解集。最后,基于TOPSIS评价方法,以上述4个优化目标为决策层,对Pareto解集进一步评价,得到兼顾大小波动调节特性和经济性最优的调压室体型。结果表明,与得分最低的方案相比,最优方案在牺牲较小调压室经济性的前提下,能够有效改善大小波动综合调节特性,实现平衡调压室建设成本和大小波动综合调节特性的目标。研究结果对水电站调压室结构设计具有重要指导意义。

水电站尾调室湿环境控制方案对比分析

尾调室作为水电站的重要组成部分,其热湿环境影响水电站的安全稳定运行。实际工程中发现,尾调室内起雾与冷凝现象严重,内部设备运行和工作人员健康受到影响。本文根据XLD水电站尾调室的实际情况,提出机械通风、冷却除湿、冷却除湿+机械通风3种湿度控制方案,并通过数值模拟的方法比较3种方案在夏季最不利条件下对湿环境的控制效果,寻找尾调室湿度控制的最优方案。结果表明:机械通风方案不能有效解决尾调室湿度过高的问题,端部及底部空气多处呈饱和状态;冷却除湿方案能起到一定除湿效果,但存在风流分布不均匀的现象,中部和端部相对湿度仍不满足要求;冷却除湿+机械通风方案能够使尾调室工作区湿度降至80%以下,室内空气温湿度分布较为均匀。

THEORETICAL,NUMERICAL AND EXPERIMENTAL STUDY OF WATER HAMMER IN PIPE SYSTEM WITH COLUMN SURGE CHAMBER

A new kind of governing equations for water hammer based on the elasticcolumn theory was proposed and adopted to analyse water hammer phenomenon in the pipe system with avertical column surge chamber and water level fluctuation in the surge chamber during pressuretransient. The wrongness existing in the classical governing equations for water hammer wasanalysed. A typical reservoir-valve pipe system was chosen as an example to verify the new governingequations numerically and experimentally. The finite difference method based on the method ofcharacteristics was used to solve numerically the nonlinear characteristic equations. The temporalevolutions of transient volume flux and head and of water level fluctuation for various surgechamber configurations were worked out, assuming that the air in the surge chamber are compressible.The relevant experiment was conducted to verify the new governing equations and numerical method.The numerical and experimental results show that the new governing equations are valid and theconventional assumption that the pressure head at the base of a surge chamber equals that of thestatic head above it during pressure transient is not always valid. The surge chamber generallyreises the period of transient pressure wave in pipe system, reduces the maximum pressure envelopeand lifts the minimum envelope substantially. The water level fluctuation in the surge chamber wasnumerically and experimentally observed. Increasing the size of the surge chamber and/or decreasingthe initial air pressure in the surge chamber enhance the effectiveness of the surge chamber insuppressing pressure wave.

长距离负扬程加压泵站调水工程水力控制方式探讨

事故掉电引发的停泵水锤是泵站调水工程安全运行最主要的威胁之一,而对于下游水位低于上游水位的长距离负扬程加压泵站调水工程而言,事故停泵易造成管道拉空,负水锤防护难度较大,因此,针对其停泵工况的水力控制研究十分重要。以某长距离负扬程泵站调水工程为例,模拟计算了事故停泵、阀门拒动这一控制性工况下的水力过渡过程,并对比分析了空气罐、空气阀与空气阀联合空气阀调压室3种水力控制方案的水锤防护效果。结果表明:对于长距离负扬程加压泵站调水系统而言,当采用空气罐的水力控制方式时,所需的空气罐体积较大,投资高昂;当单纯采用空气阀的水力控制方式时,难以有效解决管道局部高点处负压较大的问题,仍可能诱发弥合性水锤;当将部分空气阀附加一根短管组合成空气阀调压室后,能够有效控制管内负压。空气阀与空气阀调压室联合防护是一种十分经济且有效的水锤防护方案,可为这类负扬程加压调水工程的水力控制方式选取提供参考。

两机一洞尾水调压室阻抗损失系数模型试验研究

水电站引水发电系统中调压室的阻抗损失系数是影响机组过渡过程计算结果的重要因素,目前阻抗损失系数一般在行业规范推荐的范围内进行取值,往往与试验值有所偏差,不利于调压室体型的优化设计。通过采用大比尺的调压室水工模型,对两机一洞型式的水电站阻抗式尾水调压室进行大流量条件下的水力学试验,研究不同水流流态和分流比对调压室阻抗损失系数的影响,分析控制工况下调压室的流入和流出阻抗损失系数,给出了调压室阻抗损失系数与分流比的拟合公式和关系曲线。研究结果填补了两机一洞型式的水电站尾水调压室阻抗损失系数试验的空白,可为此类调压室的水力计算分析提供依据。

3-D simulation of transient flow patterns in a corridor-shaped air-cushion surge chamber based on computational fluid dynamics

The 3-D characteristics of the water-air flow patterns in a corridor-shaped air-cushion surge chamber during hydraulic transients need to be considered in the shape optimization. To verify the reliability of the water-air two-phase model, namely, the volume of fluid model, the process of charging water into a closed air chamber is successfully simulated. Using the model, the 3-D flow characteristics under the load rejection and acceptance conditions within the air-cushion surge chamber of a specific hydro- power station are studied. The free surface waves, the flow patterns, and the pressure changes during the surge wave process are analyzed in detail. The longitudinal flow of water in the long corridor-shaped surge chamber is similar to the open channel flow with respect to the wave propagation, reflection and superposition characteristics. The lumped parameters of the 3-D numerical simulation agree with the results of a 1-D calculation of hydraulic transients in the whole water conveying system, which validates the 3-D method. The 3-D flow structures obtained can be applied to the shape optimization of the chamber.

NUMERICAL STUDY OF WATER LEVEL FLUCTUATION IN BULL-HORN SURGE CHAMBER IN PIPE SYSTEM DURING WATERHAMMER

The method of characteristics was adopted to analyze water level fluctuationexisting in Bull-Horn surge chamber in reservoir-valve pipe system during waterhammer caused byvalve closure operation. The Finite Difference Method (FDM) based on the method of characteristicswas used to solve numerically the nonlinear two-parameter characteristic equations governingwaterhammer. The finite fixed mesh was applied to obtaining the discrete form of the governingequations and discrete flow-field. The temporal trends of the y -directional flow, water level,velocity of water level and head difference for different heights of water in surge chamber,diameters of cylinder, cutting angles of surge chamber, lengths of horizontal cylinder and lengthsof inclined cylinder were obtained under the condition that the air in surge chamber iscompressible. The conclusions on water level fluctuation in Bull-Horn surge chamber were given basedon the analyses of the obtained transient numerical results. These conclusions can play a guidingrole in designing pipe system and executing surge suppression.

旭龙电站尾水调压室洞间岩柱围岩宏细观特性分析

为了将连续和非连续分析方法耦合用于地下厂房围岩稳定性分析,提出了一种基于软硬混合平行黏结模型的细观参数快速标定法,可根据给定岩石的宏观力学参数快速给出其颗粒流模型细观接触参数;在此基础上,构建了基于颗粒离散元PFC 3D与有限差分FLAC 3D耦合的旭龙地下电站尾水调压室三维离散-连续耦合分析模型,研究了开挖期尾水调压室洞间岩柱围岩变形与破坏宏细观特性,以及检修期间侧向水压力对洞间岩柱稳定性的影响。结果表明:检修期间尾水调压室水压力引起的围岩变形与应力增量变化是极小的,但洞间岩柱上半段22.7 m的高度存在塑形贯通区,局部稳定性较差,有必要在工程建设期开展尾水调压室及尾水支洞岩墩塑性贯通区专项支护方案研究,以确保旭龙地下电站工程的安全建设与运行。

在倾倒边坡中建设地下调压室的工程地质研究

扎拉水电站调压室建在山体倾倒边坡内,对该边坡及围岩稳定性的系统研究至关重要。根据岩体结构和变形破坏类型的差异,采用岩体结构、岩层转角、风化等定性因素结合波速比定量因素进行综合分区;通过现场超常规原位试验,结合反演计算,综合提出各区适宜的岩体抗剪强度参数;采用数值分析法模拟倾倒边坡变形破坏模式,并通过多种解析法校验边坡稳定性。结果表明:边坡倾倒岩体可分为层状弯曲区、碎裂拉张区、散体坠覆区;厂后倾倒边坡的主要失稳形式为拉裂-滑移-剪断和块体卸荷崩落;在倾倒边坡稳定性评价中,安全系数应取现行技术标准规定范围内的较大值,有利于保障倾倒边坡滑移稳定和坡内洞室围岩变形稳定。研究成果解决了地质条件局限和水工结构要求之间的突出矛盾,在中国水利水电建设中具有开创意义,可为倾倒边坡中工程建设提供参考。

尼泊尔TNH水电站调压室优化设计

TNH水电站是“一带一路”倡议下,尼泊尔政府和中国政府合作的典型基础设施项目之一。在详细设计阶段,通过对尼泊尔TNH水电站调压室设计图纸进行分析研究,对调压室布置进行优化设计,经水力学复核、稳定分析计算,验证优化设计参数合理性。通过优化设计,减小了调压室顶拱施工难度,节省工程投资。在严苛的咨询工程师要求下,经过图纸三版升级修改工作,最终优化设计成果得到工程师认可,调压室布置图得到批复意见,为后续调压室开挖支护图、衬砌结构图打下了坚实基础。

基于水力过渡过程的西藏扎拉水电站调压室设计优化

针对西藏扎拉水电站调压室顶拱上方存在的不良地质条件问题,提出了一种利用施工支洞作为调压室上室的优化布置方案,并结合水力过渡过程计算,分析了涌浪的波动过程。结果表明:施工支洞作为调压室上室能够有效削减最高涌浪水位。当最高涌浪低于施工支洞顶拱时,涌浪不会对支洞顶拱的结构安全造成危害,也不会阻碍支洞的排气过程。利用施工支洞作为上游调压室可显著降低调压室顶拱,并成功避开不良地质带,有利于水电站安全稳定运行。

昌波水电站引水式电站水轮发电机组防飞逸保护措施方案研究

针对昌波水电站引水式电站引水距离长、设置上游调压室、蜗壳前进水管直径较大等特点,列出三种水轮发电机组防飞逸保护措施进行分析比选,经综合比选分析后,推荐采用调压室快速闸门作为水轮发电机组的防飞逸保护措施,并详细描述了调压室快速闸门方案。该研究为类似条件的水电站机组防飞逸保护措施方案选择提供参考。

西藏扎拉水电站引水发电建筑物设计

为解决扎拉水电站引水发电建筑物设计过程中存在引水隧洞穿越活动断裂,引水隧洞Ⅳ类、Ⅴ类围岩洞段占比较大,调压室顶部层间密集剪切带,巨型冲击式机组配水环管充水保压浇筑混凝土等重大技术难点,充分论证引水隧洞过活动断裂洞段增加衬砌混凝土厚度、短分节、上部设置排水洞(兼勘探洞、灌浆洞、监测洞)等措施的有效性。通过优化布置和计算线弹性有限元结构,提出了引水隧洞Ⅲ类、Ⅳ类、Ⅴ类围岩分别选取40,60,80 cm厚度衬砌结构设计,调压室选取1.5,1.0 m厚度衬砌结构设计,配水环管选取5.5 MPa的充水保压埋设方式,配水环管分区配置钢筋来优化结构设计。相关设计成果可供同类工程参考。

陡倾角岩体中阻抗式圆形调压井衬砌结构数值分析

采用三维非线性有限元对复杂地质条件下的圆形调压井衬砌及阻抗板结构受力进行了分析。提出了调压井混凝土衬砌结构与围岩联合工作的分析方法,给出了调压井混凝土衬砌结构开裂和配筋的计算公式和计算方法。通过分析计算,论证了Y岔圆形调压井空间结构衬砌的受力特征,为同类地下圆形调压井衬砌结构及阻抗板的配筋分析计算提供了一种较好的数值分析计算方法。

含气垫调压室的水电站输水系统小波动稳定分析初探

对气垫式调压室的电站输水系统的水力-机械微小波动稳定问题进行了初步分析,讨论了调速器参数、气体多变指数、气室高度、气室压力、运行水头对稳定性的影响,为气垫调压室的合理设计、安全运行提供了科学依据。

气垫调压室研究进展

结合我国首例含气垫调压室水电站——青海大干沟水电站引水系统的水力计算及模型试验研究成果 ,对气垫调压室的气体漏损及其防治对策、气体特性及其数值模拟、水力性能及稳定断面、模型试验和运行监控等方面的国内外研究进展进行综述 。

上游调压室设置条件的探讨

上游调压室设置条件是水电站引水发电管道系统初步设计的重要判据之一,本文从理论上推导了上游调压室设置条件的判别式,即压力管道中水流惯性时间常数的允许值[Tw]的大小取决于设计允许水击压力相对值ξmax、机组转速升高相对值βmax以及机组加速时间常数Ta等参数,分析了[Tw]随Ta、ξmax、βmax增大而增加的规律性,并且结合工程实例,得出了高水头水电站不设置上游调压室的[Tw]有可能远远小于2s、低水头水电站[Tw]有可能大于4s等主要结论。

基于调节保证的上游调压室最佳位置的确定

通过分析设有上游调压室水电站机组甩负荷蜗壳压力变化的特点,得出当调压室最高涌浪引起的压力上升与水流惯性引起的压力上升相等时,对应的调压室位置为最佳位置。继而结合阻抗式调压室最高涌浪计算式及水击压力计算公式,推导得出基于调节保证的调压室最佳位置计算式,同时通过数值计算对计算式进行了验证,并探讨了计算式的适用条件。最后结合工程实例分析了最佳位置随阻抗孔口面积的增大、调压室面积放大系数K的减小,而减小的规律性。

调压室非对称孔口阻抗特性的数值模拟

保证差动式调压室良好的水力特性,对于水电站的安全稳定运行具有重要意义。以某水电站上游调压室为研究对象,对其大井与升管之间的回流孔采用非对称结构设计,利用专业软件详细计算了其进出流阻抗特性。结果表明:与对称孔口情况相比,非对称回流孔的进流阻抗系数明显减小,而出流阻抗系数显著增大,从而大大改善了调压室的动态特性;在分流比固定的情况下,进出流阻抗系数基本保持不变,而且与流量变化基本无关;在分流比变化的情况下,进(出)流阻抗系数随分流比的增大而呈指数函数形式单调减小(增大)。