Contribution to the Analytical Equation Resolution Using Charts for Analysis and Design of Cylindrical and Conical Open Surge Tanks

In the event of an instantaneous valve closure, the pressure transmitted to a surge tank induces the mass fluctuations that can cause high amplitude of water-level fluctuation in the surge tank for a reasonable cross-sectional area. The height of the surge tank is then designed using this high water level mark generated by the completely closed penstock valve. Using a conical surge tank with a non-constant cross-sectional area can resolve the problems of space and height. When addressing issues in designing open surge tanks, key parameters are usually calculated by using complex equations, which may become cumbersome when multiple iterations are required. A more effective alternative in obtaining these values is the use of simple charts. Firstly, this paper presents and describes the equations used to design open conical surge tanks. Secondly, it introduces user-friendly charts that can be used in the design of cylindrical and conical open surge tanks. The contribution can be a benefit for practicing engineers in this field. A case study is also presented to illustrate the use of these design charts. The case study’s results show that key parameters obtained via successive approximation method required 26 iterations or complex calculations, whereas these values can be obtained by simple reading of the proposed chart. The use of charts to help surge tanks designing, in the case of preliminary designs, can save time and increase design efficiency, while reducing calculation errors.

多分水口长距离输水工程停泵水锤防护措施

为了能够有效避免多泵且多分水口输水系统在无防护抽水断电时可能出现较为严重的负水锤带来的危害,建立了全长106.46 km的大型供水工程的数学模型进行系统过渡过程计算,选择空气阀与两阶段液控蝶阀联合防护与单向塔防护2种方案消除其负水锤,在前者远不达理想防护效果后针对后者进行优化.结合工程实际在确定了单向塔的数量、位置以及塔高后,对不同位置单向塔的底面积进行多种方案的对比选取,最终选用塔1#的底面积为28.26 m^(2),塔2#的底面积为176.63 m^(2);为了防止单向塔漏空需要分水口以及供水终端调流阀配合关闭,在确保管道最大压力不超出其承压能力的前提下,创新性地对各分水口调流阀与供水终端调流阀的关闭时间规律进行了效果比较,使输水系统能够更加经济安全地稳定运行,为此类长距离多分水口多泵供水工程的水锤防护提供了优化方向.

航空活塞发动机稳压箱温度影响因素及高空特性研究

针对某型航空活塞发动机中冷系统,建立了系统的传热数学模型.通过与实验数据相对比可知,中冷器冷侧出口温度、热侧出口温度模拟结果误差均在1.5%以内,明确了本文构建仿真模型可行且可靠.进而,利用该模型研究了中冷系统空气速度、环境温度、增压比、进气流量等因素对稳压箱温度的影响,分析了航空活塞发动机中冷系统的高度特性.结果表明:稳压箱温度随着空气速度的增加而降低,随着环境温度、增压比及进气流量的增加而上升.稳压箱温度对增压比的敏感度最大,对环境温度的敏感度最低,对进气流量及空气速度的敏感度介于二者之间.对于所研究的航空发动机中冷系统,最高稳压箱温度及中冷系统最大换热量均出现在临界增压高度,在海平面温度为50℃的条件下,二者的值分别为82.4℃、11.5 kW.

水电机组轴系-调速耦合系统动态特性分析

水电机组轴系-调速耦合系统动态特性尚未揭示,制约机组调节优化控制。为此,建立了水电机组不同运行模式轴系-调速耦合系统非线性数学模型,研究分析了耦合系统的非线性动态响应特性。首先,采用Hopf分岔理论分析调速系统稳定域和分岔特性。进一步,仿真分析机组不同运行模式轴系-调速耦合系统的时频动态响应特性。结果表明:机组孤网和并网运行调速系统均存在超临界Hopf分岔,机组并网模式调速器参数稳定域较孤网模式增大。机组并网模式调速系统机组、电网频率动态响应存在多频特性,轴系振动会引发调压室水位动态响应超超低频振荡。并网与孤网模式相比并网模式系统动态响应超调量增大,调节时间缩短。机组孤网和并网运行轴系振动均为多频拟周期振动,但孤网模式轴系振动特性更复杂。

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。

驼峰式长距离输水管线单向调压塔水锤防护研究

驼峰式管线作为长输水系统的典型布置方式,中间凸起管段的局部水锤特性及其水锤防护问题复杂。通过驼峰式管线高点下游侧管线坡度与水力坡度的比较分析,阐明了单向调压塔对驼峰式长距离输水管线的防护机理,并推导了单向调压塔设置高度的近似解析公式。进一步基于有压输水管道特征线法,融合单向调压塔和调流阀等水力边界,建立了相应的输水系统水锤分析模型,开展了系统的水锤防护及其优化研究。分析表明,基于建立的单向调压塔设置分析方法,在驼峰式管线合理设置单向调压塔,能够有效实现系统的水锤防护,并可考虑管线布置特性进一步优化,数值计算和理论分析一致;单向调压塔直径和阻抗孔直径是评估单向调压塔水锤防护效果的重要参数,均存在一最优数值解,继续增大单向调压塔直径或阻抗孔直径对改善水锤防护效果作用很小。

阻抗孔位置及直径对含长连接管调压室阻抗特性和三维流场影响研究

含长连接管的调压室可通过在连接管内设置小于其管径的阻抗孔来增强调压室的阻抗特性。为研究长连接内阻抗孔的位置及直径两种因子对此类调压室阻抗特性的影响规律,以水头损失系数和流量系数为优化目标,以位置和直径为优化变量,基于正交优化设计方法和CFD数值模拟软件,计算分析了各组合方案下的调压室阻抗系数和三维流场的变化规律。结果表明,阻抗孔前后水流湍流强度增幅明显,距离连接管两端端部越近,对调压室大井和管道系统内流场影响程度越大;当阻抗孔位于连接管顶部与调压室大井连接处,可最大程度发挥阻抗孔的阻抗效果,以阻抗孔与连接管管径比0.8为例,水头损失系数增幅约30%;连接管直径增大有效降低调压室局部流场压强最值浮动范围;阻抗孔位于靠近连接管顶部且不在大井连接处时,水流流出调压室时连接管及下游隧洞总体湍流强度较小,流场更稳定。

秦山第二核电厂3、4号机组RIS系统硼酸再循环回路问题分析及探索

针对秦山第二核电厂3、4号机组RIS系统硼酸波动箱房间存在大量硼结晶、硼酸再循环回路运行温度较高、硼酸波动箱液位下降过快造成频繁补水的一系列问题及后果,分析出了硼酸波动箱溢流管线造成空气通路、硼酸再循环泵工作产热大、硼酸波动箱保温层设计不合理等根本原因,并通过对波动箱溢流管线加装盲板及手动球阀、拆除波动箱保温层及使用临时风机等措施取得了明显的效果;又通过探索新增电加热器逻辑、再循环泵换型、硼酸波动箱房间增加进风口和更改波动箱补水阀位置等方案进一步优化RIS硼酸再循环回路的可靠稳定运行。

巴塘水电站全风化地层调压井开挖与支护方案研究

印度尼西亚巴塘水电站调压井所处位置地质条件较差,岩体以全风化地层为主,开挖阶段初期支护安全风险大。项目部经过多种方案对比,最终选择了“灌注桩+冠”、“环梁+锚喷”的支护方式。阐述了对全风化地层情况下调压井的开挖与支护采用的设计方案和施工方法进行的研究与实施,取得了较好的效果,所取得的经验可为后续类似工程施工时参考。

上游调压室理想阻抗孔面积选择的影响因素分析

针对设置上游阻抗式调压室的引水发电系统,利用特征线法进行大波动过渡过程计算,模拟并分析了引水隧洞长度、两种导叶关闭规律、输水管道糙率以及机组转动惯量对水力过渡过程中调压室理想阻抗孔面积取值的影响。结果表明:在保证其他条件不变的情况下,引水隧洞长度、机组转动惯量以及管道糙率的取值越大,理想阻抗孔的面积越小;先慢后快的导叶关闭规律对阻抗孔面积取值的影响较先快后慢的关闭规律更大。结论对实际工程设计具有参考价值。

廊涿干渠工程运行调度方式优化及其水锤分析计算

【目的】廊涿干渠工程自试运行以来,经历了2次爆管过程。为了保证廊涿干渠正常输水,需采取降压运行和工程加固措施,将原设计下调节方式优化为中控制下调节方式,并在管道末端设置调压塔。【方法】本研究通过建立输水管道系统模型,对管道各种运行调节工况进行模拟计算,以验证新调节方式和调压塔的有效性和安全性。【结果】通过计算,确定了调流调压阀、调压塔的操作规程等设计参数。【结论】结合廊涿干渠实际运行情况,验证了降压运行和工程措施的有效性,保证了管道系统的安全。

设调压室水电站输水发电系统耦合振荡特性研究

设调压室水电站输水发电系统是复杂的水机电耦合系统,目前对耦合系统的振荡特性以及各个子系统间的耦合作用关系尚不明晰。本文首先将整个水电站系统分为“引水隧洞-调压室”子系统和“压力管道-机组”子系统,针对“压力管道-机组”子系统的稳定性提出了耦合振荡域的概念并推导了其解析公式,然后结合特征值分析法和数值模拟揭示了耦合系统的振荡特性,最后运用频域分析法探究了两个子系统间的幅频特性及相互作用关系,提出了衡量系统耦合振荡稳定性的定量指标。结果表明:当调速器参数在耦合振荡域外取值时,水电站系统恒不稳定,因此调速器参数在耦合振荡域内取值是整个水电站系统稳定的必要条件。当调速器参数在耦合振荡域内取值时,耦合系统的稳定性由低频振荡模式决定,将系统低频振荡模式的频率代入到两个子系统的幅频特性函数之积中,可以得到振荡叠加率,该值反映了系统扰动在闭环系统中增益值,具有明确的物理意义,当振荡叠加率小于1时,受扰系统趋于稳定。研究成果不仅丰富了水力过渡过程理论体系,对提高水电站运行稳定性也具有较好的工程应用价值。

Water hammer protection for diversion systems in front of pumps in long-distance water supply projects

For a water supply system with long-distance diversion pipelines, in addition to the water hammer problems that occur beyond pumps, the safety of the water diversion pipeline in front of pumps also deserves attention. In this study, a water hammer protection scheme combined with an overflow surge tank and a regulating valve was developed. A mathematical model of the overflow surge tank was developed, and an analytical formula for the height of the overflow surge tank was derived. Furthermore, a practical water supply project was used to evaluate the feasibility of the combined protection scheme and analyze the sensitivity of valve regulation rules. The results showed that the combined protection scheme effectively reduced the height of the surge tank, lessened the difficulties related to construction, and reduced the necessary financial investment for the project. The two-stage closing rule articulated as fast first and then slow could minimize the overflow volume of the surge tank when the power failure occurred, while the two-stage opening rule articulated as slow first and then fast could be more conducive to the safety of the water supply system when the pump started up.

某长距离低扬程输水工程空气阀调压室与空气阀的联合水锤防护研究

针对长距离低扬程输水工程中单个空气阀的水锤控制距离较短无法有效抑制管内真空等问题,提出了空气阀调压室与空气阀联合防护的新型水锤控制方案,并以某长距离低扬程输水工程为例,对单纯采用空气阀防护以及空气阀调压室与空气阀的联合防护方案开展了水力过渡过程数值模拟与对比分析。结果表明,单纯采用空气阀防护时主管内发生了液柱分离,且因排气过快引发了较大的冲击水锤;而采用空气阀调压室与空气阀联合防护方案不仅能够有效抑制主管内的真空,还可有效缓解排气时引发的冲击水锤,是一种经济且有效的水锤防护措施,可为其他长距离低扬程输水工程的水锤防护提供借鉴。

基于IWOA算法求解含调压井水轮机调速系统控制参数的优化分析

为了提高含调压井水轮机调速系统的控制性能,提出一种基于改进鲸鱼优化算法(IWOA)的控制参数优化方法。首先建立含调压井水轮机调速系统的数学模型,即利用连续性方程和管道传递函数建立包含调压井动态的水轮机进口水头—流量传递函数,然后与水轮机调速模型一起构成含调压井的水轮机调速系统模型。以该系统中水轮机的转速偏差时间积分值作为优化过程的适应度值,并以该适应度最小化为目标,采用IWOA对研究对象的PID控制器参数进行优化。在Matlab平台对研究对象常见运行工况进行仿真,结果表明IWOA算法具有收敛速度快、精度高等优点,寻优操作后的PID控制器使研究对象面对各类型扰动具有更好的调节及鲁棒性能。

Numerical study of flow fluctuation attenuation performance of a surge tank

The surge tank plays an important role in ensuring the stability of a water flow standard device. To study the influence of the structure and the working conditions on the regulator performance of a surge tank, a three-dimensional model, including a surge tank, the pipeline and the water tank is built, and the VOF model in the Fluent software is used to simulate the two-phase pulsatile flow in the surge tank. The inlet flow pulsation is defined by the User Defined Functions （UDF）, and the outlet flow is set to be a free jet. By calculating the flow fluctuation coefficient of the variation uader different flow conditions, the influences of the pulse frequency, the initial water level height and the baffle plate structure on the flow stability are analyzed. It is shown that the surge tank has a good attenuation effect on high-frequency pulsations, there is an optimal initial water level to suppress the fluctuations, the round holes of the baffle should ensure a certain circulation area with the bore diameter small enough to have the necessary damping effect.

RESEARCH ON THE CONDITION TO SET A TAILRACE SURGE TANK

When using the draft-tube vacuum to be less than 8.0 m as the rule to set atailrace surge tank, a mixing function that describes the process of water-hammer vacuum andvelocity-head vacuum varied with time is proposed, on the assumption that the guide vane of thehydraulic turbine and the turbine discharge were all changed linearly. An exact maximum of thedraft-tube vacuum for the first-phase water-hammer and the last-phase water-hammer is obtained.Finally a much more reasonable formula of critical tailrace length is derived. The results of twocases show that the formula proposed can determine correctly and reasonably whether a tail-racesurge tank is needed or not, and are more suitable for project design than the formula suggested bythe specification.

Influence of flow field on stability of throttled surge tanks with standpipe

The steady-state flow field characteristics have important effects on the stability of the throttled surge tank with the standpipe. This paper analyzes these effects on the basis of the numerical simulation of the flow field by using the Computational Fluid Dynamics （CFD） method. It is shown that the anticlockwise recirculation zone is formed in the standpipe, which affects the local head loss at the junction of the standpipe with the pipeline. The variation of the head loss coefficient at the junction is linearly related with the diameter ratio of the standpipe to the pipeline. The dimensionless recirculation flow rate is proportional to the square of the diameter ratio. Considering the effects of the recirculation zone, an empirical expression of the critical stability area is obtained. Comparing with the Thoma critical area, the area obtained by the present method is smaller, and the reduction depends on the diameter ratio and the ratio of the velocity head to the head losses in the tunnel. words：

非对称过水系统抽蓄机组调速系统稳定性分析

为研究非对称过水系统抽蓄电站的稳定性,基于Hopf分岔理论,先建立了带上游调压室的一管双机非对称过水系统抽蓄机组调速系统数学模型,在此基础上进行了Hopf分岔分析获得了调速系统的理论稳定域,并分析了不同控制参数下机组的动态响应特性,验证其理论稳定域;再揭示了一管双机式抽蓄机组动态响应的多尺度振荡特性及其产生机理;最后,探究了水流惯性时间常数、水轮机惯性时间常数和调压室时间常数对系统稳定性的影响规律。结果表明,带上游调压室的一管双机非对称过水系统抽蓄机组调速系统的Hopf分岔是超临界的,其稳定域由两条分岔线共同决定;调压室及机组间的水力干扰使得机组的响应特性呈现明显的多尺度振荡特性;较大的水流惯性时间常数和较小的水轮机惯性时间常数对系统稳定性有利,调压室时间常数对系统的稳定性影响呈现饱和特性。研究结果对抽蓄机组的智能控制和电站过水系统设计优化具有重要的指导意义。

提高油轮靠泊海上平台外输作业安全性的措施

油轮靠泊海上平台原油外输是一项安全风险高的作业,而且影响油轮安全外输的因素又有很多,有环境条件、靠泊系统、船舶性能、原油储罐充舱、人员能力、管理水平、信息沟通等。文章重点关注外输作业的关键环节,从油轮靠泊碰撞力和系泊力控制、外输期间原油储罐压力控制,及油轮系泊期间应急解脱三个方面进行分析,通过外输作业环境条件限制、橡胶护舷+移动式防碰靠球组合、双套储罐惰气充舱系统、快速脱钩装置等各项安全控制措施,提高了油轮靠泊平台外输作业的安全性。