Analysis on Shock Wave Speed of Water Hammer of Lifting Pipes for Deep-Sea Mining

Water hammer occurs whenever the fluid velocity in vertical lifting pipe systems for deep-sea mining suddenly changes. In this work, the shock wave was proven to play an important role in changing pressures and periods, and mathematical and numerical modeling technology was presented for simulated transient pressure in the abnormal pump operation. As volume concentrations were taken into account of shock wave speed, the experiment results about the pressure-time history, discharge-time history and period for the lifting pipe system showed that： as its concentrations rose up, the maximum transient pressure went down, so did its discharges; when its volume concentrations increased gradually, the period numbers of pressure decay were getting less and less, and the corresponding shock wave speed decreased. These results have highly coincided with simulation results. The conclusions are important to design lifting transporting system to prevent water hammer in order to avoid potentially devastating consequences, such as damage to components and equipment and risks to personnel.

Analytic study on the optimal control of water hammer waves in pipes

To realize the accurate control of water hammer in pipes by valve stroking, based on basic differential equations of water hammer subjected to initial and boundary conditions, the traveling solution of wave equations in finite region was applied to the linear water hammer problem. With the given velocity function at the valve and the introduction of curve integration independent of integral path, the exact analytic solution of dimensionless water hammer pressure was obtained in the course of valve closing. Based on the definition of eigen wave height, optimal eigen wave height and observation time, the control goal of water hammer pressure and the judgment rule of the optimal eigen wave height were determined, then the optimal velocity function in the calculated example was derived, which can reduce the water hammer pressure maximally. According to this function, a valve closing program was set, and the optimal control of water hammer could be realized.

Experimental Investigation on a Fixed Oscillating Water Column with an Impulse Turbine for Wave Energy Conversion

A fixed oscillating water column(OWC)-type wave energy converter consists of an air chamber,an air turbine and a generator.The energy conversion processes are the primary conversion in an air chamber and the secondary conversion of the turbine.For the practical use,it is necessary to develop a design method which can consider the incident wave motion,the motion of the internal free surface affected in the structure such as a partly submerged wall,the fluctuation of air pressure in an air chamber,and the rotation of the air turbine.At here,the authors carried out the wave tank tests using the model OWC equipped with the impulse turbine and a generator to obtain the experimental data needed to make this design method.As the result,the efficiencies of the three cases with different speed ratio between generator and turbine,and the effects of the curtain wall depth and the wave length on the energy conversion performance were clarified.

长输供热管线中AFT Impulse软件的水力瞬态分析与应用

结合同类煤电机组余热利用长距离大温差供热项目经验,从基本原理开始阐述,介绍了AFT Impulse软件在工程实例中的应用,逐步说明有压管道水力瞬态分析,并结合工程案例,分析出非恒定流体向恒定流体变化过程中产生的水击波对供热系统的危害,结合数学模型分析提出的心得及建议,以便将水力瞬态分析的成果在供热系统中更好地推广和应用,有效地指导设计与工程建设。

ON BASIC EQUATIONS OF WATER HAMMER

Based on the derivation of the continuity equation of water hammer, the modification coefficient used in the wave speed formula is discussed thoroughly. Mistakes presented in current formulas are analyzed. Finally in this paper a summarizing comment is given on the problem that whether or not the slope term Vsina should be included in the characteristic equations.

Water hammer in pipelines with hyperconcentrated slurry flows carrying solid particles

Water hammers in pseudo-homogeneous flows and heterogeneous flows have been investigated, and equations for the wave propagation speed and the additional pressure due to water hammer in both flows have been developed. These equations have been tested against available experimental data.

Effects of Rotor Solidity on the Performance of Impulse Turbine for OWC Wave Energy Converter

Impulse turbine, working as a typical self-rectifying turbine, is recently utilized for the oscillating water column（OWC） wave energy converters, which can rotate in the same direction under the bi-directional air flows. A numerical model established in Fluent is validated by the corresponding experimental results. The flow fields, pressure distribution and dimensionless evaluating coefficients can be calculated and analyzed. Effects of the rotor solidity varying with the change of blade number are investigated and the suitable solidity value is recommended for different flow coefficients.

不同孔间距的气泡帷幕对水中冲击波衰减特性的影响

为探究孔间距对气泡帷幕消波能力的影响效果,设计孔间距分别为2、5、8、11 cm的4种气泡帷幕发生器,分析不同孔间距的气泡帷幕对水中冲击波衰减的影响。以爆源与传感器相距60 cm、气泡帷幕处于爆源与传感器之间并距爆源水平距离50 cm作为实验工况,发现气流量的增加会提高相同孔间距的气泡帷幕对冲击波的衰减效果,并且在气流量达到40 L/min后,4种气泡帷幕的消波效果会趋于稳定。气流量相同时,随着爆源入水深度的增加,气泡帷幕的防护能力出现先上升、后下降的情况,4种气泡帷幕均在爆源入水深度60 cm时防护效果最好。对相同气流量下不同孔间距的气泡帷幕进行对比,当气流量为60 L/min时,孔间距从大到小排序,消波能力依次为54.80%、61.40%、88.56%、89.27%,表明孔间距的缩小会提高气泡帷幕的消波能力;孔间距在5 cm之后继续缩小,气泡帷幕的防护效果提升不再明显。孔间距缩小,冲击波的比冲量也会随之降低,从而大幅度削弱炸药爆炸后到达目标后的能量,减小对被保护物的破坏能力。

基于双向流固耦合的倒虹吸管道水击压力波与拱式桥架组合结构动力响应分析

在大跨度倒虹吸管道中有压闸阀关闭时通常伴随着水击现象,当水击发生时,流体与固体的耦合作用同时存在。为研究发生水击时,不同关阀时间下的压力波与考虑耦合作用时结构的动力响应情况,以大跨度倒虹吸管道与拱式桥架结构为研究对象,进行整体水力计算,基于流固耦合分析理论,将整体水力模型计算得到的水击压力波作为流体部分加载条件,在workbench平台上进行双向流固耦合分析求解桥架结构的位移、内力及应力动力响应结果。结果表明:不同关阀时间工况下,水击压力波曲线的变化趋势大致相同,结构各监测点的位移时程曲线同水击压力波曲线规律基本吻合;阀门匀速关闭时,增加闸阀的关闭时间可以作为降低倒虹吸管道水击压强的有效措施;水击力对桥架管道的影响最大,盖梁次之,拱圈最小,结构以发生顺桥向动力响应为主。

一种超高压水锤波脉冲试验系统设计

本文根据GB/T 41028-2021《航空航天流体系统液压软管、管道和接头组件的脉冲试验要求》,设计了一套液压软管脉冲测试系统。该系统基于LabVIEW和PLC控制,在阀控增压缸高压脉冲加载方案基础上,提出了比例放大器加继电器控制系统比例溢流阀的超高压脉冲加载方法,可实现最高70MPa水锤波脉冲试验。

爆炸冲击波与水膜相互作用的试验研究

为了研究爆炸冲击波与水膜的相互作用,基于水平激波管搭建冲击波与水膜相互作用的试验平台,设计一个水膜发生器,能够产生厚度为8 mm的稳定水膜。研究了1.31和1.42马赫的入射冲击波分别与距管口45、55和65 mm处的水膜相互作用,并采用纹影仪和高速摄影机对冲击波与水膜的相互作用进行了可视化研究,采用压力测试系统记录水膜前方和后方20 mm处的压力和冲量变化。研究结果表明:水膜前方的压力变化取决于冲击波的反射,且水膜产生的反射波低于刚性-固体壁面产生的反射波;水膜后方的压力变化取决于受冲击的水膜破碎时所吸收的能量,且这部分能量主要来源于冲击波后高速气流的作用,冲击波本身的作用并不明显;水膜后方的峰值压力和冲量显著增强,峰值压力的增强效果能达到50%以上,冲量的增强效果能达到10倍以上;水膜距管口越远,对峰值压力的增强效果越显著,对冲量的增强效果越微弱。

A RANS-VoF Numerical Model to Analyze the Output Power of An OWC-WEC Equipped with Wells and Impulse Turbines in A Hypothetical Sea-State

Wave energy is a renewable source with significant amount in relation to the global demand. A good concept of a device applied to extract this type of energy is the onshore oscillating water column wave energy converter(OWC-WEC). This study shows a numerical analysis of the diameter determination of two types of turbines, Wells and Impulse, installed in an onshore OWC device subjected to a hypothetical sea state. Commercial software FLUENT?,which is based on RANS-VoF(Reynolds-Averaged Navier-Stokes equations and Volume of Fluid technique), is employed. A methodology that imposes air pressure on the chamber, considering the air compressibility effect, is used. The mathematical domain consists of a 10 m deep flume with a 10 m long and 10 m wide OWC chamber at its end(geometry is similar to that of the Pico's plant installed in Azores islands, Portugal). On the top of the chamber, a turbine works with air exhalation and inhalation induced by the water free surface which oscillates due to the incident wave. The hypothetical sea state, represented by a group of regular waves with periods from 6 to 12 s and heights from 1.00 to 2.00 m(each wave with an occurrence frequency), is considered to show the potential of the presented methodology. Maximum efficiency(relation between the average output and incident wave powers) of46% was obtained by using a Wells turbine with the diameter of 2.25 m, whereas the efficiency was 44% by an Impulse turbine with the diameter of 1.70 m.

基于AFT-Impulse的FPSO生活水系统水锤防护设计

针对FPSO生活水管网系统输水距离长、管路弯曲多,以及阀门启闭频繁,极易引起管路水锤现象,致使管网系统安全运行风险增大的问题,以某FPSO生活水系统为例,结合生活水管网系统特性及水锤现象产生的机理,运用动态流体分析软件AFT-Impulse,开展水锤影响因素分析,明确水锤现象的主控因素;建立FPSO生活水系统模型,基于主控因素的影响,开展多工况多场景的稳态分析和瞬态分析,提出FPSO生活水系统水锤防护最优方案。

基于井场实测数据水击压力波波速特征分析

【目的】停泵水击压力波诊断技术用于快速定位井底裂缝进液位置,但技术关键之一的油井套管中水击压力波波速的确定仍有诸多难题。为优选现场水击波速计算方法,探讨水击波速变化规律,【方法】基于某水平页岩气井采集的19段高频停泵水击压力信号,使用反射法、倒谱法、半周期法、全周期法、傅里叶基频法及傅里叶三次谐波法等6种方法求解每段水击波速,并使用箱型图对比各方法的求解稳定性来优选求解方法;同时分析优选方法的求解结果,总结现场施工水击波速的变化规律,并基于波速相对残差法及段间波速差法,分析脱离该井波速变化规律的离群点。【结果】结果显示:对于6种波速求解方法,其结果在箱型图中离群次数分别为8、3、0、0、16和4次;对于稳定性较好的半周期、全周期及倒谱法,求解结果表明施工深度每接近井口100 m,波速降低约8 m/s;同时,波速异常段分析指出离群波速值集中在第18—20段。【结论】结果表明:最适用于水力压裂现场的波速求解方法是基于时域的半周期法、周期法和倒频域的倒谱法,其稳定性最佳;水击波速存在随施工深度减小而减小的规律,且与固井质量及固井段长相关。研究成果可为水击波速诊断技术提供波速计算的技术参考。

CO_(2)气爆水击波与地震波效应试验研究

在航道疏浚工程中对高于设计水底标高的水下礁石,多采用水下钻爆清礁工艺。而水下岩层通过钻爆清挖后仍有部分岩石未能完全清除并残留不规则,不稳定的水下浅点。实际施工中经常采用乳化炸药水下钻孔爆破或裸露爆破法清除这类孤石,裸爆相对于钻孔爆破,炸药与岩面的接触面小,炸药使用量大,会出现能量利用率低、炸药单耗高、噪音和水击波大,影响生态环境等问题。为了分析浅点爆破影响因素,进行现场监测研究,对比水下薄层岩石裸露爆破法和钻孔爆破法,在相同作用效果下,CO_(2)裸爆、钻孔CO_(2)气爆和钻孔乳化炸药爆破水击波和地震波数据。以防城港18#~22#泊位码头基槽、停泊地开挖、炸礁及清礁工程为例,根据岩层性质、岩层形态、被炸岩石顶部的水深和浅点厚度等制定药包排列和用药量方案。通过对比分析得出相同气瓶条件,CO_(2)裸爆水击波超压值是钻孔CO_(2)气爆的1.87~41.9倍。应用水下钻孔乳化炸药爆破是CO_(2)气爆水击波的7.9~18.7倍,产生的振动数值是后者的3~10倍。本文以解决实际工程问题为基本出发点,在研究水下爆破水击波传播规律的基础上,综合分析水中冲击波有害效应影响规律。

水下钻孔CO_(2)气爆和乳化炸药爆破对比分析

水下爆破作业中飞石、毒气、振动等爆破共生物严重影响水下环境安全,为完成水下炸礁爆破施工任务和不破坏水下生态环境的要求。通过长期的施工经验的思考和总结,提出了水下钻孔CO_(2)气爆代替乳化炸药爆破的施工技术方案。文章通过对比水下破岩CO_(2)气爆与乳化炸药爆破,分析在相同作用效果下,CO_(2)使用量,水击波和地震波数据,以及对鱼类的影响。总结了CO_(2)在水下膨胀破岩作业中的工艺、技术及施工方法,计算出钻孔爆破孔距、排距等相关参数。

藏东南尼都藏布流域冰湖水量变化及潜在溃决诱因评估——以塔弄错为例

藏东南尼都藏布流域冰雪崩、滑坡和泥石流等山地灾害频发,研究团队于2021年10月对流域内的塔弄错进行了水深测量和周边地貌环境调查。同时,利用短基线合成孔径雷达干涉测量(SBASInSAR)技术监测了尼都藏布流域的地表形变速率,以识别冰湖周边的潜在滑坡体、崩塌体等诱灾因素。最后,基于数值模型RAMMS和波浪传播模型,评估了不同情景下崩塌体入湖和水量变化对冰湖溃决风险的影响。结果表明,塔弄错的最大水深为29.45 m,平均水深为15.21 m,水量为1820842 m^(3)。塔弄错周边5个不稳定区域的平均形变速率远高于其他区域,将来可能会成为触发塔弄错溃坝的外界诱因。模型模拟显示,塔弄错在入湖崩塌体质量增加或水量增加情况下,产生的洪峰流量、溃口深度和坝顶承受的压力均显著增加。因此,建议在冰湖溃决风险评估工作中重点关注周边有崩塌隐患点且水量持续增长的冰湖,并实时观测崩塌区的动态变化,为下游及时做好冰湖溃决洪水的避险提供预警信息。

基于水击波的页岩油井压裂套变监测原理与应用

大规模体积压裂导致套管变形是影响页岩油气开采的重要因素之一,国内外对压裂期间的套变一直没有切实可行的方法。通过在井口安装高频压力计监测压裂停泵期间的水击波,通过水击波的波形来判断是否套变这一新方法,实现了对套变的有效监测。建立了压裂停泵水击波完备的方程组,通过对不同管径水击波数值解曲线分析,获得套变情况下波形特征。在管径不变的情况下,井口的压力-时间曲线特征为一条整体光滑的,振幅衰减的波动曲线;在有一处管径变小的情况下,曲线整体趋势不变,但振幅频率变高,且无规律性;在有两处管径变小的情况下,曲线的振幅频率及无规律性增加。通过对柴达木盆地1口井的实例应用验证了方法的正确性。该方法为页岩油气井压裂改造过程中实时监测套变情况提供了一种新的思路和方法。

水雾对爆炸冲击波衰减效应的实验研究

为了探究水雾特性与爆炸载荷衰减效果之间的关系,在爆炸驱动的激波管内两种不同特性的水雾环境下进行了不同强度的爆炸实验,并评估了两种水雾对爆炸冲击波超压和比冲量的衰减效果。实验结果表明:喷雾区域内的压力分为两个上升阶段,第一个阶段为透射冲击波的压力,第二个阶段为液滴二次雾化和弛豫过程导致的压力上升;冲击波掠过的喷雾区域越长,水雾对压力峰值和比冲量的衰减效果越好;冲击波强度的增加将削弱水雾对爆炸载荷的衰减效果;Sauter平均直径为136.04μm、体积分数为1.72×10^(-3)的水雾使压力峰值衰减了34.2%~60.9%,使比冲量衰减了9%到54%;Sauter平均直径为255.34μm、体积分数为3.43×10^(-3)的水雾使压力峰值衰减了48.4%~78.6%,使比冲量衰减了14%~66%;冲击波压力峰值的衰减率随着冲击波-雾滴之间的比例交换面积增加而线性减少。

考虑流固耦合的装配式管线水击压力波速计算研究

以装配式管线为研究对象,分析连接器密封胶圈在水击压力作用下的形变情况。基于厚壁管流固耦合水击模型,提出一种适用于装配式管线耦合水击压力波速计算的新方法。对提出的计算方法进行试验验证,并详细分析密封胶圈以及管道厚径比对装配式管线耦合水击波速的影响。研究结果表明:所提方法计算值与试验实测值吻合较好,说明所提方法是正确可靠的;密封胶圈对水击波速的衰减率随其数量的增多而增大,并且管内输送介质的体积模量越大越能体现出密封胶圈对水击波速的衰减效果;当管道厚径比小于0.05时,所提方法与薄壁管模型计算值偏差很小,说明所提方法对薄壁管和厚壁管均适用;装配式管线各管段连接处的环状空腔扮演着“水击压力缓冲环”的角色,随着管道厚径比的增加,环状空腔对水击响应的衰减作用逐渐增强,使得管内耦合水击波速呈现出先短暂增大,而后持续减小直至极限值的变化情况。