Simulation of Underground Reservoir Stability of Pumped Storage Power Station Based on Fluid-Structure Coupling

Based on global initiatives such as the clean energy transition and the development of renewable energy,the pumped storage power station has become a new and significant way of energy storage and regulation,and its construction environment is more complex than that of a traditional reservoir.In particular,the stability of the rock strata in the underground reservoirs is affected by the seepage pressure and rock stress,which presents some challenges in achieving engineering safety and stability.Using the advantages of the numerical simulation method in dealing deal with nonlinear problems in engineering stability,in this study,the stability of the underground reservoir of the Shidangshan(SDS)pumped storage power station was numerically calculated and quantitatively analyzed based on fluid-structure coupling theory,providing an important reference for the safe operation and management of the underground reservoir.First,using the COMSOL software,a suitablemechanicalmodel was created in accordance with the geological structure and project characteristics of the underground reservoir.Next,the characteristics of the stress field,displacement field,and seepage field after excavation of the underground reservoir were simulated in light of the seepage effect of groundwater on the nearby rock of the underground reservoir.Finally,based on the construction specifications and Molar-Coulomb criterion,a thorough evaluation of the stability of the underground reservoir was performed through simulation of the filling and discharge conditions and anti-seepage strengthening measures.The findings demonstrate that the numerical simulation results have a certain level of reliability and are in accordance with the stress measured in the project area.The underground reservoir excavation resulted in a maximum displacement value of the rock mass around the caverns of 3.56 mm in a typical section,and the safety coefficient of the parts,as determined using the Molar-Coulomb criterion,was higher than 1,indicating that the project as a whole is in a stable state.

Simulation Method and Feature Analysis of Shutdown Pressure Evolution During Multi-Cluster Fracturing Stimulation

Multistage multi-cluster hydraulic fracturing has enabled the economic exploitation of shale reservoirs,but the interpretation of hydraulic fracture parameters is challenging.The pressure signals after pump shutdown are influenced by hydraulic fractures,which can reflect the geometric features of hydraulic fracture.The shutdown pressure can be used to interpret the hydraulic fracture parameters in a real-time and cost-effective manner.In this paper,a mathematical model for shutdown pressure evolution is developed considering the effects of wellbore friction,perforation friction and fluid loss in fractures.An efficient numerical simulation method is established by using the method of characteristics.Based on this method,the impacts of fracture half-length,fracture height,opened cluster and perforation number,and filtration coefficient on the evolution of shutdown pressure are analyzed.The results indicate that a larger fracture half-length may hasten the decay of shutdown pressure,while a larger fracture height can slow down the decay of shutdown pressure.A smaller number of opened clusters and perforations can significantly increase the perforation friction and decrease the overall level of shutdown pressure.A larger filtration coefficient may accelerate the fluid filtration in the fracture and hasten the drop of the shutdown pressure.The simulation method of shutdown pressure,as well as the analysis results,has important implications for the interpretation of hydraulic fracture parameters.

Influence of specific speed on hydraulic performances and pressure fluctuations in mixed-flow pumps

A series of steady and unsteady numerical calculations of the internal flow in mixed-flow pumps with three different specific speeds were carried out based on the N-S equation coupled with the standard k-εturbulence model under different operating conditions to investigate the relationship between the impeller specific speed and the pump performance as well as pressure pulsations.Meanwhile,the pump performance and pressure pulsations inside the mixed-flow pump with three different specific speeds were also analyzed and compared with the corresponding test data.From the results,the averaged deviations between the predicted and tested head among different impellers are below 5%,and with respect to the equivalent impeller specific speeds of 280 and 260,the values are 4.30%and 3.69%,respectively.For all the impeller schemes,the best efficiency point of the mixed-flow pump is found at the flow rate of 1.2 Q_(d) and the higher head deviation occurs at lower flow rates.Especially,it can be found that the specific speed has a slight effect on the pressure fluctuation in the impellers.Eventually,it is determined that the pump performance curves calculated by numerical simu-lations have good agreement with the relevant experimental results,which verifies that the numerical methods used in the present study are accurate to a certain extent.Furthermore,the results also provide some references to the pressure pulsation analysis and the performance improvement of the mixed-flow pump design.

Effect of impeller reflux balance holes on pressure and axial force of centrifugal pump

The size of impeller reflux holes for centrifugal pump has influence on the pressure distribution of front and rear shrouds and rear pump chamber, as well as energy characteristics of whole pump and axial force. Low specific-speed centrifugal pump with Q=12.5 m3/h, H=60 m, n=2950 r/min was selected to be designed with eight axial reflux balance holes with 4.5 mm in diameter. The simulated Q-H curve and net positive suction head(NPSH) were in good agreement with experimental results, which illustrated that centrifugal pump with axial reflux balance holes was superior in the cavitation characteristic; however, it showed to little superiority in head and efficiency. The pressure in rear pump chamber at 0.6 times rate flow is 29.36% of pressure difference between outlet and inlet, which reduces to 29.10% at rate flow and 28.33% at 1.4 times rate flow. As the whole, the pressure distribution on front and rear shrouds from simulation results is not a standard parabola, and axial force decreases as flow rate increases. Radical reflux balance holes chosen to be 5.2 mm and 5.9 mm in diameter were further designed with other hydraulic parts unchanged. With structural grids adopted for total flow field, contrast numerical simulation on internal flow characteristics was conducted based on momentum equations and standard turbulence model(κ-ε). It is found that axial force of pump with radical reflux balance holes of5.2 mm and 5.9 mm in diameter is significantly less than that with radical reflux balance holes of 4.5 mm in diameter. Better axial force balance is obtained as the ratio of area of reflux balance holes and area of sealing ring exceeds 6.

Investigation on Reduction of Pressure Fluctuation for a Double-Suction Centrifugal Pump

Double-suction centrifugal pumps have been applied extensively in many areas,and the significance of pressure fluctuations inside these pumps with large power is becoming increasingly important.In this study,a double-suction centrifugal pump with a high-demand for vibration and noise was redesigned by increasing the flow uniformity at the impeller discharge,implemented by combinations of more than two parameters.First,increasing the number of the impeller blades was intended to enhance the bounding effect that the blades imposed on the fluid.Subsequently,increasing the radial gap between the impeller and volute was applied to reduce the rotor-stator interaction.Finally,the staggered arrangement was optimized to weaken the efficacy of the interference superposition.Based on numerical simulation,the steady and unsteady characteristics of the pump models were calculated.From the fluctuation analysis in the frequency domain,the dimensionless pressure fluctuation amplitude at the blade passing frequency and its harmonics,located on the monitoring points in the redesigned pumps(both with larger radial gap),are reduced a lot.Further,in the volute of the model with new impellers staggered at 12°,the average value for the dimensionless pressure fluctuation amplitude decreases to 6%of that in prototype pump.The dimensionless rootmean-square pressure contour on the mid-span of the impeller tends to be more uniform in the redesigned models(both with larger radial gap);similarly,the pressure contour on the mid-section of the volute presents good uniformity in these models,which in turn demonstrating a reduction in the pressure fluctuation intensity.The results reveal the mechanism of pressure fluctuation reduction in a double-suction centrifugal pump,and the results of this study could provide a reference for pressure fluctuation reduction and vibration performance reinforcement of doublesuction centrifugal pumps and other pumps.

Determination of Working Pressure for Airport Runway Rubber Mark Cleaning Vehicle Based on Numeric Simulation

In this paper,numeric simulations are performed for three dimension models built according to actual surface cleaner in airport runway rubber mark cleaning vehicle using ANSYS FLUENT software on the basis of previous research finished by the authors.After analyzing the simulated flow fields under different standoff distances between nozzle outlet and runway surface and different discharge pressures at nozzle outlet,the relationships of normal stress and shear stress at striking point to outlet pressure and standoff distance are obtained.Finally,the most appropriate discharge pressure at nozzle outlet for the studied surface cleaner model is found,and this will provide theoretical basis for future rubber mark cleaning process in airports and equipment model selection in subsequent design of airport runway rubber mark cleaning vehicles.

深层隧道进流式泵站前池流态及整流措施研究

为改善深层隧道进流式泵站前池内的旋流、偏流等不良流态,基于RNG k-ε湍流模型对前池流态进行数值模拟,研究适用于此类城市排涝泵站的整流措施。数值计算结果表明:泵站前池、进水池内存在局部立面旋滚、螺旋流、斜向流、流速分布上高下低等不良水力现象,致使泵站进水流道水力条件不佳;采用双层环形板和两组导流墩的组合式整流措施可抑制前池、进水池中的立面旋滚、螺旋流和斜向流流态,从而有效改善流道的进水条件,提高进水流道进口处流速分布均匀度,使泵进水状况变好,提高泵站运行的可靠性。

叶片数对无轴泵喷推进器性能的影响

为丰富无轴泵喷推进器噪声性能优化理论,研究了叶片数对无轴泵喷推进器性能的影响,重点探究了不同叶片数下无轴泵喷推进器内的压力脉动变化规律。基于计算流体力学中的有限体积法离散RANS方程,应用RNG k-ε湍流模型封闭计算模型,采用SIMPLEC进行压力-速度耦合,对不同叶片数下的无轴泵喷推进器内部流场进行了非定常数值模拟计算,并对计算结果进行了详细的对比分析。研究结果表明:随叶片数的增加,无轴泵喷推进器模型的扬程、效率和推力均逐渐增大,叶片表面压力分布更加均匀,叶轮轮缘和中部的压力脉动均明显降低,叶轮进出口主频处的压力脉动幅值从轮缘向中心逐渐减小。

地下泵站进水流道数值模拟与方案优化

以典型地下泵站的进水流道为研究对象,建立数值仿真模型,分析设计方案的水力特性及存在不足,并给出优化方案.研究结果表明:在原方案中,外侧水泵进水管入口中心和圆洞出口中心的连线与来流方向的夹角达到70°,水流大角度偏转,并在进水管入口出现脱流现象,水头损失系数达到2.31~2.44,水泵进水管出口的流速分布均匀度为95.09%~96.80%,速度加权平均角为86.51°~87.41°,原方案的圆洞突扩进入压力罐,然后突缩进入水泵的进水管,且压力罐内无任何导流措施,致使局部流道产生了较大的水头损失;优化方案提出了“集管+岔管”的分流措施,通过2个60°弯头实现水流流向的偏移,平面和垂直方向均没有突扩或突缩结构,水头损失系数减小至0.93~1.07,优化方案不仅改善了流道的水力性能,也避免了开挖、衬砌压力罐.研究结果可为类似地下泵站进水流道设计提供一定依据.

侧式进/出水口各孔道流量分配差异及影响因素

对于抽水蓄能电站侧式进/出水口各孔道流量分配,现有设计规范规定进/出水口相邻中边孔道的流量不均匀程度不宜超过10%,但实际工程设计难以达到此要求.本文以某抽水蓄能电站侧式进/出水口为例,通过优化进/出水口各体型参数,利用数值模拟方法研究各孔道流量等水力参数,重点分析分流墩布置对各孔道流量分配的影响及其规律,试图使进流工况和出流工况相邻中边孔道的流量不均匀程度均最小.研究表明,改变扩散段分流墩布置能有效改善流量不均匀程度.对于3墩4孔侧式进/出水口,相邻中边孔道的流量不均匀程度在出流工况下随中边孔宽度比增大而增大,在进流工况下随中边孔宽度比增大而减小;当中边孔宽度比增大且中墩后移距离减小时,出流工况和进流工况下的流量不均匀程度均减小.对于2墩3孔侧式进/出水口,相邻中边孔道的流量不均匀程度不论在出流工况下还是在进流工况下,均随中边孔宽度比增大呈先减小后增大的规律.优化后的3墩4孔侧式进/出水口的中边孔宽度比取0.228∶0.272,中墩后移距离取0.36D(D为隧洞直径),其相邻中边孔道的流量不均匀程度均较优,在出流工况下为18.47%~19.43%,在进流工况下为19.82%~19.83%;优化后的2墩3孔侧式进/出水口的中边孔宽度比取0.310∶0.345,其相邻中边孔道的流量不均匀程度均较优,在出流工况下为19.47%~19.63%,在进流工况下为18.66%~18.67%.相邻中边孔道的流量不均匀程度较难满足不宜超过10%的设计规范要求.研究成果将有助于《抽水蓄能电站设计规范》中关于进/出水口水力指标要求的完善.

海水泵站流道非对称引水流态特性数值模拟分析

为探讨海水泵站流道非对称引水流态特性,基于OpenFOAM建立了某液化天然气接收站海水泵站流道数值模型,在利用实测数据验证的基础上,模拟计算与分析了对称和非对称引水时,流道内流速与紊动动能分布特征。模拟结果表明:海水泵站非对称引水时,水流进入前池后流速较大,在低水位下水流无法充分扩散,在流道入口处形成偏流,行进至海水泵前断面水流分布已基本均匀;非对称引水时,海水泵所在进水池各断面均匀性指数平均值高于对称引水工况,且各海水泵进水池的紊动动能平均值也小于对称引水工况;从过水断面流速分布均匀性以及紊动量级来看,非对称引水对水泵运行更有利。

侧式进 出水口顶板扩张角对拦污栅断面流速分布影响规律研究

抽水蓄能电站侧式进出水口双向过流,其顶板扩张角的大小将直接影响拦污栅断面流速分布是否均匀,甚至出现反向流速。抽水蓄能电站设计规范将3°~5°作为侧式进出水口顶板扩张角的推荐范围,其依据是矩形渐扩管阻力系数最小的扩张角度,但侧式进出水口体型较之复杂很多,因此有必要进一步探讨。本文以某侧式进出水口体型为研究对象,采用数值模拟方法,研究了11种角度的顶板扩张角对出流工况和进流工况拦污栅断面流速分布的影响。结果表明:在出流工况下,随着顶板扩张角的增大,中孔拦污栅断面的主流位置由居中部逐渐向底部降低,断面流速分布由上下基本对称趋于底部大上部小的上下不对称,当顶板扩张角较大时中孔拦污栅断面上部出现反向流速;随着顶板扩张角的增大,边孔拦污栅断面流速分布由基本均匀逐渐变为底部大上部小的不均匀分布;随着顶板扩张角的增大,中、边孔孔口流速不均匀系数均逐渐增大,但中孔拦污栅断面流速分布受顶板扩张角影响更大。在进流工况下,随着顶板扩张角的增大,中、边孔拦污栅断面流速分布及孔口流速不均匀系数均无明显影响。研究成果可为优化侧式进出水口设计提供指导。

接立面转弯隧洞的侧式出水口水力特性

对于接立面转弯隧洞的侧式出水口,立面转弯隧洞的转弯段将直接影响侧式出水口的水力特性。若立面转弯隧洞参数设计不合理,极易导致侧式出水口内部发生流动分离。选取RSM紊流模型,针对接立面转弯隧洞的侧式出水口进行数值模拟,探究立面转弯隧洞曲率半径R、弯道后直隧洞长度L及转弯角度α等参数对出水口水力特性的影响规律,并对隧洞内流动过程进行了讨论。增加立面转弯隧洞曲率半径R和弯道后直隧洞长度L能显著改善出水口的水力指标。当曲率半径R≥12 D(D为隧洞直径)、弯道后直隧洞长度L≥16 D时,侧式出水口内部无明显流动分离,拦污栅断面流速分布均匀且无反向流速区。研究成果将对抽水蓄能电站侧式进/出水口的设计提供指导。

大型地埋管群地源热泵三维传热-渗流耦合模拟

为确定地下水渗流对大尺度、多分支埋管集群地源热泵系统换热区温度场和换热特性的影响,基于上海天文馆880个地埋管地源热泵场地,建立考虑地下水渗流和地质分层的三维传热-渗流耦合模型,并利用现场热响应试验对模型进行验证。结果表明:渗流作用引起管群内和支管群之间沿地下水流动方向发生温度干扰,89.5~120.3 m埋深范围内的温度干扰现象相对明显;地下水渗流有利于提高管群的换热总量,缩小夏季和冬季工况的换热量差距;换热量增加百分比随水力梯度的增加而增大,两者呈对数函数关系,当水力梯度大于0.005时,换热量增加百分比趋于平稳。

大偏角短引渠侧向进水泵站流场流态优化

为了改善大偏角短引渠侧向进水泵站前池、进水池内偏流、回流和漩涡等不良流态,以某大型大偏角短引渠侧向进水泵站工程为研究对象,采用物理模型试验和数值模拟相结合的方式对初步设计方案下的前池、进水池流态进行分析,提出流速偏差系数λ作为评价指标,对工程进行优化,探讨前池的结构性改造对水流的整流效果,得出“弧形隔墩+改变底坡坡度+开设消涡孔”的组合方案为推荐整流方案,有效解决了前池及进水池内原设计存在的不良流态。研究结果表明,该整流方案使各个机组进水池偏差系数分别下降了37.03%、12.99%、22.29%、22.04%,显著改善了前池,进水池流态。研究结果可为类似大偏角短引渠侧向进水泵站前池及进水池流场流态优化提供参考,也可为类似短引渠泵站工程和进水建筑物的设计提供参考。

水泵水轮机导水机构与转轮动应力特性分析

为探究水泵水轮机转轮和导水机构的动应力特性,通过建立水泵水轮机导水机构(固定导叶与活动导叶)及转轮的固体域模型,并基于流固耦合的方法对转轮、导水机构在水泵水轮机发电、抽水等多工况展开计算分析,以获得转轮及导水机构的应力特性。计算结果表明:转轮叶片与上冠“T”型连接处的应力集中与转轮进口处旋涡发展状态有关;转轮与活动导叶间的动静干涉是无叶区压力脉动的主要来源,且主频为叶片通过频率;较小开度或低水头工况下机组运行靠近不稳定区,活动导叶与转轮的动应力均较大,但活动导叶对水流的约束引导作用使其动应力值相比于转轮更高,且流量的增大有利于降低转轮所受动应力。因此可考虑通过改变导叶尾端与转轮进口间距,调整无叶区宽度或调整机组运行区域,避免长时间运行在低负荷、小开度工况下可进一步改善转轮所受动应力情况。

加氢站高压低温氢气泄漏扩散数值研究

为了明确加氢站发生高压氢气泄漏后形成可燃区域的分布特性,进行了某加氢站中的35 MPa和70 MPa加氢机发生泄漏事故的数值模拟。研究了泄漏孔径和氢气预冷温度对稳态可燃区域分布形态和体积的影响。计算结果表明,70 MPa加氢机泄漏形成的可燃区域体积约为35 MPa加氢机的两倍。泄漏孔尺寸对可燃区域体积有非常显著的影响。随着预冷温度的降低,射流边界层的气流速度降低,氢气质量分数增大,且后者对稳态可燃区域体积的影响更大,尤其在发生中孔泄漏时,随着氢气预冷温度从300 K降低至240 K,35 MPa加氢机泄漏形成的可燃区域体积从5590 m~3增加到16835 m~3,增长率为201.16%,同时可燃区域的形态从“平面”转换到“羽状”。

城市排水泵站水力特性及整流措施

为了解弧形进水箱涵城市排水泵站水力特性,探寻改善泵站内部不良流态的整流措施,采用数值模拟方法对城市排水泵站水力流态及整流措施进行研究,并通过物理模型对整流效果进行验证。研究结果表明:弧形进水箱涵城市排水泵站的前池存在主流偏斜与分离流动现象,前池主流集中在中上层,中下层出现大范围的立面环流,底层存在回流,进水池内流态紊乱并出现旋涡,导致水泵进水不够顺畅;设计优化的“方形立柱+组合横梁”的组合式整流措施能够改善前池和进水池的水力流态,前池内的偏流和分离流动消除,底层回流消失,进水池旋涡得到有效抑制,3台水泵进水流道入口流速分布均匀度分别提升了12.0%、8.7%、8.3%,入流速度加权平均角分别提升了7.08°、9.07°、11.40°。

综掘巷道大风量双压风筒下长压短抽除尘效果的模拟研究

煤矿井下大风量双压风筒综掘巷道具有产尘强度大、粉尘分散度高、巷道风速大等特点,严重威胁作业人员身心健康和矿井安全生产。为降低大风量综掘巷道粉尘浓度,基于CFD数值模拟软件建立了双压风筒综掘巷道物理结构,采用DPM模型,重点研究了单抽双压式通风下抽风筒入风口与巷道迎头之间的距离对掘进工作面粉尘运移规律的影响,分析了大风量双压风筒下长压短抽通风方式对司机位置作业环境的影响。结果表明:保持双压风筒出口距巷道迎头为4、5 m,压入风量为1 200 m^(3)/min条件下,当抽风筒入口与巷道迎头之间的距离为8 m时,司机位置粉尘浓度为30~90 mg/m^(3),作业环境最佳。

多水源地长距离供水工程恒定流水力仿真研究

本文基于压力管道水力学基本理论,针对长距离多泵站、多水源地供水联合运行问题,建立供水工程管网系统恒定流水力仿真模型,分别求解日常运行、常规检修与应急抢险等不同工况下管网系统中各点的压力与流量变化情况,从而检验系统的运行情况。结果表明,各工况下该供水系统压力极值都符合管道的承压标准,具备安全过流条件,可为类似供水工程的运行提供一定的参考作用。