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.

Effects of Meridional Flow Passage Shape on Hydraulic Performance of Mixed-flow Pump Impellers

During the process of designing the mixed-flow pump impeller, the meridional flow passage shape directly affects the obtained meridional flow field, which then has an influence on the three-dimensional impeller shape. However, the meridional flow passage shape is too complicated to be described by a simple formula for now. Therefore, reasonable parameter selection for the meridional flow passage is essential to the investigation. In order to explore the effects of the meridional flow passage shape on the impeller design and the hydraulic performance of the mixed-flow pump, the hub and shroud radius ratio (HSRR) of impeller and the outlet diffusion angle (ODA) of outlet zone are selected as the meridional flow passage parameters. 25 mixed-flow pump impellers, with specific speed of 496 under the design condition, are designed with various parameter combinations. Among these impellers, one with HSRR of 1.94 and ODA of 90° is selected to carry out the model test and the obtained experimental results are used to verify accuracies of the head and the hydraulic efficiency predicted by numerical simulation. Based on SIMPLE algorithm and standard k-ε two-equation turbulence model, the three-dimensional steady incompressible Reynolds averaged Navier-Stokes equations are solved and the effects of different parameters on hydraulic performance of mixed-flow pump impellers are analyzed. The analysis results demonstrate that there are optimal values of HSRR and ODA available, so the hydraulic performance and the internal flow of mixed-flow pumps can be improved by selecting appropriate values for the meridional flow passage parameters. The research on these two parameters, HSRR and ODA, has further illustrated influences of the meridional flow passage shape on the hydraulic performance of the mixed-flow pump, and is beneficial to improving the design of the mixed-flow pump impeller.

Experimental Study of the Influence of Flow Passage Subtle Variation on Mixed-flow Pump Performance

In the mixed-flow pump design, the shape of the flow passage can directly affect the flow capacity and the internal flow, thus influencing hydraulic performance, cavitation performance and operation stability of the mixed-flow pump. However, there is currently a lack of experimental research on the influence mechanism. Therefore, in order to analyze the effects of subtle variations of the flow passage on the mixed-flow pump performance, the frustum cone surface of the end part of inlet contraction flow passage of the mixed-flow pump is processed into a cylindrical surface and a test rig is built to carry out the hydraulic performance experiment. In this experiment, parameters, such as the head, the efficiency, and the shaft power, are measured, and the pressure fluctuation and the noise signal are also collected. The research results suggest that after processing the inlet flow passage, the head of the mixed-flow pump significantly goes down; the best efficiency of the mixed-flow pump drops by approximately 1.5%, the efficiency decreases more significantly under the large flow rate; the shaft power slightly increases under the large flow rate, slightly decreases under the small flow rate. In addition, the pressure fluctuation amplitudes on both the impeller inlet and the diffuser outlet increase significantly with more drastic pressure fluctuations and significantly lower stability of the internal flow of the mixed-flow pump. At the same time, the noise dramatically increases. Overall speaking, the subtle variation of the inlet flow passage leads to a significant change of the mixed-flow pump performance, thus suggesting a special attention to the optimization of flow passage. This paper investigates the influence of the flow passage variation on the mixed-flow pump performance by experiment, which will benefit the optimal design of the flow passage of the mixed-flow pump.

Robust optimization design on impeller of mixed-flow pump

To increase the robustness of the optimization solutions of the mixed-flow pump,the impeller was firstly indirectly parameterized based on the 2D blade design theory.Secondly,the robustness of the optimization solution was mathematically defined,and then calculated by Monte Carlo sampling method.Thirdly,the optimization on the mixed-flow pump′s impeller was decomposed into the optimal and robust sub-optimization problems,to maximize the pump head and efficiency and minimize the fluctuation degree of them under varying working conditions at the same time.Fourthly,using response surface model,a surrogate model was established between the optimization objectives and control variables of the shape of the impeller.Finally,based on a multi-objective genetic optimization algorithm,a two-loop iterative optimization process was designed to find the optimal solution with good robustness.Comparing the original and optimized pump,it is found that the internal flow field of the optimized pump has been improved under various operating conditions,the hydraulic performance has been improved consequently,and the range of high efficient zone has also been widened.Besides,with the changing of working conditions,the change trend of the hydraulic performance of the optimized pump becomes gentler,the flow field distribution is more uniform,and the influence degree of the varia-tion of working conditions decreases,and the operating stability of the pump is improved.It is concluded that the robust optimization method proposed in this paper is a reasonable way to optimize the mixed-flow pump,and provides references for optimization problems of other fluid machinery.

基于高隔振指标要求的船舶泵组区域隔振模块设计研究

为满足某静音型船舶对于机舱泵组的隔振指标及布置空间的高要求,该文利用区域隔振模块设备间布置紧凑、空间利用率高、隔振效果好等优点,开展该船机舱泵组区域隔振模块的设计研究。从区域隔振模块总体布置、有限元建模、中间筏架模态分析、模块模态分析、模块静力学分析、模块谐响应分析等方面入手,建立了高隔振性能区域隔振模块的设计计算分析流程,完成了该型区域隔振模块的设计及隔振指标计算评估,并对其隔振性能进行测试。结果表明,该型区域隔振模块的隔振性能可满足此类静音型船舶对于机舱泵组高隔振指标的设计要求。

电潜螺杆泵入口处气液比动态变化特性分析

随着油田开发的不断深入,螺杆泵采油技术得到进一步发展与完善,近年来,在高含气和稠油等非常规油气藏中也得到广泛应用,但由于游离气和溶解气的存在,气体进入泵内会影响螺杆泵的工作性能和使用寿命。针对这种情况,综合考虑油气水三相流体对螺杆泵运行工况的影响,结合钻井液密度、生产气油比、含水率和气体状态方程,建立了螺杆泵入口处的气液比计算模型,并以大港油田J36-6和J36-8油井的生产数据进行模拟分析。结果表明,在动液面高度一定的情况下,增加下泵深度有利于降低泵入口处的气液比,高密度、高含水和低生产气油比是保证泵入口气液比较低的关键。

立式混流泵组电机漏油技术分析与应对微探

针对某立式混流泵组电机漏油严重、运行摆度大、振动大的问题,从电机设计、制造加工以及安装等方面制定了漏油预防与处理方案,通过改进电机设计结构、修复方式和安装工艺,圆满解决了上述问题。该方案贴合设备运行工况,能显著提升泵组运行的安全和稳定性,同时可为类似泵组电机漏油故障处理提供借鉴。

抽水蓄能机组过速保护值整定原则的探讨

本文对水电机组过速保护设置的目的、意义及其整定原则进行了初步探讨。对常规混流式水电机组和抽水蓄能机组分别发生飞逸后的机组转速变化曲线的相关特性进行分析比较,分析研究了抽水蓄能机组稳态飞逸转速和甩负荷后机组最高瞬态转速的相关情况,提出了抽水蓄能机组机械过速保护值和电气保护值的整定原则和方法。同时,结合实际工程案例,应用该整定方法对某抽水蓄能电站机组过速保护的整定值进行了计算分析,验证了该整定原则的工程实用性。

一种具有锁定检测结构的新型抗SET效应DLL设计技术

针对延迟锁相环的结构和对单粒子效应敏感性的分析,提出了一种具有锁定检测结构的新型抗SET加固DLL结构,该结构能在满足原有DLL性能指标的前提下实现对SET效应的加固,保证DLL正交四相时钟的正确输出.基于65nm CMOS工艺进行电路设计仿真,结果显示在500 MHz工作频率下,此DLL功能正确,抗SET性能良好,SET阈值达到100 MeV·cm2/mg,在空间辐射环境中具有很好的稳定性.

考虑风速随机性的风电-抽水蓄能微网一次调频方法

风电主导的微电网系统惯量低,对负荷频率控制的快速性和稳定性产生负面影响。为此,提出一种考虑风速随机性的风电与抽水蓄能协同控制方法。首先,通过对风机次优功率跟踪(optimized power point tracking,OPPT)惯性控制方法在电网频率调节时受风速影响机理的分析,制定风机进行微网一次调频时的风速整定规则;然后,在获取风机参与调频整定风速区间的基础上,根据风机参与状态,设计抽水蓄能机组控制方式,并对其控制器参数进行动态调整以适应风速的不确定性,确保调频效果最佳。通过仿真分析,验证所提方法不仅能充分挖掘风机的调频潜力,而且能提高微网调频的完备性。

面向热泵供热的热电联产机组燃料节能评价

为分析热电联产机组在热泵供热系统中的燃料利用情况、开展燃料节能评价,提出了面向热泵供热的热电联产机组燃料节能评价方法。构建了热泵热电联产机组的运行结构,分析熵平衡状态和热平衡状态,利用性能系数分析热泵供热系统的热力性能;通过热泵系统的性能系数计算在额定工况下对应的供热量,根据热泵供热系统工作状态下的总煤耗计算热电联产机组的节煤率,实现热电联产机组燃料节能评价。实验结果表明,面向热泵供热的热电联产机组燃料节能评价方法可准确分析热电联产机组的性能变化情况,具有较高的评价精度。

基于抽水装置特性曲线校正的泵站优化模型

受运行时长、安装位置等多种因素影响,水泵装置理论特性曲线难以准确描述实际抽水装置的运行特性,导致通过以其为基础所构建的泵站优化模型计算得到的运行方案偏离实际。基于水泵理论曲线提出数据和机理双重驱动的参数辨识方法校正水泵装置特性曲线,通过对实测数据进行多项式拟合校正装置效率曲线,以实测数据诱导转速理论曲线整体平移可实现装置转速曲线的校正。以南水北调东线工程的泗洪泵站为例,构建考虑机组差异特性的泵站优化模型。结果表明:经过校正,效率曲线与实测数据的符合程度从校正前的0.60提升至0.99,转速曲线与实际的平均绝对误差比校正前降低了0.23 r/min;基于装置特性曲线校正的差异特性站内优化分配方案更加贴近实际运行情况,相比历史运行方案平均降低10.1%的能耗,可实现泵站高效运行与调度目标的精细控制。利用实际运行数据对泵组装置特性曲线进行校正可有效加强泵站优化分配方案对实际调度的指导作用。

基于PAC和LabVIEW的压力变送器高精度动态测试系统研究

为了实现压力变送器静态特性和动态特性的高精度测试,设计了一套基于PAC和LabVIEW的智能控制系统。该系统利用伺服泵组产生的高精度压力源施加于被测对象(压力变送器),通过对比校验装置的示值与被测对象的反馈数据,分析校验示值与被测对象反馈结果压力之间的对应关系,从而实现压力变送器的压力自动测试。同时,该系统还可以自动获取压力变送器的灵敏度、线性度、迟滞性、重复性、精度、温度漂移和零点漂移等特性参数。实验结果表明,该系统设计合理,压力测试精度高。

夏热冬冷地区游泳馆除湿热泵空调系统节能性对比分析

室内游泳馆具有高温高湿的特点。因此必须对游泳馆内空气温度、相对湿度及池水温度等因素进行高精度控制,以及时除去余热余湿,维持建筑物整体正常运行。目前室内游泳馆一般采用常规空调系统或者泳池专用除湿热泵空调系统。以上海市某室内游泳馆作为夏热冬冷地区游泳馆代表,选取冬季和夏季典型日,对常规空调系统与泳池专用除湿热泵空调系统进行节能性对比分析,结果表明在同样的负荷条件下,采用泳池专用除湿热泵空调系统的运行能耗均要低于常规空调系统,冬季泳池专用除湿热泵空调系统比常规空调系统节能约22.9%,在夏季节能23.3%左右,可见泳池专用除湿热泵空调系统的节能效果显著。

泵挂调整技术在榆树林油田低渗储层中的应用

为了解决低渗储层主力油层潜力释放难、单井举升能耗高的难题,依据低渗透砂岩油藏的油井产能方程和井筒储集效应,计算出单井的合理流压范围,确定了单井合理动液面值;分析了机采井沉没度与泵效、成本的关系,计算出合理沉没度值。在二者的基础上,优化给出了合理的泵挂深度值。现场试验结果表明:泵挂调整后,平均单井产量提高了18.2%,平均单井举升能耗降低了10%,进一步释放了主力油层潜力,降低了单井能耗。研究的计算方法可为低渗储层泵挂调整提供技术指导。

某地源热泵能源站节能调适与能效提升

为探讨地源热泵能源站在调适过程中能效提升的技术策略,以某职业学校餐旅综合楼中央空调系统为例,通过前期调研、完善监控系统和对运行数据的测试分析,编制地源热泵能源站节能调适流程。结果发现,采取优化负荷侧供水温度设定、适配两侧循环水泵的变频控制、研制开发智能化自适应动态水力平衡系统等耦合的调适措施,可在保证室内各场所热舒适的情况下,有效降低能源站的系统能耗,显著提升能源站实际能效。经委托第三方实际检测计算和鉴定,综合多层面的节能调适技术应用,可达到夏季节能率50.7%、冬季节能率40.7%的实际效果。

350 MW超临界火电机组100%容量汽泵RB试验研究及应用

某350 MW超临界火电机组配置100%汽泵和50%启动电泵,不具备汽动给水泵快速减负荷RB功能。针对电泵启动时间长触发双泵均停跳闸MFT、电泵带载启动母线欠压、运行后出力不足引起受热面断水超温等技术难点,分别制定了优化方案。在电泵启动时间控制上,采取了投备后超驰控制再循环门、联锁出口门、联启电泵液力耦合器交流辅助油泵等措施,并结合电泵带载启动欠压试验进行了验证。为了保证电泵启动后快速出力,在对汽机跟踪方式下汽机主控滑压函数和压降速率进行优化的基础上,又设计了汽泵RB快速减负荷、电泵再循环及勺管开度自适应匹配等控制功能。通过60%负荷下的汽泵RB动态试验,验证了在超临界机组应用汽泵跳闸联锁启动电泵方案的可行性。

水利工程建设中机电技术运用研究

选择普安县江西坡镇黄泥田村附近的白水水库工程作为分析对象,梳理工程中机电设备选择与设计过程中遇到的问题,重点围绕NDS系列卧式水平中开多级离心泵、立式长轴泵的运用进行分析。按照设计思路完成水利工程机电设备的选择及建设,设备投入运营至今未出现规模相当水利工程中常见的操作费时费力、可靠性低等问题,可经由计算机进行自主操控,极大地提升该水库工程的运行效率。

炼钢厂中控楼电缆夹层高压细水雾灭火系统设计分析

对中南股份炼钢厂1号、2号、3号转炉中控楼电缆夹层,进行加装高压细水雾灭火设施改造。根据消防安全要求、员工生产安全、财产安全及现场实际环境进行分析,研究确定设计相应的高压细水雾消防系统。设计分为3个防护分区,防护区最不利喷头工作压力10.0 MPa,高压泵组扬程140 m,其中容积最大防护分区内布置有54个喷头,喷雾强度取值K=1.0,项目的设计流量为540 L/min。系统选用规格为120 L/min的高压细水雾泵组系统(五用一备),储水量为18 m^(3),保证转炉工序供电运行稳定性。

无煤柱充填采煤工艺设计及试验

针对煤层回采率低以及维护效率低的问题,在对其工作面地质条件分析的基础上,确定采用高水速凝水灰比为1.5∶1的充填材料为核心实施充填采煤工艺;根据工作面断面尺寸和当前生产能力完成机械化充填设备的选型,并设计对应的充填工艺流程。最后,对机械充填采煤工艺的应用效果进行评估,并得出无煤柱充填采煤工艺可减少工作面顶底板近160mm的移近量,可实现工作面高效的生产。