斜流水泵三元流高效节能转子的优化设计分析

由于设备选型不合理、运行不当、气蚀等原因,导致泵类流体机械的运行效率偏低.基于转子叶轮的三元流理论,对某大型斜流水泵转子叶轮和导叶体的通流部分进行CFD数值模拟,分析速度场和流线,重新设计水力模型,优化流场.研究结果表明,通过对转子叶轮和导叶体的通流部分改造,可以有效提高水泵的效率和对工况的适应性,降低水泵的电耗,为同...     

应用三元流技术实施循环水系统节能改造

根据循环水泵的实际运行工况,在原来循环水系统的水泵主体、系统管路、电机等不作改动前提下,采用三元流叶轮改造技术,重新设计高效三元流叶轮,更换于原水泵叶轮,并且对水泵的过流部件进行特殊的涂层处理,优化水泵系统操作,使水泵运行效率大幅度提高,最终达到了系统节能目的。     

水泵水轮机泵工况下内部空化特性分析

为研究空化条件下水泵水轮机泵工况的内部空化特性,基于ANSYS CFX(有限元分析)软件采用k-ε湍流模型、均质多相模型和Rayleigh-Plesset方程,对某抽水蓄能电站模型机进行了全流道非定常空化流动数值计算。根据模拟结果预测了水泵水轮机泵工况工作无空化时的能量特性和空化发生时的空化性能,并与试验数据对比。结果表明:流场数值计算成功地捕获到了空化发生、发展及空间演变过程;随着空化数的变化,空泡在叶片背面进口附近产生,然后沿着流线向叶轮出口扩散,并随着流道过流面积的增大向叶片工作面扩展,直接影响叶片上的压力分布和叶片中间流线上叶片载荷分布;在空化严重时,会造成叶轮流道内流动紊乱和严重堵塞,导致效率的大幅下降,对机组安全稳定运行非常不利。     

水泵水轮机转轮加装短叶片前后的流动特性对比

为对比高水头水泵水轮机的转轮加装短叶片前后的能量特性及流动特性,基于SST湍流模型,选取4个具有代表性的水泵及水轮机工况,对有/无短叶片的水泵水轮机进行全流道三维定常计算。数值模拟结果表明,以水泵运行时加装短叶片可抑制脱流与漩涡等二次流现象,降低单个叶片承受的水力载荷,提高转轮进出口、导叶区及蜗壳静压,使泵获得更高的扬程。水轮机运行时添加短叶片可减小转轮出口环量,改善在尾水管内形成的复杂漩涡流,提高其水力效率。相同边界条件下,长短叶片转轮改善了转轮区的流动条件,从而提升了机组的能量特性及水力稳定性。     

基于水泵汽蚀现象的叶轮参数优化分析

为解决某型发动机在耐久试验中冷却水泵发生汽蚀的问题,对叶轮进行改进设计以减小水泵的汽蚀余量。考虑叶轮出口直径、叶片包角、叶轮轮毂曲率半径、隔舌间隙等参数对水泵汽蚀余量的影响,结合流体仿真软件对叶轮改进前后的压力云图、隔舌区域流体冲击载荷分布、气泡体积分数进行对比,并将改进后的水泵再次进行耐久试验。仿真和试验表明,改进后水泵的汽蚀余量明显下降,水泵上没有明显汽蚀现象,证明改进后的水泵提高了抗汽蚀能力。     

宁德电厂闭冷泵节能优化改造

通过对宁德电厂闭冷水泵进行诊断测试,发现选型裕量太大,扬程偏高,泵效率达不到设计要求,运行工况远离设计工况,制造工艺欠佳,流道对称差.后经过叶片进出口叶型优化、叶轮轴面流道型线优化、叶轮整体流道的优化、提高检修安装工艺等方法,消除了管道振动,降低了厂用电率,实现了节能降耗的目的.     

应用三元流动技术降低循环水场电耗

对中国石油化工股份有限公司济南分公司循环水系统进行三元流叶轮改造。在不改变泵体、电机、管路系统的前提下,以射流—尾迹三元流动理论为设计基础,设计制造了新型三元流叶轮,代替原泵内的普通叶轮。改造后,经过用电量统计对比,年用电量减少813万多度,节能降耗效果明显。     

Loss analysis and design optimization of a small scale mixed-flow pump turbine using the orthogonal method

为了研究各部件对小型混流式水泵水轮机水泵工况和水轮机工况下水力性能的影响,对一小型水泵水轮机进行不同流量下的全流道数值模拟,针对两工况下总压损失集中的叶轮进行正交设计优化。应用L9（3⁴）正交表,选取4个叶轮关键设计参数,以水泵工况扬程偏离率、效率和水轮机工况效率作为目标,进行4因素3水平的正交设计,并通过全流道数值模拟方法和极差分析方法进行选优。结果表明叶片出口直径对泵和水轮机工况性能影响最大,优化后水泵设计工况效率提高了1.06%,水轮机设计工况效率提高1.62%,其相应最优工况点因包角增加而向小流量工况移动。     

企业风机水泵节电方法

1　前言风机水泵是广泛使用的通用设备 ,用电量很大。据国家统计局不完全统计 :有泵类 30 0 0万台 ,80ＧＷ ;风机 70 0万台 ,30ＧＷ ,其用电量占全国发电量的 31%以上。由于多种原因 ,目前风机使用效率普遍较低 ,最低的只有 15 %左右 ;水泵的使用效率也普遍低于泵的最高效率 10 %～ 2 0 % ,电力浪费严重。因此 ,通过对风机水泵的节能监测 ,找出浪费的根源 ,采取合理的节能方法 ,是摆在我们面前的一项迫切的任务。2　风机水泵节电的主要方法及途径对机泵进行技术改造 ,如重新选型、叶型改造、切割叶轮、变速调节等 ,并加强管理、减少节流损 ,…     

交错叶片式双吸泵流动特性分析

为探究交错叶片式双吸泵的内部流动特性,本文基于CFD性能预测方法,在0.19Q_0~1.54Q_0不同流量工况下对某型号交错叶片式双吸泵全流道进行了数值模拟,并研究了泵外特性变化规律,分析泵压力、流速、流线和湍动能分布情况。结果表明:交错叶片式双吸泵效率高,额定工况下效率达到86.2%,高效区范围广,在额定流量工况附近,效率保持在80%以上;泵内部流动稳定,无明显漩涡与回流;在小流量工况下,泵内部流动变得紊乱,在叶轮流道间、叶轮与压水室交界处和隔舌附近存在明显脱流与漩涡,湍动能耗散严重,导致泵效率急剧下降。通过本文研究能对这类双吸泵的高效使用提供一定指导,并为该泵的进一步优化提供一定的参考。     

Optimization of water-cooled chiller system with load-based speed control

This study investigates the energy performance of chiller and cooling tower systems integrated with variable condenser water flow and optimal speed control for tower fans and condenser water pumps. Thermodynamic-behaviour chiller and cooling tower models were developed to assess how different control methods of cooling towers and condenser water pumps influence the trade-off between the chiller power, pump power, fan power and water consumption under various operating conditions. Load-based speed control is introduced for the tower fans and condenser water pumps to achieve optimum system performance. With regard to an example chiller system serving an office building, the optimal control coupled with variable condenser water flow could reduce the annual system electricity use by 5.3% and operating cost by 4.9% relative to the equivalent system using constant speed fans and pumps with a fixed set point for cooling water temperature control.     

Numerical analysis of two dimensional parallel flow flat-plate solar collector

Temperature distribution over the absorber plate of a parallel flow flat-plate solar collector is analyzed with one- and two-dimensional steady-state conduction equations with heat generations. The governing differential equations with boundary conditions are solved numerically using a control volume-based finite difference scheme. Comparisons of one- and two-dimensional results showed that the isotherms and performance curve, stated in terms of an effectiveness/number-of-transfer-unit relationship, for one-dimensional analysis slightly deviate from that of two-dimensional analysis, particularly under low mass flow rate conditions. In addition, collector efficiency as a function of operating point is computed and presented graphically for different collector configuration and various operating conditions. For general engineering purposes, these performance curves may be used for efficient and optimum design of liquid flat-plate solar collectors.     

蒸汽喷射式热泵变工况性能分析

采用数值模拟的方法对低压蒸汽增压利用系统中的蒸汽喷射式热泵在非设计工况下的操作性能进行研究，计算并分析了工作蒸汽压力和温度、引射流体压力及混合流体压力等热力参数对热泵操作性能的影响。数值结果表明：当混合流体的压力低于一定的数值时，喷射系数维持一定值；而热泵对引射流体压力的变化极为敏感，引射压力的微小变化可能导致热泵操作性能的急剧下降；提高工作蒸汽的压力并不一定能改善喷射泵的工作性能，这是因为提高工作蒸汽压力会增加额外的蒸汽量所致；喷射系数随工作蒸汽温度的升高而略有增大，并近似呈线性率。     

Investigation on mechanism of critical cavitating flow in liquid jet pumps under operating limits

The critical cavitating flow in liquid jet pumps under operating limits is investigated in this paper. Measurements on the axial pressure distribution along the wall of jet pumps indicate that two-phase critical flow occurs in the throat pipe under operating limits. The entrained flow rate and the distribution of the wall pressure upstream lowest pressure section does not change when the outlet pressure is lower than a critical value. A liquid–vapor mixing shockwave is also observed under operating limits. The wave front moves back and forth in low frequency around the position of the lowest pressure. With the measured axial wall pressures, the Mach number of the two-phase cavitating flow is calculated. It’s found that the maximum Mach number is very close to 1 under operating limits. Further analysis infers a cross-section where Mach number approaches to 1 near the wave front. Thus, the liquid–vapor mixture velocity should reach the local sound velocity and resulting in the occurrence of operating limits.     

3D transient CFD modelling of a scroll-type hydrogen pump used in FCVs

The scroll pump has a great potential to recirculate hydrogen in a fuel-cell vehicle (FCV) because of its high efficiency, low noise and vibration, reliable operation, and a wide range of adjustable flow. This paper presents three-dimensional transient computational fluid dynamics (CFD) modelling of a scroll-type hydrogen pump used in FCVs, including leakage flow through both the radial clearance (RC) and axial clearance (AC). A dynamic mesh was generated for the moving orbiting scroll, and high-quality hexahedral structured grids with sufficient grid-density were applied to the clearances to solve the multi-scale problem. The pressure and velocity fields were obtained at different rotating angles to reveal the dynamic characteristics in the compression chambers. The simulation results showed that the radial leakage through AC has more significant influence on the volumetric efficiency than the tangential leakage through RC, especially on scroll-type hydrogen pumps. The presented modelling and simulation methods were validated experimentally by operating a scroll air compressor at different speeds and pressure ratios. The volumetric efficiency of the scroll pump was 85.39% with 0.02 mm AC and 0.02 mm RC, 81.43% with 0.02 mm AC and 0.04 mm RC, and 70.17% with 0.04 mm AC and 0.02 mm RC. Further, it was found that the performance of scroll-type hydrogen pumps is more sensitive to rotating speed than air scroll pumps under the same conditions. With hydrogen, the volumetric efficiency increased by 30.68% when the rotating speed was increased from 3000 r·min^?1 to 6000 r·min^?1; with air, the volumetric efficiency increased by 12.81%. Therefore, it is necessary to consider both AC and RC in the CFD modelling of scroll machines, particularly in the case of hydrogen scroll pumps.     

撞击流气化炉内火焰二维温度场分布的测量

通过试验研究和理论分析,提出了一种基于彩色CCD三基色的单色法,测量了气化炉火焰温度,并计算气化火焰二维温度场.采用了多个参考点,进而提高了计算的精确性.结果表明,使用此方法能有效地检测气化火焰的二维温度场分布,并正确地反映气化燃烧状况,对工业气化炉的运行具有一定的指导意义.     

Suitability of eccentric helical pumps for turbid water deep well pumping in photovoltaic systems

The inherently slim design of the eccentric helical pump appears to make this type of pump to be attractive for delivering water from deep wells, as compared with multistage centrifugal pumps. The basis shape of the volumeflow-head (V-H characteristics) of displacement pumps promises a more economical use of the available solar energy than possible with centrifugal pumps. This article presents the results of experiments concerning the wear in eccentric helical pumps operating with water containing abrasive particles. The temporary stability of the fluid flow and of the efficiency during delivery of abrasive suspensions is demonstrated. The results are used to derive a prognosis for the expectable service life of such a pump system.     

Experimental study of gas engine driven air to water heat pump in cooling mode

Nowadays a sustainable development for more efficient use of energy and protection of the environment is of increasing importance. Gas engine heat pumps represent one of the most practicable solutions which offer high energy efficiency and environmentally friendly for heating and cooling applications. In this paper, the performance characteristics of gas engine driven heat pump used in water cooling were investigated experimentally without engine heat recovery. The effects of several important factors (evaporator water inlet temperature, evaporator water volume flow rate, ambient air temperature, and engine speed) on the performance of gas engine driven heat pump were studied in a wide range of operating conditions. The results showed that primary energy ratio of the system increased by 22.5% as evaporator water inlet temperature increased from 13 °C to 24 °C. On the other hand, varying of engine speed from 1300 rpm to 1750 rpm led to decrease in system primary energy ratio by 13%. Maximum primary energy ratio has been estimated with a value of two over a wide range of operating conditions.     

An online adaptive optimal control strategy for complex building chilled water systems involving intermediate heat exchangers

This paper presents an adaptive optimal control strategy for online control of complex chilled water systems involving intermediate heat exchangers to enhance operation and energy performances. This optimal control strategy determines the optimal settings of the heat exchanger outlet water temperature (hot side) and the required operating number of heat exchangers and pumps in order to minimize the total energy consumption of pumps under varying working conditions. Adaptive method is utilized to update the key parameters of the proposed models online. A simulated virtual platform representing a chilled water system in a super high-rise building was established to validate and evaluate the proposed optimal strategy. Test results show that the strategy has enhanced control robustness and reliability, particularly in avoiding deficit flow problem. Significant energy of chilled water pumps is saved when compared with conventional methods.     

Statistical characteristics of suction pressure signals for a centrifugal pump under cavitating conditions

Centrifugal pumps are often used in operating conditions where they can be susceptible to premature failure. The cavitation phenomenon is a common fault in centrifugal pumps and is associated with undesired effects. Among the numerous cavitation detection methods, the measurement of suction pressure fluctuation is one of the most used methods to detect or diagnose the degree of cavitation in a centrifugal pump. In this paper, a closed loop was established to investigate the pump cavitation phenomenon, the statistical parameters for PDF (Probability Density Function), Variance and RMS (Root Mean Square) were used to analyze the relationship between the cavitation performance and the suction pressure signals during the development of cavitation. It is found that the statistical parameters used in this research are able to capture critical cavitation condition and cavitation breakdown condition, whereas difficult for the detection of incipient cavitation in the pump. At part-load conditions, the pressure fluctuations at the impeller inlet show more complexity than the best efficiency point (BEP). Amplitude of PDF values of suction pressure increased steeply when the flow rate dropped to 40 m³/h (the design flow rate was 60 m³/h). One possible reason is that the flow structure in the impeller channel promotes an increase of the cavitation intensity when the flow rate is reduced to a certain degree. This shows that it is necessary to find the relationship between the cavitation instabilities and flow instabilities when centrifugal pumps operate under part-load flow rates.