Transient flow field and performance analysis of a claw pump for FCVs

The claw-type hydrogen pump has been applied in fuel cell vehicles (FCVs) because of its compact structure, high reliability, and oil-free quality. In this study, a three-dimensional transient computational fluid dynamics (CFD) modelling of a claw-type hydrogen pump used in FCVs was established. Hexahedral structured grids were generated and updated at an increment of 3° in rotating angle to ensure the mesh quality of the whole solving process. The leakage of radial clearance (RC) and axial clearance (AC) was considered. The presented modelling and simulation methods were validated by operating a claw pump at different pressure ratios. The pressure and velocity vector fields in both AC and middle plane, along with the mechanism of the fluid field distribution were analyzed in detail. The in-depth relationship amongst the fluctuation of discharge pressure, outlet mass flow rate and discharge area during the whole working process was revealed. P-θ and V-θ diagram of the whole operating cycle were analyzed. The influence of AC and RCs respectively on the volumetric efficiency of a claw pump was compared and evaluated. It is concluded that back flow in suction pipe happened near 360° as part of the discharge chamber was cut off from the exhaust port and high pressure gas from carryover flowed back into the inlet pipe. The pressure increase during the displacement process, theoretically zero, is actually significant and even comparable to the pressure increase during the compression and discharge process. In addition, volumetric efficiency is most sensitive to axial clearance, followed by radial clearance between rotor and casing, while radial clearance between the rotors has the least influence.     

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.     

基于CFD数值模拟的内燃机水泵性能预测

应用SC/Tetra软件对某内燃机冷却水泵进行三维CFD分析,得到水泵内部流动细节,如压力分布、速度分布、水力损失等。在流场分析的基础上,得到了水泵的扬程、效率等数据,通过这些数据预测内燃机水泵的性能。文中将数值计算的性能数据与试验数据对比,计算结果与试验结果吻合,验证了用CFD数值计算方法对水泵进行性能预测是有效的,且能充分反应水泵内部复杂流动情况,对水泵结构改进、性能预测与优化具有重要的理论参考意义。     

Recent progress in multiphase flow simulation through multiphase pumps

The multiphase flow pumps cover a wide range of industrial sectors extending across petrochemical, metallurgy, and dredging, chemical industry, paint, and construction. The major application is the handling of wet gas and vapor that will condense partially during the compression stage. The main progress in the area of multiphase pumps has been the innovation of a computational fluid dynamics (CFD) numerical approach to simulate three‐dimensional flows inside the pump and to predict pump performance. CFD undoubtedly constitutes one of the most promising approaches for the design, analysis, and performance assessment of complex machines. However, practical application of the CFD tool to determine the internal flow field in multiphase pumps is still far from reality owing to the limitations of a detailed three‐dimensional model of the pump and accuracy of multiphase flow simulation. This review accentuates the influence of different geometrical and dynamical parameters on the performance of the pump and the use of CFD simulation to predict the detailed flow patterns of fluid mixtures. CFD analysis has unearthed the fact that the pattern of inner flow varies with the flow rate and concentration of each phase and the rotation speed of the impeller and number of blades were also found to considerably impact pump performance.     

几种喷油泵在SC9D220柴油机上的性能对比

介绍了四种不同型号的喷油泵在SC9D220柴油机上的油耗及性能对比。通过对不同型号的喷油泵在同一台发动机上做模拟外特性试验,得出不同的性能结果。综合各方面,P7100泵用平顶柱塞效果较好,而且在工程机械上,平顶柱塞比顶隙柱塞使用寿命更具优势。此试验也为D6114系列其他型号柴油机的进一步性能优化提供了参考。     

Effect of rotational speed on unstable characteristics of lobe hydrogen circulating pump in fuel cell system

The hydrogen circulating pump is an essential component of hydrogen fuel cell systems. It plays a vital role in improving hydrogen utilization efficiency and optimizing hydrothermal control capabilities. Due to its compact design, high efficiency, and outstanding low-temperature adaption performance, the lobe hydrogen circulating pump has excellent potential for hydrogen recirculation in fuel cell vehicles (FCVs). This paper investigated the internal flow characteristics of a lobe hydrogen pump for FCV under different rotational speeds by experiments and computational fluid dynamics (CFD). Moreover, the lobe rotor domain was calculated using the dynamic mesh method. The effects of different rotating speeds on transient pressure pulsation, exhaust flow rate, external noise, and vibration were studied. The result reveals that the volumetric efficiency improves with the increased lobe rotor speed when the pressure ratio remains constant. The vibration acceleration level (VAL) and the external noise also increase. The vibration is most significant at the pump casing outlet and tends to decrease as the frequency increases. The sound pressure level spectrum has a discrete character in the low-frequency band, with peaks mainly concentrated at the rotating fundamental frequency and harmonics. The middle and high frequency bands have prominent broadband characteristics, and the energy is relatively concentrated.     

Flow field analysis and performance study of claw hydrogen circulating pump in fuel cell system

Hydrogen circulation pump is an important equipment for hydrogen fuel cell system which can recycle the unreacted hydrogen to improve the system efficiency. A mathematical model of claw pump is built and the internal flow field was simulated by dynamic mesh technology. The p-θ diagram is obtained by analyzing the gas flow characteristics. The model is firstly verified by air experiments and then the performance influenced by suction pressure, exhaust pressure, rotating speed, and clearance are analyzed. The volumetric efficiency increased by 22% when the suction pressure increases from 152 kPa to 168 kPa but decreased by 23% when the exhaust pressure increases from 172 kPa to 188 kPa. The volumetric efficiency increased by 26.7% when the rotating speed increases from 4000 rpm to 6000 rpm but decreased by 52.1% when the working clearance increases from 0.03 mm to 0.07 mm. Due to the range of working pressure ratio is small, the indicated efficiency changes slightly.     

大型双吸式离心泵内流场空化特性数值模拟分析

为探究大型双吸式离心泵的内流场空化特性,使用CFD技术的数值计算方法,在设计工况下,选用标准κ-ε湍流模型及基于Rayleigh-Plesset方程的输运空化模型,对某大型双吸式离心泵内流场空化特性进行数值模拟,经后处理得到离心泵在不同有效汽蚀余量时内部流动的压力分布、空泡体积分数分布情况,并结合试验结果进行对比分析。结果表明,利用CFD进行三维湍流数值模拟可有效反映出双吸式离心泵内流场的空化特性,数值模拟结果与试验结果较一致,为通过CFD数值模拟方法研究大型双吸式离心泵空化特性提供了参考。     

Performance prediction and evaluation of the scroll-type hydrogen pump for FCVs based on CFD–Taguchi method

To improve hydrogen utilisation and provide superior water management, the recirculation hydrogen pump is one of the key components in a fuel-cell vehicle (FCV). This work focused on the performance estimation of a scroll-type hydrogen pump for FCVs. A series of CFD simulation cases were designed using the Taguchi method and were carried out to determine the optimum conditions for volumetric efficiency, and the effects of four factors, including pressure ratio, rotating speed, axial clearance, and radial clearance. The contributions of these factors on volumetric efficiency and shaft power were quantified by the analysis of variance (ANOVA) method. The results show that axial clearance and rotating speed are the main influencing factors on volumetric efficiency, and their contribution ratios are 45.3% and 39.6%, respectively, in the operational range of the hydrogen pump for FCVs. Pressure ratio and rotating speed should be considered first to reduce shaft power, and their contribution ratios are 40.9% and 55.4%, respectively. At last, the performance maps of the scroll-type hydrogen pump were obtained to reveal the dynamic changes at various working conditions. It is found that volumetric efficiency and shaft power are more sensitive to the change in rotating speed when the pressure ratio deviates from the designed value. The results can be used as guidelines for component matching in the design and operation of PEM fuel cell systems.     

有杆泵抽油机井节点能耗及系统效率优化仿真模型及应用

机采井能耗高、系统效率低,严重制约了大庆油田有杆泵抽油系统的高效运行和区块整体经济、有效开发,机采井的能耗分析与节能优化研究已成为油田节能工作迫切需要解决的问题之一.通过对有杆泵抽油机系统效率进行组成分析,把有杆泵抽油机系统分为电机、皮带、减速箱、四连杆机构、盘根盒、抽油杆、抽油泵和管柱8个节点,建立了能耗所占比重较大的电机能耗、抽油泵能耗、抽油杆能耗和管柱能耗仿真模型以及熵权模糊优化仿真模型.根据所建立的仿真模型和大庆油田某采油厂在用的4种机型的8个节点的测试资料,利用Visual Basic 6.0开发了有杆泵抽油机系统节点能耗和系统效率优化仿真软件.仿真计算结果表明,各节点损耗大小的次序为:电机＞抽油泵＞抽油杆柱＞管柱＞皮带-减速箱＞四连杆＞盘根盒.依据仿真结果,有针对性地进行抽汲参数优化,使抽汲参数更加合理.与优化前相比,抽油机井优化后的系统效率提高了4.74个百分点.     

采用基因表达式编程的潜水泵性能预测

常规试验法和计算流体动力学(CFD)技术在研究水泵性能时都较为耗费资力。为了提高水泵性能及节约成本,以深井潜水泵为研究对象,在证明CFD仿真技术可靠的前提下,在同一水泵叶轮上装配了22种不同结构的导叶,通过模拟试验获得有效数据结果。将仿真结果分为训练样本和验证样本,选取水泵扬程和效率2项指标,使用基因表达式编程(GEP)算法训练样本构建预测模型。结果表明,GEP算法从大集合中进化得到最优模型,很好地描述了结构变量与性能之间的相关关系;构建的预测函数准确地预测出水泵扬程和效率两个性能指标,并可靠地反映出各参数影响程度。     

Applications of traditional pump design theory to artificial heart and CFD simulation

A novel heart pump model was obtained by improving the traditional axial pump design theory with the consideration of working and hydraulic situations for artificial hearts. The pump head range and the velocity triangle were introduced and an iterative approach was utilized for the initial model. Moreover, computational fluid dynamics (CFD) simulations were performed to determine relevant model parameters. The results show that this procedure can be used for designing a series of high-efficiency artificial heart pumps.     

A deep learning framework for hydrogen-fueled turbulent combustion simulation

The high cost of high-resolution computational fluid/flame dynamics (CFD) has hindered its application in combustion related design, research and optimization. In this study, we propose a new framework for turbulent combustion simulation based on the deep learning approach. An optimized deep convolutional neural network (CNN) inspired by a U-Net architecture and inception module is designed for constructing the framework of the deep learning solver, named CFDNN. CFDNN is then trained on the simulation results of hydrogen combustion in a cavity with different inlet velocities. After training, CFDNN can not only accurately predict the flow and combustion fields within the range of the training set, but also shows an extrapolation ability for prediction outside the training set. The results from the CFDNN solver show excellent consistency with conventional CFD results in terms of both predicted spatial distributions and temporal dynamics. Meanwhile, two orders of magnitude of acceleration is achieved by using the CFDNN solver compared to a conventional CFD solver. The successful development of such a deep learning-based solver opens up new possibilities of low-cost, high-accuracy simulations, fast prototyping, design optimization and real-time control of combustion systems such as gas turbines and scramjets.     

CFD analysis of Pd-Ag membrane reactor performance during ethylbenzene dehydrogenation process

In this study, the catalytic dehydrogenation of ethylbenzene (EB) to styrene production was investigated in a tubular Pd-Ag membrane reactor (MR) in presence of a commercial iron oxide catalyst. To this purpose, a 2D-axisymmetric, isothermal model based on computational fluid dynamic (CFD) method is presented to investigate the Pd-Ag MR performance during EB dehydrogenation process for styrene and hydrogen production. The proposed CFD model provides the local information of velocity, pressure and component concentration for the driving force analysis. After investigation of mesh independency of CFD model, the validation of model results was carried out by experimental data and a good agreement between model results and experimental data was achieved. It was found that the efficient removal of hydrogen in the Pd-Ag MR could significantly increase the EB conversion. Moreover, using CFD simulation runs, effects of operating parameters such as reaction temperature, pressure and gas hour space velocity (GHSV) values on the Pd-Ag MR performance with two various flow patterns was evaluated in terms of EB conversion and CO_x-free hydrogen recovery. It can be concluded that the EB conversion realized in Pd-Ag MR with countercurrent flow is higher than the ones achieved for Pd-Ag MR with cocurrent flow and also for traditional reactor (TR) during EB dehydrogenation reaction, in all the studied cases. In particular, under the optimal reaction conditions, 40% enhancement in EB conversion can be obtained in the Pd-Ag MR with countercurrent flow with respect to TR.     

基于CFD混流式水轮机上冠转轮泵结构优化研究

为研究中高水头混流式水轮机上冠转轮泵工作特性及优化可行性,以红山嘴一级电站3号水轮机为例,建立现转轮泵及11种结构优化模型,利用CFD商业软件,基于SST湍流模型对不同结构转轮泵在9种流量工况下展开数值模拟。将上冠流道泄漏水流动特性、主轴密封真空度及转轮泵效率作为研究指标,结果表明：上冠流道泄漏水流动特性依赖于转轮泵的结构类型;减小转轮泵“泵盖高度比”或斜置动泵叶对提高主轴密封真空度均有显著效果(最佳结构可提高66.9%),同时须兼顾其工作效率;额定工况下,转轮泵工作效率较低,建议转轮上冠开设合适的泄水孔补给流量提高其效率;该电站可将泵叶斜置45°、泵盖高度比H_p=0.0543的转轮泵作为最佳改进方案。     

Optimal design of a novel nested-nozzle ejector for PEMFC's hydrogen supply and recirculation system

The ejector-based hydrogen supply and recirculation system (HSRS) for a Proton Exchange Membrane Fuel Cell (PEMFC) system has the advantages of compact size and zero power consumption, compared with the HSRS using a recirculation pump. However, the conventional ejector with a single venturi nozzle can only function within a narrow power range of the PEMFC system due to its restricted primary inlet pressure. This study proposed a novel ejector design with nested nozzles to solve this problem. The key geometric parameters, including the nozzle diameters of a large nozzle (BN), a small nozzle (SN), and the axial distance between two nozzles, were optimized using CFD simulations to obtain the maximum entrainment capability. The BN mode is responsible for the stack's higher load operations, while the SN mode supports the lower power operations. Additionally, a bypass was used parallel to the nested-nozzle ejector in the HSRS to extend the ejector operating range further. The consistent CFD simulation and testing results of the nested-nozzle ejector showed effective hydrogen entrainment capability between 9% and 100% of power output for a 150 kW PEMFC stack. Moreover, the new nested-nozzle ejector HSRS showed much-reduced anode inlet pressure fluctuation compared to the HSRS using two conventional ejectors.     

Reverse running pumps analytical,experimental and computational study: A review

A pump can be used as turbine and has good application in micro-hydropower schemes. Pump as turbine (PAT) is one of the best alternatives for fulfilling the energy demands and providing the electricity in remote and rural areas. In this study a review on the work done in the area of pump working as turbine has been explained. Based upon the literature survey, analytical, experimental and computational works on pump as turbine have been discussed. Several methods for predicting the behaviour of pumps in turbine mode have been developed but no method is appropriate for the entire range of specific speeds. Computational fluid dynamics (CFD) is also used to study the reverse operation of centrifugal pumps, but still results are not yet acceptable.     

罗茨泵内部流场数值模拟研究

罗茨泵在运行中由于各种原因会出现振动大、噪音大、泄漏等问题,获得罗茨泵的流动信息对预知及解决故障问题具有非常重要的意义,建立罗茨泵流场数学模型,用CFD软件对其内部流场进行模拟,获得并分析内部介质的压力场、速度场、流量脉动曲线、进出口压差对流量影响。研究结果表明:两转子间隙处压差最大,形成较高涡流;排气口两侧有明显的涡流;出口流量在转子转动初始阶段达到峰值;进口流量和进出口压差成反比,进口流量的脉动系数和进出口压差成正比。验证了CFD数值模拟的准确性,为对罗茨泵的进一步研究和整体优化奠定了基础。     

垂直轴水轮机CFD数值模拟有效性验证

CFD方法作为垂直轴水轮机水动力性能预报和分析的一种重要手段,得到了广泛的应用,但是目前,对于垂直轴水轮机CFD数值模拟的精度和可信度缺乏系统的研究,因此针对这一问题,展开了垂直轴水轮机CFD数值模拟有效性研究,探讨了湍流模型、时间步长和网格尺度对计算结果的影响,并通过与试验结果的对比,验证了CFD方法的有效性,为以后CFD方法在垂直轴水轮机性能预报方面的应用奠定了基础.     

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。