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Design and Investigation on a Centrifugal Compressor for PEM Fuel Cell System PEM燃料电池系统离心压缩机的设计与研究
Pub Date : 2021-08-10 DOI: 10.1115/fedsm2021-65274
Bihuan Zong, W. Zhuge, Qi Ying, Haoxiang Chen, Yangjun Zhang
Proton Exchange Membrane Fuel Cell (PEMFC) is a very attractive power source to meet high efficiency and low emission. For mobility applications, PEMFC needs to have a larger power density and it can be achieved with an air compressor to intake more air for chemical reaction. Different from a turbocharger, the compressor for PEMFC is not driven by a turbine, but by an electric motor as well. Due the limitation of motor speed and compact system size, the air compressor must be in small size and operate with low rotational speed. In compressor aerodynamic study, low specific speed and small size is believed to have large loss and it needs to be further investigated and improved. In this paper, a centrifugal compressor combined with an air bearing is specially developed, with rotational speed as 120k RPM and pressure ratio as 3.5. The compressor impeller, diffuser and volute are designed by mean-line method followed by 3D detailed design. Computational fluid dynamics method is employed to predict compressor performance as well as analyze compressor internal flow field and loss mechanism. Simulation results indicate that major losses including leakage flow loss in impeller and loss in diffuser. As a result, corresponding optimization design method is proposed, the total-to-total aerodynamic efficiency of the redesigned compressor has increased 5% at design point.
质子交换膜燃料电池(PEMFC)是一种极具吸引力的高效低排放电源。对于移动性应用,PEMFC需要具有更大的功率密度,并且可以通过空气压缩机来吸入更多的空气进行化学反应。与涡轮增压器不同,PEMFC的压缩机不是由涡轮驱动,而是由电动机驱动。由于电机转速和系统体积紧凑的限制,空压机必须体积小,转速低。在压气机气动研究中,低比转速和小尺寸被认为损失大,需要进一步研究和改进。本文专门研制了一种与空气轴承相结合的离心压缩机,其转速为120k RPM,压比为3.5。采用平均线法设计了压气机叶轮、扩压器和蜗壳,并进行了三维详细设计。采用计算流体力学方法预测压气机性能,分析压气机内部流场及损失机理。仿真结果表明,主要损失包括叶轮泄漏流损失和扩散器损失。据此,提出了相应的优化设计方法,重新设计后的压气机在设计点的总气动效率提高了5%。
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引用次数: 0
0D Modeling of Fuel Tank for Vapor Generation 油箱蒸汽生成的三维建模
Pub Date : 2021-08-10 DOI: 10.1115/fedsm2021-66670
L. Romagnuolo, A. Andreozzi, A. Senatore, E. Frosina, F. Fortunato, Vincenzo G. Mirante
Petrol vapor emissions are the main source of pollution for both standard and hybrid vehicles. They are mainly generated by gasoline evaporation from the fuel tank of both running and parked vehicles; it is mostly driven by fuel temperature variation due to daily temperature changes (if parked) and heat from engine (if running). To prevent its dispersion in the environment, the vapor generated in the fuel tank is usually stored in a carbon canister filter that must be periodically “purged” in order to prevent its saturation, by venting it to the intake manifold. Canister management, made by the Engine Control Unit (ECU), becomes even more critical for hybrid-electric vehicles because thermal engine is often off, thus purging cannot take place. A pressurized fuel tank is often used for hybrid applications, to further isolate vapor from environment, making the fuel system even more complex to model. System design optimization is usually based on experience and experimental correlations, which require time and cost. Thus, comes the need for a comprehensive predictive model useful for both vehicle components (fuel tank and carbon canister) and ECU software design. A 0D Matlab® model is proposed, which can predict vapor generation from an arbitrary tank in standard and arbitrary thermal cycles, with arbitrary tank capacity, geometry and construction and at different filling levels. It is based on a system of thermo-fluid-dynamic differential equations and semi-empirical correlations that is iteratively solved in time. Model calibration has been performed by using a small size test tank and validation has been completed on full size tanks for both standard and hybrid-electric applications. The main driving force for vapor generation has been shown to be the amount of empty volume on top of the tank; other significant effects come from tank volume, material, external surface as well as fuel properties. Ongoing work is to develop and integrate a carbon canister loading/purging model, with the aim to build a full model of the vapor system.
汽油蒸气排放是标准和混合动力汽车的主要污染源。它们主要是由行驶车辆和停放车辆油箱的汽油蒸发产生的;它主要是由日常温度变化引起的燃料温度变化(如果停车)和发动机的热量(如果运行)驱动的。为了防止其在环境中分散,油箱中产生的蒸汽通常存储在碳罐过滤器中,必须定期“净化”,以防止其饱和,通过将其排放到进气歧管。由于热发动机经常处于关闭状态,因此无法进行净化,因此由发动机控制单元(ECU)进行的气罐管理对混合动力汽车来说变得更加重要。增压油箱通常用于混合动力应用,以进一步隔离蒸汽与环境,使燃料系统更加复杂的模型。系统设计优化通常基于经验和实验相关性,这需要时间和成本。因此,需要一个对车辆部件(油箱和碳罐)和ECU软件设计都有用的综合预测模型。提出了一个0D Matlab®模型,该模型可以预测任意罐在标准和任意热循环下,在任意罐容量,几何形状和结构以及不同填充水平下的蒸汽生成。它是基于一个系统的热流体动力学微分方程和半经验的相关性,是迭代求解的时间。通过使用小尺寸测试罐进行了模型校准,并在标准和混合动力应用的全尺寸罐上完成了验证。蒸汽产生的主要驱动力已被证明是罐顶的空容积量;其他重要的影响来自油箱容积、材料、外表面以及燃料特性。正在进行的工作是开发和整合碳罐装载/净化模型,目的是建立一个完整的蒸汽系统模型。
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引用次数: 0
A Unified Theory for the Pressure Change of Sudden Expansions and Contractions Based on the Momentum Balance 基于动量平衡的突然膨胀和收缩压力变化的统一理论
Pub Date : 2021-08-10 DOI: 10.1115/fedsm2021-65703
S. Müller, A. Malcherek
In this paper a unified approach based on the momentum balance is presented, capable of predicting the pressure change of sudden contractions and sudden expansions. The use of empirically determined correction coefficients is not necessary. Therefore, the momentum balance is derived similarly for both applications but with different control volumes. The control volume takes into account the specific geometry of the hydraulic structure. With a properly chosen control volume, the unified approach requires coefficients that account for the velocity as well as pressure distributions on the boundaries of the control volume. These coefficients can be obtained by parameterizing the results of numerical simulations by simple analytical functions. The numerical model itself is validated by checking the simulated pressure change against calculated or measured pressure changes. It is found that the formulation of the momentum balance for the sudden expansion is more complex compared with the sudden contraction. The prediction of the pressure change of flows through sudden expansions can be improved by applying the momentum balance non-idealized. Most of the correction coefficients originate from an inappropriate application of Bernoulli’s energy conservation principle. Consequently, this leads to a gap between theory and experimental results. The proposed unified approach solely contains physical coefficients that are used to substitute integrals by averaged expressions.
本文提出了一种基于动量平衡的统一方法,能够预测突然收缩和突然膨胀的压力变化。没有必要使用经验确定的修正系数。因此,动量平衡的推导类似于两种应用,但具有不同的控制体积。控制容积考虑了水工结构的具体几何形状。在适当选择控制体积的情况下,统一方法需要考虑控制体积边界上的速度和压力分布的系数。这些系数可以通过简单的解析函数将数值模拟结果参数化得到。通过将模拟的压力变化与计算或测量的压力变化进行对比,验证了数值模型的有效性。研究发现,与突然收缩相比,突然膨胀的动量平衡公式更为复杂。应用非理想动量平衡可以提高对突然膨胀过程中流体压力变化的预测。大多数修正系数源于对伯努利能量守恒原理的不恰当应用。因此,这导致理论和实验结果之间的差距。提出的统一方法仅包含物理系数,用于用平均表达式代替积分。
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引用次数: 0
Study on Overall Design of a Vertical Take-Off and Landing Unmanned Aerial Vehicle Powered by Electric Ducted Fans 电导扇驱动垂直起降无人机总体设计研究
Pub Date : 2021-08-10 DOI: 10.1115/fedsm2021-65556
Tawei Chou, Qi Ying, Yuping Qian, W. Zhuge, Yangjun Zhang
Facing the growing traffic fleet in the cities nowadays, it is believed that three-dimensional urban transportation could be a solution and will be introduced in the near future. Vertical take-off and landing flying platforms powered by ducted fans will attract increasingly attention because it has advantages on high propulsion efficiency, low noise, and better safety. However, unlike traditional open-blade multi-rotor drones, ducted fan drones lack a systematic design approach that comprehensively considers the overall system performance and the power unit efficiency. Current design procedure leads to insufficient load capacity and low efficiency systems. This paper proposes an overall design method for a ducted fan-type vertical take-off and landing flight platform. The ducted fan and motor of the core power unit are designed and selected aiming at improving aerodynamic efficiency and structural utilization of the system. A heavy-load vertical take-off and landing Unmanned Aerial Vehicle (UAV) powered by ducted fans with a take-off weight of 450kg is designed based on this method. CFD simulation is utilized to calculate the performance of the designed Unmanned Aerial Vehicle, and finite element analysis is carried out to examine the overall strength safety. The final design results show that the overall design method plays a great role in the development of ducted fan UAV.
面对当今城市日益增长的交通车队,三维城市交通被认为是一个解决方案,并将在不久的将来被引入。以管道风扇为动力的垂直起降飞行平台因其推进效率高、噪音低、安全性高等优点而日益受到人们的关注。然而,与传统的开叶多旋翼无人机不同,管道风扇无人机缺乏综合考虑系统整体性能和动力单元效率的系统设计方法。目前的设计程序导致系统负载能力不足,效率低下。提出了一种导管扇式垂直起降飞行平台的总体设计方法。为了提高系统的气动效率和结构利用率,对核心动力单元的导管式风机和电机进行了设计和选择。基于该方法,设计了一种起飞重量为450kg的管道风扇驱动的重载垂直起降无人机(UAV)。利用CFD仿真对设计的无人机进行性能计算,并进行有限元分析,对其整体强度安全性进行校核。最后的设计结果表明,该总体设计方法对风道风机无人机的研制起到了很大的作用。
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引用次数: 0
CFD Analysis and Wind Tunnel Testing of Human Powered Vehicle Drag Coefficients 人力动力车辆阻力系数CFD分析及风洞试验
Pub Date : 2021-08-10 DOI: 10.1115/fedsm2021-65393
T. Estrada, K. Anderson, Ivan Gundersen, Chuck Johnston
This paper presents results of Computational Fluid Dynamics (CFD) modeling and experimental wind tunnel testing to predict the drag coefficient for a Human Powered Vehicle (HPV) entered in the World Human Powered Speed Challenge (WHPSC). Herein, a comparison of CFD to wind tunnel test data is presented for ten different HPV designs. The current study reveals that streamlining the nose cone, tail cone, and wheel housing allows for a reduction of drag forces in critical areas, and a reduced drag coefficient. This allows for a selection to be made during the design phase, prior to manufacturing. Drag coefficients were found to be in the range of 0.133 < CD < 0.273, depending on the type of HPV considered. Wind tunnel testing was performed on scale models of the HPV showing agreement to the CFD results on average to within 16%. The wind tunnel testing showed a 7.7% decrease in drag coefficient from the baseline HPV of 2019 to the baseline HPV of 2020. Thus, the wind tunnel data supported by CFD analysis was used to assist in the design of the HPV.
本文介绍了一辆参加世界人类动力速度挑战赛(WHPSC)的人类动力汽车(HPV)的计算流体力学(CFD)建模和风洞试验结果。本文对10种不同的HPV设计进行了CFD与风洞试验数据的比较。目前的研究表明,流线型的前锥、尾锥和轮壳可以减少关键区域的阻力,并降低阻力系数。这允许在设计阶段进行选择,在制造之前。阻力系数的范围为0.133 < CD < 0.273,取决于所考虑的HPV类型。在HPV的比例模型上进行风洞测试,结果显示与CFD结果的一致性平均在16%以内。风洞测试显示,从2019年的基线HPV到2020年的基线HPV,阻力系数下降了7.7%。因此,利用CFD分析支持的风洞数据来辅助HPV的设计。
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引用次数: 0
Impact of Skew Vane Cut on Alternating Stress in a Low Specific Speed Radial Pump Impeller Vane Using Fluid-Structure Interaction (FSI) Simulations 斜叶片切割对低比转速径向泵叶轮叶片交变应力影响的流固耦合模拟
Pub Date : 2021-08-10 DOI: 10.1115/fedsm2021-65734
Rajavamsi Gangipamula, A. Prajapati, Ravindra S. Birajdar, S. Shukla
Numerical studies are presented on the pressure pulsations, hydraulic excitation forces and alternative stresses produced in a radial volute pump with high head application. The effect of excitation forces due to Rotor-Stator Interaction (RSI) are evaluated using One-way fluid structure Interaction in terms of alternative stresses on impeller pressure side and suction side. Initially, the pump performance parameters are predicted using steady state Computational Fluid Dynamics (CFD) simulations and compared with the available test data. Due to the transient behavior of pressure pulsations, a transient CFD simulation has been conducted using RANS models to predict the pressure pulsations and its behavior with time on impeller vane outlet and tongue locations. These unsteady pressure distributions are further coupled with the Finite element (FE) model of the impeller to solve and monitor for the stresses induced due to the transient hydraulic loading. To attenuate the alternating stresses produced due to RSI, the geometry of the vane is modified by providing a skew cut with 30° at vane outlet. The pressure pulsation amplitude and stresses are reduced by 10% and 10% respectively for a skew cut of 30° at vane trailing edge.
对径向蜗壳泵在高扬程工况下产生的压力脉动、液压激振力和交变应力进行了数值研究。采用单向流固耦合的方法,从叶轮压力侧和吸力侧交替应力的角度,评估了动静相互作用对激励力的影响。首先,使用稳态计算流体动力学(CFD)模拟预测泵的性能参数,并与现有的测试数据进行比较。由于压力脉动的瞬态特性,采用RANS模型进行了瞬态CFD模拟,预测了叶轮叶片出口和舌部位置的压力脉动及其随时间的特性。将这些非定常压力分布与叶轮的有限元模型耦合,求解和监测由瞬态水力加载引起的应力。为了衰减由于RSI产生的交变应力,叶片的几何形状通过在叶片出口提供30°的斜切来修改。当叶片后缘斜切30°时,压力脉动幅度和应力分别减小10%和10%。
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引用次数: 1
Blade Thickness Redesign to Improve Efficiency and Decrease Unsteady Pressure Pulsation of a Low Specific Speed Centrifugal Pump 低比转速离心泵叶片厚度设计提高效率,减小非定常压力脉动
Pub Date : 2021-08-10 DOI: 10.1115/fedsm2021-65088
Cheng-shuo Wu, Peng Wu, Dazhuan Wu
The existence of secondary flow in the impeller brings extra energy loss and aggravates the pressure pulsation which will worsen the hydraulic and dynamic performance of the pump. In this paper, based on the forces balance in the direction perpendicular to the streamline, an optimal design method for the blade thickness of a low specific speed centrifugal pump is proposed to suppress the secondary flow in the impeller. The origin impellers with 5 and 7 cylinder blades are redesigned and the hydraulic and dynamic performance of the model pump are investigated by numerical simulation and experimental. Results show that the blade modification proposed in this paper can effectively improve the efficiency of the model pump and reduce the internal pressure pulsations. The internal flow analysis shows that the performance improvement attributes to the suppression of secondary flow in the impeller. And the entropy generation rate is introduced to measure and locate the loss in the pump. Results show that on the one hand, the suppression of secondary flow can reduce the energy loss in the pump and improve the efficiency; on the other hand, it can repress the jet wake structure at impeller outlet and alleviate the intensity of pressure pulsations.
叶轮内二次流的存在带来了额外的能量损失,加剧了压力脉动,使泵的水力和动力性能恶化。本文基于垂直于流线方向的力平衡,提出了一种抑制叶轮二次流的低比转速离心泵叶片厚度优化设计方法。对5缸叶片和7缸叶片的原始叶轮进行了重新设计,并通过数值模拟和实验对模型泵的水力和动力性能进行了研究。结果表明,本文提出的叶片改造能有效地提高模型泵的效率,减小内压脉动。内部流动分析表明,性能的提高主要归功于抑制了叶轮内的二次流。并引入熵产率来测量和定位泵内的损耗。结果表明,抑制二次流一方面可以减少泵内能量损失,提高效率;另一方面,它可以抑制叶轮出口的射流尾迹结构,减轻压力脉动的强度。
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引用次数: 0
Numerical Study on a Flow Field in the Rinsing Process of a Beverage Can Transported With a Constant Velocity 匀速输送饮料罐漂洗过程流场的数值研究
Pub Date : 2021-08-10 DOI: 10.1115/fedsm2021-66025
Tatsuma Kawachi, Takuto Sasaki, A. Kaneko, Y. Nishio, T. Ogawa
The present study investigates the flow field in a rinsing process of a beverage can numerically and experimentally. The three-dimensional Navier-Stokes equations are solved with a finite volume method along with the volume of fluid (VOF) method for free surface. The beverage can set upside down is transported with a constant velocity and rinsed with a water jet ejected from a nozzle below the can. The case of a can at rest is also simulated. The result shows that the ejected water impinges on the can bottom and spreads along the side surface of the can. Then, as it flows down toward the can mouth, its front surface forms splashes. For the stationary can case, after the jet impinges on the can bottom, it almost evenly spreads over the side surface. The water flows downward and becomes branched flows by fingering. The time average of VOF is calculated to visualize the regions rinsed by water. For the case of a moving can, only the top region of the can is rinsed, and the ratio of the rinsed region drops to 29% from 69% for the stationary case. The computed water surfaces qualitatively agree with the experimental result, but the shape of the front surface, such as splashes and fingerings, cannot be resolved with the simulation.
本文对饮料罐清洗过程中的流场进行了数值模拟和实验研究。采用有限体积法求解三维Navier-Stokes方程,并结合自由表面流体体积法求解三维Navier-Stokes方程。倒置的饮料罐以恒定速度运输,并由饮料罐下方的喷嘴喷出的水柱进行冲洗。还模拟了罐头静止的情况。结果表明,喷出的水撞击罐底,沿罐侧表面扩散。然后,当它流向罐头口时,它的前表面形成飞溅。对于静止罐的情况下,射流撞击罐底后,它几乎均匀地扩散到侧面。水向下流动,通过指法形成分支流。计算VOF的时间平均值以显示被水冲洗的区域。对于移动的易拉罐,只有易拉罐的顶部区域被冲洗,并且冲洗区域的比例从静止情况下的69%下降到29%。计算得到的水面与实验结果定性一致,但不能解决水面前表面的形状问题,如飞溅和指迹等。
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引用次数: 0
Fluid Dynamics and Contact Stress on Hard Sealing Surface Analysis of LNG Cryogenic Ball Valve LNG低温球阀硬密封面流体动力学及接触应力分析
Pub Date : 2021-08-10 DOI: 10.1115/fedsm2021-65667
Zhen-hao Lin, Jiaqing Lu, Jun-ye Li, Jingjing Qian
LNG (liquefied natural gas) cryogenic ball valve (CBV) is an important flow control device in LNG receiving stations. Its reliability directly affects the stability of the pipeline system, especially its damage or leak in the seat seal will seriously threaten the normal operation and the safety of LNG receiving stations. When LNG flows through the CBV, due to the interaction between fluid pressure and the valve structure, the hard sealing at the valve seat is not only subjected to the pre-tightening force of saucer spring, but also affected by the fluid pressure of the complex flow. Therefore, it is necessary to study the flow characteristics in the CBV and the hard sealing performance affected by the LNG. In this paper, the fluid dynamics and the contact stress on hard sealing performance in the CBV are analyzed. The pressure drop, pressure, and velocity distributions were analyzed, respectively. The contact stress on the hard sealing surfaces of the CBV with fluid pressure was analyzed by the fluid-structure coupling method. This work has a certain reference value for researching and mastering the hard sealing performance of cryogenic ball valves.
LNG(液化天然气)低温球阀(CBV)是LNG接收站中重要的流量控制装置。其可靠性直接影响管道系统的稳定性,特别是其阀座密封的损坏或泄漏将严重威胁LNG接收站的正常运行和安全。LNG流经CBV时,由于流体压力与阀门结构的相互作用,阀座处的硬密封不仅要承受碟形弹簧的预紧力,还要受到复杂流动流体压力的影响。因此,有必要对CBV内的流动特性以及LNG对其硬密封性能的影响进行研究。本文分析了影响CBV硬密封性能的流体力学和接触应力。分别分析了压降、压力和速度分布。采用流固耦合方法,分析了流体压力作用下CBV硬密封面上的接触应力。本工作对研究和掌握低温球阀的硬密封性能具有一定的参考价值。
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引用次数: 0
How to Improve Accuracy of Existing Ultrasonic Water Meters 如何提高现有超声波水表的精度
Pub Date : 2021-08-10 DOI: 10.1115/fedsm2021-63247
I. Gryshanova, I. Korobko
In present paper, the focus is given to possible ways of increasing accuracy for existing ultrasonic time-of-flight water meters. We will consider transducers with coaxial reflectors working at laminar, transitional and turbulent regimes within their measurement range. Considering error curves of such meters, we can easily resume that they are non-linear and not simply corrected using only one polynomic function. Measurements in laboratory and field conditions demonstrate that there is a shift in the ultrasonic meter’s calibration factor. The deviation of readings starts at Re = 5 000–10 000 and the maximum value is reached at Re = 160. Great inaccuracies referred to the transition from laminar flow to turbulent take place abruptly, which lead to undesirable errors. To understand this phenomenon, the theoretical basis of ultrasonic measurements was analyzed and revealed that typical algorithm for determination of the calibration factor is very questionable since it contains simplified information about velocity profile distribution. Trying to fix this problem, we applied computational fluid dynamics (CFD) modelling of ultrasonic meters with different variants of flow straighteners. Ranges of applicability of a particular turbulence model for a correct description of the velocity profile and other flow parameters in metrological purposes have been evaluated. Due to applied techniques, the flow profile sensitivities of various meter configurations are investigated at different Reynolds numbers comparing to real experiments. To get an improved ultrasonic meter design recirculation zones and flow separation regions inside the flow transducer have been eliminated. As a result, the accuracy of the ultrasonic water meter has increased. Simulations demonstrated reasonable agreement to the error curves obtained on the calibration facility for a whole measurement range.
本文重点讨论了提高现有超声飞行时间水表精度的可能途径。我们将考虑具有同轴反射器的换能器在其测量范围内在层流,过渡和湍流状态下工作。考虑到这类仪表的误差曲线,我们可以很容易地恢复它们是非线性的,而不是简单地用一个多项式函数来修正。在实验室和现场条件下的测量表明,超声波仪表的校准系数有一个变化。读数偏差在Re = 5 000 - 10 000处开始,在Re = 160处达到最大值。从层流到湍流的转变是突然发生的,这导致了不希望出现的误差。为了理解这一现象,分析了超声测量的理论基础,揭示了典型的确定校准因子的算法由于包含了速度剖面分布的简化信息而存在很大的问题。为了解决这一问题,我们应用计算流体动力学(CFD)对不同流量矫直器的超声波流量计进行建模。在计量目的中,对正确描述速度剖面和其他流动参数的特定湍流模型的适用范围进行了评估。由于应用技术的原因,本文与实际实验对比,研究了不同雷诺数下不同仪表结构的流型灵敏度。为了改进超声波流量计的设计,消除了流量传感器内部的再循环区和流动分离区。从而提高了超声波水表的精度。仿真结果表明,在整个测量范围内,所得到的误差曲线与标定装置上得到的误差曲线具有较好的一致性。
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引用次数: 1
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Volume 2: Fluid Applications and Systems; Fluid Measurement and Instrumentation
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