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1
Sheth, K. K., G. L. Morrison und W. W. Peng. „Slip Factors of Centrifugal Slurry Pumps“. Journal of Fluids Engineering 109, Nr. 3 (01.09.1987): 313–18. http://dx.doi.org/10.1115/1.3242666.
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Experiments have been carried out in order to determine the effects on slip factor due to the various parameters affecting the performance characteristics of a centrifugal slurry pump. The experiments were conducted with water, sand slurry, and a glass bead slurry at three different pump speeds. Measurements of power, flow rate, head developed by the pump and the density of the slurry were made in order to obtain the characteristic curves of the pump. Using Euler’s equation, equations were derived for calculating the slip and friction factors of the flow. The deduced slip factors for centrifugal slurry pump can be correlated well with suggested non dimensional groups. It shows a consistent trend of decreasing slip factor with increasing slurry mixture density and impeller rotation, or with a decreasing through flow rate. The sizes of the sand and glass bead particles are significantly different (0.71 mm versus 0.09 mm), however, the data correlations do not suggest its effect on the slip factors significantly as the other parameters. The slip factors deduced from head-flow rate curves are more reliable than those deduced from power-flow rate curves, since the shut-off power measurements are likely subjected to errors associated with the particles settling, or the transient effect if the measurements are taken momentarily.
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Sun, Datong, und Mauricio G. Prado. „Single-Phase Model for Electric Submersible Pump (ESP) Head Performance“. SPE Journal 11, Nr. 01 (01.03.2006): 80–88. http://dx.doi.org/10.2118/80925-pa.
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Summary This paper presents a new incompressible single-phase model for ESP head performance. Sachdeva (1988, 1994) and Cooper and Bosch (1966) developed models for ESP channels and for inducers, respectively. The model presented in this paper is based on 1D approximation along an ESP channel. The new derived pressure ordinary differential equation (ODE) for frictionless incompressible flow (Bird 1960) is consistent with the pump Euler equation. New models for pump frictional and shock losses have been proposed. Finally, a comparison between the predicted pump performance and the pump performances derived from the affinity law for different rotational speeds is presented. The single-phase model can predict ESP performance under different fluid viscosities and also is the basis of a gas/liquid model for ESP head performance. Introduction ESPs are dynamic multistage devices that use kinetic energy to increase liquid pressure. The relationship between the head developed by the pump and the flow rate through the pump for a certain rotational speed is usually known as the pumphead performance curve. This curve is experimentally determined by the pump manufacturer using water as the working fluid. As a consequence, published pumphead performance curves can be used for any other low-viscosity, single-phase liquid, independent of its density. Pump performance, however, is significantly affected by the presence of free gas or high-viscosity fluids. The U. of Tulsa Artificial Lift Projects (TUALP) is currently conducting experimental as well as theoretical research to improve the understanding of pump performance when handling viscous fluids and two-phase flow mixtures at different pump rotational speeds. A better understanding of the pump performance under those conditions will certainly contribute to a reduction in the uncertainty of engineering tools for the selection, design, and operation of ESPs in more challenging applications. This paper presents the new single-phase model developed for the prediction of an ESP's performance. The model consists of the mass and momentum equations, based on the streamline approach or 1D assumption. In the momentum equations, the calculation of the friction factor proposed by Sachdeva is improved by incorporating the channel curvature, channel rotation, and channel cross-sectional effects. A new shock loss model, including rotational speeds, has been proposed. The new single-phase model is capable of predicting the pump performance for different pump rotational speeds and for different fluid viscosities.
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Yedidiah, S. „An overview of methods for calculating the head of a rotodynamic impeller and their practical significance“. Proceedings of the Institution of Mechanical Engineers, Part E: Journal of Process Mechanical Engineering 217, Nr. 3 (01.08.2003): 221–32. http://dx.doi.org/10.1243/095440803322328872.
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This paper explains why Euler's equation and the airfoil theory, while analytically correct, sometimes produce disappointing results. It also emphasizes the merits of a recently developed approach and demonstrates its usefulness in solving problems encountered in practice. The subject matter relates, directly, only to rotodynamic pumps. However, with proper modifications, it can be easily expanded to other fluids machines.
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Lee, Y. T., C. Hah und J. Loellbach. „Flow Analyses in a Single-Stage Propulsion Pump“. Journal of Turbomachinery 118, Nr. 2 (01.04.1996): 240–48. http://dx.doi.org/10.1115/1.2836631.
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Steady-state analyses of the incompressible flow past a single-stage stator/rotor propulsion pump are presented and compared to experimental data. The purpose of the current study is to validate a numerical method for the design application of a typical propulsion pump and for the acoustic analysis based on predicted flowfields. A steady multiple-blade-row approach is used to calculate the flowfields of the stator and the rotor. The numerical method is based on a fully conservative control-volume technique. The Reynolds-averaged Navier–Stokes equations are solved along with the standard two-equation k–ε turbulence model. Numerical results for both mean flow and acoustic properties compare well with measurements in the wake of each blade row. The rotor blade has a thick boundary layer in the last quarter of the chord and the flow separates near the trailing edge. These features invalidate many Euler prediction results. Due to the dramatic reduction of the turbulent eddy viscosity in the thick boundary layer, the standard k–ε model cannot predict the correct local flow characteristics near the rotor trailing edge and in its near wake. Thus, a modification of the turbulence length scale in the turbulence model is applied in the thick boundary layer in response to the reduction of the turbulent eddy viscosity.
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Chami, Francis A. „Use of Simplified Mathematical Formulations in Multi-phase Thermal Pump (MPTP) for Theoretical Prediction of Working Conditions“. Tanzania Journal of Engineering and Technology 30, Nr. 2 (31.12.2007): 130–38. http://dx.doi.org/10.52339/tjet.v30i2.406.
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In this work mathematical expressions have been formed and solved to get predictions of working parameters of multiphase thermal pump (MPTP). MPTP is a simple pump which uses steam to pump water. The results have been comparedwith data found experimentally. Experimental and theoretical values for a range of pressures versus velocity differed byapproximately 8.7% up 12% Through dimensional analysis dimensionless parameters were found Re, Eu, Fo and h/d pmp .These helped to further elucidate the pump’s pumping phenomenon. It was experimentally shown that the Reynoldsnumber found theoretically gave limit of flow operating regime of the pump that it is in the transition regime. Above thisthe pump failed to operate. The Euler dimensionless number gave the dependency of interface velocity on pressurerelation, when pressure was raised the velocity increased. The relation between the two parameters was found to beapproximately quadratic. The Fourier dimensionless number gave the influence of heat transfer properties of thematerial of the pump to the operating characteristics. It was experimentally found that the influence of the overall heattransfer coefficient and heat transfer were the main driving forces behind the operation of the pump. Average interfacevelocities in the pump were found using pipe flow energy and mass conservation equations. Conditions for operation(pumping and suction) of the pump have been established based on the formed mathematical formulations.
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Hatami, Hamed, Ahmad Bagheri und Reza Ansari. „An Analytical Investigation for Vibration Characteristics of a Beam-Type Liquid Micro-Pump“. International Journal of Applied Mechanics 12, Nr. 02 (März 2020): 2050016. http://dx.doi.org/10.1142/s1758825120500167.
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This paper studies the characteristics of a micro-beam interacting with an incompressible fluid in a fluid chamber with an opening in its bottom face for fluid flow. The Euler–Bernoulli equation for transverse deformation of an elastic beam is coupled with the fundamental hydrodynamic equation, which is solved by Galerkin and separation of variables method. The 2D fluid flow assumption in Cartesian coordinate has been used. Natural frequencies and mode shapes of wet beam are calculated and compared with the dry beam. The effects of geometrical parameter changes are also computed as a benchmark for the design of the micro-pump. It is observed that fluid coupling causes a decrease for beam’s natural frequencies, especially in higher modes. Furthermore, since the results of the dry and wet beam show a small discrepancy in lower modes, the mode related to the dry beam was employed as the trial function in the forced vibration analysis of the coupled system.
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Zhang, Heng, und Yan Chao Yin. „Turbulence Numerical Simulation and Particle Track Analysis of Slurry Pump Impeller“. Advanced Materials Research 655-657 (Januar 2013): 336–39. http://dx.doi.org/10.4028/www.scientific.net/amr.655-657.336.
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In order to improve the pump wear performance and optimize pump design, the Euler-Lagrange approach is chosen to simulate the flow in the impeller. The fluid phase is treated as a continuum by solving the N-S equations, while the dispersed phase is solved by using Lagrange Method through the calculated flow field. The results show that the reflex appears in the blade inlet of pressure sides in high flow conditions, but appears in the blade inlet of suction sides in low flow conditions, which possibly induce the cavitation erosion. In low flow conditions, reflex and eddies appear in the blade outlet of both the pressure sides and the suction sides, and the reflex areas even extend to the middle of blades. In the range of simulated conditions, the suction sides don’t collide with particles. The pressure sides collide with particles in the form of continuous impact in low flow conditions but scratch in high flow conditions.
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Mata, V., S. Provenzano, J. L. Cuadrado und F. Valero. „Inverse dynamic problem in robots using Gibbs-Appell equations“. Robotica 20, Nr. 1 (Januar 2002): 59–67. http://dx.doi.org/10.1017/s0263574701003502.
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In this paper, two algorithms for solving the Inverse Dynamic Problem based on the Gibbs-Appell equations are proposed and verified. Both are developed using mainly vectorial variables, and the equations are expressed in a recursive form. The first algorithm has a computational complexity of O(n2) and is the least efficient of the two; the second algorithm has a computational complexity of O(n). This algorithm will be compared with one based on Newton-Euler equations of motion, formulated in a similar way, and using mainly vectors in its recursive formulation. The O(n) proposed algorithm will be used to solve the Inverse Dynamic Problem in a PUMA industrial robot.
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Liu, Ya Jun, Shu Yan Zhan, Jia Kun Ye und Wen Hua Xie. „New Designs in Fuel Dispensing System to Control Maximum Flow of Volatile Liquid“. Applied Mechanics and Materials 868 (Juli 2017): 75–80. http://dx.doi.org/10.4028/www.scientific.net/amm.868.75.
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The dispenser is a fuel pumping and measurement device used in the service station. During the refueling process of volatile liquid, the cavitation phenomenon occur easily due to the large flow rate. The serious cavitation will not only reduce the pumping efficiency, produce loud work noise, but also aggravate the pollution of oil and gas and the energy consumption of the system. Therefore, it is necessary to control the maximum flow rate of the pump. Based on this problem, this paper firstly designs a new flow control valve, and a method of mathematical modeling is proposed to analyze the flow field distribution and the working principle of the whole device based on Euler equation and Bernoulli equation. Then we combine this new hydraulic device to the variable frequency dispenser, a new design of the dispenser structure and a control mode of the maximum flow are proposed. The theoretical research shows that the maximum flow can be limited by optimizing diameter ratio of that flow control valve.
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Valera, A., V. Mata, M. Vallés, F. Valero, N. Rosillo und F. Benimeli. „Solving the inverse dynamic control for low cost real-time industrial robot control applications“. Robotica 21, Nr. 3 (13.05.2003): 261–69. http://dx.doi.org/10.1017/s0263574702004769.
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This work deals with the real-time robot control implementation. In this paper, an algorithm for solving Inverse Dynamic Problem based on the Gibbs-Appell equations is proposed and verified. It is developed using mainly vectorial variables, and the equations are expressed in a recursive form, it has a computational complexity of O(n). This algorithm will be compared with one based on Newton-Euler equations of motion, formulated in a similar way, and using mainly vectors in their recursive formulation. This algorithm was implemented in an industrial PUMA robot. For the robot control a new and open architecture based on PC had been implemented. The architecture used has two main advantages. First it provides a total open control architecture, and second it is not expensive. Because the controller is based on PC, any control technique can be programmed and implemented, and in this way the PUMA can work on high level tasks, such as automatic trajectory generation, task planning, control by artificial vision, etc.
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Quan, Hui, Baiheng Fu, Rennian Li, Guangxian Li, Zhengjie Zhang und Jin Li. „Mathematical model of energy conversion mechanism in screw centrifugal pump based on load criteria of blade airfoil“. Engineering Computations 34, Nr. 7 (02.10.2017): 2168–88. http://dx.doi.org/10.1108/ec-04-2017-0155.
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Purpose To analyze the work principle and capacity of energy conversion in each segment of profile lines, the energy transfer from impeller to transmission medium is separated into head coefficient and load coefficient to analyze the energy transfer process. The concepts of airfoil lift coefficient and drag coefficient are used; the third manifestation of the Euler equations is used as well. Design/methodology/approach The numerical simulation of energy conversion mechanism based on load criteria of vane airfoil has been established in screw centrifugal pump to explain its energy conversion mechanism in an impeller. Upon this basis, the velocity and pressure along the entire blade are investigated through the numerical simulation of internal solid–liquid flow in the pump. The energy conversion process under load criteria in the blade airfoil has also been obtained. Findings The research suggests that the mathematical model of energy conversion mechanism based on the load criteria of the vane airfoil is reliable in the screw centrifugal pump. The screw centrifugal blade has twice or even several times the wrap angle than the ordinary centrifugal blade. It is a large wrap angle that forms the unique flow channel which lays the foundation for solid particles to pass smoothly and for soft energy conversion. At the same time, load distribution along the profile line on the long-screw centrifugal blade is an important factor affecting the energy conversion efficiency of the impeller. Originality/value The quantitative analysis method of energy in the screw centrifugal pump can help the pump designer improve certain features of the pump and shorten the research cycle.
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Sazonov, Yuri Appolonievich, Mikhail Albertovich Mokhov, Inna Vladimirovna Gryaznova, Victoria Vasilievna Voronova, Vladimir Valentinovich Mulenko, Khoren Arturovich Tumanyan, Mikhail Alexandrovich Frankov und Nikolay Nikolaevich Balaka. „Prototyping and Study of Mesh Turbomachinery Based on the Euler Turbine“. Energies 14, Nr. 17 (26.08.2021): 5292. http://dx.doi.org/10.3390/en14175292.
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This paper presents a scientific development aimed at improving the efficiency of turbomachines through the joint use of rotary-vane and vortex workflows. In the well-known Euler turbine, the rotor flow channels represent a set of curved pipes. The authors propose to consider in more detail the possibilities of using such rotating pipes in the implementation of an ejection (vortex) workflow. A hybrid pump was considered with the conclusion that its workflow can be described using two Euler equations. The results of computer simulation indicate that hybrid turbomachines are promising. The use of additive technology allowed the creation of micromodels of the Euler turbine with various rotor designs. Laboratory hydraulic tests showed that the liquid inlet to the rotor is possible in pulse mode. Laboratory tests of micromodels using compressed air showed that gas (or liquid) motion through curved pipes could be carried out from the rotor periphery to its center and then back, albeit through another curved pipe. The research results demonstrated that the scientific and technical potential of the Euler turbine is not yet fully unlocked, and research in this direction should continue. The study results are applicable in various industries including the energyeconomy, robotics, aviation, and water transport industries.
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Simon, Frank, R. Roncen, P. Vuillemin, P. Klotz, Fabien Méry und E. Piot. „Design and optimization of acoustic liners with a shear grazing flow: OPAL software platform description“. INTER-NOISE and NOISE-CON Congress and Conference Proceedings 263, Nr. 6 (01.08.2021): 508–18. http://dx.doi.org/10.3397/in-2021-1496.
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In the context of aircraft noise reduction in varied applications where a cold or hot shear grazing flow is present (i.e., engine nacelle, combustion chamber, jet pump, landing gear), improved acoustic liner solutions are being sought. This is particularly true in the low-frequency regime, where space constraints limit the efficiency of conventional liner technology. Therefore, liner design must take into account the dimensional and phenomenological characteristics of constituent materials, assembly specifications and industrial requirements involving multiphysical phenomena. To perform the single/multi-objective optimization of complex meta-surface liner candidates, a software platform coined OPAL (OPtimisation of Acoustic Liners) was developed. Its first goal is to allow the user to assemble a large panel of parallel/serial elementary acoustic layers along a given duct. Then, the physical properties of this liner can be optimized, relatively to weighted objectives, for a given flow and frequency range: impedance target, maximum absorption coefficient or transmission loss with a total sample size and weight... The presentation will focus on the different elementary bricks and assembly of a problem (from 0D analytical coarse designs in order to reduce the parameter space, up to 2D plan or axisymmetric high-order Discontinuous Galerkin simulations of the Linearized Euler Equations).
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Roncen, Remi, Pierre Vuillemin, Patricia Klotz, Frank Simon, Fabien Méry, Delphine Sebbane und Estelle Piot. „Design and optimization of acoustic liners with a shear grazing flow: OPAL software platform applications“. INTER-NOISE and NOISE-CON Congress and Conference Proceedings 263, Nr. 6 (01.08.2021): 152–63. http://dx.doi.org/10.3397/in-2021-1308.
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In the context of noise reduction in diverse applications where a shear grazing flow is present (i.e., engine nacelle, jet pump, landing gear), improved acoustic liner solutions are being sought. This is particularly true in the low-frequency regime, where space constraints currently limit the efficiency of classic liner technology. To perform the required multi-objective optimization of complex meta-surface liner candidates, a software platform called OPAL was developed. Its first goal is to allow the user to assemble a large panel of parallel/serial assembly of unit acoustic elements, including the recent concept of LEONAR materials. Then, the physical properties of this liner can be optimized, relatively to given weighted objectives (noise reduction, total size of the sample, weight), for a given configuration. Alternatively, properties such as the different impedances of liner unit surfaces can be optimized. To accelerate the process, different nested levels of optimization are considered, from 0D analytical coarse designs in order to reduce the parameter space, up to 2D plan or axisymmetric high-order Discontinuous Galerkin resolution of the Linearized Euler Equations. The presentation will focus on the different aspects of liner design considered in OPAL, and present an application on different samples made for a small scale aeroacoustic bench.
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Zhu, Jianjun, Haiwen Zhu, Guangqiang Cao, Jiecheng Zhang, Jianlin Peng, Hattan Banjar und Hong-Quan Zhang. „A New Mechanistic Model To Predict Boosting Pressure of Electrical Submersible Pumps Under High-Viscosity Fluid Flow with Validations by Experimental Data“. SPE Journal 25, Nr. 02 (12.12.2019): 744–58. http://dx.doi.org/10.2118/194384-pa.
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Summary As the second most widely used artificial-lift method in petroleum production (and first in accumulative production), electrical submersible pumps (ESPs) increase flow rates by converting kinetic energy to hydraulic pressure. ESPs are routinely characterized with water flow, and water performance curves are provided by the manufacturers (catalog curves) for designing ESP-based artificial-lift systems. However, the properties of hydrocarbon fluids are very different from those of water, especially the dynamic viscosities, which can significantly alter the ESP performance. Most of the existing methods to estimate ESP boosting pressure under high-viscosity fluid flow involve a strong empirical nature, and are derived by correlating experimental/field data with correction factors (e.g., Hydraulic Institute Standards 1955). A universally valid mechanistic model to calculate the ESP boosting pressure under viscous fluid flow is not yet available. In this paper, a new mechanistic model accounting for the viscosity effect of working fluids on ESP hydraulic performance is proposed, and it is validated with a large database collected from different types of ESPs. The new model starts from the Euler equations for characterizing centrifugal pumps, and introduces a conceptual best-match flow rate QBM, at which the outlet flow direction of the impeller matches the designed flow direction. The mismatch of velocity triangles, resulting from the varying liquid-flow rates, is used to derive the recirculation losses. Other head losses caused by flow-direction change, friction, leakage flow, and other factors. are incorporated into the new model as well. QBM is obtained by matching the predicted H-Q performance curve of an ESP with the catalog curves. Once QBM is determined, the ESP hydraulic head under viscous-fluid-flow conditions can be calculated. The specific speed (NS) of the studied ESPs in this paper ranges from 1,600 to 3,448, including one radial-type ESP and two mixed-type designs. The model-predicted ESP boosting pressure with water flow is found to match the catalog curves well if QBM is properly tuned. With high-viscosity fluid presence, the model predictions of ESP boosting pressure also agree well with the corresponding experimental data. For most calculation results within medium to high flow rates, the model prediction error is less than 15%. Unlike the empirical correlations that take experimental data points as inputs, the mechanistic model in this study does not require entering any experimental data, but can predict ESP boosting pressure under viscous fluid flow with a reasonable accuracy.
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Yan, Peng, Ning Chu, Dazhuan Wu, Linlin Cao, Shuai Yang und Peng Wu. „Computational Fluid Dynamics-Based Pump Redesign to Improve Efficiency and Decrease Unsteady Radial Forces“. Journal of Fluids Engineering 139, Nr. 1 (10.10.2016). http://dx.doi.org/10.1115/1.4034365.
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In this study, a double volute centrifugal pump with relative low efficiency and high vibration is redesigned to improve the efficiency and reduce the unsteady radial forces with the aid of unsteady computational fluid dynamics (CFD) analysis. The concept of entropy generation rate is applied to evaluate the magnitude and distribution of the loss generation in pumps and it is proved to be a useful technique for loss identification and subsequent redesign process. The local Euler head distribution (LEHD) can represent the energy growth from the blade leading edge (LE) to its trailing edge (TE) on constant span stream surface in a viscous flow field, and the LEHD is proposed to evaluate the flow field on constant span stream surfaces from hub to shroud. To investigate the unsteady internal flow of the centrifugal pump, the unsteady Reynolds-Averaged Navier–Stokes equations (URANS) are solved with realizable k–ε turbulence model using the CFD code FLUENT. The impeller is redesigned with the same outlet diameter as the baseline pump. A two-step-form LEHD is recommended to suppress flow separation and secondary flow encountered in the baseline impeller in order to improve the efficiency. The splitter blades are added to improve the hydraulic performance and to reduce unsteady radial forces. The original double volute is substituted by a newly designed single volute one. The hydraulic efficiency of the centrifugal pump based on redesigned impeller with splitter blades and newly designed single volute is about 89.2%, a 3.2% higher than the baseline pump. The pressure fluctuation in the volute is significantly reduced, and the mean and maximum values of unsteady radial force are only 30% and 26.5% of the values for the baseline pump.
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Куликов, А. А., А. Ф. Смоляков, И. В. Иванова und И. Н. Дюкова. „Thermodynamic analysis of dynamic processes in a centrifugal pump“. Известия СПбЛТА, Nr. 221() (28.12.2017). http://dx.doi.org/10.21266/2079-4304.2017.221.197-217.
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Предложена термодинамическая и математическая модель процессов энер- гообмена в центробежном насосе. Для процесса повышения в насосе давления несжимаемой жидкости получено выражение. Из первого закона термодинамики выведена формула для КПД центробежного насоса. Построена физическая и математическая модель, позволяющие получить уравнение Эйлера для лопастных машин из первого закона термодинамики. Показано, что термодинамическая и математическая модели, примененные для лопастных машин, могут быть использованы для анализа процесса дросселирования. The proposed thermodynamic and mathematical model of processes of energy exchange in a centrifugal pump. For the process of increasing the pump pressure of an incompressible fluid is obtained the expression. From the first law of thermodynamics the formula for the efficiency of centrifugal pump. A physical and mathematical model that allows to obtain the Euler equation for blade machines from the first law of thermodynamics. It is shown that the thermodynamic and mathematical models applied in kind for blade machines can be used for the analysis of process throttling.
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Al-Safran, Eissa, Ahmed Aql und Tan Nguyen. „Analysis and Prediction of Fluid Flow Behavior in Progressing Cavity Pumps“. Journal of Fluids Engineering 139, Nr. 12 (28.08.2017). http://dx.doi.org/10.1115/1.4037057.
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A progressing cavity pump (PCP) is a positive displacement pump with an eccentric screw movement, which is used as an artificial lift method in oil wells. Downhole PCP systems provide an efficient lifting method for heavy oil wells producing under cold production, with or without sand. Newer PCP designs are also being used to produce wells operating under thermal recovery. The objective of this study is to develop a set of theoretical operational, fluid property, and pump geometry dimensionless groups that govern fluid flow behavior in a PCP. A further objective is to correlate these dimensionless groups to develop a simple model to predict flow rate (or pressure drop) along a PCP. Four PCP dimensionless groups, namely, Euler number, inverse Reynolds number, specific capacity number, and Knudsen number were derived from continuity, Navier–Stokes equations, and appropriate boundary conditions. For simplification, the specific capacity and Knudsen dimensionless groups were combined in a new dimensionless group named the PCP number. Using the developed dimensionless groups, nonlinear regression modeling was carried out using large PCP experimental database to develop dimensionless empirical models of both single- and two-phase flow in a PCP. The developed single-phase model was validated against an independent single-phase experimental database. The validation study results show that the developed model is capable of predicting pressure drop across a PCP for different pump speeds with 85% accuracy.
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Ferrari, Alessandro, Michele Manno und Antonio Mittica. „Cavitation Analogy to Gasdynamic Shocks: Model Conservativeness Effects on the Simulation of Transient Flows in High-Pressure Pipelines“. Journal of Fluids Engineering 130, Nr. 3 (01.03.2008). http://dx.doi.org/10.1115/1.2842226.
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A comparison between conservative and nonconservative models has been carried out for evaluating the influence of conservativeness on the prediction of transient flows in high-pressure pipelines. For the numerical tests, a pump-line-nozzle Diesel injection system was considered because the pipe flow presented interesting cases of cavitation. The validity of a conservative model in the simulation of cavitating transient flows was substantiated by the comparison between computed pressure time histories and experimental results at two pipeline locations in the injection system. Although nonconservative models can assure satisfactory accuracy in the evaluation of the wave propagation phenomena, they introduce fictitious source terms in the discretized equations. Such terms are usually negligible, but can play a significant role in the presence of acoustic cavitation, i.e., pressure-wave-induced cavitation, producing errors in the pressure-wave speed prediction. A theoretical analysis based on unsteady characteristic lines was carried out, showing that the cavitation desinence is a shock gas-dynamic-like event, whereas cavitation inception is a supersonic expansion. The Rankine–Hugoniot jump conditions were applied to evaluate the shock wave speed in the presence of cavitation. Analytical relations to calculate the flow property variations across the cavitation-induced discontinuities were also derived. A previously published analytical expression of the sound speed in a homogeneous two-phase flow model was also derived from the eigenvalues of the Euler flow equations for the two distinct phases and a comparison was made with Wallis’ formula, which is commonly applied to cavitating flow simulation in transmission lines. Finally, a novel algorithm for calculating the shock speed, as is predicted by nonconservative models, was presented and applied to Burgers’ equation, pointing out the contribution of internal fictitious fluxes in the shock-speed wrong estimation.
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Akbarovich, Abdurakhmonov Akmalzhon, und Gaybnazarov Egamnazar Eryigitovich. „Theoretical study of the process of interaction of particles of weed impurities in the flow of raw cotton with the working bodies of the cleaning machine“. Journal of Textile Engineering & Fashion Technology 6, Nr. 4 (28.07.2020). http://dx.doi.org/10.15406/jteft.2020.06.00244.
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The article proposes to use the Euler equations to describe the motion of a stationary flow in the cleaning zones, which allows determining the laws of pressure, density and velocity distribution along the arc of contact of a moving layer of raw cotton with a mesh surface in the process of impact impact with spikes on the pulp. It has been established that the pressure, densities and flow rates along the cleaning arc as a result of hammer spikes vary in steps, with a decrease in pressure and density and an increase in the flow velocity along this arc.
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d’Agostino, Luca, Lucio Torre, Angelo Pasini und Angelo Cervone. „On the Preliminary Design and Noncavitating Performance Prediction of Tapered Axial Inducers“. Journal of Fluids Engineering 130, Nr. 11 (23.09.2008). http://dx.doi.org/10.1115/1.2979007.
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A reduced order model for preliminary design and noncavitating performance prediction of tapered axial inducers is illustrated. In the incompressible, inviscid, irrotational flow approximation, the model expresses the 3D flow field in the blade channels by superposing a 2D cross-sectional vorticity correction to a fully guided axisymmetric flow with radially uniform axial velocity. Suitable redefinition of the diffusion factor for bladings with non-negligible radial flow allows for the control of the blade loading and the estimate of the boundary layer blockage at the specified design flow coefficient, providing a simple criterion for matching the hub profile to the axial variation of the blade pitch angle. Carter’s rule is employed to account for flow deviation at the inducer trailing edge. Mass continuity, angular momentum conservation, and Euler’s equation are used to derive a simple second order boundary value problem, whose numerical solution describes the far-field axisymmetric flow at the inducer discharge. A closed form approximate solution is also provided, which proved to yield equivalently accurate results in the prediction of the inducer performance. Finally, the noncavitating pumping characteristic is obtained by introducing suitably adapted correlations of pressure losses and flow deviation effects. The model has been verified to closely approximate the geometry and noncavitating performance of two space inducers tested in Alta’s Cavitating Pump Rotordynamic Test Facility, as well as the measured pumping characteristics of a number of tapered-hub inducers documented in the literature.
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Böhl, P., B. King und H. Ruhl. „Vacuum high-harmonic generation and electromagnetic shock“. Journal of Plasma Physics 82, Nr. 2 (11.03.2016). http://dx.doi.org/10.1017/s0022377816000210.
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When one takes into account the presence of virtual charged states in the quantum vacuum, a nonlinear self-interaction can arise in the propagation of electromagnetic fields. This self-interaction is often referred to as ‘real photon–photon scattering’. When the centre-of-mass energy of colliding photons is much lower than the rest energy of an electron–positron pair, this quantum effect can be included in the classical field equations of motion as a vacuum current and charge density using the Heisenberg–Euler Lagrangian. Using analytical and numerical methods for subcritical fields, the intrinsic solution to Maxwell’s equations has been found for counterpropagating probe and pump plane waves in the presence of vacuum four- and six-wave mixing. In the corresponding all-order solution for the scattered probe, a route to vacuum high-harmonic generation is identified in which a long phase length can compensate for the weakness of interacting fields. The resulting shocks in the probe carrier wave and envelope are studied for different parameter regimes and polarisation set-ups. In this special issue, we study two additional set-ups: that of a slowly varying single-cycle background to highlight the effect of an oscillating background on the probe harmonic spectrum, and that of a few-cycle probe to highlight the smoothing of the harmonic peaks produced by a wider spectrum of probe photons. We also correct sign errors in an earlier publication.