scholarly journals Dynamic Pressure Gradient Model of Axial Piston Pump and Parameters Optimization

2014 ◽  
Vol 2014 ◽  
pp. 1-10 ◽  
Author(s):  
Shi Jian ◽  
Li Xin ◽  
Wang Shaoping
Keyword(s):  
Pressure Gradient ◽  
Dynamic Pressure ◽  
Parameters Optimization ◽  
Piston Pump ◽  
Opening Angle ◽  
Vertex Angle ◽  
Flow Noise ◽  
Flow Fluctuation ◽  
Large Pressure ◽  
Piston Chamber

The unsteady pressure gradient can cause flow noise in prepressure rising of piston pump, and the fluid shock comes up due to the large pressure difference of the piston chamber and discharge port in valve plate. The flow fluctuation control is the optimization objective in previous study, which cannot ensure the steady pressure gradient. Our study is to stabilize the pressure gradient in prepressure rising and control the pressure of piston chamber approaching to the pressure in discharge port after prepressure rising. The models for nonoil shock and dynamic pressure of piston chamber in prepressure rising are established. The parameters of prepressure rising angle, cross angle, wrap angle of V-groove, vertex angle of V-groove, and opening angle of V-groove were optimized, based on which the pressure of the piston chamber approached the pressure in discharge port after prepressure rising, and the pressure gradient is more steady compared to the original parameters. The max pressure gradient decreased by 70.8% and the flow fluctuation declined by 21.4%, which showed the effectivness of optimization.

FUNDAMENTAL ANALYSIS OF THREE-DIMENSIONAL ‘NEAR FLING’

1993 ◽  
Vol 183 (1) ◽  
pp. 217-248 ◽  
Author(s):  
S. Sunada ◽  
K. Kawachi ◽  
I. Watanabe ◽  
A. Azuma
Keyword(s):  
Numerical Calculation ◽  
Hydrodynamic Force ◽  
Dynamic Pressure ◽  
Three Dimensional ◽  
Added Mass ◽  
Opening Angle ◽  
Rotation Axes ◽  
Adequate Accuracy ◽  
Series Of Experiments ◽  
The Moment

A series of experiments on three-dimensional ‘near fling’ was carried out. Two pairs of plates, rectangular and triangular, were selected, and the distance between the rotation axes of the two plates of each pair was varied. The motion of the plates as well as the forces and the moment were measured, and the interference between the two plates of a pair was studied. In addition, a method of numerical calculation was developed to aid in the understanding of the experimental results. The interference between the two plates of a pair, which acted to increase both the added mass of each plate and the hydrodynamic force due to dynamic pressure, was noted only when the opening angle between the plates was small. The hydrodynamic forces were strongly influenced by separated vortices that occurred during the rotation. A method of numerical calculation, which took into account the effect both of interference between the plates and of separated vortices, was developed to give adequate accuracy in analyzing beating wings in ‘near fling’.

A Fast and Effective Method for the Optimization of the Valve Plate of Swashplate Axial Piston Pumps

2021 ◽  
Author(s):  
Gianluca Marinaro ◽  
Emma Frosina ◽  
Kim Stelson ◽  
Adolfo Senatore
Keyword(s):  
Numerical Model ◽  
Dynamic Pressure ◽  
Valve Plate ◽  
Lumped Parameter Model ◽  
Piston Pump ◽  
Axial Piston Pump ◽  
Flow Ripple ◽  
Lumped Parameter ◽  
Pressure Ripple ◽  
Axial Piston

Abstract This research presents a lumped parameter numerical model aimed at designing and optimizing an axial piston pump. For the first time, it has been shown that a lumped parameter model can accurately model axial piston pump dynamics based on a comparison with CFD models and experimental results. Since the method is much more efficient than CFD, it can optimize the design. Both steady-state and dynamic behaviors have been analyzed. The model results have been compared with experimental data, showing a good capacity in predicting the pump performance, including pressure ripple. The swashplate dynamics have been investigated experimentally, measuring the dynamic pressure which controls the pump displacement; a comparison with the numerical model results confirmed the high accuracy. An optimization process has been conducted on the valve plate geometry to control fluid-born noise by flow ripple reduction. The NLPQL algorithm is used since it is suitable for this study. The objective function to minimize is the well-known function, the Non-Uniformity Grade, a parameter directly correlated with flow ripple. A prototype of the best design has been realized and tested, confirming a reduction in the pressure ripple. An endurance test was also conducted. As predicted from the numerical model, a significant reduction of cavitation erosion was observed.

scholarly journals Stability of lubricated viscous gravity currents. Part 1. Internal and frontal analyses and stabilisation by horizontal shear

2019 ◽  
Vol 871 ◽  
pp. 970-1006 ◽  
Author(s):  
Katarzyna N. Kowal ◽  
M. Grae Worster
Keyword(s):  
Viscous Fluid ◽  
Pressure Gradient ◽  
Dynamic Pressure ◽  
Jump Discontinuity ◽  
Local Analysis ◽  
Instability Criterion ◽  
Shear Stresses ◽  
Horizontal Shear ◽  
Dynamical Regimes ◽  
Inner Region

A novel viscous fingering instability, involving a less viscous fluid intruding underneath a current of more viscous fluid, was recently observed in the experiments of Kowal & Worster (J. Fluid Mech., vol. 766, 2015, pp. 626–655). We examine the origin of the instability by asking whether the instability is an internal instability, arising from internal dynamics, or a frontal instability, arising from viscous intrusion. We find it is the latter and characterise the instability criterion in terms of viscosity difference or, equivalently, the jump in hydrostatic pressure gradient at the intrusion front. The mechanism of this instability is similar to, but contrasts with, the Saffman–Taylor instability, which occurs as a result of a jump in dynamic pressure gradient across the intrusion front. We focus on the limit in which the two viscous fluids are of equal density, in which a frontal singularity, arising at the intrusion, or lubrication, front, becomes a jump discontinuity, and perform a local analysis in an inner region near the lubrication front, which we match asymptotically to the far field. We also investigate the large-wavenumber stabilisation by transverse shear stresses in two dynamical regimes: a regime in which the wavelength of the perturbations is much smaller than the thickness of both layers of fluid, in which case the flow of the perturbations is resisted dominantly by horizontal shear stresses; and an intermediate regime, in which both vertical and horizontal shear stresses are important.

scholarly journals Development and Forcing of the Rear Inflow Jet in a Rapidly Developing and Decaying Squall Line during BAMEX

2009 ◽  
Vol 137 (4) ◽  
pp. 1206-1229 ◽  
Author(s):  
Joseph A. Grim ◽  
Robert M. Rauber ◽  
Greg M. McFarquhar ◽  
Brian F. Jewett ◽  
David P. Jorgensen
Keyword(s):  
Pressure Gradient ◽  
Dynamic Pressure ◽  
Radar Data ◽  
Squall Line ◽  
System Evolution ◽  
Formative Stage ◽  
Bow Echo ◽  
Mesoscale Convective ◽  
Forcing Mechanisms ◽  
Inflow Jet

Abstract This study examines the development, structure, and forcing of the rear inflow jet (RIJ) through the life cycle of a small, short-lived squall line over north-central Kansas on 29 June 2003. The analyses were developed from airborne quad-Doppler tail radar data from the NOAA and NRL P-3 aircraft, obtained over a 2-h period encompassing the formation, development, and decay of the squall line during the Bow Echo and Mesoscale Convective Vortex Experiment (BAMEX). The strengthening of the system-relative rear inflow to 17 m s−1 was concurrent with the formation of a bow echo, an increased dynamic pressure gradient beneath the rearward-tilted updraft, and two counterrotating vortices at either end of the bow. The later weakening of the RIJ to 8 m s−1 was concurrent with the weakening of the bow, a decreased dynamic pressure gradient at midlevels behind the bow, and the weakening and spreading of the vortices. In a modeling study, Weisman quantified the forcing mechanisms responsible for the development of an RIJ. This present study is the first to quantitatively analyze these mechanisms using observational data. The forcing for the horizontal rear inflow was analyzed at different stages of system evolution by evaluating the contributions of four forcing mechanisms: 1) the horizontal pressure gradient resulting from the vertical buoyancy distribution (δPB), 2) the dynamic pressure gradient induced by the circulation between the vortices (δPV), 3) the dynamic irrotational pressure gradient (δPI), and 4) the background synoptic-scale dynamic pressure gradient (δPS). During the formative stage of the bow, δPI was the strongest forcing mechanism, contributing 50% to the rear inflow. However, during the mature and weakening stages, δPI switched signs and opposed the rear inflow while the combination of δPB and δPV accounted for at least 70% of the rear inflow. The δPS forced 4%–25% of the rear inflow throughout the system evolution.

Frequency Dependent Ion Rejection Properties of Active Nanoporous Membranes

2013 ◽  
Author(s):  
Vishnu-Baba Sundaresan
Keyword(s):  
Pressure Gradient ◽  
Flow Rate ◽  
Electrical Power ◽  
Water Desalination ◽  
Small Scale ◽  
Feed Water ◽  
Ion Rejection ◽  
Large Pressure ◽  
Dissolved Ions ◽  
Neck Diameter

Selective rejection of dissolved salts in water is achieved by large pressure gradient driven flows through tortuous structures and cylindrical nanopores. The flow rate through the membrane is dependent on the area of the membrane and pressure gradient that can be sustained by the membrane. The electrical power required for generating large pressure gradients increases the operational cost for desalination units and limits application of contemporary technologies in a wide variety of applications. Due to this limitation, small scale operation of these desalination systems is not economical and portable. Further, recently proposed desalination systems using carbon nanotubes and nanofluidic diodes have limited lifetime due to clogging and fouling from contaminants in feed water. In order to develop a desalination system that is not limited by cost, scale of operation and application, an active nanopore membrane that uses multiphysics interactions in a surface-functionalized hyperboloidal nanopore is developed. An active nanopore is a shape-changing hyperboloidal pore that is formed in a rugged electroactive composite membrane and utilizes coupled electrostatic, hydrodynamic and mechanical interactions due to reversible mechanical oscillations between the charged pore walls and dissolved ions in water for desalination. This novel approach takes advantage of the shape of the pore to create a pumping action in the hyperboloidal channel to selectively transport water molecules. In order to demonstrate the applicability of this novel concept for water desalination, the paper will use a theoretical model to model the ion rejection properties and flow rate of purified water through an active nanoporous membrane. This article examines the effect of the geometry of the nanopore and frequency of operation to reject dissolved ions in water through a multiphysics model. It is estimated that the neck diameter of the active nanopores is the most dominant geometrical feature for achieving ion rejection, and the flux linearly increases with the frequency of operation (between 2–50Hz). The threshold neck diameter of the nanopore required for achieving rejection from multiphysics simulation is observed to be 100nm. The flux through the membrane decreases significantly with decreasing diameter and becomes negligible at 10nm effective neck diameter.

Comparative study of the operational properties of deviated and straight gas-lift wells and sensitivity analysis of pressure gradient

2020 ◽  
pp. 108-117
Author(s):  
V.J. Abdullaev ◽  
Keyword(s):  
Pressure Gradient ◽  
Gas Flow ◽  
Dynamic Pressure ◽  
Flow Simulation ◽  
Mathematical Expression ◽  
Flow Properties ◽  
The Difference ◽  
Gas Lift ◽  
Working Agent ◽  
Deviated Wells

The article presents a benchmarking analysis of the complex well body structure effect on the hydraulic parameters of the liquid-gas flow pattern in deviated wells. The difference between the consumption of the working agent (gas) required to lift the same amount of liquid from the same depth in vertical and inclined gas-lift wells is shown. Considering the complexity of the hydrodynamic flow properties in deviated wells, the impossibility of analytical flow simulation, the article provides the problem study using statistical methods and gives its practical solution. The article presents a mathematical expression to determine the dynamic pressure gradient using this method, that is, by group calculation of indicators of gas-lift wells with an deviated body, and its numerical value was found.

Study of the Dynamic Characteristics of Piston Chamber Pressure and its Optimizing

2014 ◽  
Vol 602-605 ◽  
pp. 277-282
Author(s):  
Bin Qu Yan ◽  
Shu Mei Chen ◽  
Chuan Ming Chen
Keyword(s):  
Dynamic Response ◽  
Operating Conditions ◽  
Piston Pump ◽  
Cylinder Block ◽  
Chamber Pressure ◽  
Excessive Pressure ◽  
New Type ◽  
The Stability ◽  
The Impact ◽  
Piston Chamber

In order to develop a new type of high-performance axial piston pump, the impact of the dynamic response characteristics of piston chamber pressure to the stability of cylinder block were analyzed. This paper a new type of valve plate which combined two fixed throttling grooves with a triangular groove (called three-level gain) was put forward so as to reducing the excessive pressure adjustment of the dynamic response of piston chamber pressure and improving the stability of cylinder block. The simulation results indicate that not only the cavitation is reduced, but also the stability of the dynamic response of piston chamber pressure is remained at various swash plate angle which makes it applicable to variable piston pump. The results also indicate that the flow pulsation of variable displacement pump is significantly decreased in different operating conditions.

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