Spherical Pump Research Articles

Frictional moment and wear modelling for incomplete spherical pistons in a spherical pump

PurposeBecause of the specific structure and working mechanism, piston speed is only half of its shaft, which causes severally friction between piston and cylinder. Therefore, the main purpose of this paper is to investigate the friction and wear characteristics of the incomplete spherical piston in spherical pump comprehensively. Finally, to search the low-friction and wear-resistance structural pattern of the piston, and enhance the durability of spherical pump.Design/methodology/approachThe non-linear frictional moment model for incomplete spherical piston in spherical pump was derivated quantificationally. Parameter sensitivity analyses were conducted to find the low-friction structural pattern of the piston. The theoretical wear model of piston–cylinder pair is proposed as well.FindingsTo reduce the frictional moment between incomplete piston and cylinder, the optimised diameter ratio between piston pin and piston should be 0.12 based on the parameter sensitivity analyses. The maximum frictional moment is approximately 2.5 times of the minimum. The total efficiency should be considered synthetically based on the thickness of specific working medium.Originality/valueThe proposed non-linear frictional moment model offers the quantitative estimations. Parameter sensitivity analyses were conducted to find the low-friction structural pattern of the piston. The wear behaviours of the piston and cylinder were analysed to investigate the wear characteristics of the piston.

Experimental test and theoretical modeling on the working characteristics of spherical water pump

This paper investigates working characteristics of a spherical water pump through the experimental test and theoretical modeling. Both theoretical models of displacement and the real time delivered flow are established precisely based on the working principles of spherical pump, under spherical and polar coordinate systems, to investigate the effects structural parameters on flow characteristics. A test rig is established to investigate and validate the working characteristics of spherical pump. Performance such as leakage characteristics, flow characteristics, power consumption and noise radiation are tested, and the theoretical models are validated under multiple working conditions. Results indicate the proposed models are effective to characterize the working properties of spherical water pump, which also demonstrates reasonable performance on the power consumption and noise radiation characteristics. These studies provide fundamental principles for abiding in designing the high-performance spherical water pump.

Hydrostatic Bearing Characteristics Investigation of a Spherical Piston Pair with an Annular Orifice Damper in Spherical Pump

The spherical pump is a totally new hydraulic concept, with spherical piston and hydrostatic bearing, in order to eliminate the direct contact between the piston and cylinder cover. In this paper, the governing Reynolds equation under spherical coordinates has been solved and the hydrostatic bearing characteristics are systematically investigated. The operating sensitivities of the proposed spherical hydrostatic bearing, with respect to the piston radius, film beginning angle, film ending angle, film thickness, and temperature, are studied. The load carrying capacity, pressure drop coefficient, stiffness variation of the lubricating films, leakage properties, and leakage flow rates are comprehensively discussed. The related findings provide a fundamental basis for designing the high-efficient spherical pump under multiple operating conditions. Besides, these related results and mechanisms can also be utilized to design and improve other kinds of annular orifice damper spherical hydraulic bearing systems.

Theoretical modeling and numerical simulation of dynamic contact characteristics of a spherical pump with variable friction coefficient

In this paper, the dynamic contact characteristics between a piston system and a cylinder block in a spherical pump are studied theoretically and numerically. The theoretical contact model between a piston and a cylinder is established based on its structural and operational properties, to obtain the maximum contact force quantitatively. The effects of different structural parameters and working pressures on the contact force are analyzed and discussed. The relationship between friction coefficient and rotation speed is presented. The contact pairs are modeled numerically using the finite-element method and augmented Lagrange algorithm to obtain both the tangential and normal contact characteristics. Both static and dynamic contact characteristics of the piston are analyzed and discussed. These proposed studies can provide practical suggestions on improving the wear resistance performance and durability of the spherical pump.

Friction and wear modeling of rotary disc in spherical pump

PurposeRotary disc is a key component in the compact spherical pump, connecting shaft and piston, bearing hydraulic force conformally and constituting dynamic working chambers alternatively. Motion of rotary disc comprises two components. One is rotating around its own axis and the other is sliding on a cone surface. Therefore, it is necessary to investigate the friction and wear mechanism between rotary disc and cylinder under a complicated operation condition.Design/methodology/approachStructural properties of rotary disc are analyzed first. Frictional moment of rotary disc is modeled based on its structural characteristics and working mechanism, and the constraints of the structural parameters are considered. Besides, the concept of dimensionless contact area is proposed. Comparison is performed between the proposed concept and the frictional moment to determine an optimized beginning angle for spherical pump with a given displacement. The wear model of rotary disc is also established based on its kinematic property, a velocity coefficient is proposed and its common values are presented.FindingsEffects of structural parameters, i.e. beginning angle and ending angle on the frictional moment, are obtained quantitatively. The frictional moment increases with beginning and ending angle with different rates. While the dimensionless contact area decreases with beginning angle. The larger the piston angle, the larger the velocity coefficient will be. The rotary disc wears severely with a larger beginning angle and smaller ending angle, while it has the smallest wear rate under a smaller beginning angle and a larger ending angle.Originality/valueThe originality lies in modeling the complex contact force of rotary disc based on its specific structure. These conclusions can be used to optimize the structural parameters of rotary disc.

Lubrication regime analysis for spherical pump

PurposeThis paper aims to investigate the lubrication regime in spherical pump, especially under different structural parameters and operational conditions.Design/methodology/approachA ball-on-plane configuration is adopted to represent the contact model between spherical piston and cylinder cover. The governing equations, which include the Reynolds and elasticity equations, are solved and validated by Jin–Dowson model. Both minimum film thickness and lambda ratio (ratio of minimum fluid film thickness to combined surface roughness of the piston and cylinder cover) of the equivalent model are obtained using an established model.FindingsThe results indicate that piston diameter and radial clearance are the two main factors affecting the pump lubrication regime. Other related parameters such as rotation speed of the piston, load, viscosity of working medium, material matching and surface roughness of piston and cylinder cover also have different impacts on the lubrication regime of the spherical pump.Originality/valueThese results emphasize the importance of the design and manufacturing parameters on the tribological performance of spherical pumps and these are also helpful in improving the spherical pump lubrication regime and enlarging its life cycle. This is to certify that to the best of the authors’ knowledge, the content of this manuscript is their own work. This manuscript has only been submitted to this journal and never been published elsewhere. The authors certify that the intellectual content of this manuscript is the product of their own work and that all the assistance received in preparing this manuscript and sources has been acknowledged.

Normal contact analysis for spherical pump based on fractal theory

Abstract Spherical pump has a ball-in-socket contact pattern between piston and cylinder. Therefore, traditional Hertz contact theory is not applicable and fractal theory is employed to investigate the conformal contact between piston and cylinder in this paper. The asperities contact on roughness surface is regarded as Hertz contact and friction effects are considered. Besides, the contact coefficient is proposed, which is affected by the structural parameters of piston radius and radial clearance as well as the material properties. Effects of fractal parameters, structural parameters, material property and friction coefficient on normalized normal contact stiffness are investigated and analyzed. Results indicate the normal contact stiffness can be improved by enlarging piston radius, material hardness and decreasing radial clearance, friction coefficient.

Dynamic lubrication analysis for a spherical pump

Dynamic lubrication analyses for a spherical pump, consisting of a piston and cylinder, are presented. Contact forces between piston and cylinder are modeled first using an equivalent ball-on-plane model. Both the effects of external loads and operating conditions are considered in a dynamic elastohydrodynamic lubrication model, which is derived from Reynolds equation. Two assumed time-dependent sine-wave and square-wave loads are applied to the model. Fluid film thicknesses are estimated using the model and assumed loads, effects of different structural, and operational parameters, such as piston diameter, radial clearance, applied load, piston speed, lubricant viscosity, and surface roughness, on fluid film thickness are investigated. Fluid film thickness reactions of more realistic smooth and continuous sine wave loads are compared to discontinuous ones in order to verify whether or not assumed ideal loads are acceptable and reliable. Results indicate that piston diameter, speed, lubricant viscosity have positive relations on the dynamic lubrication performance, and increasing these values can improve the dynamic lubrication regime. While the parameters such as radial clearance, applied load, and surface roughness have the verse effects. Furthermore, the impacts of all the above parameters on fluid film are different either. These obtained results can be used to effectively optimize spherical pump lubrication performance.

Tangential contact analysis of spherical pump based on fractal theory

Abstract The tangential contact between piston and cylinder in spherical pump is investigated using both analytical method and fractal theory. The analytical model is established firstly, friction coefficient between piston and cylinder is considered. Effects of operating conditions and structural parameters are analyzed. Besides, a fractal contact model for spherical pump is proposed, and the model is validated by Jiang's general contact model and experimental results. Variation of the tangential contact stiffness with factors such as fractal dimension, characteristics length, friction coefficient, material hardness, yield stress, elastic modulus and loaded force are studied comprehensively. Results indicate these parameters have complex effects on tangential contact stiffness under different operating conditions, the related conclusions can also be utilized to analyze the tangential contact characteristics of spherical surfaces.

Kinematic modeling, analysis and test on a quiet spherical pump

In this paper, design and modeling of a novel spherical pump are undertaken. Both sound and vibration properties of the pump are studied experimentally. The working mechanism of the pump is analyzed firstly, and then structural design and kinematic theory are modeled by using two different coordinate systems. Nonlinear kinematic constraint equations are developed using a generalized computational method for spatial kinematic analysis. These equations are solved to yield the displacement, angular velocity and acceleration properties of motion parts with different structural parameters. Sound and vibration characteristics of the spherical pump and traditional solenoid pumps are studied experimentally at different rotating speeds of 1000, 1500, 2000, 2500 and 3000rev/min. Results indicate that sound pressure levels of the proposed spherical are reduced to 40.7dB(A), which are 11.1dB(A) lower than the traditional solenoid pump׳s 51.8dB(A) at the rated operating conditions. The sound spectra are analyzed in detail in order to investigate the causes, which are structural pattern and working mechanisms. The proposed spherical pump has many advantages and can be utilized as a substitute for other pumps in some special fields, such as hospital facilities and household appliances.

Analysis on the Side Leakage Amount of the Friction between Piston and Cylinder Block in Axial Piston Pump

The spherical distribution pairs of the plunger and the cylinder friction, has an important influence on the performance of spherical port plate axial piston pump. Based on the analysis of fluid viscosity change with pressure and temperature, considering friction differential pressure flow and shear flow, establishes the mathematics model of the friction pair of leakage. The simulation analysis using MATLAB software, the leakage flow rate is not proportional to pressure, but with the increase of pressure leakage flow was increased, and with the increase of pressure viscosity coefficient and temperature coefficient of viscosity, the leakage flow rate correction coefficient increases obviously, so in the choice of the hydraulic oil cylinder hole, should choose a relatively moving average leakage rate had no effect the piston ring slot.

The Slipper Shoe Mounting Hole Calculation Method Limitation Analysis for Spherical Swashplate Type Axial Piston Pump

Take conical cylinder spherical swashplate type axial piston pump as research object, the calculation method limitation of slipper shoe mounting hole which located in mounting plate is analyzed. First of all ,the motion characteristics and the trace of slipper shoe is derived, then,based on above results, the sipper shoe mounting hole size current calculation methods in engineering and it’s limitations is analyzed,the conclusion is that: current design methods is parameter averaging method and also is an approximate method, in theory is not accurate and in engineering is unreasonable. In order to deign the slipper shoe mounting hole accurately, this paper recommends the most reasonable method is using slipper movement envelope to determine its shape and size.

Investigation of spatial Einstein–Podolsky–Rosen aspects in the degenerate optical parametric oscillator

We present a study of quantum spatial correlations in the transverse cross-section of the beam emitted by a degenerate optical parametric oscillator with spherical mirrors and finite-size pump. We show that these correlations are at the origin of efficient quantum noise reduction in proper combinations of field quadratures detected over symmetrical regions in the beam transverse section; moreover they offer the possibility of investigating EPR aspects for continuous variables. We discuss different regimes and show that EPR correlations arise over a broad range of values for the frequency spacing among adjacent transverse modes and for realistic values of the waist of the pump beam.

Quantum images in optical parametric oscillators with spherical mirrors and Gaussian pump

We perform a study of the quantum image phenomenon appearing below threshold in the optical parametric oscillator for the near and far field, for the case of a cavity with spherical mirrors and Gaussian pump profile. Because of the finite size of the pump, the whole set of Gauss-Laguerre cavity modes are coupled and therefore an analytical solution cannot be found. We propose a numerical treatment taking into account the mode couplings up to a finite order, and using an input-output formalism we evaluate the correlation functions for an arbitrary quadrature component of the signal field in the frequency domain. Major quantum spatial features of the plane-wave pump case are shown to persist when the pump waist is progressively decreased to realistic experimental values.

Efficient frequency-doubled single-frequency Nd:YAG laser

The design and operation of an efficient stable frequency-doubled single-frequency Nd :YAG laser providing a unidirectional harmonic output is discussed. Efficient resonant cavity designs utilizing the Nd:YAG rod as an internal focusing element were used to provide adequate TEM 00 -mode volume in the rod and a small beam waist at the nonlinear crystal (Ba 2 NaNb 5 O 15 ) for optimum intracavity second-harmonic generation (SHG). Various two-component low-loss intracavity mode filters were investigated and a double Fabry-Perot ( F-P ) fused-quartz etalon arrangement devised to obtain single-frequency operation with relative ease. The unidirectional harmonic output geometry uses a 45° mirror which favors s -polarized laser oscillations at 1.06 μm and very effectively transmits the second harmonic p -polarized radiation. Other component designs include short-radius mirror coatings highly reflective at 1.06 and 0.53 μm, and antireflection (AR) coatings on the nonlinear crystal for both wavelengths. Relative phase differences between the fundamental and harmonic radiations are uncritical and compensable by adjusting the nonlinear crystal temperature. The techniques adopted have proven adequate and stable unidirectional single-frequency power outputs of 0.3-0.5 W were obtained consistently from a 5- by 50-mm Nd:YAG rod pumped effectively with 850 W with a tungsten-iodine lamp in a spherical pump cavity.

Upconversion: Imaging with Planar and Spherical Pump Beams

The imaging properties of nonlinear image upconverters with planar and spherical pump beams are discussed. We show the applicability of the fourier transform formalism and holographic analogy to the spherical pump beam case. Experimental results of upconversion with a spherical pump beam are presented and discussed.