A numerical and experimental investigation of parametric effect on flow ripple

2015 ◽  
Vol 229 (16) ◽  
pp. 2939-2951 ◽  
Author(s):  
Bing Xu ◽  
Kok-Meng Lee ◽  
Yuechao Song ◽  
Qiannan Wang ◽  
Huayong Yang
Keyword(s):  
Simulation Model ◽  
Working Conditions ◽  
Flow Rate ◽  
Piston Pump ◽  
Cylinder Block ◽  
Leakage Flow ◽  
Oil Film ◽  
Flow Ripple ◽  
Leakage Flow Rate ◽  
Fluid Compressibility

This paper presents a parametric study on flow ripple for guiding the design of a piston pump. For the purpose of minimizing flow ripple, a detailed simulation model is built. In this simulation model, a modified method for computing precisely leakage flow rate from the oil film between valve plate and cylinder block, the oil film between cylinder block and piston, and the oil film between the slipper and the swash plate is proposed. Then the influence of fluid characteristics, such as the fluid compressibility and viscosity and the air contained in the fluid, is taken into consideration in the simulation model. In addition, the motion of the piston, cylinder, and slipper is referenced in one simulation model making the simulation model closer to a real pump. Validated using test results obtained from the secondary source method, the computational accuracy with the modified simulation has been adequately improved for analyzing the parametric effects on flow ripple and optimizing the design of a piston pump. The findings conclude that for the same working conditions, the fluid compressibility has been identified to be the most significant cause responsible for flow ripple. The leakage flow rate and fluid viscosity play the next important roles on the generation of flow ripple as compared to the effects due to the piston movement. When there is no cavitation in the working conditions, the effect of the air contained in the fluid on flow ripple can be neglected.

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

2014 ◽  
Vol 635-637 ◽  
pp. 341-345 ◽  
Author(s):  
Wei Wang
Keyword(s):  
Flow Rate ◽  
Piston Pump ◽  
Cylinder Block ◽  
Correction Coefficient ◽  
Leakage Flow ◽  
Fluid Viscosity ◽  
Axial Piston Pump ◽  
Viscosity Change ◽  
Leakage Flow Rate ◽  
Axial Piston

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.

scholarly journals Impact of Orifice-to-Pipe Diameter Ratio on Leakage Flow: An Experimental Study

Water ◽  
2019 ◽  
Vol 11 (10) ◽  
pp. 2189
Author(s):  
Tingchao Yu ◽  
Xiangqiu Zhang ◽  
Iran E. Lima Neto ◽  
Tuqiao Zhang ◽  
Yu Shao ◽  
...  
Keyword(s):  
Experimental Study ◽  
Flow Rate ◽  
Pipe Wall ◽  
Pressure Head ◽  
Diameter Ratio ◽  
Pipe Diameter ◽  
Leakage Flow ◽  
Leakage Flow Rate ◽  
Different Shapes ◽  
Real Scale

The traditional orifice discharge formula used to estimate the flow rate through a leak opening at a pipe wall often produces inaccurate results. This paper reports an original experimental study in which the influence of orifice-to-pipe diameter ratio on leakage flow rate was investigated for several internal/external flow conditions and orifice holes with different shapes. The results revealed that orifice-to-pipe diameter ratio (or pipe wall curvature) indeed influenced the leakage flow, with the discharge coefficient ( C d ) presenting a wide variation (0.60–0.85). As the orifice-to-pipe diameter ratio decreased, the values of C d systematically decreased from about 12% to 3%. Overall, the values of C d also decreased with β (ratio of pressure head differential at the orifice to wall thickness), as observed in previous studies. On the other hand, orifice shape, main pipe flow velocity, and external medium (water or air) all had a secondary effect on C d . The results obtained in the present study not only demonstrated that orifice-to-pipe diameter ratio affects the outflow, but also that real scale pipes may exhibit a relevant deviation of C d from the classical range (0.61–0.67) reported in the literature.

scholarly journals Effect of hydraulic and geometric factors upon leakage flow rate in pressurized pipes

RBRH ◽  
2021 ◽  
Vol 26 ◽  
Author(s):  
Mayara Francisca da Silva ◽  
Fábio Veríssimo Gonçalves ◽  
Johannes Gérson Janzen
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Flow Rate ◽  
Leakage Flow ◽  
Cfd Simulations ◽  
Mean Velocity ◽  
Leakage Flow Rate ◽  
Geometric Factors ◽  
Leakage Area ◽  
Computational Fluid Dynamics Cfd

ABSTRACT Computational Fluid Dynamics (CFD) simulations of a leakage in a pressurized pipe were undertaken to determine the empirical effects of hydraulic and geometric factors on the leakage flow rate. The results showed that pressure, leakage area and leakage form, influenced the leakage flow rate significantly, while pipe thickness and mean velocity did not influence the leakage flow rate. With relation to the interactions, the effect of pressure upon leakage flow rate depends on leakage area, being stronger for great leakage areas; the effects of leakage area and pressure on leakage flow rate is more pronounced for longitudinal leakages than for circular leakages. Finally, our results suggest that the equations that predict leakage flow rate in pressurized pipes may need a revision.

scholarly journals Leakage Characteristic Identification of Labyrinth Seals on Reciprocating Piston through Transient Simulations

2019 ◽  
Vol 2019 ◽  
pp. 1-12
Author(s):  
Lingzi Wang ◽  
Jianmei Feng ◽  
Mingfeng Wang ◽  
Zenghui Ma ◽  
Xueyuan Peng
Keyword(s):  
Flow Rate ◽  
Pressure Ratio ◽  
Piston Compressor ◽  
Pressure Change ◽  
Labyrinth Seal ◽  
Relative Molecular Mass ◽  
Geometrical Parameters ◽  
Leakage Flow ◽  
Reciprocating Motion ◽  
Leakage Flow Rate

In the reciprocating labyrinth piston compressor, the characteristic of the internal leakage is crucial for the leakage management and performance improvement of the compressor. However, most of the published studies investigated the rotor-stator system, and those who study the reciprocating piston-cylinder system basically focus on the effects of the geometrical parameters. These conclusions could not directly be applied to predict the real-time leakage flow rate through the labyrinth seal because of the fast reciprocating motion of the piston, which will cause continually pressure change in two compression chambers, and then the pressure fluctuation will affect the flow through the labyrinth seal. A transient simulation model employing the multiscale dynamic mesh, which considers the effect of the reciprocating motion of the piston in the cylinder, is established to identify the characteristics of the internal leakage. This model was verified by a specially designed compressor, and the influence of various parameters was analyzed in detail. The sealing performance decreased linearly with the increase in the pressure ratio, and higher pressure inlet leads to higher leakage flow under the same pressure ratio. The labyrinth seal performance positively correlated to the increase of the rotational speed. Leakage characteristics of five working mediums were carried out, and the results indicated that the relative leakage decreased with an increase in the relative molecular mass. From this study, the realistic internal leakage flow rate under different operating parameters in the reciprocating labyrinth piston compressor could be predicated.

Theoretical and Simulation Investigations on Flow Ripple Reduction of Axial Piston Pumps Using Nonuniform Distribution of Pistons

2020 ◽  
Vol 143 (4) ◽  
Author(s):  
Fei Lyu ◽  
Shaogan Ye ◽  
Junhui Zhang ◽  
Bing Xu ◽  
Weidi Huang ◽  
...  
Keyword(s):  
Flow Rate ◽  
Optimization Design ◽  
Nonuniform Distribution ◽  
Piston Pump ◽  
Axial Piston Pump ◽  
Flow Ripple ◽  
Distribution Rule ◽  
Dynamic Simulation Model ◽  
Ripple Reduction ◽  
Axial Piston

Abstract The output flow ripple of the axial piston pump is one of the excitation sources for the hydraulic system vibration. The amplitudes of its specific harmonics must be reduced to avoid the resonance with the hydraulic pipeline. In this paper, a method on the nonuniform distribution of the pistons is put forward to adjust the flow ripple. The deflection angles of the pistons are used to describe the distribution rule. The distribution rule is imported to the Fourier expansion of the flow rate of each single-piston chamber, and then every single flow rate is superposed to obtain the Fourier coefficient of total flow rate that becomes the function of deflection angles. After this, objective optimization design is carried out to reduce the amplitudes of specific harmonics. Finally, the dynamic simulation model of the nonuniformly distributed axial piston pump is established to verify the effects of objective optimization. The results show that the amplitude of the ninth harmonic of the flow ripple can be reduced by about 40%, and the reductions are about 99% for the 18th and 27th harmonic.

Analysis of Static Characteristics of Pressure Seal in Actual High Pressure Pump

2011 ◽  
Author(s):  
Isao Hagiya ◽  
Katsutoshi Kobayashi ◽  
Yoshimasa Chiba ◽  
Tetsuya Yoshida ◽  
Akira Arai
Keyword(s):  
High Pressure ◽  
Flow Rate ◽  
High Speed ◽  
Control Volume ◽  
Leakage Flow ◽  
High Pressure Pump ◽  
Flow Rates ◽  
Leakage Flow Rate ◽  
Rotor Dynamic ◽  
Pressure Seal

We predicted the leakage flow rates of a pressure seal in an actual high-pressure multistage pump. Since the pressure of the actual pump is higher than that of a model pump, accurate prediction of leakage flow rate and rotor dynamic forces for an actual pump is more difficult than that for a model pump. A non-contacting seal is used as a pressure seal to suppress leakage flow for high-pressure multistage pumps. When such pumps are operated at high speed, the fluid force acting on an eccentric rotor may cause vibration instability. For vibration stability analysis, we need to estimate static and dynamic characteristics of the pressure seals, i.e., leakage flow rate and rotor dynamic coefficients. We calculated the characteristics of the pressure seal based on Iwatsubo group’s method. The pressure seal we developed has labyrinth geometry consisting of grooves with different sizes. This method numerically calculates the characteristics of the grooved seal by using a three-control-volume model and a perturbation method. We compared the calculated and measured leakage flow rates. We found that the calculated results quantitatively agreed with the measured one in the actual pump and the characteristics of pressure and velocity for the seal with non-uniform-sized grooves were clarified.

Estimating HP-IP Mid-Span Packing Leakage in Combined Cycles

2006 ◽  
Author(s):  
Tsatsu Fiadjoe
Keyword(s):  
Flow Rate ◽  
Combined Cycle ◽  
Variation Method ◽  
Leakage Flow ◽  
Steam Turbines ◽  
Multiple Test ◽  
External Cooling ◽  
Temperature Method ◽  
Leakage Flow Rate ◽  
Combined Cycles

When a turbine has combined High Pressure (HP) and Intermediate Pressure (IP) sections, there is a steam flow path between the sections. In Combined Cycle steam turbines this internal leakage flow rate needs to be determined for the steam turbine performance calculations. However, since the leakage is internal to the turbine, it cannot be measured directly. One method which has been employed in determining the Mid-packing leakage flow rate is the Variation of Initial and/or Reheat Temperature method. This method is described in the paper “Estimating The Leakage From HP To IP Turbine Sections” presented by J.A. Booth and D.E. Kautzmann. It involves using the convergence of IP efficiency plots from multiple test runs to estimate the HP-IP leakage flow rate. Although this method has been employed successfully in large steam applications, it has generally not produced consistent results for Combined Cycle steam turbines. The lack of convergence for Combined Cycles may be due to the fact that some of the assumptions made in applying the method to large steam applications are not valid for Combined Cycle applications. Some of the assumptions which need to be reviewed and modified for Combined Cycle application are as follows: • Constant IP efficiency for all test runs; • Constant throttle flow during all test runs; • Constant section pressure ratios for all test runs; • No influence of external cooling or admission flows. This paper reviews the modifications to the traditional Initial and/or Reheat temperature variation method to make the Mid-Packing leakage calculations more consistent for Combined Cycle applications. Some data has shown that incorporating these additional changes improves the convergence of Mid-packing leakage determination.

Discharge Flow Ripple of Axial Piston Pump with Conical Cylinder Block

2010 ◽  
Vol 34-35 ◽  
pp. 440-445
Author(s):  
Lei Li ◽  
Jian Ke ◽  
Jia Xu ◽  
Wang Yong
Keyword(s):  
Block Design ◽  
Cone Angle ◽  
Point Of View ◽  
Piston Pump ◽  
Cylinder Block ◽  
Axial Piston Pump ◽  
Discharge Flow ◽  
Flow Ripple ◽  
Displacement Pump ◽  
Axial Piston

The discharge flow ripple is a crucial criterion for evaluating the piston pump. This research examines the discharge flow ripple of axial piston pump with conical cylinder block by developing a comprehensive mathematical model based upon the Bernoulli equation and the continuity equation. The novel aspect of this research is that it includes the analysis of cylinder block cone angle. From the results of this research, it can be concluded that cylinder block cone angle has a significant impact on the discharge flow ripple, and utilizing a conical cylinder block design is more feasible than cylindrical cylinder block from a flow ripple point of view. This conclusion can be used to guide the up-front design for the variable displacement pump.

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