High-pressure Piston Research Articles

Research on characteristics of high-pressure and high-speed micro axial piston pump

Research on characteristics of high-pressure and high-speed micro axial piston pump

Volumetric efficiency in motor-driven two-dimensional piston pumps with leakage and reverse flow under high pressure

This paper presents a volumetric efficiency model for high-pressure motor-driven 2D piston pumps, incorporating key factors such as axial internal and external leakage, circumferential leakage, and reverse flow. The model integrates hydraulic fluid compressibility and variations in flow coefficients to improve simulation accuracy. Co-simulation using AMESim and Simulink, along with experimental validation, demonstrates the model’s reliability across various operating conditions. The results show that rotational speed enhances volumetric efficiency due to its minimal effect on leakage and reverse flow, while pressure significantly reduces efficiency, particularly through reverse flow and circumferential leakage. Reducing trapped volume proves to be an effective strategy for minimizing reverse flow and improving overall pump performance. Additionally, refining flow coefficients to improve the accuracy of the simulation model remains an important area for further development.

Transient numerical simulation and characteristic study of flow field in high-pressure piston pump

Transient numerical simulation and characteristic study of flow field in high-pressure piston pump

Influence of structural parameters of distributor disk on flow pulsation in axial piston pumps

Firstly, a virtual prototype of axial piston pump AMESim is used to observe the effects of outlet pressure, swashplate inclination, bulk modulus (compressibility), density, dynamic viscosity, air viscosity, air content, dead space volume, leakage of mating clearance of the moving parts, plunger cylinder clearance, eccentricity, contact length of the copper bushing of the high-pressure piston pump, and the over-flow area of the flow distributing disk on the swashplate torque, the pressure in the plunger chamber, the pulsation in the flow rate, and the backing-up. To explore the influence of fluid noise, mechanical noise and air noise. After comparison, the overflow area of the disk, which has the greatest influence on the noise, is selected as the research object, in which the structural parameters of the disk are the most important influencing factors. Finally, it is found that too large or too small overflow area will aggravate the fluid noise and mechanical noise of the piston pump. Therefore, the optimized design of the structure of piston pump flow distribution plate is of great significance to reduce the vibration and noise of the hydraulic system. This study catches the optimization method of axial piston pump flow distribution shock, which can provide a reference for the design and optimization of axial piston pumps.

Contribution To the Evaluation of Soot Deposit Thickness Evolution and Its Impact on Heat Transfer Within Heavy Diesel Engines: An Innovative Simplistic Procedure

This study deals with a numerical procedure designed and built to evaluate the evolution of soot deposits thickness and their impact on heat transfer for a high-pressure common rail 16V280 marine diesel engine piston. Using a combination of 3D numerical computations and an iterative calculation algorithm, this work reveals the complex relationship between soot deposit, temperature distribution, and piston thermal dynamics. Non-uniform soot deposit distribution is observed, concentrated at the piston bowl peripheral regions. This distribution aligns with theoretical expectations, indicating the influence of the swirl effect. The presence of soot deposits alters the temperature distribution, implying displacement of high-temperature zones towards the bowl region of the piston. The reduction in surface temperature of approximately 14%, is attributed to the lower heat transfer coefficient of deposited layers. This greatly influences the distribution of thermo-mechanical stresses of the piston. The proposed procedure offers an approach to assess the impact of soot deposit on heat transfer. In addition, this study contributes to a better understanding of realistic piston conditions and addresses the challenges introduced by soot deposits in heavy-duty diesel engines by combining the proposed procedure with investigations based on CFD software tools.

Influences of flame remelting and WC-Co addition on microstructure, mechanical properties and corrosion behavior of NiCrBSi coatings manufactured via HVOF process

We investigated the microstructures, mechanical properties, and corrosion behavior of NiCrBSi coatings upon the addition of the WC-Co powder in various amounts (0, 5, 10, 15, and 20 wt%) using the high velocity oxy-fuel process on low-carbon steel. Additionally, flame remelting was performed at 1100 °C for 1 min following thermal spraying of the coatings. The microstructures of the coatings were examined using X-ray diffractometry and scanning electron microscopy, and the mechanical properties of the coatings were assessed via Vickers microhardness and ball-on-disk tests. The corrosion behavior of the coatings was evaluated using potentiodynamic polarization testing in a 20 vol.% sulfuric acid solution. The results demonstrated that an increase in the WC-Co amount enhanced the hardness and wear resistance of the coatings. For 10–20 wt% WC-Co addition, small cracks were observed in the as-sprayed coatings owing to the heat applied during thermal spraying and rapid cooling, respectively. The presence of porosity directly affects the corrosion behavior of the coatings. Flame remelting led to better cohesion and the distribution of the γ-Ni and WC phases, reducing microdefects, such as pores and cracks. The mechanical properties of the coatings improved as the WC-Co amount increased after flame remelting, resulting in the formation of intermetallic compounds (FeB, CoSi2, and Ni2Si) along with the WC phase. The flame-remelted NiCrBSi/ 10 wt% WC-Co coating demonstrated high hardness and low wear and corrosion rates (1072.26 HV, 4.8 × 10−6 mm3/m, and 0.560 mm/year, respectively). Therefore, WC-Co addition and the flame remelting process significantly enhanced the properties of NiCrBSi coatings. This study highlights the substantial contributions of WC-Co addition and the flame remelting process in enhancing the mechanical properties and corrosion resistance of NiCrBSi coatings. These findings offer valuable insights for optimizing the performance of commercially available coatings in various real-world applications in maintaining power plants and industrial components like high-pressure pump piston rods, acid-resistant pumps in oil refineries.

Experimental investigation for the operational performance improvement of cryogenic piston-type pump using subcooling effect for liquid hydrogen stations

This paper investigates the impact of subcooling degree and exhaust pressure on the performance of a high-pressure piston pump for pressurizing cryogenic liquid. We fabricate a lab-scale cryogenic liquid pump, conduct experiments with liquid nitrogen, and observe the significant effect of subcooling changes on the pump performance. The lab-scale pump achieves up to 30 bar of exhaust pressure and up to 45.4 g exhaust mass per cycle. This paper introduces the concept of duty cycle for the exhaust mass as a measure of pump performance. The results show that as the subcooling degree and the exhaust pressure increase, the duty cycle and the exhaust mass also increase, improving the pump performance. However, the increase in performance does not happen proportionally, and an optimal subcooling degree must be selected. This paper establishes a generalized computational model to predict the pump performance, achieving the mean absolute errors of 1.8 bar and 0.3 g/s in pressure and mass flow rate, respectively. The model can predict the exhaust mass during one stroke cycle of the pump with an approximation error of 10 %. In addition, the model predicts that pressurizing liquid hydrogen to 900 bar requires subcooling degree and its duty cycle cannot reach 100 % by reduction of specific volume. The findings suggest that subcooling can be used to enhance cryogenic liquid pump performance, and the optimal subcooling degree can be determined during the design of piston pumps to achieve high pressure.

Analysis of the Design of Henry Muncaster’s Two-Cylinder Compound Vertical Steam Engine with Speed Control

This article offers an analysis, from the mechanical engineering viewpoint, of an invention by Henry Muncaster from 1912: the two-cylinder compound vertical steam engine with speed control. This is an invention with a large number of components (106) that was used as an engine in boats and railways. The ultimate objective of this investigation was to determine the operating conditions (maximum pressures of water vapor in the admission of high- and low-pressure cylinders) according to the criteria of resistance of materials since there is no information about this. Therefore, two critical operating conditions were simulated that resemble the start-up of the machine (flywheel locked as the most unfavorable situation) in order to determine those operating conditions that ensure both its safety and optimal operation. For this, a static linear analysis based on the finite element method (FEM) of the 3D CAD model was carried out under real operating conditions, according to the criteria of resistance of materials, using the Autodesk Inventor Nastran 2023 software. The results of the static linear analysis (von Mises stress, displacement and safety factor) confirmed the maximum values of the vapor pressure in the admission of the cylinders: 0.3 MPa on the high-pressure piston plunger and 0.15 MPa on the low-pressure piston plunger.

Analysis of lubricating characteristics of high-pressure radial piston pump with thermo-elastohydrodynamic coupling

The behavior of piston-cylinder interfaces takes important influences on lubricating characteristics of the high-pressure piston pump. For the sake of revealing the lubricating characteristics of radial piston pumps, a transient thermo-elastohydrodynamic lubrication model to analyze the interface between piston and cylinder is established with considering the effects of the bushing elastic deformation, viscosity-temperature-pressure, heat conduction and piston tilting, on the basis of coupling the finite element method and finite difference method. Furthermore, the influences of design parameters (camshaft speed, inlet pressure and average clearance) on the load carrying capacity, leakage, viscous friction, and temperature rise of the friction-pair interfaces are analyzed. The results indicate that the average clearance has the most significant influence on the lubrication performance. Increasing the average clearance from 2 to 6 μm resulted in a substantial decrease in load carrying capacity by approximately 50% and friction force by approximately 65%. The temperature rise showed a significant reduction of 55%, while the leakage increased by approximately 3-fold.

Research on the High Speed of Piston Pumps Based on Rapid Erecting of Launch Vehicles

Rapid erection is a key technology for modern warfare in vehicle weapon launch systems. It is challenging to attain rapidity with the hydraulic erecting system because of the intensified cavitation in the piston chamber at high speeds, which reduces volumetric efficiency and increases flow pulsation in the typical high-pressure axial piston pump. In this paper, an improved scheme for the cylinder window area overflow surface was proposed to solve this problem. Based on the full cavitation model and the compressible model, a numerical model of the internal flow in the piston pump was developed, and the effect of rotational speeds on the flow and cavitation characteristics of the pump was analysed. The results show that after the improvement, the maximum flow of the pump is increased from 1.765 kg/s to 2.295 kg/s, an increase of 30.028%, and the maximum speed corresponding to the volumetric efficiency of more than 90% is increased from 1500 rpm to 2100 rpm. At high speeds, the improved block can effectively suppress the cavitation and backflow in the piston chamber, improve the volumetric efficiency of the piston pump and reduce the flow pulsation, which is conducive to reducing the vibration and noise of the pump body.

A new test method for simulating wear failure of hydraulic pump slipper pair under high-speed and high-pressure conditions

In practical engineering, it is very difficult to obtain data on the slipper wear of hydraulic pumps, especially under high-speed, high-pressure conditions, which limits the development of fault diagnosis technology for hydraulic pumps. At present, a test method that can accurately simulate the operating state of the slipper pair under high-speed and high-pressure conditions does not exist. The reliable load-bearing design of the slipper pair is difficult to carry out effectivetest verification, which limits the development of high-speed and high-pressure piston pumps. Therefore, an experimental design method was proposed to directly simulate the high-speed, high-pressure friction state of the slipper pair based on the change law of reprinting residual pressing force.

Study on Friction Characteristics of Slipper Pair of Large Displacement High-Pressure Piston Pump

The reference value of the oil film thickness and friction coefficient of the slipper pair is critical to the development of the piston pump, especially for 750 mL/r displacement piston pumps. To explore the computing method and range of the reference value mentioned applicable to 750 mL/r displacement piston pumps, this study aims to propose the modified calculation model of the oil film thickness based on the real clearance flowrate and obtain the value range of the friction coefficient of the slipper pair. Through the friction test of the slipper pair, the mean deviation ratio of the oil film thickness between the modified value, theoretical value, and the measured value was calculated and compared, respectively. The variation law of the friction under the influence of different speeds and working pressures was analyzed. Finally, the range of the equivalent friction coefficient with the upper and lower limit surfaces was obtained. The results show that the mean deviation ratio between the modified oil film thickness value and the measured value is mainly within 6%, while that of the theoretical method is mainly from 6% to 8%, and the mean of the difference between the two deviation ratios is about 3%, verifying the feasibility of the modified model used for the calculation of the reference value. Meanwhile, the value of the equivalent friction coefficient fluctuates in the range of 0.006–0.018, which is affected more significantly by the working pressure than the speed, suggesting that the working pressure can be given priority as the design basis of the friction coefficient for 750 mL/r displacement piston pumps.

Modeling and Characteristic Analysis of a Cylinder Block/Valve Plate Interface Oil Film Model for 35 MPa Aviation Piston Pumps

Oil film characteristics are critical to the high-reliability operation of high-pressure aviation piston pumps (APPs). However, there is still a lack of research on oil film modeling and characteristic analysis of high-pressure APPs. This paper takes the oil film at the cylinder block/valve plate interface of a 35 MPa high-pressure APP as the research object. By introducing a full oil film computational fluid dynamics (CFD) model considering non-isothermal and cavitation effects under multi-field coupling conditions, a cylinder block/valve plate interface oil film model is established, which includes a viscous wedge geometric model, multi-body dynamics model, and full oil film CFD model. The mesh independence test and force balance error analysis ensure the accuracy of the model calculation. Based on the established model, the oil film’s lubricating, sealing, load-bearing, and overturning characteristics are comprehensively and systematically analyzed, and the evolution law of different oil film characteristics with pressure changes is revealed. Moreover, suggestions for improving the structure and operating conditions of a 35 MPa high-pressure APP are proposed to optimize the oil film characteristics of the cylinder block/valve plate interface.

Numerical Simulation and Experimental Research on Oil Film Characteristics of High-Pressure Piston Pump Slipper Pair

The high-pressure axial piston pump is widely used in the field of coal machinery equipment due to its compact structure, high power density, and easy variable control. Failure affects pump performance. In this paper, the sliding shoe pair of the high-pressure plunger pump is taken as the research object, the variation law of the oil film pressure field is numerically simulated by Matlab software, and the high-pressure pump sliding shoe pair test bench is built. The full-cycle dynamic evaluation of the influence of the speed change of the drive shaft on the oil film characteristics is obtained.

Study on wear characteristics of friction pair in high pressure and high-speed axial piston pump

Axial piston pump is the core component of electro-hydraulic control system. High-pressure and high-speed development of the axial piston pump can significantly improve the power density of the system, but it also causes a series of problems, such as the reduction of energy conversion efficiency, the enhancement of solid-liquid coupling, the intensification of vibration and noise, and the deterioration of service conditions of friction pairs, which poses a serious challenge to the service reliability of the axial piston pump. Therefore, the friction wear experiments of key friction pairs of axial piston pump are carried out in this paper to explore the influence of various factors on the friction wear performance and the wear mechanism of friction pairs under normal stress. And the results are expected to be used to find out the matching materials of friction pairs which is the key to improve the working efficiency and the service reliability of axial piston pump.

Capped piston: A promising design to reduce compressibility effects, pressure ripple and cavitation for high-speed and high-pressure axial piston pumps

Raising rotational speed and operating pressure is an effective way to increase the power density of axial piston pumps. However, the axial piston pump with standard hollow pistons suffers from problems of volumetric losses, pressure ripple, and cavitation at high rotational speed and operating pressure. To reduce these fluid-related problems, the capped piston design is a promising alternative to the standard piston design by minimizing the dead volume. The capped pistons have been applied in commercial axial piston pumps but it remains unclear how the flow characteristics of axial piston pumps benefit from them. Therefore, this paper aims to clarify the mechanism of capped pistons in improving the flow characteristics of axial piston pumps. A computational fluid dynamics model is developed to compare the pump’s flow characteristics between standard and capped pistons. The simulation results show that compared with the standard hollow pistons, the capped pistons can significantly reduce the compressibility effects, pressure ripple, and cavitation over a wide range of operating conditions.

Optimization of the outlet unloading structure to prevent gaseous cavitation in a high-pressure axial piston pump

Raising the pressure rank of axial piston pumps is an effective way to enhance the power density. However, when hydraulic fluid switches between the suction and discharge areas in the valve plate at a high level of pressure, the effective delivery flow rates of pumps decrease and may cause vibrations, noise and gaseous cavitation. Increasing the inlet pressure is a common method used to reduce gaseous cavitation; however, this requires additional equipment to pressurize the inlet line, which reduces the power density of the pump. This study proposed a new approach to reduce gaseous cavitation by modifying the shape of the unloading holes for pumps. A computational fluid dynamics (CFD) model was established to examine the influences of the unloading holes of the valve plate on gaseous cavitation. The simulation results revealed that a crescent-shaped unloading hole in the valve plate can effectively decrease the gaseous cavitation by redistributing the damage power of cavitation. Moreover, the crescent-shaped design of the unloading hole can increase the unloading rate by 64.39% at an inlet pressure of 1.1 MPa and rotational speed of 1600 r/min compared to that of traditional unloading holes. As a result, cavitation in the pump can be reduced effectively by an improved unloading rate, which has great practical significance for suppressing the cavitation phenomenon and decreasing vibration and noise in the pump.

Study on the Fast Extension Mechanism of Double-Cavity Shock Absorber with High-Pressure Piston

Double-cavity shock absorber with high-pressure piston is the core component of the nose landing gear of the carrier-based aircraft, and its fast-extension performance seriously affects the safety of the catapult-assisted takeoff. The design of a carrier-based aircraft in our country is carried out based on the traditional method of fast-extension dynamics, and it is found that the fast-extension capability is larger than designed. This paper analyzes the working principle of the high-pressure piston shock absorber and explains that the high-pressure air cavity pushes the piston rod to extend rapidly, which will cause the cavitation phenomenon in the main oil chamber. Thus, the cavitation in the main oil chamber makes the traditional modeling method of oil-liquid resistance force no longer applicable. Then, the axial force modeling method of shock absorber considering the cavitation effect is proposed. Based on the carrier-based aircraft, the dynamic response of the shock absorber in the process of fast extension is calculated and then it is compared with the calculation results of the traditional dynamic method. It is found that due to the cavitation effect caused by the forced fast extension section of the high-pressure air plug shock absorber, the fast extension work increases by 67.6%, thus, revealing the fast extension mechanism of the double-chamber shock absorber with high-pressure piston and successfully explaining the phenomenon of the fast extension ability exceeding the expectation of the shock absorber.

Dependence of the Characteristics of a High-Pressure Piston Pair on the Properties of PES-3 Working Fluid and the Pressure Distribution in the Piston-Cylinder Gap

The use of the liquid PES-3 in a high-pressure piston pair is modeled and the parameters of the piston pair are determined. Equations are derived for a mathematical model describing the variation of the pressure in the gap between the piston and cylinder. The distribution of the pressure in the gap between the piston and cylinder is calculated for piston pressures below 1.6 GPa. The profiles of the gaps between a deformed piston and the cylinder are calculated for different piston pressures and the dependences of the piston downstroke velocity and gap efficiency on the piston pressure are calculated for different gaps of the undeformed piston pair. The results of this study can be used for the design of piston pairs operating in PES-3 fluid at pressures ranging from 0.01–1.6 GPa.

The Use of Acoustic Emission Elastic Waves for Diagnosing High Pressure Mud Pumps Used on Drilling Rigs

Although mud pumps are vital components of a drilling rig, their failures are frequent. The identification of technical condition of these high-pressure piston pumps is difficult. There are no reliable criteria for the assessment of mud pump condition. In this paper, faults of the pump valve module are identified by means of acoustic emission (AE) signals. The characteristics of these signals are extracted by wavelet packet signal processing. This method has been verified by experiments conducted on a NOV (National Oilwell Varco) -made triplex 14-P-220 mud pump (mounted in the drillship). The results show that the wavelet packet signal processing method can effectively extract the frequency band energy eigenvalues of the signals. Besides, some operational problems associated with high pressure piston mud pumps are presented. A non-invasive method for diagnosing the technical condition of such pumps is being developed at the Maritime University of Szczecin.