High-pressure Hydraulic Pump Research Articles

Experimental Study of Jet Cavitation Erosion Applicable to Oil and Water-Hydraulic Equipment

Abstract Hydraulic components, such as valves, pumps, and actuators, include many narrow passages in the form of nozzles, orifices, and gaps. Cavitation can occur when jets flow from high to low pressure through such sections, making it unavoidable for jets containing cavitation bubbles to impinge on the inner walls of hydraulic components. This report summarizes a series of experiments involving erosion tests, flow visualization, and pressure measurements with hydraulic oils and municipal water. For the erosion tests, the ASTM G134, Standard Test Method for Erosion of Solid Materials by a Cavitating Liquid Jet, method of jet cavitation erosion is used to evaluate the eroded mass loss and the specimen’s surface damage. The experimental apparatus consists of a stainless steel cylindrical chamber, a high-pressure hydraulic pump, and auxiliary hydraulic components. The main test parameters are the standoff distance, cavitation number, nozzle outlet geometry, specimen surface shape, and liquid type. The specimen mass is measured, and the eroded surfaces are recorded at specific intervals. For the visualization tests, an acrylic chamber and a digital video camera are used. Video frames are extracted as pictures and are processed by superposition. For the pressure measurements, pressure-sensitive films are used to estimate the pressure distributions on the impinged surfaces. The films are bonded on the specimen surface beforehand, exposed to the cavitating jets for a short period, and then analyzed using an image analysis system. Overall, by comparing the mass loss, surface damage, visualization pictures, and pressure mapping, the effects of the experimental parameters on the erosion characteristics are examined. Moreover, design approaches that are applicable to both oil and water-hydraulic components are proposed in order to reduce erosion by cavitating jets.

Surface texture characterization of alpha-beta titanium alloy (Ti6Al4V) after hydrostatic burnishing

The ball burnishing process with hydrostatic tools is very economical finishing process for various types of machine parts. This process reduces the height of surface unevenness, introduces compressive stresses at high depth (approx. 1 mm) and increase the hardness of the surface layer. The paper presents effect of the ball burnishing process parameters with hydrostatic tools on the surface structure geometry of titanium alloy. This shows how the surface roughness can be reduced after preceding operation by the ball burnishing process. This process changes the surface stereometrics of the previously milled surface. Burnishing with hydrostatic tools can be easily and effectively used either on conventional or on CNC machines. The Ecoroll burnishing system used in this research consists of a high-pressure hydraulic pump (model 4.0 HGP) and the 6 mm diameter burnishing tool both connected via high-pressure hoses. The burnishing tool is based on a hydrostatics principle; the key element is a 6mm ball made of ceramics. The input process parameters considered in the paper included: burnishing rate, applied pressure and line to line pitch. It also showed a positive effect of hydrostatics burnishing on roughness and geometric structure of the surface. In most cases, the result is anisotropic surface, reduced roughness, reduced amplitude values of parameters such as: Sa, Sz. The biggest impact on the value of indicators of geometric structure comes from pressure, the smaller (but still significant) impact results from a tool speed and line to line pitch

Simulation of fluid structure interaction in a novel design of high pressure axial piston hydraulic pump

Abstract A novel type of an axial, piston-driven high pressure hydraulic pump with variable capacity marks a significant improvement in the area of the hydraulic machinery design. Total discharge from hydrostatic forces eliminates a need for a servomechanism, thus simplifying operation, reducing weight and introducing the possibility of the pump displacement control by computer. PWK-type pumps, invented in the Gdansk University of Technology, offer high efficiency for pressure levels up to 55 MPa, ability to work self sucking even at high speed. However, the heart of the new invention, the commutation unit, creates harmful pressure peaks. Those peaks can be mitigated by the introduction of a compensation chamber with elastic walls. Owing to the dynamic character of events taking place in the pump, a need for computer simulation arouse in order to understand phenomena leading to the occurrence of pressure peaks and choose compensation chamber parameters accordingly. A CFD package alone would not be sufficient to reliably represent the interaction between the compensation chamber wall and the working fluid. This paper presents Fluid Structure Interaction approach comparing 3 different models: 2 simplified models of the pump and a full pump model.

Development of Test System for Subsea Tree Equipment

A test system for subsea tree equipment is developed for tree function testing after repair. The test system mainly consists of hydraulic unit and electric unit. The hydraulic unit is developed by revamping an old hydraulic power unit, which consist of six components, including reservoir, flush/fill pump circuit, high pressure hydraulic pump circuits, accumulator group, hydraulic supply circuits and fluid return circuit. The electric unit for subsea tree is developed by using NI Compact DAQ system, In order to control the hydraulic unit and acquire the pressure signals easily. The test procedures for flowloops, valve, and hydrostatic hydraulic pressure cycling are proposed based on the factory acceptance testing of subsea tree. A test for a repaired subsea tree is performed by using the developed test system. The results show that the repaired subsea tree is good enough after repair, and verify that the developed test system works well.

Design of Measurement and Control System for Medium and High Pressure Hydraulic Pump Test Platform Based on PXI Bus Structure

Based of PXI (PCI Extensions for Instrumentation) bus structure, a measurement and control system for medium and high pressure hydraulic pump test platform is designed in this paper. This system is comprehensive testing equipment which has adopted the traditional technologies include hydraulic, computer, virtual instrument and detecting. Its measurement and control system has introduced new techniques with combining PXI bus structure and relay, which can realize manual/automatic synchronical operation and one key operation. Use graphic language Lab VIEW 9.0 as its developing platform, the system realizes synchronically display of the mechanical instrument and the virtual instrument which has increased the test accuracy and speed.

A novel high-temperature and high-pressure hydraulic pump based on mononeuron control

Based on structures and characteristics of traditional hydraulic pumps, this paper proposes a novel high-temperature and high-pressure hydraulic pump (HHHP) that can work under 150°C and 28 MPa to overcome problems of traditional high-temperature plunger pumps. The HHHP is designed with the structure of mechanical division and double cylinder parallel. The control signals of two cylinders are two separate triangle waveforms with 90° phase difference. Because the output waveforms of two cylinders have the same characteristics as the control signals, the HHHP can obtain a stable output after two separate waveforms are superposed. A mononeuron self-adaptive PID control algorithm is also improved by modifying parameters K and η. Two improved controllers are used to control the two cylinders, respectively, making two displacements of plungers match each other. Therefore, reduced fluctuations and stable pressure output is obtained. Besides simulation, tests on the built prototype test system are carried out to verify the performance of HHHP. Results show that the improved control approach can limit fluctuations to a lower level and the HHHP system attains good outputs under different signal periods and different pressures.

볼과 소켓의 정밀 체결을 위한 회전성형 장치

A double roll rotary forming equipment is presented in this paper. The equipment is developed for joining the socket with the ball of a concave piston assembly with its geometrical tolerance requirements satisfied. The equipment is composed of a lathe, a double roll system and a roll pressing unit driven by the hydraulic system. The workpiece rotates by spindle chuck of the lathe while the double roll system approaches perpendicularly to the central line of the workpiece. The equipment is successfully applied to precision joining of the ball and the socket fur the concave piston assembly of a high pressure hydraulic pump.

유한요소법을 이용한 고압유압펌프용 오목형 피스톤 조립체의 소켓 형상 설계

A systematic approach to socket shape design of a concave piston assembly for a high pressure hydraulic pump of an excavator is presented in this paper. A design model is given and a methodology of socket shape design is proposed. An axisymmetric rigid-plastic finite element method is employed for predicting the approximate socket shape formed by a rotary forming process as well as for simulating the test process for separating the shoe from the piston assembly designed. It is verified that the predictions are in good agreement with the experiments. The approach is successfully applied to developing an optimal concave piston assembly.

Analysis of the steady-state performance of a multi-plunger hydraulic pump

In this article the steady-state performance of a multi-plunger low-flow high-pressure hydraulic pump has been studied. The variation of the chamber volume with shaft rotation, along with the various flow and torque losses, demands a structured approach to arrive at its mathematical model. A bondgraph simulation technique has been used to model the system, where various losses are lumped in suitable resistive elements. Using the standard procedure, experiments have been conducted for a wide range of operating conditions. The trends of the various loss coefficients are identified. The performance of the pump has been experimentally verified.

Tribological Interaction between Piston and Cylinder of a Model High Pressure Hydraulic Pump

Conventional high-pressure hydraulic piston pumps require a delicate balance between clearance, surface finish, and pump materials if a long, efficient life is to be maintained. A cam-operated single cylinder pump has been used to test several pump material combinations using two chemically different hydraulic fluids. The main parameters monitored were the degree of mutual electrical insulation attained and the physical drag of the piston on the cylinder due to both viscous shear and asperity interaction. It was found that for hardened steel pistons and cylinders an optimum surface finish of approximately 8 μinches CLA gave the best results with both fluids. Results are explained on the basis of micro-asperity hydrodynamic lift. Presented at the 29th Annual Meeting in Cleveland, Ohio, April 28–May 2, 1974