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The purpose of this study is to analyze the speed characteristics of the water hydraulic axial piston motor. The speed performance of water hydraulic piston motor which uses water as medium is different from that mineral oil one.

To analyze the speed characteristics of the water hydraulic motor, the speed model of a swash plate water hydraulic piston motor is developed theoretically and a simulation model with AMESim is built.

The effects of clearance between friction pairs and input pressure on the speed are analyzed and compared between the theoretical and numerical models.

The results of the theoretical and simulation models both verify that the clearance of friction pairs is the key factor in the hydraulic piston motor’s speed.

The purpose of this paper is to analyze the cavitation characteristics of a water hydraulic axial piston motor (WHAPM) to improve the water motor performance, to reduce the vibration and noise and to prolong the service life of the motor.

The computational fluid dynamics (CFD) software PumpLinx is chosen to do cavitation analysis of the WHAPM. In this case, first, cavitation mechanism of the water piston motor is analyzed in depth. Then, considering the effects of bubble dynamics, the rate of phase transition, turbulence effects and non-condensable gas, the full cavitation model is selected, the dynamic CFD numerical model of internal flow field on the water hydraulic piston motor is established based on PumpLinx software and the fluid cavitation inside is numerically studied. Finally, the influence of the valve plate and pistons on motor cavitation is analyzed.

Research results show that there are two serious cavitation regions: one is the pressure transition region of the valve plate that is near the top dead center, and the other is the low-pressure region of the piston that is near the low-pressure transition area. Moreover, the more serious cavitation area is on the valve plate region.

The simulation results show that the proposed algorithm is able to detect the cavitation characteristics of the water piston motor. Besides, it is deduced that valve-plate structure optimization is more important than pistons to reduce cavitation influence.

In recent years water hydraulic systems have become of major interest because of the human friendly and environmental safety aspects. The piston pump is one of the most frequently used hydraulic units in recent engineering techniques. In a water hydraulic piston pump, poor lubrication is more likely to happen than in a oil hydraulic one because of differences in properties between water and oil. There are some key problems, such as corrosive wear and erosion, which are briefly investigated in this paper. Many new materials have been developed, which give longer life expectancies in water without corrosion and erosion. Recently, a new type of seawater hydraulic piston pump with better suction characteristics had been developed at Huazhong University of Science and Technology, China. Much of this research has concentrated on new materials, structure and experiments, which are also specially introduced in this paper.

The purpose of this paper is to present some design guidelines for the selection of the materials of the main frictional pairs in a water hydraulic piston pump.

In the research, a specified test bench that can simulate the typical frictional pairs in a water hydraulic piston pump was built. The friction and wear behaviors of the three pairs in the pump with different materials combinations were tested on the test bench. The tested materials included metal, engineering ceramics and plastics. Some surface engineering technologies including plasma surface spray, laser clad and heat treatment were applied and tested. The matching schemes included hard‐to‐hard (such as ceramics‐to‐ceramics) and hard‐to‐soft (such as metal‐to‐plastics, ceramics‐to‐plastics).

Some principles for the materials selection in a water hydraulic piston pump were obtained. According to the test results, the combination schemes for the main frictional pairs in a water hydraulic piston pump were proposed.

A test apparatus that could simulate the movement of main frictional pairs in a water hydraulic piston pump more really than the other general materials machines was developed. Some materials including metal, engineering ceramics and plastics and some engineering technologies were tested. The research described here is an important foundation for the development of a water hydraulic piston pump.

SOME of the general principles of the mechanics of fluids—such for example as the laws of liquid equilibrium—have been known since very early times. Because of this the ancient Egyptians were able to produce advanced systems of irrigation and the Romans, much later, their urban water supplies. The crude water wheel, its motive power a bullock or a donkey, replaced man‐power and supplied water to the irrigation ditch while the bucket‐type pump, arranged in stages for short lifts, made deep mining possible. It is somewhat surprising to find that, as early as the seventeenth century, working hydraulic systems were in existence where, cither by a system of balanced buckets or other devices, the prototype of the modern selector valve enabled a continuous supply of water to be maintained.

Aiming at improving the mechanical efficiency, the applicability and the working life of high water-based hydraulic motor (HWBHM) under working conditions at low speed and high pressure, the friction performance of different matching materials for piston slipper – crankshaft pair with high water-based hydraulic fluid (HWBHF) under working conditions at low speed and high pressure – were studied.

The friction experiments for different materials (316L, 316L with surface coating OVINO – tetrahedral amorphous carbon [TAC; 316L-TAC] – 316L with surface coating OVINO-graphite intercalated compound [GIC; 316L-GIC] and polyetheretherketone [PEEK] reinforced with 30 per cent carbon fiber [PEEK-30CF]) under HWBHF lubrication were implemented on a pin-disk friction abrasion machine to determine the variations of coefficient of friction (CoF) and wear rate for each matching materials. In addition, the roughness and the morphology of worn surface of different matching materials were quantitatively characterized.

The study revealed that material combinations have different friction performances. Test results showed that the abrasion of matching type stainless steel (SS) and SS is rather serious, and the method of surface coating could improve the friction performance of SS when friction with other materials. For matching type of SS with surface treatment (SS-ST) and SS-ST, 316L-GIC and 316L-GIC have relatively stable CoF, and the wear rate was smaller than other matching materials, while 316L-TAC and 316L-TAC has the smaller CoF than that of 316L-GIC. Matching materials 316L-GIC with PEEK-30CF of matching type SS-ST and PEEK-30CF has more stable COF and better wear resistance than those of other matching materials.

This research has laid a foundation for the improvement of service life and working efficiency of friction pair in HWBHM under working conditions at low speed and high pressure.

A neural network is employed to analyze axial piston pump of hydrostatic circular recessed bearing. Owing to complexity of the system, the neural network is used to predict the bearing parameters of the experimental system. The system mainly consists of cylinder block, piston, slipper, ball‐joint and swash plate. The neural model of the system has three layers, which are input layer with one neuron, hidden layer with ten neurons and output layer with three neurons. It can be outlined from the results for both approaches neural network could be modeled bearing systems in real time applications.

This paper presents an investigation for analyzing the efficiency of axial piston pumps in a variety conditions using a proposed neural network. Since slippers affect the performance of the system considerably, the effects of surface roughness on lubrication have been studied in slippers with varying hydrostatic bearing areas and surface roughness. The neural network structure is very suitable for this kind of system. The network is capable of predicting the leakage oil quantity of the experimental system. The network has parallel structure and fast learning capacity. It is also easy to see from the experimental results that the leakage oil quantity was caused by surface roughness, orifice diameter and the size of hydrostatic bearing area, loading pressure and the number of rotations. It can be outlined from the results for both approaches, neural network could be modeled slipper bearing systems in real time applications.

THE development of aircraft penumatic equipment has progressed so satisfactorily in recent years that actuation of vital services by means of compressed air is becoming increasingly popular. In this brief review of developments to date an attempt will be made to show how the air which has been made available as a result of compressor improvements is utilized and by way of introduction it may be of interest to recall some of the bold experiments which were made in earlier years.

The balanced vane pump is a common transmission component in hydraulic systems. Since the physicochemical properties of water and seawater are different from that of mineral oil, some problems can occur, for instance, poor lubrication, more leakage, and more corrosion. The paper aims to demonstrate the technical feasibility for the water hydraulic vane pump.

The material combinations were selected based on related research in literature. The volumetric efficiency and suction performance were measured in the current experiment. The relations between gap clearances and leakage flow, the contact and the friction forces between a vane tip and a cam contour were simulated based on mathematic models.

The soft‐hard material combinations in the prototype pump show preferable friction characteristics during tests. The axial clearances are the main channels of leakage flow. Pin type vane pump can reduce the contact force of the vane tip.

This paper outlines some key problems of the water hydraulic vane pump, such as the friction pair material,the structure, and the contact force of the vane tip by means of testing the basic performance of pump and mathematic model.