Water Hydraulic Motor Research Articles

Water hydraulic high-speed solenoid valve Part 1: Development and static behaviour

This study is concerned with the development of a novel water hydraulic high-speed solenoid valve with a two-stage mechanism. By virtue of the two-stage mechanism and the proposed particular design, which use the leakage flow through the clearance between the main poppet and sleeve as the internal pilot flow, it is possible for the developed valve to have unique features, such as no internal leakage, a switching time of approximately 2 ms, maximum flowrate of 9 1/min and maximum pressure of 14 MPa. Based on the preliminary experimental results using a fabricated prototype valve, the performance of the developed valve has been improved. It can be seen from the experiment that the static flow characteristic according to the duty ratio of the improved valve is very satisfactory. As an application of the developed valve, the speed control of a water hydraulic motor has been conducted using the pulse width modulated (PWM) control of the developed valve. It was found that the developed valve is suitable for the PWM control method and can be implemented as the flow control valve of water hydraulic systems.

Fault diagnosis of water hydraulic actuators under some simulated faults

Water hydraulics captured the imagination of engineers some 2500 years ago and recently it has revived to become a powerful alternative in areas where the environment and health are of great concern. Previously, this field of knowledge suffered some setbacks as technology was still at its developing stage, but with better tolerances and the availability of better materials, this technology is now a reality. This paper focuses on the fault diagnosis of the condition of hydraulic actuators working on the principle of tap water hydraulic power systems. Two common actuators were explored, namely a water hydraulic cylinder and a water hydraulic axial piston motor. Possible real-life faults were simulated on the actuator’s internal component. The cylinder was operated with worn piston or rod seals whereas the motor has worn capstan and piston shoes in place. These actuators were operated to capture their unique vibration signals in their faulty states to be compared with their ‘healthy’ condition state. Both actuators were loaded in steps for trend observation in the vibration signatures. Results show that, in general, there is a change in vibration signals, flow rate and average operation duration when more load is added to the actuators. If a fault has occurred internally, it will also correspond to another change in the above parameters in the spectra plotted. With this knowledge, LabVIEW software can be written to set warning levels that will trigger an alarm when a fault is impending.

Investigation of valve plate in water hydraulic axial piston motor

This paper has introduced the developments of water hydraulic axial piston equipments. According to the effects of physico-chemical properties of water on water hydraulic components, a novel valve plate for water hydraulic axial motor has been put forward, whose moment exerted by the fluid field between valve plate and bearing plate is balanced entirely. The material screening experiment of valve plate is done on the test rig. Through numerical simulation the effects of some geometry parameters on the performance of water hydraulic motor have been studied. The silencing grooves on the valve plate in water hydraulic motor can reduce the pressure shock and the occurrence of cavitation effectively. It is evident that the appropriate structure should change the wear status between matching pairs and reduces the wear and specific pressure of the matching pairs. The specimen with the new type valve plate is used in a tool system.

DEVELOPMENT OF A LOW-PRESSURE WATER HYDRAULIC MOTOR

A compact and lightweight water hydraulic motor has been developed with the aim of applying to water hydraulic systems that utilize tap water as the transfer medium of energy. The developed water hydraulic motor, which drives in the low-pressure range equal or less than 2.0MPa, has power equivalent to 100W. Structurally based on a balanced vane type motor, it has achieved high efficiency and durability through structural improvements, use of most suitable materials selected in order to minimize energy losses.

VELOCITY CONTROL OF WATER HYDRAULIC MOTOR

Two simple velocity control systems of a water hydraulic motor are experimentally compared in this study; one with commercial pressure compensated proportional flow control valve and another with parallel-connected low-cost on/off solenoid valves. The aim of the study is to define suitability of these control techniques in a system where good velocity control accuracy is a significant requirement.

The development of a flexible bushing seal for rotating shafts

Pressures and speeds now specified for rotary shaft sealing duties frequently exceed the capabilities of rotary shaft lip seals, compression packings or even mechanical face seals. Elaborate pressure balancing arrangements, additional lubrication or cooling may be required to establish a viable sealing system which could still be running close to the operational limitations of the chosen seal type. A measure of unreliability is almost inevitable under such conditions. This paper describes a new and radical approach to the sealing of rotary shafts based on a no-contact self-energized flexible throttle which may be used in endless or split form. The elimination of any seal contact pressure whilst achieving leakage rates of acceptably low levels - lower than many conventional packings for example - has a dramatic effect on power consumption and seal environment temperatures. By taking the conventional rigid throttle bush theory and translating the idea into a pressure responsive flexible clearance seal, PV conditions exceeding 1000 bar m/s have been sustained repeatedly with a variety of fluids. No separate energization of the seal other than by system pressure is normally required. The product is already being used or investigated in water turbine, pump, hydraulic motor and marine sterngland duties and has been evaluated theoretically and practically by BHRA at Cranfield and the National Centre of Tribology, Risley.