Li Zhuangyun

Research on the Flow and Cavitation Characteristics of Multi-Stage Throttle in Water-Hydraulics

Abstract In water-hydraulic power systems cavitation is more likely to happen than in oil-hydraulic power systems because of the high vaporous pressure of water. A multi-stage throttle, which consists of two or more orifices in a throttle, is an effective way to avoid or reduce cavitation damage. In this research, the cavitation characteristics of two-stage throttles are analysed theoretically and compared with a single-stage. Then, experiments are conducted to investigate the flow and cavitation characteristics of multi-stage throttles including two kinds of two-stage throttles and one of a three-stage kind. All the experiments are carried out under the two cases with and without backpressure, respectively. The working medium is tap water. Experimental results show that the shape of the multi-stage throttle and operating conditions have remarkable effects on the flow and cavitation characteristics.

Lubrication and tribology in seawater hydraulic piston pump

Water hydraulic systems have provoked major interest because of the human friendly and environmental safety aspects. Piston pump is one of the most frequently used hydraulic units in recent engineering technique. In water hydraulic piston pump, poor lubrication is more likely to happen than in oil hydraulic one because of difference in properties between water and oil. So there are some key problems such as corrosive wear and erosion, which are investigated briefly. Many new materials have been developed, which give longer life expectancies with water without corrosion and erosion. A new type of seawater hydraulic piston pumps with better suction characteristics had been developed at HUST. Much of this research has concentrated on new materials, structure and experiments, which are also specially introduced.

Materials screening of matching pairs in a water hydraulic piston pump

Purpose – 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.Design/methodology/approach – 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).Findings – 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 pum...

Flow and cavitation characteristics of a damping orifice in water hydraulics

Abstract The flow in damping orifices when using water as the working media is of high Reynolds number and cavitation is inevitable. In this article, experimental studies are made on the flow and cavitation characteristics of water hydraulic orifices and the coefficient formulae in previous documents are testified with the Reynolds number ranging from 104 to 105. All the orifices are made of transparent materials, so the flow and the occurrence process of the cavitation can be observed with the naked eye. The experiments for each orifice are carried out under the two cases with and without backpressure, respectively. Experimental results show that the flow coefficient with backpressure is larger than the case without it. The larger the aspect ratio, the less the flow characteristics are influenced by backpressure. The cavitation first occurs at the inlet of orifices and then shifts to the outlet gradually. When there is cavitation happening at the outlet, flow saturation emerges simultaneously.

Study of the key problems in a water hydraulic piston pump and its applications

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.

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.

Evaluation for adhesion strength of coating and substrate by burying beforehand specimen

Adhesion strength is an important target in evaluating the quality of coating layers. The traditional way of adhesion strength test is bonding pull-off method for thick layers and scratch test for thin films. The drawbacks of these two methods are discussed in this paper, and an evaluating method for adhesion strength of coating by burying beforehand specimen is proposed. The adhesion strength of samples is measured with two methods. The dispersity of testing data is lower than that in the ASTM-C663-79 Standard.