Applied Mechanics and Materials Vols. 241-244

Abstract: An energy recovery method during the durable test is put forward in this essay, and the durable test-bed of the hydraulic pump is developed. The efficiency and accuracy data acquisition is realized by using High-Speed High-Resolution sensor and data collection module. Control automation is come true by using PLC, industrial tablet PC and electric command device. The instrument panel constructed by LabWindows/CVI made the operation more concision, flexible and easy-to-use. This test bed has been put into use for a year and shows that the system can realize duration and efficient test of hydraulic pump easily and reliable.

Abstract: This paper analyzes the principle and structure of the relay valve, and AMEsim software is used to build up a relay valve model which can be used to simulating fault. And the model has been verified by comparing to the routine test data. Considering failure mechanism of various components of the relay valve, a modified relay valve model which can simulate some kinds of typical fault is built up. The braking system performance is researched under different kinds of fault. By analyzing and classifying the characteristics of brake cylinder pressure curve, piston displacement curve under kinds of fault condition, the fault reasons and actual fault location can be detected, which provides help for the relay valve maintenance and fault detection.

Abstract: A new type of cooling device used for server is designed in this paper. A server is used as a research object. A mathematical model of thermal analysis is established and a temperature distribution is simulated for this case. Then simulated heat dissipation effects of air cooling and evaporative cooling are compared to analyze the feasibility of the plan of forced convection evaporative cooling. The results show that the temperature distribution obtained in the case is more uniform and the temperature of the CPU is more stable when cooled by forced convection evaporative cooling.

Abstract: An investigation of the cryogenic oil mist flow field of nozzle was carried out in this study. A domain of the nozzle jet area was modeled with Pro/ENGINEER. CFD (Computational Fluid Dynamics) analysis was used to state the velocity field of different distances from the outlet of nozzle. The simulating velocity field was verified with the experimental results. Experimental results on velocity were measured by SYT-2000 digital multipurpose wind speed gage. The orthogonal experiment was designed to investigate the main effects parameters on velocity and temperature. It indicates that higher flow of cold air and smaller diameter of nozzle’s outlet will generate higher velocity. The temperature of cold air has most influence on the temperature of measuring point. Finally the optimum structure of the spraying nozzle was proposed.

Abstract: The signal strength, linearity, stability and measurement range of vortex flowmeter are primarily decided by the shape and geometrical parameters of bluff body. A circular cylinder with a slit was found to produce better vortex signal properties by experiments. Based on previous research, pressure distributions of flow past a circular cylinder are studied by numerical simulation. It is found that the intensity of pressure fluctuation caused by vortex shedding of the circular cylinder with a slit is stronger than that of circular cylinder and 0.2d downstream from the center line of slit at one side of cylinder is found to be an optimal position to detect the vortex signal, where d denotes the diameter of the cylinder. Finally the evolution process of vortex shedding is analyzed to explain why the intensity of pressure varies at different positions.

Abstract: The paper focuses on the interphase force of the gas-liquid two-phase flow in the horizontal pipe design and designs a new interpahse force quantitative detection devices. On the basis of analyzing the physical models and the mathematical models, the devices got the more accurate differential pressure and the two-phase flow phase holdup, avoiding many factors by using the capacitance sensor which is made up of the complete closure outer electrode and flow media as the inner electrode. Finally, the devices achieved the quantitative detection of the interphase force through the differential pressure and the phase holdup. The experiments proved that the devices can better reflect the interphase force changes of the gas-liquid two-phase flow in the horizontal tube and reached the design goal very well.

Abstract: In this paper, the theoretical model of entrainment force perpendicular to horizontal flow direction in gas-liquid two-phase flow was researched, then the entrainment forces were acquired by the interphase force detection device on the experimental device of gas-liquid two-phase, with working pressure of 0.05, 0.10 and 0.15MPa. The characteristics of entrainment force was analyzed at last. The results showed that the variation of entrainment force between phases obtained by experiment was in good agreement with theoretical analysis, moreover no correlation with working pressure.

Abstract: Four transitions of a new high speed on/off valve are investigated. Energy losses passing through the on/off valve are analyzed. The useful mathematical equations of energy losses related to the geometric parameters of the on/off valve and hydraulic system parameters are deduced. How to decrease energy losses in the design of the on/off valve is discussed.

Abstract: A testing system scheme with power recycle for hydraulic pumps’ durability is present, which is based on a hydraulic motor with hydraulicly overridden pressure compensation. The hydraulic motor can adaptively adjust its displacement to meet the demand of displacement match of the power feedback in the system. The system pressure can be set by adjusting the starting control pressure of the motor. The rotating speed of the pump is guaranteed by the control of the driven electrical motor. A hydraulic bridge unit is used to guide the flow from the outport of the pump to the fixed inlet port of the hydraulic motor and thus causes the motor to rotate in a certain direction to drive the pump in order to recycle the power.

Abstract: The fluid-structure coupling vibration due to the output flow ripple of pump or water hammer phenomenon does harm to piping system. Multi-physics field factor, especially the thermal field, should be considered while the vibration characteristics are analysed. A novel mathematical model based on Wiggert and Hatfield’s method of characteristic (MOC) is constructed, which is used to describe the vibration characteristics of the pipeline system at different temperatures. A simulation using one classic problem of pressure jump from the upstream is performed to verify the relationship between the temperature and pipeline coupling vibration.