Advanced Materials Research Vols. 516-517

Abstract: The vapor compression distillation assembly is a phase-change water recovery technology which will reclaim water from urine, whose evaporator is a rotating container involving boiling heat transfer. The production rate of the apparatus depend on the bubble detachment diameter. In the article, based on the force equilibrium of bubble, the bubble detachment diameter formula is obtained, in which, the flow velocity along axis is neglected because it is very slow. The formula is very significant to the design of the apparatus and other relative apparatus.

Abstract: The present paper investigates an approach that seeks to reduce the storage of the traditional hole-map method and enhance the reliability. The new composite method is based on the least hole-mapping model, which efficiently reduces the area of the hole-mapping region, and incorporates an ADT search procedure to improve the identification method of the points inside the fringe cells which would otherwise become ambiguous. Through a donor-search judgment, the identification can be accomplished efficiently even for a coarse hole-cutting model. Also a new method named ‘inverse mark’ is developed here using mesh nodes’ information to automatically identify exterior points, which are initial points to advance inside the grid region. Results have shown that the composite method is able to get rid of the restriction of high level approximation, decrease efficiently the amount of Cartesian grid and save storage memory. The present approach is of great efficiency and good reliability to complex configurations including small gap regions.

Abstract: Inspired by the increasing interests on mixing effectiveness of opposed impinging jets, a numerical work is carried out to study the flow characteristics. The fluid temperature is used as a passive tracer to evaluate the mixing rate in the current mathematical models. The effect of Reynolds number on the mixing performance is discussed. Furthermore, in order to enhance the mixing efficiency and reduce the energy cost, unsteady flow pulsations are induced at the jet inlets. The numerical results indicate that the mixing efficiency can be improved by the unsteady flow pulsations via adjusting the hydrodynamics characteristics in the opposed jets.

Abstract: Through finite volume method, this study establishes a steady state flow and heat transfer model of a single phase flow flowing vertically upward in annular space. The model sets the inner cylinder of the annular space as a heating body with fixed heat generation rate. Flow and heat transfer boundary layers are set between the flow and the inner cylinder wall, in order to give more accurate description of momentum and heat coupling and transfer processes between the fluid and the solid near the wall. Compared with the constant physical property model, the variable physical property model, in which the fluid density, heat transfer coefficient, and viscosity change along with the temperature, has relatively lower heat transfer capacity and a little bit lower interface shear stress between the fluid and the solid heat transfer surfaces. Through the comparison between Re and Ri of the constant physical property model and the variable physical properties model, it can be concluded that the physical property changes of the fluid have gradually lower impact on flow and heat transfer processes along with the acceleration of the forced circulation of the fluid.

Abstract: A new type of mechanical vacuum pump is introduced in this paper. It is composed of two conjugated rotors spinning in opposite directions. The shape of rotor looks like a claw, and it is called a claw vacuum pump. A zero dimensional model was used in this paper to analyze the performance of this vacuum pump. The whole system was decomposed into five subsystems. Each subsystem has its own values in temperature, pressure and mass. The pressure variations and the temperature variations as well as the work required to complete the whole cycle were calculated with this model. It was found that the major leakage route is from exit port to chamber. The averaged outlet temperature may reach 483K. However, inner leakage may ease the problem of high temperature flow.

Abstract: In this study, mathematical model of fuel droplet evaporation is developed. Basic relationship of gas phase model is proposed by summarizing a large number of droplet evaporation gas phase models. Predictions of gas phase model are compared in forced convection. The results show that: Predictions are strongly dependent on the choice of gas phase models. Predictions of Ranz model and Haywood model are accurate with the experimental results. Evaporation time which is predicted by the gas phase models considering Stefan flow is longer than those without considering Stefan flow. For different gas phase models, droplet evaporation time is directly proportional to environmental pressure and inversely proportional to ambient temperature and Reynolds number.

Abstract: 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.

Abstract: Cavitation is an important factor on influencing the safety and efficiency of hydraulic machinery. So cavitation characteristics and mechanism are the work targets of many scholars. And how to reduce the risk of cavitation is also a hot issue. In this paper, geometry structure of hydrofoil is changing, with different number and angle of hole. Flow fields of hydrofoil are analyzed and compared, and then the effect of drilling angle on flow field of hydrofoil is given. This study introduces geometry optimization ideas for improving cavitation in the area of hydromachinery.

Abstract: In this paper, the helical inlet port of CZ4B26 diesel engine is studied. Its3-D solid models of port with the axial deviation and rotated port are made to research the effect on helical inlet port performance. Based on the validation of CFD precision by test, the numerical simulation of flow characteristics in ports-valve-cylinder system is carried out. The results showed that the axial deviation of the port and rotated port have a range of effects on the performance of inlet port.

Abstract: As we known, the energy efficiency of pump-control system is higher than valve-control system. So, using pump-control system to replace valve-control system has a positive meaning to improve the energy efficiency in hydraulic press machine. In order to research the performance of servo pump used in hydraulic press machines, the present study is conducted. First, a test bench for comparison of pump-control and valve-control system is established. In this test bench, the pump of former valve-control system and the servo pump are settled. These two pumps are switched by solenoid to supply oil for the hydraulic system. Then, host PC, target PC, I/O board and other hard-wares are connected. Soft-wares and the corresponding driver board are applied to collect data. In order to test the performances of the pressure, velocity and displacement under the condition of the valve-control system and pump-control system, the two systems are tested with the same working conditions. The performance of repeatability and energy efficiency are also obtained. The results show that it’s feasible to apply servo pump to hydraulic press machine. And under the pump-control condition, the velocity and pressure performance of press machine is more stable.