Advanced Materials Research Vols. 945-949

Abstract: The impinging streams mixer is a new type micromixer. The cavitation phenomenon occurring in the mixers with T-shaped impinging streams (TS), conical impinging streams (CIS), vortex streams(VS) were investigated, respectively. The distribution of flow field in the mixer was simulated and calculated by commercial software Fluent 6.2.1. The results showed that under the same working conditions, a more obvious hydrodynamic cavitation may occur in the CIS type impinging stream than that in the CIS type or the VS type, and the vortex flow lead to an extension of the material residence time in the mixer. The distribution of turbulent kinetic energy and gas holdup were obtained by numerical simulating hydrodynamic cavitation under different entrance pressure conditions. It is showed that when the outlet pressure keeps a constant value, hydrodynamic cavitation can be enhanced by increasing the entrance pressure. The above research can be contributed to the producing of biodiesel and the solving of the key technical problem of oil and alcohol heterogeneous mixing.

Abstract: The unsteady pressure fluctuation is one of the major factors affecting the operational stability of a fire turbopump. Based on the experimental operation conditions of the turbopump, the inner unsteady flow field in the turbopump is simulated by computational fluid dynamics (CFD), and the pressure fluctuations at the zones near the turbine suction chamber, the turbine impeller inlet, the turbine outlet and the interface of pump impeller/volute are investigated by time-frequency analysis methods. The results show that high pressure fluctuation can be observed near the interface of turbine impeller-guide vane and the interface of pump impeller–volute caused by rotor-stator interaction (RSI). Moreover, turbine pressure fluctuation frequencies are identified as the 14 times and 26 times of rotating frequency and the fluctuant amplitude depends on the guide vane inlet angle; whereas, pump pressure fluctuation frequencies are observed at the times of the blade passing frequency (BPF), while the frequencies higher than 10 times of BPF have less effect on the pump vibrations. The results of unsteady pressure pulsation could be used to guide the optimum design of the fire turbopump, which is in favor of obtaining more stable performance of the turbopump.

Abstract: Aiming at the lack of research for key parameters of the cage-type trim of sleeve-type steam trap, the numerical simulation calculation was carried out for the cavitation flow in valve, the influences of orifice types, orifice diameter, guide sleeve types on cavitation were researched. The distribution of pressure, velocity and vapor volume fraction on flow field were got for different sleeve parameters. The results show that using multi-stage sleeve, and decreasing the orifice diameter properly can suppress the occurrence and development of cavitation, and the double orifices structure sleeve is more favorable to anti-cavitation, the gap sleeve is superior to the guide sleeve. It can provide certain references for the research of anti-cavitation and multi-stage depressurization valves.

Abstract: In this paper, we research and develop a new machine called large highland hydraulic intelligent pesticide spraying machine. The pesticide spraying machine adopts hydraulic electric control technology, and adapts to all tall or short crops for pesticide spraying. The machine employs large intelligent computer control technology, and adjusts the spraying dose according to the pest density measured by intelligent sensors. Furthermore, the machine adopts the technology of self-filter and dilutes the pesticide with absorption water automatically. This paper presents hydraulic control system, and puts forward the hydraulic control principle of the walking part, the hydraulic control principle of the work part and main technical parameters.

Abstract: During design the electro-hydraulic servo system, usually choose components based on load matching principle. This paper introduces a selection method of power element parameters based on MATLAB. Compared with the previous analytic method, it greatly save the design time and improve the accuracy.

Abstract: People are constantly committed to seeking new ways that energy saving ventilation can improve indoor air quality. In this paper, methods of theoretical analysis and numerical simulation combining established indoor ventilation jet crash fluid dynamics model to simulate the indoor air, thermal comfort and indoor air quality issues.

Abstract: In order to study the internal flows and hydraulic loss of reducing cross, numerical simulation was carried out on a horizontally installed reducing cross. Three schemes of pipe diameters were studied. The time-averaged N-S equations of three-dimensional steady flows in the reducing pipe were calculated by CFX 14.5 based on the standard - two equation turbulence model together with standard wall function. The results show that the higher the inlet velocity, the hydraulic loss become larger when the split ratios are same for the reducing cross. With the uniform inlet velocities the higher the inlet velocity, the quicker the increasing rate of the hydraulic loss in main pipe, as well as the branch pipe. The integral change rules of hydraulic loss are similar with the condition of uniform flow rate inflow when the flow patterns at inlet are uniform. But with the same spilt ratio, the hydraulic loss of uniform velocity inflow is markedly less than that of uniform flow rate inflow in both main pipe and branch pipe. The bigger the differences of the diameters between the main pipe and the branch pipe, the larger the hydraulic loss of the branch pipe.

Abstract: The nonlinear stiffness and damping properties of the hydro-pneumatic suspension system are introduced, and the nonlinear mathematical model of it is established. Using MATLAB 2009b to establish the computer simulation program and draw out the nonlinear stiffness curve and damping properties curve of the hydro-pneumatic suspension system. Then, researching the influences of related parameters' changes on the nonlinear stiffness and damping properties of the hydro-pneumatic suspension system. The simulation of vehicle dynamic performance research's foundation is provided.

Abstract: To determine the static port’s installation accuracy requirement, the relationship between the step height and the static source error are studied by numerical simulation. It is found that the static pressure is higher than the pressure in far field when the step height is small, which is opposite when the step height is great. And the relative static source error is less than 0.18% when step height is within 0mm to 0.15mm. Besides, the maximum relative error caused by the uncertainty of the step height is found less than 0.06% if the installation accuracy of the static port is 0mm~0.1mm. By comparing the maximum static source error specified by airworthiness regulations, the static port’s installation accuracy requirement of 0.1mm is found to be appropriate.

Abstract: Effects of T-shaped micro-channel structure sizes on the formation of micro-liquid column formed by vertical-shear-flow were studied. The method of CFD based on VOF (Volume of Fluid) model was used in the computation. H₂O and C₅H₃ were used as continuous-phase and as dispersed-phase. Interface-tracking method was used to get data of the two phases. The size parameters include crossing angle (∠β), width ratio of vertical channel and main channel (W₂/W₁), depth ratio of vertical channel and main channel (D₂/D₁), depth-width ratio of main channel (D₁/W₁). The above parameters affect the forming time of micro-liquid columns, the order of importance is D₂/D₁,∠β, D₁/W₁, W₂/W₁; And for the length, the order is∠β, D₂/D₁, D₁/W₁, W₂/W₁. For the shortest forming time, the optimized parameters of ∠β, D₂/D₁, D₁/W₁ and W₂/W₁ are 90°, 1.00, 1.00 and 1.60. To get the shortest micro-liquid columns, the optimized parameters of ∠β, D₂/D₁, D₁/W₁ and W₂/W₁ are 60°, 1.00, 1.00 and 1.60.