网幕通道式液体获取装置水平出流性能研究

为研究网幕通道式液体获取装置水平出流性能,以矩形多孔网幕通道为对象,构建基于体积流量边界的水平出流模型,并搭建实验平台,对网幕阻力系数与出流过程网幕两侧压差分布进行测试。研究了水平出流过程网幕穿透压损与局部流量等参数的沿程变化规律,对比分析了网幕选型与通道尺寸对装置出流性能的影响。结果表明:模型预测结果与文中实验数据吻合良好,平均相对误差为3.5%;网幕穿透压损与局部取液量均沿流动方向逐渐增大,且不均匀性随流量增大而加剧,通道出口处网幕穿透压损取得最大值,具有最大的泡破风险;相同流量下,细孔网幕通道出流均匀性更高,针对低流量与高流量工况,分别采用粗孔和细孔网幕时泡破风险更低;通道质量一定时,减小长宽比,有利于穿透压损和流量均匀分布,同等质量增量下增加通道宽度更有利于降低穿透压损。

Influence of Blade Outlet Angles on Separation Performance of Guide Vane Type Axial Flow Cyclone Tube

The influences of the internal and external outlet angles on separation performance and flow field are compared and analyzed. Two arc functions are employed for controlling the internal and external angles. The separation process in the cyclone tube is calculated by using two-fluid model based on the Eulerian-Eulerian method.The results show that the structure with the internal outlet angle smaller than the external one is more beneficial to the separation performance. It is found that the small internal angle can help increase the swirl number,while the small external angle can help increase the friction coefficient. Several groups of numerical simulations are conducted for the air intake unit of the gas turbine in practice. When the internal outlet angle is 35° and the external outlet angle is 40°,the blade has sufficient cyclone strength and the separation rate of particles with diameters of 10—100 μm is between70%—98%. The small blade angle is more conducive to the separation of fine particles,leading to violent collision of large particles on the outer wall and reduction of separation efficiency. In addition,reducing the external angle is conducive to the discharge of large particles.

Effects of Clearance between Rotor and Ground on the Performance of an Open Cross-Flow-Type Nano-Hydraulic Turbine

Flows through an open cross-flow-type nano-hydraulic turbine are numerically simulated to investigate the effects of the clearance Hc between the rotor and the ground on the turbine performance. A two-dimensional particle method is employed, which was successfully used for flow simulations of impulse-type and open cross-flow-type nano-hydraulic turbines in the authors＇ previous works. When the clearance Hc is smaller than a critical value, the simulated turbine performance decreases with decreasing Hc, in good agreement with the experiment. The simulations make it clear that such a reduction of turbine performance is attributable to an increase in the circumferential component of the water velocity at the rotor outlet. The simulations also demonstrate that the effect of the tip speed ratio of the rotor on the relation between Hc and turbine performance can be analyzed.

High Performance Double-Interleaved Dual Boost Converter and 3 Phase Grid Connected Converter for Wind Turbine

This paper proposes a high performance double-interleaved dual boost （DIDB） technique to solve the problems of high ripple current, large inductor size and the requirement of step-up transformer in many case found in the conventional DC-DC boost converter. The 3-phase grid connected converter with decoupling control give an independent control between active and reactive power using the load current feed-forward. With this technique, the disturbance rejection and the output power quality can be improved. Experiments are conducted with three case studies： 1） a test of the DIDB converter to determine current ripple and voltage gain, 2） a test of the 3-phase grid connected converter to determine DC-link voltage regulation, power factor and total harmonic distortion （THD）, and 3） a test of the overall system with a 7.5 kW wind turbine simulator by step and various input wind speeds to determine the output power at the grid side and verify the maximum peak power tracking （MPPT） performance. The results can confirm that the DIDB converter gives lower ripple current and higher voltage gain than the conventional converter. For the grid side, the 3-phase grid connected converter can regulate the DC-link with fast dynamic response to disturbance rejection and low overshoot while complying with the THD standard defined in IEEE 519-1992. In addition, the MPPT controller is able to achieve the maximum energy capture with the various input wind speeds.

Effects of Measuring Positions on the Measured Aerodynamic Performance of a Centrifugal Compressor

This paper performs a numerical simulation of three-dimensional flow field in a centrifugal compressor with long inlet and outlet pipes using CFX software.By arranging virtual probes at different positions in both inlet and outlet planes,the aerodynamic performance of the centrifugal compressor is measured and compared with each other.Then effects of measuring positions on measurement results are discussed.The results show that it will generate notable measuring errors of the pressure ratio and efficiency if the inlet total pressure is measured using a single-point probe.The inlet total pressure data can be accurate when they are measured using a 3-point rake.The outlet total pressure and total temperature data can not be accurate if they are respectively measured at one circumferential position even using a multi-point rake.Increasing tangential measuring positions at the outlet is effective to improve the test accuracy.When the outlet total pressure and total temperature are respectively measured at 3 tangential positions,the data can be almost accurate.