A Design of Magic Tee with Coplanar Arms

Magic tee is a widely used component in microwave systems; the four arms of conventional magic tee direct at four different directions, which give inconveniences to the assemblage of a system. In this paper, a broad-wall slot directional coupler and an E-plane dielectric loaded waveguide phase shifter is used to form a magic tee with four arms in the same E-plane. The magic tee is analyzed exactly with mode match method; and the simulated annealing method is used to optimize the performance of the magic tee. Simulation results are presented, which show good performance.     

气体非稳定爆轰波在具有声学吸收壁的直角三通弯管中传播特性研究

本文实验研究了丙烷、氧气和空气的预混气体非稳定爆轰波在具有声学吸收壁的直角三通弯管中传播特性，分析了声学吸收材料厚度对非稳定爆轰波传播特性的影响．实验结果表明，在直角三通弯管中安装声学吸收材料对气体非稳定爆轰波有明显的衰减作用，在弯管前后非稳定爆轰波的传播速度和压力都有很大程度的减小．而且随着声学吸收材料厚度的增加，气体非稳定爆轰波强度衰减幅度增大．这一实验结论对工业安全具有重要的参考价值．     

Two-phase flow in a horizontal equal-sided impacting tee junction

Pressure-drop and phase-distribution data were generated for air–water flows in a horizontal impacting tee junction. All three sides of the junction (37.8-mm i.d.) were oriented horizontally. The data correspond to a junction pressure of 1.5 bar (abs), ambient temperature, inlet flow regimes of wavy, stratified, and annular, and a wide range of mass splits at the junction. Most of the range for the phase-distribution data corresponds to conditions that were untested in previous investigations. In general, it was found that the phases did not distribute themselves evenly between the two outlets unless the mass split is equal. There is a serious lack of data in the literature on the two-phase pressure drop in impacting tee junctions and therefore, the present data add substantially to the existing data. A mechanistic model capable of predicting the phase distribution and pressure drop was developed and shown to be in general good agreement with the present data and others from the literature.     

T型混合反应器内共沉淀法制备吡啶硫酮铜

在T型混合反应器内通过喷射共沉淀方法合成了吡啶硫酮铜(CPT).利用扫描电镜和小角度光散射实验手段研究了分散液中吡啶硫酮铜的形貌和大小。通过喷射共沉淀方法获得的初级吡啶硫酮铜颗粒为棒状, 在分散液中这些棒状颗粒易发生团聚, 形成分形维数为2.1的团聚体。用平均回转半径(R_g)表征分散液中团聚体的平均大小, 考察了反应温度和反应物化学计量比(吡啶硫酮钠/硫酸铜)对团聚体大小的影响, 随着反应温度的降低, 团聚体的回转半径逐渐减小;过量的吡啶硫酮钠也有利于降低团聚体的大小, 当吡啶硫酮钠过量量达到~25%时, 进一步增大吡啶硫酮钠的过量量, 团聚体的回转半径不再发生明显变化。     

T型混合反应器内共沉淀法制备吡啶硫酮铜

在T型混合反应器内通过喷射共沉淀方法合成了吡啶硫酮铜(CPT)。利用扫描电镜和小角度光散射实验手段研究了分散液中吡啶硫酮铜的形貌和大小。通过喷射共沉淀方法获得的初级吡啶硫酮铜颗粒为棒状,在分散液中这些棒状颗粒易发生团聚,形成分形维数为2.1的团聚体。用平均回转半径()表征分散液中团聚体的平均大小,考察了反应温度和反应物化学计量比(吡啶硫酮钠/硫酸铜)对团聚体大小的影响,随着反应温度的降低,团聚体的回转半径逐渐减小;过量的吡啶硫酮钠也有利于降低团聚体的大小,当吡啶硫酮钠过量量达到~25%时,进一步增大吡啶硫酮钠的过量量,团聚体的回转半径不再发生明显变化。     

Large-eddy simulation of fluid mixing in tee with sintered porous medium

Mixing processes of hot and cold fluids in a tee with and without sintered copper spheres are simulated by FLUENT using the large-eddy simulation (LES) turbulent flow model and the sub-grid scale (SGS) Smagorinsky-Lilly (SL) model with buoyancy. Comparisons of numerical results of the two cases with and without sintered copper spheres show that the porous medium significantly reduces velocity and temperature fluctuations because the porous medium can effectively restrict the fluid flow and enhance heat transfer. The porous medium obviously increases the pressure drop in the main duct. The porous medium reduces the power spectrum density (PSD) of temperature fluctuations in the frequency range from 1 Hz to 10 Hz.     

A Compact Monopulse Radial Line Slot Array Antenna at Millimeter Wavelengths

This paper describes the design and performance of a radial line slot array antenna (RLSA) which generates sum or difference far field patterns. The antenna consists of rectangular waveguide to radial line transition, radial line and slot arrays etched on the upper plate of the radial line. A novel rectangular waveguide to radial line transition is designed to build up the dominate TEM mode in radial line to excite the slot arrays which are arranged in concentric rings on the upper plate of the radial line. The antenna radiates linear polarization at Ka band. Monopulse operation is obtained by a sum and difference network which is a compact eight-port comparator consisting of coplanar magic tees. The sum and difference network is waveguide structure whose loss is less than that of microstrip structure at millimeter wave lengths. The monopulse performances can be used in monopulse tracking and anti-collision application etc. Genetic algorithm (GA) is applied to optimize the parameters of the transition and antenna to obtain good performances. Note: Part of this paper has been presented in the oral session ThuA5 on Transmission Lines and Antennas in IRMMW-THz2006 Conference, pages: 535.Number: 376636Title: Radial line slot array antenna at millimeter wave lengths     

Experimental investigation of two-phase flow splitting in an equal-sided impacting tee junction with inclined outlets

Phase-distribution data have been generated for two-phase (air-water) flow splitting at an impacting tee junction with a horizontal inlet and inclined outlets. This investigation also considered the possibility of full separation at the junction and the effect of the outlet angle of inclination on partial separation at various inlet conditions. A flow loop with the ability to incline the outlets from horizontal to vertical was constructed. The operating conditions were as follows: test section inside diameter (D) of 13.5 mm, nominal junction pressure (P_s) of 200 kPa (abs), near ambient temperature (T_s), inlet superficial gas velocities (J_G1) ranging from 2.0 to 40 m/s, inlet superficial liquid velocities (J_L1) ranging from 0.01 to 0.18 m/s, inlet qualities (x₁) ranging from 0.1 to 0.9, mass split ratios (W₃/W₁) from 0 to 1.0, and inlet flow regimes of stratified, wavy, and annular. The data reveal that the degree of maldistribution of the phases depended on the inlet conditions, the mass split ratio at the junction, and the inclination angle of the outlets.