Numerical Investigation of Flow Fields in Inductively Coupled Plasma Wind Tunnels

Numerical simulations of 10 kW and 110 kW inductively coupled plasma （ICP） wind tunnels were carried out to study physical properties of the flow inside the ICP torch and vacuum chamber with air as tile working gas. Two-dimensional compressible axisymmetric Navier- Stokes （N-S） equations that took into account 11 species and 49 chemical reactions of air, were solved. A heat source model was used to describe the heating phenomenon instead of solving the electromagnetic equations. In the vacuum chamber, a four-temperature model was coupled with N-S equations. Numerical results for tile 10 kW ICP wind tunnel are presented and discussed in detail as a representative case. It was found that the plasma flow in the vacuum chamber tended to be in local thermoehemical equilibrium. To study the influence of operation conditions on the flow field, simulations were carried out for different chamber pressures and/or input powers. The computational results for the above two ICP wind tunnels were compared with corresponding experimental data. The computational and experimental results agree well, therefore the flow fields of ICP wind tunnels can be clearly understood.     

Turbulent drag reduction by spanwise slot blowing pulsed plasma actuation

This work studies the turbulent drag reduction (TDR) effect of a flat plate model using a spanwise slot blowing pulsed plasma actuator (SBP-PA). Wind tunnel experiments are carried out under a Reynolds number of 1.445 × 104. Using a hot-wire anemometer and an electrical data acquisition system, the influences of millisecond pulsed plasma actuation with different burst frequencies and duty cycles on the microscale coherent structures near the wall of the turbulent boundary layer (TBL) are studied. The experimental results show that the SBP-PA can effectively reduce the frictional drag of the TBL. When the duty cycle exceeds 30%, the TDR rate is greater than 11%, and the optimal drag reduction rate of 13.69% is obtained at a duty cycle of 50%. Furthermore, optimizing the electrical parameters reveals that increasing the burst frequency significantly reduces the velocity distribution in the logarithmic region of the TBL. When the normalized burst frequency reaches f+ = 2πfpd/U∞ = 7.196, the optimal TDR effectiveness is 16.97%, indicating a resonance phenomenon between the pulsed plasma actuation and the microscale coherent structures near the wall. Therefore, reasonably selecting the electrical parameters of the plasma actuator is expected to significantly improve the TDR effect.     

纳米钼粉制备用高频感应等离子体装置的设计与优化

针对制备纳米钼粉的设备普遍存在能耗高和可操作性低的问题，文中设计了一种高频感应等离子体装置，并对多处结构进行了优化。设备使用10 kW电源，具有功率低和体积小的特点；进料器为分离式结构，可以均匀加料且无振动干涉；进料器与反应器用卡套式管接头连接，使用标准零件，连接牢固且成本低；反应器的边气和反应气进口各2个，冷却水进口有3个，进气和冷却都更均匀，冷却范围覆盖整个等离子体区域，可有效避免石英管过热损坏；收集器是双层结构，外层是箱体，内层是过滤网和收集皿，收集皿从箱体底部安装，卸料时打开收集皿底部的卸料孔即可，操作简单方便。