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471.
本文给出了用激光多普勒测速仪(LDA)测量涡旋式电弧等离子体化学反应器流场的实验研究结果。实验表明:这类等离子体反应器中,旋流切向速度分量和轴向速度分量径向分布划分成近轴、过渡和近壁区。喷入电弧等离子体射流对等离子体反应器流场的影响区域是近轴区,对过渡区和近壁区没有影响。提高旋流强度,轴向截面上旋流的两个速度分量径向分布分别呈相似的分布形式,等离子体反应器呈层流流动状态。 相似文献
472.
473.
主要研究等离子电弧加热弯曲成形过程中薄板的厚度、长度、宽度以及薄板扫描线距自由端的距离等对等离子电弧弯曲成形的影响。 相似文献
474.
《中国航空学报》2021,34(4):518-525
Plasma figuring process enables the correction of metre-scale optical surfaces, which has advantages such as rapid convergence to ultra-precision accuracy level, no subsurface damage, ease of upscale thanks to the conditions of operation at atmospheric. Such attributes make plasma figuring a highly competitive technology. To maintain a stable discharge of plasma for long period, a robust Plasma Delivery System (PDS) is required for large optics manufacturing. A dedicated PDS, mainly based on an L-type radio frequency (RF) network and an inductively coupled plasma (ICP) torch, had been previously proposed and designed. This study addresses the requirement for improving the robustness and securing the performance of the plasma etching. Due to the complexity of interactions of PDS parameters, single variable optimization is conducted for adjusting the impedance of the plasma torch. The PDS optimization is analysed based on ignition power demand, test repeatability and reflected power values. The results show that reflected power values are controllable within 10 W, when the RF power is supplied from 200 W up to 800 W. Finally, plasma processing is carried out on fused silica glass, using the optimum parameters of the PDS. 相似文献
475.
等离子体激励低速分离流动控制实验研究 总被引:3,自引:1,他引:2
通过风洞流动显示实验,研究了等离子体激励低速条件下对平板表面分离剪切层的控制特性.结果表明等离子体激励在失速迎角附近可以有效抑制平板上的流动分离,实现流动的完全再附.在大迎角下可以显著减小平板完全分离后分离区的宽度.对比五种不同电极的实验,发现对于给定的输入电压及频率,负极宽度越宽,电极内侧正向间距越宽,其流动控制效果越好.最后通过改变发烟钢丝的位置和来流状况,证明了等离子体对周围流场的吸附和加速作用,对等离子体激励控制流动分离的机理进行了分析. 相似文献
476.
477.
Punam Kumari Prasad Asit Saha 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2021,67(1):9-19
Bifurcation analysis of ion-acoustic wave (IAWs) solutions of the nonlinear Schrödinger equation (NLSE) is explored for the first time in an electron-ion (e-i) magnetized solar wind plasma. The existence of ion-acoustic (IA) periodic, superperiodic, kink, antikink, compressive and rarefactive solitary wave solutions are revealed. Special values of Solar wind plasma parameters at a normalized distance from the Sun are considered for numerical simulation. The IA wave solutions are derived analytically. These solutions are analyzed numerically considering the influence of parameters, namely, wave number (k), velocity (V) of traveling wave and nonextensive parameter (q). Computational simulation reveals that only IA periodic wave grows in amplitude as waves moves from the Sun. 相似文献
478.
R.P. Aswathy G. Manju 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2021,67(4):1254-1260
The seasonal and solar activity variation of the post sunset F- region zonal plasma drift, at the magnetic equatorial region over Indian longitudes is analyzed using the Republic of China Satellite-1 data from January 2000 to April 2004. The post sunset F- region zonal drifts are observed to be higher in the years of high solar activity in comparison with low solar activity, while seasonally the drifts are minimum in summer with much higher values in other seasons. The seasonal and solar activity variations of zonal plasma drift are attributed to the corresponding variations in the neutral winds. The dependences of the F region peak vertical drift on the zonal plasma drift at 18.5 IST (Indian Standard Time) and the time difference of the conjugate points sunset times, are quantitatively analyzed. Further an integrated parameter (incorporating the above mentioned two independent factors), which is able to predict the peak vertical drift and growth rate of Rayleigh Taylor instability is proposed. The other major outcome of the study is the successful prediction of the Equatorial Spread F (ESF) onset time and duration using the new integrated parameter at 18.5 IST. ESF irregularities and associated scintillations adversely affect communication and navigation systems. Hence, the present methodology for the prediction of the characteristics of these nocturnal irregularities becomes relevant. 相似文献
479.
推进器羽流的电磁矢量控制是基于电磁位形的改变使得喷射的羽流改变方向。为了原理性验证电推进羽流电磁矢量控制技术,针对螺旋波电推进器,开展了磁场位形调制仿真设计和试验验证。说明了电磁矢量调制线圈能够改变磁场位型,并且在试验过程中验证了等离子体羽流随磁场位型变化而产生的羽流方向偏转。在周期性磁场调制过程中,验证了等离子体密度参数随之周期性涨落。螺旋波电推进羽流方向最大偏转角度60°,可控偏转频率15Hz,说明了电推进羽流电磁矢量控制的可行性。 相似文献
480.
《中国航空学报》2020,33(12):2999-3010
Technological miniaturization has enabled the development of small satellites weighing as little as 1 kg. Unfortunately, there is still a lack of suitable efficient micropropulsion systems at these scales. The pulsed plasma thruster is a structurally simple form of electric propulsion. This simplicity also makes it ideally suited for miniaturization. Its history can be traced back to applications in satellites that are much larger than micro/nano-satellites. The vast majority of modern pulsed plasma thrusters use solid polytetrafluoroethylene (PTFE) as a propellant. Unfortunately, at lower discharge energy levels such as those necessitated by the power limitations of micro/nano-satellites, PTFE has a tendency to exhibit carbon deposition, which can ultimately lead to thruster failure. In this new era of small satellites, it is important to consider alternative propellants in the miniaturization of pulsed plasma thrusters. This brief review discusses the needs and limitations of small satellites and alternative propellants that may be able to meet these needs. Such propellants may be able to offer advantages such as a longer thruster lifetime, a higher specific impulse, or a higher thrust-to-power ratio. This would enable the development of different types of pulsed plasma thrusters that can be tailored towards specific mission requirements. 相似文献