Electric discharge control of flow separation on oblique airfoil

The possibility of controlling flow separation on an oblique airfoil using dielectric-barrier discharge has been experimentally studied. The experiments were performed at subsonic flow velocities in a broad range of the angle of attack. The results of measurements of the velocity and surface pressure fields and an analysis of the flow patterns show that the application of electric discharge allows the interval of the angles of attack for separation-free flow past the airfoil to be significantly increased. Various discharge regimes have been studied, including those with continuous activation by single voltage pulses with a frequency of 0.5–5 kHz and by pulse trains at a repetition rate of 1–100 Hz. The efficiency of the flow separation control has been studied as dependent on the electrical parameters, frequency characteristics, and position of the discharge relative to the flow separation line.     

Boundary layer separation in a laminar supersonic flow with energy supply source

The influence of electric discharge in a supersonic gas flow on the separation of a laminar boundary layer has been studied by numerical methods. The discharge is modeled by an energy supply source with preset intensity and configuration. It is established that the behavior of flows in the system with thermally insulated and isothermally cooled walls differs in a broad range of the heat source power. The possibility of controlling the boundary layer separation is demonstrated.     

梳状电极结构对大气压表面放电的影响

研究了梳状电极结构对大气压表面放电的影响,发现频率固定时放电电流随着外加电压的增加而增加,而电压固定时在某个频率范围内放电电流有最大值;在相同的电压和频率下较宽的电极条宽可以产生较大的放电电流,而电极条间距对放电电流几乎没有影响;用整块金属板做接地电极相比于梳状接地电极可以产生较大的放电电流;另外,较厚的高压电极可以在介质板表面产生更明亮、厚度更大的放电等离子体.     

Localization of a Pulse-Periodic Surface Discharge Blown over by Viscous Gas

The paper deals with the problems associated with the dynamics of development of a creeping discharge on the surface of a dielectric plate in a flow of viscous gas. It is demonstrated that conditions exist under which a discharge separates from the substrate surface. The pattern of temperature relaxation in the boundary layer is investigated, and the frequency mode is determined in which the process of separation may be suppressed.     

Suppressing a Laminar Flow Separation Zone by Spark Discharge at Mach Number M = 1.43

The influence of flow perturbations generated by an electric discharge on the region of interaction between a shock wave and laminar boundary layer in the flow on a flat plate at a Mach number of M = 1.43 has been experimentally studied. The oblique shock wave generated by a wedge mounted above the plate induced separation of the flow, while perturbations in the flow were introduced by a spark discharge on the model plate surface. It is established that the discharge leads to the formation of turbulent and thermal spots. The turbulent spot suppresses the separation zone, while the thermal spot leads to a local increase in the boundary layer thickness in the interaction zone.

     

Preparation of gas separation membranes by plasma polymerization with fluoro compounds

Plasma polymerization coatings were applied for the preparation of gas separation membranes. Mainly fluoro compounds were used as coating materials. The membranes showed good separation characteristics with high flux for gaseous systems. The plasma polymerization composite parameter given by W/FM plays an important role in obtaining excellent separation characteristics. The correlation between the conversion rate DR/FM, where DR is the deposition rate of plasma polymer, and W/FM is useful to consider the plasma polymer character under the different plasma polymerization conditions (discharge power W and monomer flow rate F). The proper conditions for membrane preparation lie in the intermediate region between the region in which the monomer flow rate is deficient and that in which the discharge power is deficient. Furthermore, the plasma polymerization coatings with the higher molecular weight monomer gave the higher separation characteristics. Plasma polymer composite membranes in this study showed superiority for the molecular sieve type of separation over the solution-diffusion type of separation.     

Operating parameters of a hollow-cathode-discharge melting furnace

The factors influencing the operation and discharge beam power are examined in detail. After start-up, when the cathode is heated to its operating temperature, the discharge is stable over a wide variety of conditions. The interaction of cathode/anode separation, cathode geometry, beam-constricting magnet settings and argon flow rate are considered in relation to beam power. A restricting condition is shown to exist if the discharge beam broadens to a width greater than the internal diameter of the furnace. Evidence supporting the theory that the dischange begins between one and two diameters above the bottom inside the cathode is also presented.     

内压缩空分流程增压空气流路组织的比较

通过对两种容量内压缩流程空分设备的计算 ,对氧气压力为 3 1MPa的内压缩空分流程增压空气流路的组织进行了分析比较 ;指出采用中抽流程比较经济 ,并给出了两种容量空分设备配套空气增压机的最佳末级排压。     

射频等离子体放电的宏观参数与PET表面改性的关系

通过射频等离子体放电，采用O2，CF4及CH4／CF4混合气体等离子体对PET表面进行处理。改变射频等离子体放电的宏观参数，如放电时间、放电功率、电极间距离和复合参数，详细地研究了这些参数对PET表面改性的影响。结果表明：碳氟混合气体等离子体在PET表面的沉积速率为正值，在PET表面形成了聚合物；而O2和纯CF4气体的沉积速率为负值，两者在PET表面产生刻蚀效应。增加等离子体放电功率和放电时间，聚合或刻蚀效果更明显；而增加电极间距离和复合参数，聚合或刻蚀效果明显减弱。     

新型PDP放电单元着火特性的研究

采用数值方法 ,研究了新型荫罩式PDP(SM PDP)放电单元的着火特性 ,并与传统表面放电式PDP(ACC PDP)作了比较。计算了沿不同放电路径下的气体着火电压 ,讨论并分析了两种结构中 ,某些结构参数的变化对于着火特性的影响。模拟发现 ,SM PDP单元的着火电压要低于ACC PDP ,且在两种结构中 ,电极间距、放电空间大小、介质层对着火电压的影响程度也有一些不同。     

碳氢化合物对泵压流程空分设备安全性的影响及措施

泵压流程空分设备的安全隐患主要来自高压换热器。本文根据甲烷、乙烷、丙烷和乙烯四种烃类形成固相析出的条件 ,评估在不同的液氧泵排压情况下高压换热器的安全性 ,理论上液氧以 0 3MPa以上的压力在换热器内蒸发是安全的 ,但工程上应从更安全的角度来考虑。因此当液氧泵排压低于 1MPa时 ,应设置辅助蒸发器进行全浸式液氧蒸发和采取 1%至 3%液氧稀释排放措施 ,以确保装置的安全性。     

Current density distribution measurement of negative point-to-planecorona discharge

The current density distribution on the plate electrode of a point-to-plane corona discharge is measured with a computer-controlled measuring system. The measurements are taken by rotating the plate which consist of built-in arrays of orthogonal probes. The current-density distribution can be measured for different separation distances between the point electrode and the plane electrode while the applied high voltage can be varied from the voltage required for the onset of corona discharge to 30 kV. The current-density distribution of a single needle is symmetric around its center point within the accuracy of the measurement system. However, the current-density distribution is radially nonuniform. The computer-controlled measuring system is capable of measuring the current distribution of single point and multipoint electrodes     

Sensing and control of flow separation using plasma actuators

Single dielectric barrier discharge plasma actuators have been used to control flow separation in a large number of applications. An often used configuration involves spanwise-oriented asymmetric electrodes that are arranged to induce a tangential wall jet in the mean flow direction. For the best effect, the plasma actuator is placed just upstream of where the flow separation will occur. This approach is generally more effective when the plasma actuator is periodically pulsed at a frequency that scales with the streamwise length of the separation zone and the free-stream velocity. The optimum frequency produces two coherent spanwise vortices within the separation zone. It has been recently shown that this periodic pulsing of the plasma actuator could be sensed by a surface pressure sensor only when the boundary layer was about to separate, and therefore could provide a flow separation indicator that could be used for feedback control. The paper demonstrates this approach on an aerofoil that is slowly increasing its angle of attack, and on a sinusoidally pitching aerofoil undergoing dynamic stall. Short-time spectral analysis of time series from a static pressure sensor on the aerofoil is used to determine the separation state that ranges from attached, to imminent separation, to fully separated. A feedback control approach is then proposed, and demonstrated on the aerofoil with the slow angle of attack motion.     

建立快速测定空分设备液氧中氧化亚氮的分析方法

介绍一种利用毛细管热导检测器气相色谱法(GC-TCD)测定空分设备液氧中氧化亚氮的检测方法。比较了填充柱和毛细管柱、脉冲放电检测器和热导检测器的优缺点,从生产实际出发,确定选择10m的毛细管PQ柱和热导检测器的搭配,对空分设备旁冷凝器的液氧中氧化亚氮含量进行监控。实际运用情况表明:该方法具有分析准确、过程时间短和稳定性好的优点。     

空分设备冷箱内配管优化设计

随着空分设备向大型化、多样化发展,冷箱内部管道不断增多,配管难度也越来越高。对冷箱内配管进行优化设计,以提高空分设备运行的安全性和经济性。文章从单元设备、阀门及冷箱板开孔位置布置,与单元设备相连管道布置,换热器热端管道布置,水平管道敷设和排放管道引出方式等10方面,介绍杭氧对冷箱内配管所做的优化设计,旨在提高空分设备的经济性和运行安全性。     

Steadying the instability of a glowing discharge in a longitudinal air stream

We have studied experimentally the temperature of a gas and the strength of the electric field for a glowing discharge in a longitudinal stream of air. We have derived a two-dimensional distribution of the reduced field strength E/N in the gas discharge tube. Numerical studies have been conducted into the kinetics of a dry-air plasma. We have calculated the ionization factors, and the factors for adhesion and separation of electrons. Through comparison of experimental and theoretical data we propose a model for the contraction of the glowing discharge with an adhesive instability mechanism.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 60, No. 3, pp. 458–463, March, 1991.     

Performance characteristics of energy separation in a steam-operated vortex tube

Energy separation performance of a steam-operated vortex tube is experimentally investigated, and some reasonable criteria and expressions to estimate the energy separation performance are also introduced. The performance characteristics defined by the above expressions are the same as those of ideal gas in the high superheated region, and are well expressed independently of the degree of superheat, total mass flow rate and discharge resistance. When steam is in the wet region at the nozzle outlet, the performance considerably decreases because of the energy waste from moisture vaporization. And no energy is separated when the dryness fraction is less than approximately 0.98. Some technical data including the optimum operating conditions are also offered.     

液氧管路泄漏的应急处理

KDON-6800/2000型空分设备液氧去喷射器阀门前法兰出现液氧大量泄漏,在不影响生产、不进行空分设备停车后排液的情况下,尝试着对泄漏点进行应急处理,效果良好。介绍液氧泄漏现象、堵漏的工具和效果,分析应急处理方法的意义以及注意事项。     

Preparation of Superhydrophilic and Underwater Superoleophobic Nanofiber‐Based Meshes from Waste Glass for Multifunctional Oil/Water Separation

The deterioration of water resources due to oil pollution, arising from oil spills, industrial oily wastewater discharge, etc., urgently requires the development of novel functional materials for highly efficient water remediation. Recently, superhydrophilic and underwater superoleophobic materials have drawn significant attention due to their low oil adhesion and selective oil/water separation. However, it is still a challenge to prepare low‐cost, environmentally friendly, and multifunctional materials with superhydrophilicity and underwater superoleophobicity, which can be stably used for oil/water separation under harsh working conditions. Here, the preparation of nanofiber‐based meshes derived from waste glass through a green and sustainable route is demonstrated. The resulting meshes exhibit excellent performance in the selective separation of a wide range of oil/water mixtures. Importantly, these meshes can also maintain the superwetting property and high oil/water separation efficiency under various harsh conditions. Furthermore, the as‐prepared mesh can remove water‐soluble contaminants simultaneously during the oil/water separation process, leading to multifunctional water purification. The low‐cost and environmentally friendly fabrication, harsh‐environment resistance, and multifunctional characteristics make these nanofiber‐based meshes promising toward oil/water separation under practical conditions.     

Sliding electric arc discharge as a means of aircraft trajectory control

The dynamics of sliding electric arc discharge and the formation of shock waves in the stages of leader motion and the electric arc development in a supersonic air flow behind the shock wave have been studied for an initial pressure of 0.09–0.5 atm (bar). The air flow in the discharge was imaged using an optical system comprising a shadow device (IAB-458), an optical interference attachment (RP-452), and a modified ruby laser (OGM-20) producing 10–15 output pulses per pumping pulse. Stable initiation of sliding electric arc discharge takes place in a supersonic air flow behind the shock waves with 1.7<M<3.4. This discharge produces shock waves leading to separation of the boundary layer and to an increase in the pressure at the surface. These shock waves can be used for modifying gasdynamics in the air flow streamlining the surface and for controlling the motion of an aircraft.