A Method for Studying Clusterization Processes in a Free Impulse Jet

The possibility of using impulse gas jets for studying clusterization processes is considered. The composition of a molecular beam for an impulse supersonic Ar jet was studied using the mass-spectrometry technique. It was established that the clusterization processes proceed identically during a continuous flow and in a quasi-stationary section of an impulse jet. It was shown that the pulsed technique ensures the reproduction of condensation processes over a wide range of gas-dynamic parameters with a considerable decrease in material and energy consumption.     

A modified setup for gas-dynamic research and technological development

A modified variant of the LEMPUS-1 experimental setup is described, which was designed in order to extend the possibilities of performing investigations of plasma-chemical reactions and cluster-formation processes in gas jets in a pulse outflow regime, as well as technological processes during cluster-ion surface treatment. This setup provides the mass spectroscopy of molecular beams that are formed from supersonic gas jets and gas mixtures, studying of the plasma-chemical reactions that are initiated in jets by self-sustained and nonself-sustained discharges, studying of the cluster formation processes in gas mixtures, simulation of the supersonic-outflow processes with high flow rates from sonic and supersonic nozzles. Installing high-performance oil-free vacuum pumps makes it possible to investigate the processes in gas jets in the presence of hydrocarbon contaminants. Equipping the setup with ionization and flow-acceleration systems provides studying of the interaction processes of clusters and ions with a solid surface during gas-jet treatment of coatings.     

Pulsed blowdown-electron gun facility for low-temperature and high-pressure supersonic flow electronic transition lasers

The design of a small compact pulsed blowdown apparatus coupled to a cold cathode electron gun is described. This system allows the excitation of a gas mixture in supersonic flow at temperatures of 80 and 120 K and density of 1 amagat with a maximum electron beam current density of 20 A cm(-2) at 300 kV and pulse length of 0.5 mus. With this facility it has been possible, using aerodynamic cooling, to achieve high-power, long-pulse ultraviolet laser operation in a high-pressure active medium on XeF and Ne ii ion transitions. A strong increase in fluorescence intensity was also obtained for numerous atomic lines and molecular bands of interest for the developement of high-power, high-efficiency, visible and ultraviolet lasers.     

Supersonic turbine stator design using dense gas with numerical method

In recent years, interest in renewable energy as a substitute for power generation using coal has increased. As a next-generation power system, the Organic Rankine cycle (ORC) system, which requires a multi-stage turbine or a supersonic turbine to generate a high power, has been shown to have high potential for such uses. In this paper, a dense gas is chosen as a working fluid and a supersonic nozzle is designed for a supersonic turbine with advantages in terms of cost, power density and layout. Two stators are designed using the Method of characteristics (MOC) for air and dense gas. To validate the numerical model, the nozzle designed for the air is compared to that of a PIV experiment from the open literature, and the results indicate a reasonable agreement. The nozzle for the dense gas is different as that needed for air. Therefore, the modified MOC is applied based on a polytropic assumption. In conclusion, an estimation of the performance is implemented with loss coefficients for a different number of blades. The number of blades is shown to be proportional to the loss coefficient. For example, the case with the biggest numbers of blades is affected the most by the shock effect that occurs at the trailing edge.

     

Characteristic analysis of supersonic impinging jet in laser machining

The interaction of a gas jet with a workpiece in laser machining is investigated by studying the influence of the processing parameters on the dynamic characteristic of the gas flow in the hole, mainly including the mass flow rate and the thrust. The modeling of a supersonic turbulent jet impinging on a plate with a hole concentric with the jet is presented. Numerical simulations are carried out using an explicit, coupled solution algorithm with solution-based mesh adaptation. The model is able to make quantitative predictions of the effect of the standoff distance on the mass flow rate and the axial thrust. It is revealed that the shape of the hole has weak effects on shock structure, but it can improve the dynamic characteristic slightly. The standoff distance has great effect not only on the shock structure, but also on the jump and fluctuation of the thrust for the different exit Mach number.     

静压气体轴承超声速现象的研究与发展

简述了静压气体轴承的类型及发展,回顾了静压气体润滑轴承中超声速流动现象的理论与试验研究,比较分析了它们的特点与不足,指出供气压力低、承载能力小是传统气体轴承不可克服的缺点。根据气体动力学理论和已进行的相关试验。详细分析了超声速静压气体润滑轴承的性能优势,即没有供气压力的限制,承载能力可以随供气压力的提高成比例提高。计算流体力学的发展为超声速气体轴承的研究提供了有力的技术工具,根据气体轴承内各段不同的流动特点,采用分场计算的方法可以得到精确的气体润滑模型,最后指出了超声速静压气体轴承将成为气体轴承的一个新的发展方向。     

Cutoff probe using Fourier analysis for electron density measurement

This paper proposes a new method for cutoff probe using a nanosecond impulse generator and an oscilloscope, instead of a network analyzer. The nanosecond impulse generator supplies a radiating signal of broadband frequency spectrum simultaneously without frequency sweeping, while frequency sweeping method is used by a network analyzer in a previous method. The transmission spectrum (S21) was obtained through a Fourier analysis of the transmitted impulse signal detected by the oscilloscope and was used to measure the electron density. The results showed that the transmission frequency spectrum and the electron density obtained with a new method are very close to those obtained with a previous method using a network analyzer. And also, only 15 ns long signal was necessary for spectrum reconstruction. These results were also compared to the Langmuir probe's measurements with satisfactory results. This method is expected to provide not only fast measurement of absolute electron density, but also function in other diagnostic situations where a network analyzer would be used (a hairpin probe and an impedance probe) by replacing the network analyzer with a nanosecond impulse generator and an oscilloscope.     

Measuring the mechanical recoil impulse of a polymeric target upon impact of a high power electron beam

A method for measuring the mechanical recoil impulse of a target produced by the relativistic electron beam of the Calamary accelerator is described. A detector based on a piezoelectric sensor is used in measurements. Results of measurements are presented for the mechanical recoil impulse produced by the relativistic electron beam with an energy as high as 300 keV, a current of up to 30 kA, and a duration of ~100 ns that is incident on an epoxy target. The energy flux density on the target surface is varied in the range of 1–10 GW/cm². The maximum measured impulse value is 0.32 N · s at an energy flux density of 10 GW/cm² (an energy fluence of 810 J/cm2).     

Shock tube coupled to the time-of-flight mass spectrometer via a molecular beam sampling system

A method for continuous mass spectrometric analysis of high-temperature reacting gas mixtures is described. The apparatus consists of a unique combination of three devices: the shock tube, the time-of-flight mass spectrometer, and the supersonic molecular beam. The driven section of the shock tube constitutes the reservoir of a supersonic molecular beam by which gas is continuously extracted from the reaction zone and introduced through a two-stage high-capacity vacuum system into the ionization region of the mass spectrometer. The shock tube and the mass spectrometer are coupled at right angles to one another. This configuration avoids excessive pressure buildup in the mass spectrometer system. The apparatus has an estimated mass resolution of 100 amu, a frequency range of 10-100 kHz, and can be operated over a wide range of shock conditions during the complete high-temperature pulse.     

高能聚焦超声清洗聚能器和工具的有限元分析

依据高能聚焦超声清洗原理,研究了高能聚焦超声清洗技术,并且对安装工具后的聚能器进行了有限元分析.试验表明,高能聚焦超声清洗是一种高效、洁净、可连续清洗的先进清洗方法.     

在线补偿天然气流量积算仪

设计了基于ARM9核心的天然气流量积算仪,接收流量变送器输出的模拟信号、脉冲信号或HART信号,设计了压力传感器和温度传感器接口电路;基于WinCE平台上开发了系统软件,输入天然气各种组分及其摩尔分数或百分比后,根据AGA8-92计算方法建立起压缩因子和温度、压力关系的三维数据表,为了保证实时性,利用线性插值方法快速求出测量工况下的压缩因子,将天然气体积流量折算为标准状态下的体积流量,实现在线补偿.可输出4～20 mA电流和脉冲.     

新型材料改性方法——常温超音速冷喷涂制备功能涂层

介绍一种新型材料表面改性技术－冷喷涂技术，即气体在常温下或在有限加热温度下，利用超音速气流将涂层粉末喷射到基板形成保护涂层。相对热喷涂技术而言，其不存在高温氧化、气化、晶化等影响涂层性能的效应出现，具有独到之处。结合工程实际简化建模，并完成气、固两相射流的流场计算结果。定量研究了冷喷涂试验中两相射流流对涂层效果的影响程度。还对该试验装置进行了锌粉、陶瓷粉的膜制备试验，取得了预期效果。     

超声波冲击提高高强度装甲钢焊接接头疲劳强度的应用研究

通过残余应力、疲劳寿命的对比,研究了超声波冲击处理对装甲钢焊接接头的疲劳寿命影响。试验结果表明,在相同载荷与试验条件下,受到超声处理的高强度装甲钢焊接接头疲劳寿命远远高于未受冲击处理的焊接接头。     

A study on prediction of the base pressures for an axi-symmetric body

A flow modeling method has been developed to analyze the flow in the annular base (rear-facing surface) of a circular engine nacelle flying at subsonic speed but with a supersonic exhaust jet. Real values of exhaust gas properties and temperature at an altitude of 30,000 feet are employed. Potential flows of the air and gas streams are computed for the flow past a separated wake. Then a viscous jet mixing is superimposed on this inviscid solution. Conservation of mass, momentum and energy for the wake flow field is achieved by multiple iterations with modest computer requirements.     

Application of the Shack–Hartmann Wavefront Sensor for Monitoring the Parameters of a Supersonic Gas Jet

Results of an experimental study of the density distribution in a small-size (1–2 mm in diameter) supersonic gas jet in vacuum are reported. The measurements are performed by the developed Shack–Hartmann wavefront sensor, which consists of a microlens array with 100 × 100 elements and a video camera with a resolution of 2048 × 2048 pixels. The reliability of measurements in terms of the space and time resolution, as well as in terms of the minimum levels of phase changes induced by the tested object, is analyzed.     

基于小波包方法的超声速气膜气动光学效应相干结构

当高速成像制导导弹在大气中飞行时,其光学窗口承受着严重的气动加热。超声速气膜冷却方法可以有效地隔离外部加热,但是超声速气膜流动会引起光束退化,降低图像质量。为了研究超声速气膜气动光学效应,本文构建了主流马赫数为3.4,设计喷流马赫数为2.5,实际测得喷流马赫数为2.45的超声速气膜实验装置。利用基于纳米粒子的平面激光散射技术获得了高时空分辨率流场图像,并对气膜冷却流动的密度场进行重构,利用光线追迹法获取了对应密度场的光程差。通过将光程差分布和K-H涡对比后发现,光程差的波谷位置对应于涡卷的中心,而光程差的波峰对应于涡卷中心之间的连接部分。但是,随着涡结构的发展破碎,对应关系不再成立。根据超声速气膜NPLS流场图像结果,利用分形原理获取的分形维数结果,将其沿流向划分为三个区域,其对应平坦度分别为3.4,2.9,3.6,验证了区域2更适合进行相干结构提取。     

超声波气体流量计作为结算表的探讨

针对目前太原煤炭气化公司焦化厂超声波气体流量计运行现状,经过现场考察与比对实验,参照近期超声波气体流量计计量数据,通过记录、分析、研究等环节,特对超声波气体流量计的使用情况做出探讨.     

水下航行器燃气涡轮动力系统的多目标函数优化

通过分析水下航行器燃气涡轮机主要结构参数对发动机性能的影响,给出了涡轮动力系统主要结构参数优化的数学模型,对单级、冲动式(带小反力度)、超音速、多速制的燃气涡轮机的设计实例运用遗传算法进行了多目标函数优化设计计算。     

Production of a slit skimmer for use in cold supersonic molecular beams

Cold molecular beams generated by skimming pulsed supersonic gas expansions normally employ conical skimmers. The use of slit shaped skimmers instead of conical skimmers can afford significant signal enhancements. At this time, however, slit shaped skimmers are not available commercially. We describe a straightforward method for producing functional slit skimmers.     

Stability analysis of the confined mixing layer

This paper investigates the linear stability of confined mixing layers with special emphasis on effects of heat release and compressibility. Velocity and density profiles for laminar flows are obtained by solving the compressible boundary-layer equations. The results show that reflection of supersonic disturbances by the walls makes the confined supersonic mixing layer more unstable than the unconfined free shear layer. Decreasing the distance between the walls makes the flow more unstable. However, subsonic disturbances are relatively unaffected by the walls. Mach number hardly changes the growth rates of supersonic disturbances. The most unstable supersonic disturbances are three-dimensional in confined flows.