化学激光器喷注器的流量标定

 为了给燃烧驱动连续波DF/HF化学激光器中喷注器的设计提供参考,采用原级标准（质量-时间法）,对5种不同结构的喷注器进行了流量标定实验,研究了喷注器的流量特性。采用边界层的相关理论,对实验结果进行了科学解释。实验结果显示：随着入口压力的升高,流量系数增大,流量系数的范围是0.677~0.772;在入口压力相同的条件下,流量系数随着通径的增大而增大,随着长度的增大而减小;斜孔的流量系数比尺寸相同的垂直孔略小。     

Development of an on-column enrichment technique based on C18-functionalized magnetic silica nanoparticles for the determination of lidocaine in rat plasma by high performance liquid chromatography

In this study, a novel on-column enrichment technique filled with C(18)-functionalized magnetic silica nanoparticles was successfully developed for the determination of lidocaine in rat plasma by high performance liquid chromatography (HPLC). The synthesized Fe(3)O(4)@SiO(2)-C(18) nanoparticles were locally packed into the capillary by the application of magnets. Lidocaine in the sample solutions pumped into the capillary tube could be easily adsorbed by Fe(3)O(4)@SiO(2)-C(18) through hydrophobic interaction by the interior C(18) groups, and eluted by acetonitrile solution. Different extraction conditions were investigated. Method validations including linear range, quantification limit, detection limit, precision, accuracy and recovery were also studied. The results showed that the proposed method based on on-column enrichment by Fe(3)O(4)@SiO(2)-C(18) was a novel, little solvent and efficient approach for the determination of lidocaine in the complex plasma samples.     

柱头进样结合气相色谱质谱分析动物源食品中热不稳定性氨基甲酸酯类农药

对柱头进样结合气相色谱-质谱法(GC/MS)应用于复杂基体中热不稳定性氨基甲酸酯农药检测的可行性及可靠性进行了探讨.在常规不分流进样和柱头进样模式下,对13种氨基甲酸酯类农药的热不稳定性进行了比较.以猪肉、鸡蛋、牛奶为研究基体,采用乙腈提取,凝胶渗透色谱结合中性氧化铝固相萃取柱净化,柱头进样-GC/MS检测.研究表明:...     

Beam tail effect of a performance-enhanced EC-ITC RF gun

The beam tail effect of multi-bunches will influence the electron beam performance in a high intensity thermionic RF gun. Beam dynamic calculations that illustrate the working states of single beam tail and multi-pulse feed-in of a performance-enhanced EC-ITC （external cathode independent tunable cavity） RF gun for an FEL （free electron laser） injector are performed to estimate the extracted bunch properties. By using both Parmela and homemade MATLAB codes, the effects of a single beam tail as well as interactions of multi-pulses are analyzed, where a ring-based electron algorithm is adopted to calculated RF fields and the space-charge field. Furthermore, the procedure of unexpected deviated-energy particles mixed with an effective bunch head is described by the MATLAB code as well. As a result, the performance-enhanced EC-ITC RF gun is proved to have the capability to extract continual stable bunches suitable for a high requirement THz-FEL.     

Velocity measurements based on shadowgraph-like image correlations in a cavitating micro-channel flow

Cavitation is generally known for its drawbacks (noise, vibration, damage). However, it may play a beneficial role in the particular case of fuel injection, by enhancing atomization processes or reducing nozzle fouling. Studying cavitation in real injection configuration is therefore of great interest, yet tricky because of high pressure, high speed velocity, small dimensions and lack of optical access for instance. In this paper, the authors proposed a simplified and transparent 2D micro-channel (200–400 μm), supplied with test oil at lower pressure (6 MPa), allowing the use of non-intrusive and accurate optical measurement techniques. A shadowgraph-like imaging arrangement is presented. It makes it possible to visualize vapour formations as well as density gradients (refractive index gradients) in the liquid phase, including scrambled grey-level structures connected to turbulence. This optical technique has been already discussed in a previous paper (Mauger et al., 2012), together with a Schlieren and an interferometric imaging technique. In this paper, the grey-level structures connected with turbulence are considered more specifically to derive information on flow velocity. The grey-level structure displacement is visualized through couples of images recorded within a very short time delay (about 300 ns). At first, space and space–time correlation functions are calculated to characterize the evolution of grey-level structures. Space–time correlations provide structure velocity that slightly under-estimates the real flow velocity deduced from flowmeter measurements. Since the grey-level structures remain correlated in time, a second velocity measurement method is applied. An image correlation algorithm similar to those currently used in Particle Image Velocimetry (PIV) is used to extract velocity information, without seeding particles. In addition to the mean velocity of grey-level structures, this second method provides structure velocity fluctuations. In particular, an increase in structure velocity fluctuations is observed at the channel outlet for a critical normalized length of vapour cavities equals to 40–50%, as expected for the real flow velocity fluctuations. The present study is completed by a parametric study on channel height and oil temperature. It is concluded that none of them significantly impact the critical normalized length for which the fluctuation increase is observed, even though the magnitude of these fluctuations is larger for the higher channel.     

Evaluation of X-ray sources for quantitative two- and three-dimensional imaging of liquid mass distribution in atomizing sprays

Quantitative measurement of liquid mass distribution is demonstrated in an impinging-jet atomizing spray using a broadband, ∼80 keV X-ray tube source for 2-D radiography and 3-D computed tomography (CT). The accuracy, precision, and sensitivity of these data are evaluated using narrowband, ∼10 keV, synchrotron radiation from the Argonne National Laboratory Advanced Photon Source (APS) at the same flow conditions. It is found that the broadband X-ray tube source can be used for 2-D measurement of the equivalent path length (EPL) and 3-D CT imaging of liquid mass distribution with typical error of 5–10%. Data are compared for cases with and without the use of potassium iodide (KI), which at 15% concentration by mass increases the attenuation coefficient eightfold and enables 2-D and 3-D measurement of EPL with a signal-to-noise ratio (SNR) of 5:1 down to 15 μm. At this concentration, the effects of energy-dependent attenuation (i.e., spectral beam hardening) are negligible for EPL up to 5 mm. Hence, the use of broadband X-ray tube sources is feasible for many practical engineering sprays with a dynamic range in EPL of ∼330:1. The advantages and limitations of using broadband and narrowband X-ray sources are discussed, and recommendations for improving performance are presented.     

Vaporization of a liquid hexanes jet in cross flow

The vaporization characteristics of a liquid hexanes jet in a lab-scale test section with a plain orifice-type injector were experimentally investigated. The experimental measurements were carried out on the basis of the infrared laser extinction method using two He–Ne lasers (one at 632.8 nm and the other at 3.39 μm). The momentum flux ratio (q_F/A) was varied from 20 to 60 over 20 steps, and the supplying air temperature (T_A) was changed from 20 to 260 °C over 120 steps. The objectives of the current study were to assess the vaporization characteristics of a liquid hexanes jet and to derive a correlation between flow conditions and hexanes vapor concentration in a jet-in-crossflow configuration. From the results of the experimental measurement, it was concluded that hexanes vapor concentration increased with the increase of the momentum flux ratio and the supplying air temperature. An experimental correlation between flow conditions and hexanes vapor concentration (Z_F) was proposed as a function of the normalized horizontal distance (x/d_o), the supplying air temperature (T_A), the momentum flux ratio (q_F/A), the fuel jet Reynolds number (Re_F), and the fuel jet Weber number (We_F).     

Development of a novel high volume band compression injector for the analysis of complex samples like toxaphene pesticide

A new type of injector has been developed for gas chromatographic analysis. The injector has high volume and band compression (HVBC) capabilities useful for the analysis of complex samples. The injector consists essentially of a packed liner operated at room temperature while a narrow heated zone is used to axially scan the liner selectively desorbing the compounds of interest. The scanning speed, distance and temperature of the zone are precisely controlled. The liner is connected to an interface which can vent the solvent or any undesirable compounds, and transfer the analytes to an analytical column for separation and quantification. The injector is designed to be compatible with injection volumes from 1 to more than 250microL. At a low sample volume of 1microL, the injector has competitive performances compared to those of the "on-column" and "split/splitless" injectors for the fatty acid methyl esters and toxaphene compounds tested. For higher volumes, the system produces a linear response according to the injected volume. In this explorative study, the maximum volume injected seems to be limited by the saturation of the chromatographic system instead of being defined by the design of the injector. The HVBC injector can also be used to conduct "in situ" pretreatment of the sample before its transfer to the analytical column. For instance, a toxaphene sample was successively fractionated, using the HVBC injector, in six sub-fractions characterized by simpler chromatograms than the chromatogram of the original mixture. Finally, the ability of the HVBC injector to "freeze" the separation in time allowing the analyst to complete the analysis at a later time is also discussed.     

Density gradients in packed columns: I. Effects of density gradients on retention and separation speed

Density gradients in packed capillary columns operating under the extreme pressure drops typical for solvating gas chromatography were investigated by on-column spectroscopic measurements and compared to a theoretical model. Laser-induced fluorescence was used to follow the elution of various analytes, and Raman spectroscopy was used to measure the density of the mobile phase, each with respect to column position. Mobile phase linear velocity initially increases gradually, and then rises rapidly near the column outlet. High flow rates near the column outlet are offset by a loss of mobile phase solvating power which ultimately limits the speed of separation. These results represent an extreme case for illuminating factors affecting supercritical fluid separation techniques in general.     

光阴极RF腔中微波过程研究

由于光阴极RF腔注入器中电子束的脉冲结构由激光控制的特点,根据其电子束脉冲结构的特点,利用微波腔的等效电路,给出了这种微波腔中微波场变化公式,和关于光阴极RF腔的最佳耦合计算公式,并以CAEP光阴极RF腔注入器为例进行理论分析,给出这些变化对电子束参数(如能散度)的影响. 关键词： 光阴极RF腔注入器 光阴极 注入器 能散度