Mid-infrared laser-absorption diagnostic for vapor-phase measurements in an evaporating n-decane aerosol

A novel three-wavelength mid-infrared laser-based absorption/extinction diagnostic has been developed for simultaneous measurement of temperature and vapor-phase mole fraction in an evaporating hydrocarbon fuel aerosol (vapor and liquid droplets). The measurement technique was demonstrated for an n-decane aerosol with D ₅₀∼3 μ m in steady and shock-heated flows with a measurement bandwidth of 125 kHz. Laser wavelengths were selected from FTIR measurements of the C–H stretching band of vapor and liquid n-decane near 3.4 μm (3000 cm ⁻¹), and from modeled light scattering from droplets. Measurements were made for vapor mole fractions below 2.3 percent with errors less than 10 percent, and simultaneous temperature measurements over the range 300 K<T<900 K were made with errors less than 3 percent. The measurement technique is designed to provide accurate values of temperature and vapor mole fraction in evaporating polydispersed aerosols with small mean diameters (D ₅₀<10 μ m), where near-infrared laser-based scattering corrections are prone to error.     

Tunable diode laser absorption sensor for the simultaneous measurement of water film thickness,liquid- and vapor-phase temperature

A four-wavelength near-infrared (NIR) tunable diode laser sensor has been developed for the simultaneous measurement of liquid water film thickness, liquid-phase temperature and vapor-phase temperature above the film. This work is an important improvement of a three-wavelength concept previously introduced by Yang et al. (Appl. Phys. B 99:385, 2010), which measured the film thickness in environments with known temperature only. In the new sensor, an optimized combination of four wavelengths is chosen based on a sensitivity analysis with regard to the temperature dependence of the liquid water absorption cross section around 1.4 μm. The temperature of liquid water and the film thickness are calculated from absorbance ratios taken at three wavelength positions assessing the broad-band spectral signature of liquid water. The vapor-phase temperature is determined from the absorbance ratio of two lasers rapidly tuned across two narrow-band gas-phase water absorption transitions. The performance of the sensor was demonstrated in a calibration cell providing liquid layers of variable thickness and temperature with uncertainties smaller than 5% for thickness measurements and 1.5% for liquid-phase temperatures, respectively. Experiments are also presented for time-resolved thickness and temperature measurements of evaporating water films on a quartz plate.     

Novel method for simultaneous measurement of film thickness and mass fraction of urea–water solution

Quantitative knowledge of the film thickness and mass fraction of the urea-water solution is very crucial in many practical applications. Film thickness or mass fraction can only be determined individually by conventional measurement techniques. We develop a novel measurement method to measure the film thickness and mass fraction of ure~water solution simultaneously. The absorption coefficients of urea-water solution （5 50 wt%） are measured, a pair of optimized wavelengths is then chosen to achieve high measurement sensitivity. Cross validation is also performed and uncertainties of the technique are smaller than 0.68% for thickness measurements and 1.86% for mass fractions.     

Numerical simulation of laser ignition of a liquid fuel film

Numerical simulations were used to examine a set of interrelated physicochemical processes involved in the ignition of a liquid fuel film by a low-power laser beam. The delay time of ignition of a liquid fuel film and the ignition zone location were determined. The scale of influence of the power and radius of the laser beam on the ignition characteristics was determined. The ignition criteria of ignition were identified.     

Simultaneous diode-laser-based in situ measurement of liquid water content and oxygen mole fraction in dense water mist environments

We performed what we believe are the first simultaneous in situ measurements of liquid water and oxygen concentrations in a dense water mist environment. Direct absorption tunable diode laser absorption spectroscopy was used to make oxygen concentrations and simultaneously quantify the liquid water via optical density measurements. This spectrometer with an absorption path length of only 36.8 cm was successfully tested during full-scale fire suppression tests with scattering losses up to 99.9%. The simultaneous oxygen and liquid water concentration measurements agree with fire suppression model calculations.     

Optical measurement of instantaneous liquid film thickness based on total internal reflection

An optical method of measuring the instantaneous transparent liquid film thickness, based on the effect of total internal reflection by the gas-liquid interface, is represented. A light circle whose diameter is proportional to the liquid film thickness and eccentricity is proportional to the slope gradient of the liquid film surface in the measurement region is formed around a small-size light source in the plane of vessel bottom. Using several light sources, the method allows measurement of the liquid film thickness field. The method is implemented in a multichannel meter of transparent liquid film thickness and curvature surface, with computer image processing.     

Determination of thin film refractive index and thickness by means of film phase thickness

A new approach for determination of refractive index dispersion n(λ) (the real part of the complex refractive index) and thickness d of thin films of negligible absorption and weak dispersion is proposed. The calculation procedure is based on determination of the phase thickness of the film in the spectral region of measured transmittance data. All points of measured spectra are included in the calculations. Barium titanate thin films are investigated in the spectral region 0.38–0.78 μm and their n(λ) and d are calculated. The approach is validated using Swanepoel’s method and it is found to be applicable for relatively thin films when measured transmittance spectra have one minimum and one maximum only.      

微纳间隙受限液体的界面黏着机理研究

利用球-盘接触黏着试验仪对微量受限液体的界面黏着行为的研究发现：临界体积范围内（皮升到纳升）的受限液滴达到临界厚度后将出现自动铺展和瞬时收缩行为（分别对应球-盘趋进和分离过程）,并同时提供一定幅值的法向黏着力及伴随出现力的突变;该界面黏着力与液滴体积、球的直径等相关,并很好地揭示了昆虫或树蛙爪垫与光滑表面间的湿黏着行为.在进一步试验的基础上,利用球—面接触模型的毛细黏着力公式对所观察到的试验现象进行了机理揭示,认为临界体积受限液滴出现的自动铺展和瞬时收缩行为与接触副的刚度相关,最大法向黏着力随液体体积的减小而减小,与接触副之间受限液体的中心区厚度有关.结合生物黏着爪垫进行了受限液体界面黏着控制机理的分析,可以指导仿生黏着爪垫的设计与控制. 关键词： 生物黏着爪垫 毛细黏着力 受限液体     

Interaction of a premixed flame with a liquid fuel film on a wall

In piston engines and in gas turbines, the injection of liquid fuel often leads to the formation of a liquid film on the combustor wall. If a flame reaches this zone, undesired phenomena such as coking may occur and diminish the lifetime of the engine. Moreover, the effect of such an interaction on maximum wall heat fluxes, flame quenching, and pollutant formation is largely unknown. This paper presents a numerical study of the interaction of a premixed flame with a cold wall covered with a film of liquid fuel. Simulations show that the presence of the film leads to a very rich zone at the wall in which the flame cannot propagate. As a result, the flame wall distance remains larger with liquid fuel than it is for a dry wall, and maximum heat fluxes are smaller. The nature of the interaction of flame wall interaction with a liquid fuel is also different from the classical flame/dry wall interaction: it is controlled mainly by chemical mechanisms and not by the thermal quenching effect observed for flames interacting with dry walls: the existence of a very rich zone created above the liquid film is the main mechanism controlling quenching.     

Polarization modulation imaging ellipsometry for thin film thickness measurement

A polarization modulation (PM) imaging ellipsometer is proposed and setup in order to measure precisely the thickness of thin film. Five images are collected sequentially by CCD camera with respect to five pre-determined azimuth angles of a quarter wave plate (QWP) during measurement. Then two-dimensional (2-D) distributions of the ellipsometric parameters ψ and Δ over the full dynamic range are obtained. Conceptually, PM imaging ellipsometer integrates the features of phase shift interferometry with conventional photometric ellipsometry by rotating the QWP sequentially to produce polarization modulation that is able to measure the thickness of a thin film in two dimensions precisely and quickly. The basic principle of PM imaging ellipsometer is derived wherein features such as common path configuration, full dynamic range of measurement, and insensitive to non-uniform response of the CCD are analyzed. The experimental results verify the ability and performance of PM imaging ellipsometer on 2-D thin film thickness, while the errors regarding the ellipsometric parameters measurements are discussed.     

EUV reflectometry for thickness and density determination of thin film coatings

An EUV reflectometer for the analysis of surfaces and thin films regarding refractive index, surface roughness, and mass density at the wavelength of 12.98?nm was developed. The setup uses a laser produced plasma source with an oxygen gas puff target for the generation of narrow-band EUV radiation and a flexible Kirkpatrick–Baez optics for focusing. We present EUV reflectometry (EUVR) measurements conducted on a series of carbon thin films to determine thickness and mass density of the coatings. In case of the thickness measurements results are compared to data obtained from nondestructive standard methods, i.e., grazing incidence X-ray reflectometry and spectroscopic ellipsometry. In addition, we propose a method to deduce the mass density of a sample directly from the fitted index of refraction obtained from EUVR measurements.     

How topological rearrangements and liquid fraction control liquid foam stability

The stability of foam is investigated experimentally through coalescence events. Instability (coalescence) occurs when the system is submitted to external perturbations (T1) and when the liquid amount in the film network is below a critical value. Microscopically, transient thick films are observed during film rearrangements. Film rupture, with coalescence and eventual collapse of the foam, occurs when the available local liquid amount is too small for transient films to be formed. Similar experiments and results are shown in the two-bubble case.     

Correlation of thickness and magnetization in LCMO film

High quality thin films of La_0.67Ca_0.33MnO₃ (LCMO) of different thickness were grown on LAO substrates by pulsed laser deposition (KrF, λ = 278 nm). The AFM images suggest a twodimensional step-growth. DC magnetization measurements of the films in a field of 500 Oe show that the magnetic ordering temperature is the same for all the films in both FC and ZFC conditions and is the same as that for the bulk. However, a difference is seen between the FC and ZFC magnetization of the films. There seems to be a systematic in this difference with respect to the thickness of the film, with the difference decreasing with thickness. We suggest that the difference in the magnetization under FC and ZFC conditions may be due to strain-induced anisotropy arising from the lattice mismatch between the substrate and the film or due to the shape anisotropy due to epitaxial growth Article presented at the International Symposium on Advances in Superconductivity and Magnetism: Materials, Mechanisms and Devices, ASMM2D-2001, 25–28 September 2001, Mangalore, India.     

大口径光学元件薄膜厚度均匀性修正

 研究了2.2 m高真空箱式镀膜机镀膜时的实际膜厚分布情况。对非球面和平面光学元件,分别采用行星夹具和平面公转夹具并利用修正板调节膜厚均匀性。从实验上实现了大口径薄膜均匀性的调节,并获得较为理想的结果。口径在700 mm范围内,对于凹面均匀性可以控制在0.7%以内,平面均匀性在1%以内;口径在1 200 mm范围内凹面元件均匀性可控制在1%以内,平面1 300 mm口径以内窗口均匀性可控制在1%以内。镀制了口径在400~1 300 mm的多种天文观测上使用的反射镜、增透膜等,获得了理想的光谱曲线与较好的使用效果。     

Structural relaxation behavior of a 30% mole fraction mixture of DMSO and water

The Brillouin spectra of a 30% DMSO-water mixture are analysed at various temperatures from −80°C to +25°C.These measurements, together with the ultrasonic absorption values obtained in the literature, are used to compute the viscoelastic parameters over a large temperature range.In particular,the values of mean structural relaxation times are in good agreement with the literature but a rather broad distribution is found. This fact is confirmed by means of photon correlation technique.     

A novel combustion system for liquid fuel evaporating and burning

To utilize sustainable biofuel, the current study proposes a novel combustion technique that directly burns liquid ethanol without a spray system. Two swirling air flows are induced by tangentially injected the gas from two concentric tubes at different stages. The liquid ethanol is fed by a liquid tank at the center. At the beginning methane flame assists in preheating the system to vaporize liquid ethanol and ignite the vapor. Thereafter methane is switched off, and liquid ethanol can be continuously vaporized through self-burning released heat. The heat and mass transfer processes are examined to illustrate such self-sustained burning–heating–evaporating system. The ethanol flow rate is gradually increased to provide different heat output. The flame structures, temperature distributions and pollutant emissions are carefully examined. The results show that the ethanol can be steadily burned to provide heat output between 0.7 and 2.5?kW. Generally a blue flame is obtained, and the NO_x and CO concentrations are ultralow. By increasing ethanol flow rate to exceed 8?mL/min, an unsteady, sooting flame is observed owing to incomplete evaporation and poor mixing. A parametric study is conducted to evaluate the influences of liquid tank position, flow rate and tip structure on the combustion characteristics. Additionally, an optimal operation condition is proposed. The current study provides a promising method to burn low-boiling liquid fuel in a clean, efficient and compact way.