A calibration-independent laser-induced incandescence technique for soot measurement by detecting absolute light intensity

Laser-induced incandescence (LII) has proved to be a useful diagnostic tool for spatially and temporally resolved measurement of particulate (soot) volume fraction and primary particle size in a wide range of applications, such as steady flames, flickering flames, and Diesel engine exhausts. We present a novel LII technique for the determination of soot volume fraction by measuring the absolute incandescence intensity, avoiding the need for ex situ calibration that typically uses a source of particles with known soot volume fraction. The technique developed in this study further extends the capabilities of existing LII for making practical quantitative measurements of soot. The spectral sensitivity of the detection system is determined by calibrating with an extended source of known radiance, and this sensitivity is then used to interpret the measured LII signals. Although it requires knowledge of the soot temperature, either from a numerical model of soot particle heating or experimentally determined by detecting LII signals at two different wavelengths, this technique offers a calibration-independent procedure for measuring soot volume fraction. Application of this technique to soot concentration measurements is demonstrated in a laminar diffusion flame.     

Two-dimensional measurement technique for birefringence vector distributions: measurement principle

The two-dimensional measurement principle for a birefringence vector distribution in transparent materials is analyzed. The system nonuniformity that results from the system components makes the two-dimensional measurement principle quite different from that of a point-measurement method, and the measurement principle requires a two-dimensional analysis. A pulsed optical phase modulation is employed to simplify the two-dimensional mathematical analysis. As a result, concepts are proposed of the system function that characterizes the system nonuniformity that results from the system components and of the intrinsic function that is related to the birefringence vector distribution in a birefringent sample. The influence of the system nonuniformity on the two-dimensional measurement is eliminated by measurement of the intrinsic function, whereas its two values allow for the mathematical separation of the birefringence vector components. The effectiveness of the two-dimensional analysis is illustrated by measurement of a birefringence vector distribution, which is induced by an internal stress distribution in a poly(methyl methacrylate) plate, owing to the photoelastic effect.     

Concurrent measurement of temperature and soot concentration of pulverized coal flames

This paper presents a novel instrumentation system for the concurrent measurement of temperature and soot concentration of pulverized coal flames. The system operates on the two-color principle, combining CCD camera optical sensing and digital image processing techniques. The temperature and its distribution in a flame are calculated from the ratio between the grey-levels of corresponding pixels within two images captured at two carefully selected wavelengths. The soot concentration distribution of the flame is represented and estimated using the KL factor that is derived from intermediate information obtained during the temperature measurement. The system is calibrated using a tungsten lamp as a standard temperature source. The maximum relative error in the temperature measurement is 1.83%. Experimental results obtained on a 0.5 MW/sub th/ combustion test facility show that the temperature distribution of a coal-fired flame ranged from 1380 to 1700/spl deg/C, while the KL factor ranged from 0.18 to 0.33.     

Speckle technique for measurement of turbulence characteristics

The possibilities of speckle photography for determination of the characteristics of turbulence for gas-dynamic flows are analyzed. It is shown that by using two-exposure speckle photography, the energy spectrum and the scales of turbulence can be calculated, while one-exposure speckle photography provides information on the energy and anisotropy of turbulent pulsations. Academic Scientific Complex “A. V. Luikov Heat and Mass Transfer Institute, Academy of Sciences of Belarus,” Minsk, Belarus. Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 69, No. 5, pp. 805–810, September–October, 1996.     

Modified sonic technique for crack velocity measurement

Four modifications to the Kerkhof method of measuring crack velocities in glass greatly sharpened the timing Wallner lines and permitted measurements over the full range of crack velocities.

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Résumé On montre que quatre modifications de la méthode de Kerkhof pour mesurer les vitesses de fissuration dans le verre affinent les lignes de Wallner apparaissant en fonction du temps, et permettent des mesures sur la gamme entière des vitesses de fissuration.

     

动态压力测试技术介绍

动态压力特性是表征非稳态流动过程的有效参量,对应的测试技术是相关领域科研及工程作业的重要内容。该文分别对动压传感器的原理、标定、动压测试系统的安装与使用进行了总结和介绍,阐述一些测试过程的注意事项和关键环节,为科研工作者和工程技术人员开展相关工作提供了借鉴。     

Self-calibrating ultrasonic technique for crack depth measurement

A configuration of transducers together with a self-calibrating measurement technique is proposed to investigate the reflection and transmission of surface waves by a surface-breaking or near surface defect. By means of this technique, the ratio of the reflection and transmission coefficients (R/T and/orT/R) can be obtained in a reliable and accurate manner. The reflection and transmission of surface waves for oblique incidence on a surface breaking crack is investigated in detail. Information onT/R for the latter case can be used to determine the depth of the crack. The experimental measurements ofT/R show excellent agreement with theoretical results.     

Orientation-averaged light-extinction characteristics of compound particles including aggregate effects

Orientation-averaged light-extinction characteristics of compound sulfate-carbon-soot particles have been analyzed with a discrete-dipole algorithm (DDSCAT code) for r1/r2 (ratio of primary-particle radius to secondary-particle radius) in the range 7 to 1 and for wavelengths from 0.4 to 0.8 microm. It was found that compound particles above a particle radius of approximately 0.2 microm exhibit light-extinction characteristics that closely match those of a pure sulfate particle. The shielding of the carbon particle by the primary particle apparently reduces the absorption effect of the soot particle over the range of all possible orientations. In light of the fact that soot particles tend to be small in comparison with host sulfate particles, the light-extinction characteristics of compound particles are dictated by the optical properties of the host particles. This result has been applied for aerosol aggregates with log-normal size distributions. For r1/r2 > or = 2 the aggregate extinction coefficient of a group of compound particles remains within 12% of that of a group consisting only of sulfate particles. This allows for effective calculation of the overall aerosol light extinction on the basis of the optical and geometrical properties of the constituent particles without having to include a compound-geometry effect.     

Oscillating-cup technique for yield stress and density measurement

We discuss a possibility for simultaneous measurement of different viscometric properties by the oscillating-cup technique. The emphasis is on the following problems related to liquid metal viscometry: identification of non-Newtonian fluid flow and combined viscosity/density measurement. The cases of Bingham and Newtonian fluids are analysed in detail. The basic features of nonlinear fluid flow, viscometer oscillations, modelling of experiment and data processing are systematized and interpreted in terms of linear viscous fluids.     

电流脉冲加热瞬态热物性测量技术

对国内外电流脉冲加热技术的发展状况进行了综述评价.针对获取温度方法不同,主要介绍了黑体法、积分球法和激光偏振法三种基本形式的测量系统,进而介绍了扩展参数测量装置.又较为详细地介绍了作者自己研制的测量装置和特点.最后作者展望了电流脉冲加热技术的最新研究动态和发展方向.     

An experimental micromechanics measurement technique for submicrometre domains

Orthogonal arrays of dots applied to surfaces can be used to directly measure microscopic strain fields. The spatial and strain resolution are both limited by the size of the dots placed on the surface. Two techniques using the beam of a scanning electron microscope (SEM) have been developed which make possible the placement of very fine dots with diameters of only 0.5 and 0.02 m, respectively, on the surface of the specimen, allowing local strain measurements on the scale of 0.2–10 m when specimens are loaded in the SEM. Measurements of strains fields around the tips of growing cracks in both polymers and polymeric composites are presented to illustrate the capabilities of the technique.     

Optimal intensity-modulation projection technique for three-dimensional shape measurement

A new pattern projection technique for measuring three-dimensional topography is presented, called the optimal intensity-modulation projection technique. The proposed technique dramatically shortens the measurement time and improves stripe detection accuracy compared with previous methods. Furthermore, the method deals reliably with discontinuous patterns and multiple objects.     

Two-color laser-induced incandescence (2C-LII) technique for absolute soot volume fraction measurements in flames

A two-color version of the laser-induced incandescence (2C-LII) technique was implemented for measuring absolute soot volume fraction in flames. By using a calibrated tungsten ribbon lamp, soot peak temperatures were measured as a function of fluence at several locations in an ethylene diffusion flame by using a steeply edged laser beam profile. Above a certain fluence threshold, peak temperatures were tightly distributed just above 4000 K independent of the particle size and number density. Radial profiles of soot volume fraction were obtained and compared (not calibrated) with results from the laser extinction technique. Good agreement showed the validity of the 2C-LII technique at a controlled fluence.     

Transient two-dimensional fuel-concentration measurement technique

We propose a nonintrusive experimental technique, the transient fuel-concentration measurement technique (TFMT), that is capable of being used to measure two-dimensional profiles of transient fuel concentrations over an open liquid fuel surface. The TFMT is based on single-wavelength holographic interferometry; its response time is less than 1 mus and spatial resolution is 0.1 mol. %/0.1 mm. It was applied to measure both methanol vapor and n-propanol vapor concentrations. To assess the accuracy of the technique, our results were compared with steady-state methanol and n-propanol fuel-vapor concentrations measured by other researchers with a microsampling technique combined with gas chromatography. We found the TFMT to be accurate for on-line monitoring of two-dimensional profiles of fuel-vapor concentrations.     

机床几何精度的在线激光测量与快速校准技术

为了改善机床的几何精度,达到高精度的三维空间定位,必须对它的垂直度误差与直线度误差进行测量与校正.传统的激光测量方法花费时间长,成本高.由ISO及ASME提出并由波音公司等应用的体对角线测量方法虽然速度快、成本低,但不能有效分离误差源.现介绍一种由美国光动公司发明的基于体对角线分步(或矢量)激光测量方法,该方法速度快、准确度高、成本低,可以分离误差源并对其提供补偿与校正.