No description available.

Techniques have been developed for measuring the temperature, stable species concentrations, and atomic radical concentrations during a transient combustion event. They combine the features of direct sampling with two spectroscopic techniques to produce relatively simple diagnostic techniques to obtain time-resolved measurements. In this study, a transient event was provided by a propagating hydrogen/air flame. Stable species were detected downstream of the sampling orifice by electron impact fluorimetry, while temperatures and atomic hydrogen concentrations were measured by atomic resonance absorption spectroscopy. The calculation of stable species concentrations from time-varying fluorescence signals was straightforward, however conversion from absorption measurements to temperatures and atomic radical concentrations required the development of a computer model of the radiation source and the absorption by the sample. The model of the source was validated by comparing predicted and recorded spectra of hydrogen Lyman-α emissions, while the absorption model for the sampled gas was tested by comparing the temperatures predicted by absorption measurements with those recorded at a range of known temperatures. These direct sampling spectroscopic techniques minimize time-history distortions inherent in other direct sampling techniques, and are capable of tracking local temperatures and species concentrations during the passage of a propagating flame front. / Graduation date: 1990

No description available.

No description available.

No description available.

Thesis (Ph. D. in Mechanical Engineering)--Vanderbilt University, Dec. 2007. / Title from title screen. Includes bibliographical references.

Call number: LD2668 .T4 1955 W43 / Master of Science

When trace quantities of an alkali element are added to a flame, its optical and electrical properties change significantly. Addition of alkali seed to both premixed and diffusion flames has been used in the development of two new techniques, one for flame temperature measurement and the other for enhanced mixing. Advantage has been taken of the spectral characteristics of alkali seeds in the development of a non-invasive optical flame temperature measurement technique. The strongest resonance line of alkalis is in fact a doublet, and the two peaks can be subjected to different optical treatment. A cesium-seeded flame was exposed to radiation which was selectively filtered to yield different apparent source temperatures at the wavelengths corresponding to the doublet resonance lines. The ratio of the emission peak heights at the two wavelengths relates directly to flame temperature. This technique allows real-time measurement of flame temperatures up to 2800 K. A second process has been investigated which takes advantage of the enhanced electrical conductivity of alkali-seeded diffusion flames. The study first required a characterization of electrical discharges through planar diffusion flames. Because of the increase in conductivity, alkali-seeded diffusion flames can carry current when a transverse electric potential is applied. The behavior of diffusion flames carrying electrical current has been investigated. The dependence on electrode position and gap is reported and the behavior is contrasted with that described in the literature for premixed flames. A planar diffusion flame was subjected to a steady magnetic field parallel to the flow direction while an orthogonal, oscillating current passed through the flame sheet. A Lorentz body force was induced on the flame sheet which acted to move it alternately toward the fuel and oxidizer streams, improving bulk mixing in the flame. High-speed video images of the oscillating flame were analyzed to obtain its maximum lateral velocity. The results compared well with predictions from a simple theoretical model. / Graduation date: 1992

The Babington principle nebulizer, useful for the introduction of samples containing suspended solids, or having high viscosities, into flames or plasmas, has been developed and characterized. Smaller versions of the nebulizer have been shown to provide higher sensitivity and reduced memory relative to the larger devices used previously. Data showing the sensitivities observed with a Babington type nebulizer and a flame emission spectrophotometer at varying flow rates of both the nebulizing gas and the sample solution are presented, along with an evaluation of several nebulizer configurations and tip sytles. The effect of nebulizing gas orifice size upon sensitivity is discussed. Although the Babington principle nebulizer will tolerate samples of varying viscosity, the nebulization efficiency is affected by the sample solution viscosity. A Babington type nebulizer employing a sample heater has been constructed and evaluated using motor oils of differing grades, and has been shown to reduce the effect of viscosity for this class of samples. This heated Babington type nebulizer has been used to develop a method for the analysis of wear metals in oil which does not require sample pretreatment. The effect of polymeric viscosity index improving additives commonly added to motor oils on the sensitivity of the method has been explored, as well as the effect of different complexing agents which may be used in the preparation of standards. A new method is described for numerically evaluating the inverted Abel integral equation, used to extract information about interior regions of flames and plasmas from spatially resolved data obtained from side-on measurements. This method, based upon cubic spline approximations, is compared to modifications of two methods drawn from the literature over a range of data set sizes and with varying amounts of noise superimposed upon the signal. The results of this study give a basis for selecting the best method for transforming experimental data of varying quality, and also for estimating the reliability of the results of the computation. An appendix describes the design and development of an instrument, computer interface, and software package which allow spatial mapping of spectroscopic sources at high speed. Suggestions are given for future work in these areas.

Thesis (Sc.D.)--Massachusetts Institute of Technology, Dept. of Chemical Engineering, 1981. / MICROFICHE COPY AVAILABLE IN ARCHIVES AND SCIENCE. / Bibliography: leaves 936-960. / by James D. Bittner. / Sc.D.