Multiangular Absorption Diagnostics of a Turbulent Argon-Methane Jet

Absorption techniques are being applied to three-dimensional combustion diagnostics. Convolution, Fourier transforms, and iterative algorithms have already been proven in x-ray absorption tomography and interferometric applications. They are currently being tested and compared on their ability to determine typical pollutant and radical concentrations as they appear in flames or exhausts. The effect of the number of scans is analyzed for parallel beams. A tradeoff exists between accuracy and the number of viewing angles. A five-angle procedure gives 10% accuracy with a moderately filtered convolution algorithm. An experiment feasibility study shows that the near time-continuous three-dimensional maps of concentration as low as 1 ppm can be obtained at repetition rates up to 20 KHz. The potential of this method was demonstrated in the laboratory. A diluted methane jet was observed at several sections along its axis. Time-averaged two-dimensional profiles were reconstructed from the absorption scans effected from six and twelve angles. The theoretically predicted dependence of the accuracy on the number of observation angles was verified. Real-time experiments are now being prepared.

[1]  R. Gordon.  A tutorial on art (algebraic reconstruction techniques) , 1974 .

[2]  Norman Chigier,et al.  A laser tomographic investigation of liquid fuel sprays , 1980 .

[3]  R S Ledley.  Introduction to computerized tomography. , 1976, Computers in biology and medicine.

[4]  T. G. Kyle,et al.  The effect of pressure and temperature on the half-width of the methane absorption at 3.39μ , 1972 .

[5]  C K Patel,et al.  Laser Detection of Pollution , 1978, Science.

[6]  A. C. Riddle,et al.  Inversion of Fan-Beam Scans in Radio Astronomy , 1967 .

[7]  Gabor T. Herman,et al.  Image Reconstruction From Projections , 1975, Real Time Imaging.

[8]  B. F. Logan,et al.  The Fourier reconstruction of a head section , 1974 .

[9]  E. David Hinkley,et al.  Laser monitoring of the atmosphere , 1976 .

[10]  Steven A. Tretter,et al.  Introduction to Discrete-Time Signal Processing , 1976 .

[11]  H. Barrett,et al.  Computerized tomography: taking sectional x rays , 1977 .

[12]  P. Hanst,et al.  Infrared Spectroscopy and Infrared Lasers in Air Pollution Research and Monitoring , 1970 .

[13]  J. Bendat,et al.  Random Data: Analysis and Measurement Procedures , 1987 .

[14]  Robert J. Santoro,et al.  Optical tomography for flow field diagnostics , 1981 .

[15]  G. Herman,et al.  Algebraic reconstruction techniques (ART) for three-dimensional electron microscopy and x-ray photography. , 1970, Journal of theoretical biology.

[16]  R. Goulard,et al.  Retrieval of arbitrary concentration and temperature fields by multiangular scanning techniques , 1976 .

[17]  M. Schlindwein.  Iterative Three-Dimensional Reconstruction from Twin-Cone Beam Projections , 1978, IEEE Transactions on Nuclear Science.

[18]  M. Chahine.  Inverse Problems in Radiative Transfer: Determination of Atmospheric Parameters , 1970 .

[19]  H. Fleming,et al.  INDIRECT MEASUREMENTS OF ATMOSPHERIC TEMPERATURE PROFILES FROM SATELLITES: I. INTRODUCTION , 1966 .

[20]  D. Sweeney,et al.  Measurement of three-dimensional temperature fields above heated surfaces by holographic interferometry , 1974 .

[21]  Robert D. Matulka,et al.  Determination of Three‐Dimensional Density Fields from Holographic Interferograms , 1971 .

[22]  G. N. Ramachandran,et al.  Three-dimensional reconstruction from radiographs and electron micrographs: application of convolutions instead of Fourier transforms. , 1971, Proceedings of the National Academy of Sciences of the United States of America.

[23]  R. Hanson,et al.  Shock tube spectroscopy: advanced instrumentation with a tunable diode laser. , 1977, Applied optics.

[24]  Y. S. Kwoh,et al.  A generalized |ω|-filter for 3-D reconstruction , 1977, IEEE Transactions on Nuclear Science.

[25]  R. A. Brooks,et al.  Principles of computer assisted tomography (CAT) in radiographic and radioisotopic imaging , 1976, Physics in medicine and biology.