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原文传递 LAMINAR FLAME COMBUSTION DIAGNOSTICS USING IMAGING FOURIER TRANSFORM SPECTROSCOPY.

题名：	LAMINAR FLAME COMBUSTION DIAGNOSTICS USING IMAGING FOURIER TRANSFORM SPECTROSCOPY.
作者：	Rhoby,, M. R.; Gross, K. C.
关键词：	Combustion diagnostics, Image processing
摘要：	Combustion diagnostics is a mature field of inquiry with a host of pre-existing experimental research methods. Currently, however, no one method captures timeresolved scalar profile estimates of temperature and major species concentrations with a single instrument. Imaging Fourier transformspectroscopy (IFTS) has the potential to fill that void. IFTS offers several unique advantages for combustion diagnostics such as portability, ease of operation, and the combination of imaging and wide band spectral data. Moderate spectral resolution (up to 0.25cm??1) across a wide band pass (1.5 ?m to 5.5 ?m) captures radiance from many major combustion species simultaneously. High-speed imagery existing within the interferometric measurement can be used with existing flow field analyses performed by infrared cameras. This work provides IFTS with the capability to measure time-resolved 3D imaging of scalar values in laminar axisymmetric flames. This will make IFTS a useful tool for future work in understanding combustion phenomenon, validating chemical kinetic models, verifying numerical simulations, and system performance estimate. Using an IFTS camera, data of a partially-premixed ethylene Hencken burner flame produced at equivalence ratios of 0.8, 0.9, 1.1, and 1.3 was captured. A novel calibration methodology was developed for high-temperature flame sources. A single-layer radiative transfer model retrieved path-averaged temperature, H2O, CO2 and CO column densities that agreed well with previous results. For the = 1.1 flame, the spectrally estimated temperature for a single pixel T = (231819)K, compared to reported laser absorption measurements, T = (2348115)K, and a NASA CEA equilibrium calculation, T = 2389K. Near the base of the flame, absolute concentrations of H2O, CO2, and CO were (12.51.7)%, (10.11.0)%, and (3.80.3)%, respectively. These compared favorably with CEA values of 12.8%, 9.9% and 4.1%. This work helps to establish IFTS as a valuable combustion diagnostic tool and also motivated the need for a multi-layer radiative transfer algorithm and time-resolved spectra reconstruction. Using CFD simulations and measurements of a laminar H2 flame, an algorithm for reconstruction of spectra as a function of the buoyancy-driven harmonic flame period is demonstrated. It is shown that the combination of a band integrated intensity value and its temporal derivative define a unique configuration of the flame’s scalar fields at any time. Through selectively averaging over an ensemble of measurements, interferograms representing the scalar fields at various times can be created and converted into "snapshot" spectra. Integrated line-of-sight radiance profiles reconstructed at various times in a flame’s period compare favorably to previously reported measurements. Comparisons to previously reported values of a similar flame are favorable and agree to within a maximum difference of 18.5%. An inversion method is developed to estimate radially-resolved scalar values and is tested against several simulated laminar flames. Empirical functions estimate flame edge values, improving starting estimates for an onion-peeling process. A three-point, sliding onion-peel inversion provides a fast and flexible, yet reliable estimation of the radial scalar profiles. A global parameter minimization utilizes all data simultaneously for an optimized solution. Results of the inversion agreed with truth to within 1-10%. Flexibility for complex profile shape and sensitivity to trace species is demonstrated. The combination of the "snapshot spectra" algorithm and the scalar field inversion method was applied to measurements of radiation from an unsteady laminar hydrogen flame. Temperature and water concentrations were resolved radially at two different "snapshot" times in the period of the flame’s harmonic motion. Measured results compared favorably with previously reported values of a similar flame and CFD simulations. Temperatures agree to within 11% and water concentration values agree to within 19%. This work demonstrates the ability of IFTS to make time-resolved 3-D maps of scalar values of an unsteady, axisymmetric laminar flame.
报告类型：	科技报告