Simultaneous imaging of CH^*, C2∗, and temperature in flames using a DSLR camera and structured illumination

Abstract

Measurement of chemical species and temperature mapping in flames is essential to understanding the combustion process. Multiple cameras are conventionally employed for measurement in such scenarios making the experimental setup not only cost-intensive but also challenging. To circumvent this, structured illumination (SI)-based methods are reported for multispecies chemiluminescence (CL) imaging using a single camera. In this paper, we demonstrate four-channel SI-based imaging for simultaneous snapshot CH∗ and C2∗ CL imaging and two-color pyrometry for temperature profiles in a butane diffusion flame. We demonstrate our approach using individual species and multiple species imaging. Taking the advantage of the axisymmetric nature of the flame, the Abel transform is performed on the line-of-sight averaged images to obtain deconvoluted images. The deconvoluted maps of temperature are compared with the temperature data obtained by using a physical thermocouple probe.

Comparison between Different Optical Configurations of Active-FRAME Setup in Multispectral Imaging of Flames

“…Active FRAME is based on the active illumination of the sample using lasers thus the laser source is modulated using a grating [16]. Conversely, in passive FRAME, the optical signals emerging from the sample, i.e., dye-doped droplet fluorescence or flame luminosity are spatially encoded on the way to the camera [24,25]. In active FRAME, the coded signal pertaining to each species is recorded in the form of a first-order peak in the Frequency domain (Fourier space) as a result of spatial encoding of the laser sheet.…”

Denoising of Images for Temperature and Chemiluminescence Measurements of Premixed Flames Applying the Abel Transform

“…Full-field optical techniques are usually used to make this kind of measurement because they give a global description of the process and do not disturb the sample. On the other hand, simultaneously measuring several variables is preferable because this avoids the lack of correlation between them [9,[16][17][18][19]. However, a complex optical setup is usually employed for measurement in such cases, making the task costly and challenging [16,18].…”

“…On the other hand, simultaneously measuring several variables is preferable because this avoids the lack of correlation between them [9,[16][17][18][19]. However, a complex optical setup is usually employed for measurement in such cases, making the task costly and challenging [16,18].…”

“…This study, as in others, corroborates that the maximum temperature value is obtained at a value of Φ = 1.05 for LPG fuel. Other variables that can be connected directly to the flame equivalence ratio are the temperature and radical intensities (chemiluminescence) [10][11][12][13][14][15][16][17][18][19]. In a combustion process, some released species are OH, CH, CH 2 O, and C 2, which have a specific emission spectrum [10][11][12][13][14][15][16][17][18][19].…”

“…Other variables that can be connected directly to the flame equivalence ratio are the temperature and radical intensities (chemiluminescence) [10][11][12][13][14][15][16][17][18][19]. In a combustion process, some released species are OH, CH, CH 2 O, and C 2, which have a specific emission spectrum [10][11][12][13][14][15][16][17][18][19]. In these combustion flames, the presence of radicals C * 2 and CH * are inherent in the reaction zone.…”