Analysis and Characterization of Premixed CH₄/Air Flame Based on Invariant Transform of 2D CH∗-Chemiluminescence Measurements

Abstract

This work describes the development of a flame analysis and characterization technique based on the application of invariant transform to the measured optical data of flame images. In this technique, we utilize matrix-norm analysis to obtain the scalar quantity of the post-transform images, which are specific to each global equivalence ratio, or flame state. To demonstrate the potential of the proposed technique, the invariant transform of a time-resolved projection image of a CH₄/air flame captured by a CCD camera was compared with those obtained by computed tomographic reconstruction (CT) at three different equivalence ratios: 0.97, 1.09, and 1.29. The results show that the invariant transform can determine flame states more effectively than the projection and reconstruction data. It is also found that if care is taken in selecting an appropriate nonlinear kernel function for a particular flame image data, a tradeoff between computational time and the ability to extract flame information is optimized. Thus, it is feasible to implement the technique as an online visualization and analysis tool for combustion process monitoring and control.

Keywords:

• CH∗-Chemiluminescence
• Computed tomographic reconstruction
• Invariant transform
• Matrix-norm
• Premixed flame
• Projection

The authors gratefully acknowledge the support provided by the Joint Graduate School of Energy and Environment, King Mongkut's University of Technology Thonburi, the Department of Mechanical Engineering, King Mongkut's University of Technology North Bangkok, and the Royal Golden Jubilee Scholarship program of the Thailand Research Fund. The use of facilities at the Institute of Computer Science, Albert-Ludwigs-University of Freiburg, Germany, and the flame images provided by CORIA, INSA de Rouen, France, are also appreciated.

Notes

where A = gray scale image normalized to [0, 1]. K₁ = 2.6, K₂ = 0.2, K₃ = 0.5, K₄ = 0.2. B₁ = 3.0, B₂ = 5.0, B₃ = 7.0, B₄ = 6.0.