Three-dimensional flame measurements with large field angle.

Kuanliang Wang,Fei Li,Hui Zeng,Xilong Yu

doi:10.1364/oe.25.021008

Kuanliang Wang, Fei Li + Show 2 more

Open Access

https://doi.org/10.1364/oe.25.021008

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Abstract

A system for three-dimensional computed tomography of chemiluminescence was developed to measure flames over a large field angle. Nine gradient-index rods, with a 9 × 1 endoscope and only one camera are used. Its large field of view, simplicity, and low cost make it attractive for inner flow field diagnostics. To study the bokeh effect caused by the imaging system on reconstruction solutions, fluorescent beads were used to determine the blurring function. Experiments using a steady diffusion flame were conducted to validate the system. Three models, namely the clear-imaging, out-of-focus imaging, and deconvolution models, were utilized. Taking the bokeh effect into account, the results suggest that based on run-times the deconvolution model provides the best reconstruction accuracy without increasing computational time.

Highlights

Using just the emitted photons of combustion reaction, chemiluminescence measurements of combustion provide an important indicator of heat release rates [1,2,3,4], equivalence ratios [2, 5], excited species concentrations [6, 7], without the need for lasers to be subjected to harsh conditions
Three-dimensional computed tomography of chemiluminescence (CTC) (3D-CTC) has been widely studied because of the great improvements in optical sensing capabilities and computing technologies, and the high resolution and instantaneous 3D measurements that have become achievable in practice
To measure the flame under large field angles while mitigating blurring, we propose a low-cost 3D-CTC system that combines a gradient-index (GRIN) lens with a customized fiber with nine inputs and one output

Summary

Introduction

Using just the emitted photons of combustion reaction, chemiluminescence measurements of combustion provide an important indicator of heat release rates [1,2,3,4], equivalence ratios [2, 5], excited species concentrations [6, 7], without the need for lasers to be subjected to harsh conditions. Floyd et al [8] systematically studied various projection models and reconstruction algorithms, as well as resolutions from different viewpoints and noise They greatly reduced the equipment required in performing CTC that enable high resolution 3D measurements to be much more viable. In their experiments [9], ten commercial cameras in combination with mirrors provided simultaneous multi-directional projections of the flame.

CTC technique formulation

Coordinates calibration

Flames for the validation experiment

Results

Conclusion