Three-dimensional flame measurements with large field angle.

Area of Science:

• Optical diagnostics
• Combustion science
• Imaging systems

Background:

• Accurate measurement of inner flow fields in flames is crucial for combustion research.
• Traditional imaging systems often face limitations in field of view and cost.
• Understanding optical system effects like bokeh is vital for accurate reconstruction.

Purpose of the Study:

• To develop a cost-effective 3D computed tomography system for chemiluminescence measurements.
• To investigate and mitigate the impact of the bokeh effect on flame reconstruction.
• To compare different imaging models for optimal reconstruction accuracy.

Main Methods:

• A 3D computed tomography system utilizing nine gradient-index rods and a 9x1 endoscope with a single camera was designed.
• Fluorescent beads were employed to characterize the blurring function (bokeh effect) of the imaging system.
• Three reconstruction models (clear-imaging, out-of-focus, deconvolution) were applied to experimental data from a steady diffusion flame.

Main Results:

• The developed system offers a large field of view, simplicity, and low cost, suitable for inner flow field diagnostics.
• The bokeh effect was quantified using fluorescent beads.
• The deconvolution model demonstrated superior reconstruction accuracy compared to other models when accounting for the bokeh effect, without increasing computational load.

Conclusions:

• The 3D computed tomography system is effective for large-field chemiluminescence measurements.
• Incorporating the bokeh effect into the deconvolution model significantly improves reconstruction accuracy.
• This approach provides a practical and computationally efficient solution for flame diagnostics.