Single-sensor filter-intensified fiber optic 4D tomographic CH* chemiluminesence flame measurements

Abstract

Chemiluminesence is one of the most common reacting flow visualization techniques, in which a narrowband wavelength associated with species radicals is captured on an image sensor. This technique can provide key insights into flame physics, particularly when a full 3D field can be extracted. Tomographic imaging can capture 3D instantaneous information, but becomes impractical to use when the technique is extended to larger, heavier high-speed imaging equipment. This has resulted in many researchers using fiber-based endoscopes (FBE) to capture multiple views on a single image sensor. However, the introduction of the fiber bundle and corresponding equipment to image specific combustion radicals results in a low SNR imaging environment when captured at high repetition rates. Additionally, when varying equivalence ratios, the signal can become further diminished because the combustion radicals signal weakens at fuel rich and fuel lean conditions. Therefore, this work determines the efficacy of using a filter-intensified FBE approach to capture the CH* radical of a hydrocarbon flame under varying equivalence ratio conditions by comparing the resulting reconstructions to previous quantitative flame measurements.

A Survey for 3D Flame Chemiluminescence Tomography: Theory, Algorithms, and Applications

“…A nine inputs optical fiber bundle-based experimental setup was proposed by Q. Lei et al to transmit the CH* chemiluminescence signals of the swirl flame in the gas turbine to one high-speed camera (Dong et al, 2021b;Rising et al, 2021). Recently, considering the drawbacks of FBT of low SNR imaging and signal diminishment with various equivalence ratios, C. Rising et al proposed a filter-intensified FBE approach to capture the CH* radical and obtained more precise reconstruction results (Ishino and Ohiwa, 2005).…”