Development and Validation of Evaluation Methods for 3D Flame Propagation Speed of Turbulent Non-premixed Edge Flames via Tomographic Chemiluminescence

This work reports the development and validation of evaluation methods for measurements of 3D, instantaneous, local flame propagation speed on a turbulent methane jet diffusion flame. Despite its fundamental importance to turbulent flame research, the experimental measurements for 3D flame propagation speed are scarce due to the complexity of turbulent flame surfaces and the mathematical challenges. Existing evaluation methods based on surface fitting and normal vectors cannot be readily extended to a laboratory-scale, turbulent flame. Two new methods were therefore developed to address this issue. The methods were validated numerically with artificially created phantoms and experimentally with 3D flame structures obtained by tomographic chemiluminescence on a turbulent jet flame. The methods were demonstrated to be able to evaluate the 3D flame propagation speed of complex flame structures with significantly enhanced accuracy and robustness. Based on the evaluations, the relationship between flame propagation speed and curvature was studied on the presented flame.