Numerical simulation of non-premixed laminar jet diffusion flames using adaptive mesh refinement
Diluted methane non-premixed laminar jet diffusion flames are numerically simulated to investigate their structure and stability in 0-gravity environment. The simulation results are compared with experimental data on flame stabilization in microgravity environment. The numerical model adopts a structured grid, axi-symmetric finite-volume method for spatial discretization and a semi-implicit time marching scheme. A detailed finite rate mechanism based on four-step reduced chemistry is employed to model the reaction phenomena. Adaptive mesh refinement (AMR) technique is implemented to enhance the computational efficiency. AMR technique helps to track the moving diffusion flames and locally refine the flame region to efficiently improve the accuracy of the solution.
AMR code is validated using a classical Burke-Schumann type of diffusion flame (BSDF) in normal gravity for steady and unsteady cases. Comparison between the numerical and experimental results is made in terms of the flame blowout curve. The comparison yielded a quantitatively similar blowout data when the fuel jet velocity is less than 0.4 m/s while only, qualitatively similar blowout data when the fuel jet velocity is greater than 0.4 m/s. Numerical parametric study is performed to quantify the sensitivity of the model with respect to various parameters and indicate the possible causes for the apparent lack of quantitative agreement at higher fuel jet velocities. Flame blowout is found to be most sensitive to heat loss from the flame and oxygen content in air. Flame internal structure is studied through visualization and analysis. Lastly, some recommendations for future research into flame structure, stability and emissions are presented.