Numerical optimization of flame stability in a swirl combustion chamber with helical tapes

Abstract

In this study, the effects of forced vortices on non-premixed flames' reaction are investigated using Computational Fluid Dynamics (CFD) in a cylindrical chamber with an internal helix. For this purpose, using the Response Surface Method (RSM), optimization has been performed to increase the flame's stability by considering two parameters of the geometric variable and the objective function of increasing its thermal efficiency. Two different geometrical parameters of the helix, i.e., width and pitch, are varied, and their effects on vortex generation and mixing inside the chamber are investigated for various Reynolds numbers. Results show that combustion's overall efficiency could be improved by carefully altering the helix's width and pitch. This study indicates that helical tapes can increase the combustion rate at lower equivalence ratios, which reduces the concentration of greenhouse gases and pollutants in combustion. By decreasing the width and the step rates of helical tape, the flame moves closer to the chamber's centerline, and the reaction zone elongates axially. Hence, the average temperature of the chamber is comparatively increased. Studies show that by doubling the Reynolds number, the reaction rate increases, and the chamber average temperature increases by about 28%. The best performance is achieved when helical tape with a small pitch and width is used.