Numerical Prediction of a Turbulent Flow with Double Annular Jets for Different Reynolds Numbers

Abstract

This research undertakes a numerical investigation of an axisymmetric double-jet semi-confined annular flow produced by a burner. The endeavor aims to thoroughly decipher the behavior of these turbulent flows within a double annular jet, with a focus on characterizing the mixing and recirculation regions. Analyses of the annular jet were conducted for three distinct Reynolds numbers (6683, 8874, and 11065). Numerical simulations were performed using a computational fluid dynamics (CFD) calculation code, employing two turbulence models-k-epsilon and SST k-ω. The governing differential equations, discretized for the flow, were solved via the finite volume method, utilizing the semi-implicit method algorithm for pressure-linked equations. Findings revealed the existence of three recirculation zones separated by the annular jets. The first, a minute zone, is situated between the two annular jets. The second, a medium-sized zone, resides just behind the nozzle near the injection axis, below the primary jet. The third, a large zone, is positioned near the upper wall of the combustion chamber. It was observed that the size of the initial small recirculation zone exhibited negligible variation with changes in the Reynolds number. However, the second medium-sized zone experienced notable alterations with the Reynolds number. The third large zone generated an extensive toroidal vortex at higher Reynolds numbers. These recirculation zones offer potential for control to optimize fuel-air mixing, aiming to achieve near-perfect combustion while minimizing pollutant emissions. The numerical simulation results generally exhibited strong agreement with experimental findings.