Study of instabilities on laminar-turbulent transition in a 4 lug-bolt in a confined diffusion flame

Velocity fluctuation in a diffusion methane-oxygen flame for three different injection velocities is analyzed numerically in this paper. The work states a 4 Lug-Bolt arrange where oxygen is injected by a central nozzle and methane by four peripheral nozzles. The aim of the numerical simulation is to study the mechanism that affect the mixture process in a diffusion flame by means of Kelvin-Helmholtz instabilities. The simulation is realized with the Reynolds-Averaged Navier-Stokes technique and the realizable k-ε turbulence model is considered in order to model the Reynolds stress tensor. The results show a recirculation zone which is the essential mixture mechanism and has relevant participation on the instabilities development in confined diffusion flames. Furthermore, predictions exhibit a wave frequency increment and wave length instability decrement as velocity injection increase. Therefore, in diffusion flames the Kelvin-Helmholtz instability affects the mixing and reaction zone.