Numerical Analysis of a Diffusion Flame Under Water Mist Jet Influence

A water mist jet for a steam generator of direct contact with a diffusion flame is numerically analyzed in this paper. Numerical simulation is conducted for an 8 Lug-Bolt array in a confined system. The diffusion flame is modelled in the Eulerian Eulerian multiphase approach where the reaction species are oxygen which is injected by a 16.9 mm central nozzle, methane by four peripheral 5.86 mm nozzles as the water mist and with a droplet size of 10μm. Numerical simulations are developed with the Reynolds Averaged Navier-Stokes and the Realizable k-ε turbulence model is considered. The Eddy Dissipation Model is implemented in order to calculate the effect of turbulent chemical reaction rate. Predictions show some instabilities that are located within the flame structure as long as the fuel moisture percentage is less than 1%. If the mist fraction for vaporization increases, the instabilities do not affect the internal flame structure but instabilities becomes relevant to the end of the calculus domain. The decrement about 60% of the water mist velocity due to a vapor gap around the micro droplets is the mean cause of the instabilities. Therefore, a very precise control of the numerical parameters is so important for multiphase approximations.