Heat transfer characteristics of premixed flame impinging upwards to plane surfaces inclined with the flame jet axis

Abstract

A theoretical model of premixed turbulent flames impinging obliquely on a flat surface has been developed to predict the influences of jet Reynolds number, ratio of plate separation distance to nozzle diameter, plate inclination angle and equivalence ratio on the heat transfer characteristics. The model is based on numerical solution of the coupled governing differential equations for conservation of mass, momentum and energy. Methane and air have been considered as fuel and oxidizer respectively. Global two-step irreversible reaction kinetics has been employed for the oxidization of methane. The RNG k–ε model has been used to compute the turbulence, and the Discrete Ordinates model has been used for radiative transfer in the flame. It has been observed that the heat flux distribution for an inclined plate is asymmetric about the transverse axis of tilt that divides the plate into uphill and downhill part. The heat flux in the uphill part is higher as compared to that at corresponding locations in downhill part. The local heat flux in the downhill part of the plate increases with a decrease in the plate inclination angle, while in the uphill part, the local heat flux at locations away from the plate centre is almost independent of the plate inclination angle. The local heat flux decreases with an increase in heating height. A fuel rich mixture increases the plate heat flux. The average Nusselt number, increases with an increase in jet Reynolds number, Re, and a decrease in the plate inclination angle. The increase in is profound at higher values of Re and for a decrease in plate inclination angle from 10° to 0°.