IMPINGING JET FLAMES

An experimental investigation has been made of a flame impinging at an angle of 20° on the hearth of a furnace. Measured velocity and temperature profiles in the flame were found to have the same reduced form as profiles obtained for a plane heated impinging jet, by Mathieu. Direct comparison of results obtained in the furnace with those obtained by Mathieu show that when account is taken of differences in initial and boundary conditions then predictions can be made of fluid dynamic and thermal boundary layer characteristics as well as rates of convective heat transfer in impinging flames. Heat transfer measurements show that total heat transfer can be increased by a factor of three by direct impingement of the flame on the furnace hearth. Convective heat transfer, which is of little significance for flames without impingement, amounts to 70 per cent of the total heat transfer in the region of impingement. A twofold increase in the momentum of the flame resulted in a proportional increase in local heat transfer coefficients. The Reynolds number exponent in the Nusselt-Reynolds number relationship was found to be 0·8. © 1968.