PREMIXED FLAME STABILIZATION IN AN AXISYMMETRICAL CURVED-WALL JET

The flame stabilization and flow field characteristics of premixed fla mes in an axisymmetric curved-wall jet utilising the Coanda effect are investigated experimentally. The advantages of this flow field includ e the formation of a recirculation zone near the burner tip and the en hancement of turbulence by the radially inward velocity component of t he jet. Results show that the blow-off velocity is much higher and the fame height is reduced significantly as compared to a tube jet burner . The condition of maximum blow-off velocity occurs when the mixture i s rich and the equivalence ratio increases as the nozzle exit area dec reases. Velocity fields measured by laser Doppler velocimetry confirm the existence of a recirculation zone and flame stabilization in this zone. Flashback is effectively prevented by adjusting the slit width i n the axisymmetric curved-wall jet burner. The combined effects of fla me height reduction, extended blow-off condition, prevention of flashb ack, and easy controllability of the flame height through the adjustme nt of slit width provide promising characteristics for applications in practical burner design. (C) 1998 by The Combustion Institute.