Burner lip temperature and stabilization of a non-premixed jet flame

This experimental study addresses issues on heat transfer between the nozzle and the base of a non-premixed methane/air jet-flame. The burner lip temperature as well as temperature gradients at the top of the straight tube burner are systematically thermocouple-monitored, along with axial and radial positions of the flame attachment location by means of CH*-chemiluminescence imaging. The effects on lip temperature are tested for several parameters: flame state, either attached or lifted; aerodynamic conditions, over a very wide range of fuel injection velocities, covering both laminar and turbulent pipe flow for the inlet fuel, as well as momentum and velocity ratios between fuel and coflow both lower and greater than unity; nozzle rim coating, either uncoated or black-coated; initial reactant temperature, with preheating temperatures from 295 K to 1000 K; and burner material thermal conductivity, between 2.7 and 400 W/(mK). The observed phenomena are described and discussed in relation with changes of these parameters. Some conclusions are also drawn as for the relative importance of the different modes of heat transfer in the flame attachment zone, towards a better understanding of the flame stabilization process. In particular, flame attachment height measurements reveal a critical value towards high lip temperature obtained with low burner thermal conductivity. Eventually, this work allowed identification of four regions depending on fuel injection velocity, each associated with particular evolutions in terms of flame location and lip temperature. (C) 2013 Elsevier Inc. All rights reserved.