Heat Transfer Study of the Hencken Burner Flame

The Hencken burner flame is often used in combustion laser diagnostics as a calibration flame because of its near adiabatic condition. For a fast burning H₂ flame, it can tolerate high flow rate and the flame is indeed near adiabatic; however, for a slow burning CH₄ flame, the flow rate is not always high enough to maintain near adiabatic conditions. The heat transfer of the H₂ and CH₄ Hencken burner flames are studied numerically and experimentally. Three heat loss mechanisms are analyzed: the burner surface radiation, the hot gas radiation, and the convection heat transfer between the main flow and the co-flow. The surface radiation produces negligible temperature drop while the gas radiation and the convection heat loss contribute significant temperature drop. Reducing the co-flow rate can decrease the convection heat loss slightly. The temperature drop caused by the heat loss is inversely proportional to the main flow rate. Increasing the burner size and running the flame premixed mode can increase the flow rate and reduce the temperature deviation from the adiabatic equilibrium value. Based on the heat loss and temperature drop analysis, suggestions are given to maintain the flame at near adiabatic conditions.