Adiabatic premixed combustion in a gaseous fuel porous inert media under high pressure and temperature: Novel flame stabilization technique

This work presents an experimental investigation to study the characteristics of combustion using a premixed methane-air mixture within a non-homogeneous porous inert medium (PIM) under high pressure and temperature. In order to obtain a stable flame under these operating conditions within PIM, a novel flame stabilization technique in porous inert media (PIM) combustion under high pressure and temperature has been developed and evaluated. The proposed technique avoids the draw backs of the hitherto developed techniques by properly matching the flow and flame speeds and, consequently, ensuring a stable combustion, for a wide range of operating pressure and temperature. The success of this technique permits the extension of PIM combustion to new applications such as gas turbines. The validity of this new technique has been assessed experimentally in detail by analyzing combustion inside a prototype burner. The effects of various operating conditions, such as initial preheating temperature and elevated pressure, have been examined for an output power range between 5 and 40 kW. The experiments covered a broad spectrum of operating conditions ranging from a mixture inlet temperature of 20 °C and pressure ratio of 1 up to a temperature of 400 °C and a pressure ratio of 9. Evaluation of the results revealed excellent flame stability with respect to both flashback and blow-out limits throughout all the operating conditions studied, including relative air ratios far beyond the normal lean limit. While the blow-out stability showed no significant dependence on pressure, it was strongly determined by the preheating mixture inlet temperature. A remarkable broadening of the stability range from 0.6 to 1.0 on preheating to 400 °C was observed. This reveals the potential of pre-heat temperature to improve the dynamic modularity of the burner.