Novel flame stabilization technique in porous inert media (PIM) combustion under high pressure and temperature

This work presents an experimental investigation to study the characteristics of almost adiabatic combustion using a premixed methane-air mixture within a nonhomogeneous porous inert medium (PIM) under elevated pressure and temperature. To obtain a stable flame under these operating conditions within PIM, a new flame stabilization technique has been developed. The proposed technique avoids the drawbacks of the previous techniques by properly matching flow and flame speeds for a wide range of operating pressures and temperatures. 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 an initial 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 very good 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. The superiority of the new concept was confirmed by extremely lowCOemissions, where a zero value was recorded throughout the whole investigation. The NO_x emissions revealed remarkable performance as compared with conventional PIM techniques at ambient conditions. A nontrivial dependence of NO_x emissions on pressure at low relative air ratios has been observed. Application of this new PIM combustion technique, with its outstanding low emissions performance, will assist in solving present and future issues of environmental pollutant emission regulations.