Local Reaction Zone Thickness of Non-Premixed Flames of Propane with Highly Preheated Low-Oxygen Concentration Air

Abstract

To investigate the instantaneous structure of the local reaction zone of the HiCOT (High Temperature Air Combustion Technology) flames, the characteristics of ion current obtained from the non-premixed flames of propane with highly preheated low-oxygen air have been closely examined. Luminous region is seen in the non-premixed flames of propane with highly preheated regular air and in the downstream part of the non-premixed flames of propane with highly preheated low-oxygen air. On the other hand, non-luminous region is seen only in the upstream part of the non-premixed flames of propane with highly preheated low-oxygen air. The ion current fluctuations, obtained from the non-luminous region of the HiCOT flames, look quite similar with those obtained from turbulent premixed flames in the reaction sheet regime. It has been clearly shown from the ion current that homogeneous combustion does not occur but the local reaction zone exists separately from burnt and unburnt gases. The thickness of the local reaction zone in the non-luminous region of HiCOT flames is not broadened but is similar to that of the laminar premixed flames. Thickness of the local reaction zone in the non-premixed flames of propane with highly preheated regular air is estimated approximately twice as much as that in the non-luminous region of the HiCOT flames.