Hydrogen Addition Effects on Swirl Stabilized Methane Flame

Abstract

Effect of hydrogen addition in methane-air premixed flames has been examined from a swirl stabilized combustor under confined flame conditions. Different swirlers have been examined to investigate the effect of swirl intensity on enriching methane-air flame with hydrogen in a laboratory-scale pre-mixed combustor operated at 5.81 kW. The flame stability was examined at same head load (5.81 kW) for various parameters such as amount of hydrogen addition, combustion air flow rates and swirl strengths. This was done by comparing adiabatic flame temperatures at the lean flame limit. The combustion characteristics of hydrogen enriched methane flames at constant heat load but different swirl strength were examined using particle image velocimetry (PIV), OH chemiluminescence, micro-thermocouples diagnostics to provide information on velocity and temperature field, and combustion generated OH concentration in the flame. Gas analyzer was used to obtain NOx and CO concentration at the exit. The results show that the the lean stability limit is mostly extended by hydrogen addition, but it can reduce in case of higher swirl intensity operating at lower adiabatic flame temperatures. The addition of hydrogen increases the NOx emission; however, this effect can be reduced by increasing either the excess air or swirl intensity. The results of NOx and CO emissions were also compared with a diffusion flame type combustor. The NOx emissions of hydrogen enriched methane premixed flame was found to be lower than the corresponding diffusion flame under the fuel lean condition.