Blow-Off Limits, Flame Structure, and Emission Characteristics of Lean Partially Premixed Swirl-Stabilized Flames with NH₃/CH₄

Abstract

Recently, ammonia/methane mixtures have been considered as potential alternative fuels. The present study experimentally investigates the blow-off limits, flame structure, and pollutant emission of ammonia/methane mixtures in a partially premixed swirl-stabilized burner. The effects of fuel composition and the equivalence ratio are also studied. The results show that the NH 3 /CH 4 flame can be stabilized at an equivalence ratio of 0.55. The addition of methane has a positive effect on the blow-off limits. For the chemiluminescence profile, the OH* distribution and CH* distribution of NH 3 /CH 4 flames show a similar tendency under various conditions. The peak OH* and CH* radiances monotonically decrease with increasing E NHd 3 , while the maximum NH 2 * shows an opposite trend. The influence of the equivalence ratio on OH* and CH* in the NH 3 /CH 4 flames is negligible. However, when E NHd 3 is 60%, the equivalence ratio has a significant effect on NH 2 *. In terms of pollutant emissions, the peaks of NO and NO 2 emissions are all found around an E NHd 3 of 20%. When the equivalence ratio reaches 1.0, NO and NO 2 emissions are as low as 15 and 10 mg/m 3 , respectively. At the same time, both CO and unburned NH 3 emissions increase. Therefore, further studies on the application of secondary air or improvement of the fuel injection method to improve the combustion efficiency and reduce the pollutant emissions for ammonia combustion are still needed.