Analyzing the combustion characteristics of premixed methane-oxygen with different hydrogen addition ratios in a catalytic micro-combustor

Abstract

Experimental and numerical study of premixed methane-oxygen combustion characteristics in a catalytic micro-combustor with different hydrogen addition ratios has been presented in this paper. The objective is to examine the effects of platinum catalysts and hydrogen additions on methane and oxygen combustion. The simulation of a three-dimensional micro rectangular model was carried out with a gas phase reaction mechanism combined with a surface reaction mechanism, and the model was validated with experimental results with a maximum deviation of just 1.56 percent. In the experimental phase, the effects of flammability limit, equivalence ratio, and inlet velocity were studied, while in the numerical phase, the effect of hydrogenation on combustion characteristics was investigated. Experimental results show that adding 10 % hydrogen to a premixed methane-oxygen mixture significantly increases its flammability limit. The maximum external wall temperature along the centerline was observed at an equivalent ratio of 1. Additionally, an increase in the inlet velocity leads to a corresponding increase in the external wall centerline temperature. Catalytic reaction wall temperatures show a gradual decline, with the highest temperatures located at the inlet. An observed trend revealed a decrease in the external wall centerline temperature as the hydrogen addition increased from 0 % to 40 % due to the reduced total heating value of the blended fuel. Due to its higher reactivity and ability to promote complete combustion, hydrogen also plays an important role in CH4 and O2 conversion. In addition, CO and CO2 emissions decreased with increased hydrogen percentage in fuel mixtures. Furthermore, hydrogen addition can reduce external wall heat losses as well. After adding 0–40 % hydrogen to a premixture of (CH4–O2) fuel, the total heat loss of the external wall was reduced from 19.48 W to 17.11 W.