Quantitative analysis of the carbon generation characteristics during Mg/CO2 combustion: Implications for suppressing carbon deposition

Carbon deposition can significantly reduce the working stability and specific impulse performance of magnesium/carbon dioxide (Mg/CO2) powder rocket engines; however, few studies have quantitatively analyzed carbon generation characteristics during the Mg/CO2 combustion process. Therefore, this study presents a quantitative analysis of the carbon generation characteristics and degree of heterogeneous reaction during Mg/CO2 combustion in a closed high-temperature furnace. The analytical methods used include elemental analysis (EA) and inductively coupled plasma-optical emission spectrometry (ICP-OES). Experimental results showed that increasing the ambient temperature and decreasing the particle size both effectively suppressed carbon generation through a heterogeneous reaction, which is discussed from a thermodynamic perspective. When the particle size was 5 μm, the degree of heterogeneous reaction increased from 16.2% to 26.6% as the ambient temperature decreased from 1573 K to 1173 K; and when the ambient temperature was 1573 K, the degree of heterogeneous reaction increased from 16.2% to 23.2% as the particle size increased from 5 μm to 160 μm. Excessive CO concentration on the surface of Mg particles resulted in a large amount of carbon deposition, along with an insufficient Mg burnout rate. The proportion of Mg in the two pretreated powder samples participating in the heterogeneous reaction is reduced by 41% and 52%, respectively, compared with that in the source powder. Moreover, the combustion performance of pretreated Mg powder is typically excellent in CO2 due to the micro-explosion phenomenon. These findings are expected to contribute to improved working stability and specific impulse performance of Mg/CO2 powder rocket engines intended for Mars exploration.