TY - JOUR
T1 - Micron-sized aluminum particles induced kinetic acceleration in methane oxidation
T2 - A shock tube study
AU - Li, Yaowen
AU - Wu, Jinghua
AU - Wang, Jun
AU - Shao, Jiankun
N1 - Publisher Copyright:
The Combustion Institute
PY - 2026/1/1
Y1 - 2026/1/1
N2 - Methane (CH4) is regarded as a promising alternative fuel for advanced propulsion systems, while its practical application is often constrained by kinetic inertness. In this study, the kinetic acceleration of CH4 oxidation induced by micron-sized aluminum (Al) particles was investigated using a shock tube coupled with laser absorption spectroscopy over the temperature range of 1400–1850 K, at a pressure of 1.0 atm, and oxygen (O2) concentrations ranging from 8% to 20%. Experimental results reveal that the ignition promotion by Al particles is strongly dependent on O2 concentration and test temperature. Significant activity was observed only when temperatures exceeded 1593 K, 1503 K, and 1466 K at O2 concentration of 12%, 16%, and 20%, respectively, leading to average reductions in ignition delay times (IDTs) of 29.1%, 40.5%, and 47.5%, and 50% CH4 consumption times of 22.1%, 36.7%, and 44.7%. Evaluations based on the measured IDTs and CH4 time histories for the CH4 mixtures (without Al) demonstrate that the FFCM-2 model yields the most accurate predictions compared to GRI 3.0, Aramco 3.0 and Nuig1.3. A detailed CH4-Al kinetic model was constructed by coupling FFCM-2 and an Al sub-mechanism. Based on this coupled model, detailed kinetic analyses reveal that this acceleration stems from the coupling between Al and hydrocarbon chemistry. The Al oxidation reaction (Al + O2 <=> AlO + O) replaces the classical chain-branching reaction (H + O2 <=> O + OH) as the most significant promoting step governing global reactivity. In addition, the generated active intermediate aluminum monoxide (AlO) directly scavenges formaldehyde (CH2O) via the reaction CH2O + AlO <=> AlOH + HCO, and aluminum dioxide (AlO2) facilitates carbon monoxide (CO) consumption via a parallel oxidation channel (CO + AlO2 <=> CO2 + AlO). This study provides important insights into the research of high-energy metal enhanced combustion. Novelty and significance statement: CH4 is a promising alternative fuel for advanced propulsion systems but is constrained by kinetic inertness, and the addition of high-energy Al particles can significantly enhance its reactivity. The IDTs and CH4 time-histories of CH4 and CH4/Al mixtures were systematically measured using a shock tube and laser absorption spectroscopy. To the best of our knowledge, this is the first systematic investigation into the kinetic acceleration of CH4 oxidation induced by micron-sized Al particles in this regime. Experimental results reveal that the ignition promotion by Al particles is strongly dependent on O2 concentration and test temperature. Detailed kinetic analyses based on the CH4-Al kinetic model demonstrate that this acceleration stems from the coupling between Al and hydrocarbon chemistry. This investigation provides important insights into the research of high-energy metal enhanced combustion.
AB - Methane (CH4) is regarded as a promising alternative fuel for advanced propulsion systems, while its practical application is often constrained by kinetic inertness. In this study, the kinetic acceleration of CH4 oxidation induced by micron-sized aluminum (Al) particles was investigated using a shock tube coupled with laser absorption spectroscopy over the temperature range of 1400–1850 K, at a pressure of 1.0 atm, and oxygen (O2) concentrations ranging from 8% to 20%. Experimental results reveal that the ignition promotion by Al particles is strongly dependent on O2 concentration and test temperature. Significant activity was observed only when temperatures exceeded 1593 K, 1503 K, and 1466 K at O2 concentration of 12%, 16%, and 20%, respectively, leading to average reductions in ignition delay times (IDTs) of 29.1%, 40.5%, and 47.5%, and 50% CH4 consumption times of 22.1%, 36.7%, and 44.7%. Evaluations based on the measured IDTs and CH4 time histories for the CH4 mixtures (without Al) demonstrate that the FFCM-2 model yields the most accurate predictions compared to GRI 3.0, Aramco 3.0 and Nuig1.3. A detailed CH4-Al kinetic model was constructed by coupling FFCM-2 and an Al sub-mechanism. Based on this coupled model, detailed kinetic analyses reveal that this acceleration stems from the coupling between Al and hydrocarbon chemistry. The Al oxidation reaction (Al + O2 <=> AlO + O) replaces the classical chain-branching reaction (H + O2 <=> O + OH) as the most significant promoting step governing global reactivity. In addition, the generated active intermediate aluminum monoxide (AlO) directly scavenges formaldehyde (CH2O) via the reaction CH2O + AlO <=> AlOH + HCO, and aluminum dioxide (AlO2) facilitates carbon monoxide (CO) consumption via a parallel oxidation channel (CO + AlO2 <=> CO2 + AlO). This study provides important insights into the research of high-energy metal enhanced combustion. Novelty and significance statement: CH4 is a promising alternative fuel for advanced propulsion systems but is constrained by kinetic inertness, and the addition of high-energy Al particles can significantly enhance its reactivity. The IDTs and CH4 time-histories of CH4 and CH4/Al mixtures were systematically measured using a shock tube and laser absorption spectroscopy. To the best of our knowledge, this is the first systematic investigation into the kinetic acceleration of CH4 oxidation induced by micron-sized Al particles in this regime. Experimental results reveal that the ignition promotion by Al particles is strongly dependent on O2 concentration and test temperature. Detailed kinetic analyses based on the CH4-Al kinetic model demonstrate that this acceleration stems from the coupling between Al and hydrocarbon chemistry. This investigation provides important insights into the research of high-energy metal enhanced combustion.
KW - Aluminum particles
KW - Ignition delay time
KW - Laser absorption spectroscopy
KW - Methane oxidation
KW - Shock tube
UR - https://www.scopus.com/pages/publications/105047249767
U2 - 10.1016/j.combustflame.2026.115237
DO - 10.1016/j.combustflame.2026.115237
M3 - Article
AN - SCOPUS:105047249767
SN - 0010-2180
VL - 293
JO - Combustion and Flame
JF - Combustion and Flame
M1 - 115237
ER -