Combustion simulations of AlH3 and ethanol nanofluid by ReaxFF

Abstract

To alleviate the growing energy crisis, ethanol has been developed and applied gradually as an ideal biofuel to replace gasoline. The AlH3 nanoparticle is an excellent fuel additive with broad applications. In this work, the ReaxFF-lg reactive dynamics simulations were proceeded to explore the detailed mechanisms of AlH3 and ethanol nanofluid fuel. At varying temperatures, AlH3 exhibits different morphologies: branch-like expansion at the lower temperatures; micro-explosion and reaggregation into larger clusters at high temperatures. Overall, AlH3 accelerates the decomposition of ethanol and shortens the ignition delay. AlH3 also reduces the activation energy for ethanol decomposition from 79.09 to 69.05 kJ/mol. The conversion of coordination number for Al-O bonds indicates that Al2O3 is the final product of Al element. The simulation results reveal a new mechanism: AlH3 promotes the dissociation of H in the hydroxyl, making the initial decomposition of ethanol to C2H5O (CH3CH2O, CH3CHOH and CH2CH2OH) selective. The released H forms more OH and HO2 radicals to promote the conversion of intermediates to stable products. The Al2O3 oxide layer delays the ethanol combustion kinetics as well. This study provides an atomic perspective on the combustion mechanisms of AlH3 and ethanol nanofluid fuel and is expected to guide the development and application of AlH3-based fuels.