Molecular Dynamics (ReaxFF MD) Simulation of Hydrogen Effects on Air Heater Combustion

As a fuel commonly used by air heaters for ground tests of high-speed aircraft, the combustion mechanism of ethanol in air heaters is still unclear, especially the atomic-level chemical mechanism of important intermediate products represented by hydrogen in maintaining stable flame combustion needs to be further studied. In this paper, the combustion process of ethanol/oxygen mixtures under different hydrogen additions was simulated using the reactive force field (ReaxFF) molecular dynamics (MD) method. The results show that increasing the proportion of hydrogen in the mixed gas can not only reduce the ignition delay time of ethanol combustion but also promote the consumption of ethanol and accelerate the progress of the combustion reaction. It was also found that hydrogen and ethanol produced a competitive relationship for oxygen, which changed the ideal stoichiometric ratio (1:3) of complete combustion of ethanol and oxygen and significantly affected the intermediate products and reaction paths of ethanol and oxygen. In addition, increasing the combustion reaction temperature will affect the reaction path of ethanol/oxygen, and the number of intermediate products produced will reach the peak faster and then decompose. Theoretical support for a deeper understanding of the intermediate product hydrogen in the combustion of the three-component air heater of ethanol/liquid oxygen/air and also for improving the combustion efficiency of liquid rocket engine fuel are provided in this study.