Molecular dynamics simulation of bulk nano-oxygen-bubble fuel under high-pressure transport and sudden pressure drop process

Abstract

Aiming at the injection process of bubbly flow fuel, the molecular dynamics simulation was performed to study the change of bulk nano-oxygen-bubble (BNB) fuel during high-pressure transport and sudden pressure drop process. The static processes of BNB fuel containing different oxygen molecules numbers are explored in depth at normal temperature and pressure and pressure increase as well as the dynamic process under high-flow-rate-coupled sudden pressure drop. The results show that after adding BNB, the BNB contour increases first and then decreases. Increasing the number of oxygen molecules added at normal temperature and pressure shortens the BNB stabilization time and improves BNB stability. The BNB inner density in fuel is much smaller than that in water. Under high-pressure condition, the BNB which can be stabilized in the fuel at normal temperature and pressure quickly dissolves and disappears due to the increase in solubility of oxygen, resulting in a decrease in the oxygen molecule potential energy. Increasing the number of oxygen molecules added has only a weak slowing down effect on the dissolution rate. During the high-speed jetting of fuel at the nozzle, BNB promotes fuel droplet fragmentation and increases the oxygen concentration around the fuel droplet. In this process, the oxygen molecules do work on the fuel and their kinetic energy decreases. Increasing the number of oxygen molecules added reduces fuel breakup time and improves the quality of gas mixture formed. The results of this study can provide a reference for the micro-mechanism of BNB on improving the atomization characteristics of bubbly flow fuel.