Explosion characteristics of hydrous bio-ethanol in oxygen-enriched air

Hydrous bio-ethanol is a promising alternative fuel, which consumes less energy during the production than anhydrous bio-ethanol. However, hydrous bio-ethanol features a slow burning rate, leading to low combustion stability, or even misfire especially at a high water content. Preliminary research has shown that oxygen-enriched combustion (oxy-combustion) effectively solves the slow burning rate issue. However, oxy-combustion might increase the potential explosion hazard. Therefore, it is essential to study the explosion characteristics of hydrous bio-ethanol oxy-combustion before its application in practical engines. In this paper, an explosion characteristic study of hydrous bio-ethanol was carried out in a constant volume combustion chamber (CVCC). Hydrous bio-ethanol with 20 vol% water (E80W20) was selected for the investigations considering the tradeoff between production energy saving and burn rate. The boundary conditions for the experiments are initial pressures of 1-4 bar, initial temperatures of 358-418 K, air with the oxygen concentrations of 21-25% and equivalence ratios of 0.7-1.4. Explosion parameters such as explosion pressure, maximum rate of pressure rise, deflagration index, and combustion duration were analyzed. The results showed that both the explosion pressure and maximum rate of pressure rise increased linearly with the initial pressure. Deflagration index increased linearly with the oxygen concentration but it was insensitive to the initial temperature. In most cases, the deflagration index was lower than 20 MPa.m/s, revealing that E80W20 is relatively safe when it is combusted with air with a 23% oxygen content. This work paves the way for the application of hydrous bio-ethanol oxy-combustion in practical engines.