Accelerating Laminar Flame Speed of Hydrous Ethanol via Oxygen-Rich Combustion

To investigate the laminar flame characteristics of hydrous ethanol, experiments were conducted in a constant volume combustion chamber. The laminar burning velocity and Markstein length of ethanol with water content from 0 to 20% by volume were measured over a wide range of equivalence ratios from 0.7 to 1.4 under the initial condition of 388 K and 0.1 MPa. Calculations of the laminar burning velocity with the constant pressure method (CPM) and constant volume method (CVM) were compared and discussed. Apart from experiments, numerical studies were carried out in CHEMKIN based on the Marinov's and Olm's ethanol oxidation mechanism. Moreover, the combustion of hydrous ethanol with 20% water by volume in oxygen-enriched air (O-2 = 23% by volume) was also studied. Results indicated that the overall trends of laminar burning velocity versus the equivalent ratio were basically consistent between the experiment and the simulation, but the results obtained by CVM were larger than those obtained by CPM and closer to the simulation results. The peak value of laminar burning velocity decreased from 0.638 to 0.591 m/s when the water content increased from 0 to 20% in CVM calculation, but the peak laminar burning velocity of hydrous ethanol with 20% water in oxygen-enriched air enhanced to 0.771 m/s, meaning that the oxygen-enriched air can effectively offset the negative impacts of water. Moreover, the Markstein length of hydrous ethanol decreases with increasing equivalence ratios.