Numerical study on spray and flame lift-off length of acetonebutanol-ethanol and diesel blends in a constant volume chamber

Acetone-butanol-ethanol mixture (ABE) is being studied as an alternative fuel because it not only preserves the advantages of oxygenated fuels, but also lowers the cost of fuel recovery for butanol during fermentation. The previous experimental study on spray and flame lift-off length for diesel with 20% addition of ABE mixture, shows a shorter and narrower spray and a much longer flame lift-off length compared to those of neat diesel, which leads to considerably less soot emission level of ABE20. In this study, a detailed mechanism capable of predicting the ignition delay for ABE as well as ABE-diesel blends is implemented to the KIVA-3V program to simulate the spray dynamics and lift-off length inside the constant volume chamber. The presented model is able to capture the trends with regard to ignition delay, combustion duration and peak pressure. The overall predictivity for ABE20 is better than that of D100. Spray penetration and the lift-off length for both fuels are simulated and the numerical definition for lift-off length is discussed. It is found that the threshold temperature to define lift-off length can be uniform under different ambient temperatures, but varies with respect to oxygen concentration. The simulations also agree with the measurements in predicting the lift-off length decreases as temperature and oxygen concentration increases. Finally, the simulation sooting tendency is presented to show that, due to the improved spray and combustion process of ABE-diesel blend, the soot emission level is much less than conventional diesel fuel.