Effects of Direct Water Injection on DI Diesel Engine Combustion

Abstract

<div class="htmlview paragraph">The effects of in-cylinder water injection on a direct injection (DI) Diesel engine were studied using a computational fluid dynamics (CFD) program based on the Kiva-3v code. The spray model is validated against experimental bomb data with good agreement for vapor penetration as a function of time. It was found that liquid penetration increased approximately 35% with 23% of the fuel volume replaced by water, due mostly to the increase in latent heat of vaporization.</div> <div class="htmlview paragraph">Engine calculations were compared to experimental results and showed very good agreement with pressure, ignition delay and fuel consumption. Trends for emissions were accurately predicted for both 44% and 86% load conditions. Engine simulations showed that the vaporization of liquid water as well as a local increase in specific heat of the gas around the flame resulted in lower Nitrogen Oxide emissions (NOx) and soot formation rates. Using stratified fuel-water injection increases soot at 86% loads due in part to late injection. Because NOx decreased at all loads, the injection timing can be advanced to minimize fuel consumption and soot.</div>