Prediction of Liquid and Vapour Penetration of Early-Injection Diesel Sprays

Transient liquid and vapor penetration of diesel sprays is numerically investigated for conditions corresponding to early-injection timings; this injection approach can be followed since it allows sufficient fuel-ambient mixing avoiding NO and soot-forming combustion. Model validation takes place against experimental data available for injection into an optically accessible constant volume chamber using a single-hole injector nozzle. A parametric analysis on the effect of ambient temperature and density, injection duration, multiple injection strategy and nozzle hole diameter is performed to enlighten the development of the injected sprays for various early-injection strategies. The model is found to predict reasonably well the experimental trends both for steady-state and transient injection events. Accurate prediction of the influence of the injection parameters, particularly during the initial liquid spray formation, which strongly affects the transient spray development, may assist engine developers to the design of more efficient combustion systems.