Atomization and Sprays, Vol.20, No.3, 241-250, 2010
COMPUTED AND MEASURED FUEL VAPOR DISTRIBUTION IN A DIESEL SPRAY
There is limited quantitative experimental data on fuel vapor concentrations in high-pressure vaporizing full-cone sprays injected into diesel engines. As a result, the accuracy of multidimensional models, which are routinely employed to compute such sprays, has not been quantitatively assessed. In this work, quantitative fuel vapor concentrations obtained from multidimensional computations of a diesel spray with three models are compared with measured concentrations in the vapor-phase portion downstream of liquid drop vaporization. The three models employed are a Lagrangian-drop Eulerian-fluid (LDEF) spray model, a gas jet model, and a virtual-liquid source (VLS) model. Comparison of the vapor fraction along the axial centerline during the transient development of the spray shows that the computed values are generally lower than the measured values, and the leading edge of the computed profiles shows shallower gradients of vapor fraction than in the measured spray. In the case of radial distribution, the peak values of measured and computed vapor fractions agree within 20% when the profiles are quasi-steady. The three models show similar agreement close to the orifice, but the LDEF model shows the better agreement farther downstream at quasi-steady state. During transient development, there is greater disagreement between the computed and measured profiles. The computed width of the vapor phase of the spray is generally larger than the measured one, although the half-widths show agreement within 10%. In general, the gas jet and VLS vapor fraction values are within 5% of each other at the centerline during transient development but differ more at the edge of the spray.