Fuel Spray Trajectory and Dispersion in a D.I. Diesel Combustion Chamber 890462
Experiments and modeling of the fuel spray trajectory and dispersion influenced by both a swirling gas flow and wall impingement were performed under simulated direct injection (D.I.) diesel engine conditions at a high pressure and high temperature. A spray was injected into the steady swirling gas flow and impinged on the simulated piston cavity wall in a constant-volume bomb. High-speed Schlieren photographs provided the informative data on the behavior of the spray vaporizing in such diesel-like circumstances. A simplified computational model was developed to describe the spray trajectory and the fuel vapor dispersion in the D.I. diesel combustion chamber. The model includes the effects of the breakup on the trajectory and the vaporization of the spray, and the effects of the swirling gas flow and the wall impingement on the dispersion of the fuel vapor. Some experimental results and empirical equations on the behavior and the vaporization of the free and impinging sprays were incorporated in the model for the purpose of a simple description of such spray processes. The dispersion of the fuel vapor and enthalpy are, however, computed by solving the conservation equations by the finite difference technique. The model was used to predict the three-dimensional distribution of the fuel vapor concentration in the constant-volume bomb. The computed results were compared with the Schlieren photographic measurements taken under the various swirling gas flow conditions. From these comparisons, it can be considered that the model is adequate to predict the spray trajectory and the fuel vapor dispersion in the D.I. diesel combustion chamber.