Experimental and Numerical Analyses of Liquid and Spray Penetration under Heavy-Duty Diesel Engine Conditions

摘要

The modeling of fuel sprays under well-characterized conditions relevant for heavy-duty Diesel engine applications, allows for detailed analyses of individual phenomena aimed at improving emission formation and fuel consumption. However, the complexity of a reacting fuel spray under heavy-duty conditions currently prohibits direct simulation. Using a systematic approach, we extrapolate available spray models to the desired conditions without inclusion of chemical reactions. For validation, experimental techniques are utilized to characterize inert sprays of n-dodecane in a high-pressure, high-temperature (900 K) constant volume vessel with full optical access. The liquid fuel spray is studied using high-speed diffused back-illumination for conditions with different densities (22.8 and 40 kg/m3) and injection pressures (150, 80 and 160 MPa), using a 0.205-mm orifice diameter nozzle. High-speed Schlieren imaging is used to analyze the influence of these boundary conditions on the spray penetration. Simulations of the fuel spray are performed using a dedicated computational mesh with refinements at the known location of the jet to capture the smallest scales of interest. Using a blob injection model refined with a primary atomization and secondary breakup model, correct trends and good agreement are achieved for both liquid and spray penetration. The capability of capturing the trends at largely varying boundary conditions with a single computational approach provides a solid base for future work.