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September 2011
Fabian Fischer
Primary Breakup Model Considering the Spray Core Development
For the e ective reduction of pollutant emissions in direct injection Diesel and gasoline engines an accurate simulation of the internal combustion process is a very valuable tool. However, this requires the availability of reliable predictions of the spray characteristics and the resulting fuel mixture formation. Since it is widely accepted that spray characteristics are strongly a ected by the internal nozzle ow, primary breakup models that employ this nozzle ow information are essential. In this work a new primary breakup model in the Euler-Lagrange framework is presented. Besides the consideration of nozzle speci c local ow features, it features a separate treatment of the dense spray core in the vicinity of the nozzle.
The model is validated extensively and successfully on a detailed experimental data set of the primary breakup region of two di erent sprays injected from so-called principle nozzles. This data set features density distributions obtained with X-ray measurements, droplet sizes as well as data rates obtained with PDA measurements and optically obtained spray angles. Moreover, LDV measurements of the corresponding nozzle ows are available. This allows assessment of the nozzle ow simulations, which serve as initial boundary conditions for the primary breakup model. In the course of the validation it is demonstrated that the new primary breakup model is highly sensitive to the initially provided nozzle ow information. It is able to distinguish local di erences within the spray of one nozzle as well as the di erences between the two sprays. The quantitative agreement between experiment and simulation is also good. Furthermore, it is found that transient mean ow variations may have a signi cant in uence on the spray breakup.
Besides the extensive validation on principle nozzles, the new primary breakup model is also applied to real nozzle geometries. This includes three di erent Diesel nozzles and two di erent multi-hole gasoline injectors. For all considered operation conditions the simulation yields good results concerning the examined spray properties. In particular, the qualitative e ect of altering the operation conditions or changing the nozzle geometries is reproduced very well.
The model is validated extensively and successfully on a detailed experimental data set of the primary breakup region of two di erent sprays injected from so-called principle nozzles. This data set features density distributions obtained with X-ray measurements, droplet sizes as well as data rates obtained with PDA measurements and optically obtained spray angles. Moreover, LDV measurements of the corresponding nozzle ows are available. This allows assessment of the nozzle ow simulations, which serve as initial boundary conditions for the primary breakup model. In the course of the validation it is demonstrated that the new primary breakup model is highly sensitive to the initially provided nozzle ow information. It is able to distinguish local di erences within the spray of one nozzle as well as the di erences between the two sprays. The quantitative agreement between experiment and simulation is also good. Furthermore, it is found that transient mean ow variations may have a signi cant in uence on the spray breakup.
Besides the extensive validation on principle nozzles, the new primary breakup model is also applied to real nozzle geometries. This includes three di erent Diesel nozzles and two di erent multi-hole gasoline injectors. For all considered operation conditions the simulation yields good results concerning the examined spray properties. In particular, the qualitative e ect of altering the operation conditions or changing the nozzle geometries is reproduced very well.
Schlagwörter: Strömungslehre; Aerodynamik; Primary Breakup Model; Spray Core Development
Forschungsberichte Strömungslehre und Aerodynamik
Herausgegeben von Prof. Dr.-Ing. Cameron Tropea, Darmstadt
Band 25
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