Coupling of nozzle flow and spray simulation for validation of breakup models in GDI engines
This computational study utilizes the latest simulation tools to determine the validity of breakup models for use in gasoline direct injection engines. The main objective was to resolve if the primary breakup and subsequent secondary breakup models used previously for diesel injectors can similarly be applied to gasoline injectors. Furthermore, the coupling method was applied to several geometrically dissimilar nozzles in order to procure design correlations. In order to accomplish this several steps were taken. First, workflow was established in order to realize the nozzle to spray coupling method. Next, the workflow was applied to a gasoline nozzle and several tests were performed to determine the optimal approach for nozzle flow simulations. Subsequently, this information was applied to a multi-hole gasoline injector in order to validate methods and breakup models by comparison with experimental data. As a final step, the verified model was utilized in a numerical study to relate nozzle and spray results to design parameters. As a result of this study it was found that the coupling method is easily applicable to gasoline injectors and the optimal coupling location is just before the step hole. The primary breakup model, in which the droplet injection is controlled, was found to adequately handle the breakup mechanisms present in gasoline injectors. Although, due to low Weber numbers aerodynamic forces were not taken into account within the primary breakup length resulting in additional adjustment of the breakup models. Moreover, the primary model did not account for breakup due to non-axial energy, which would consequently lead to higher breakup close to the nozzle and lower overall penetration of the spray, negating the need for model adjustment. Finally, regarding the design correlations, increasing the L/D ratio was found to significantly decrease non-axial energy and consequently decrease the near cone spray angle resulting in decreased spray penetration. Additionally, the conicity factor was similarly shown to be a significant design parameter displaying linear correlations to outlet vapor area, non-axial energy, penetration, and the spay angle.^
"Coupling of nozzle flow and spray simulation for validation of breakup models in GDI engines"
Dissertations and Master's Theses (Campus Access).