An Improved Fuel Spray Breakup Model for Advanced Internal Combustion Engine Configurations
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Lack of oil resources and increasing effects of global warming have emphasized and led to stricter regulation standards. To meet the current demands, the engines need to be highly efficient in terms of fuel efficiency and performance. One of the fundamental ways to achieve this goal is by studying the fuel atomization and the combustion process. However, there are several challenges involved in studying the process of atomization and combustion only through experimental approaches as they involve numerous parameters. A suitable supplement or alternative to the experimental approach is the numerical approach. Advances in high performance computing, have led to advancement in the study of fluid flows. Several programs have been developed for studying sprays in an engine. KIVA, is one of the earliest computer programs written for the numerical calculation of transient, two and three dimensional, chemically reactive fluid flow. It has the ability to calculate air flows in complex geometries with fuel spray dynamics and evaporation, mixing of fuel and air, and combustion with resultant heat release and exhaust product formation. Based on user feedback, this program has been improved several times. This work is based on KIVA-3V. The main focus of this thesis is the Taylor Analogy breakup (TAB) model in KIVA-3V. The TAB model is based on the analogy between an oscillating droplet and a spring mass system. Several studies conducted using this model have unanimously reported inaccuracies due to its small breakup time and its inability to accurately predict the droplet breakup. The small breakup time associated with model can be traced back to its two proportionality constants related to the aerodynamic and the surface tension forces. Changes in the value of these constants has been reported to influence the breakup time. A new breakup time associated with the intact breakup length is connected to the proportionality constants. The breakup model is modified to incorporate all the changes. The new modified breakup model is validated against three different experimental data. In all the cases, there is an agreement between the numerical and the experimental data.