Improved Modeling of Drop Vaporization and Combustion in Sprays
Final progress rept. 1 Jul 1998-30 Jun 2001
PURDUE UNIV LAFAYETTE IN SCHOOL OF MECHANICAL ENGINEERING
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In this work, multicomponent and single component droplet vaporization characteristics are investigated by employing computational models. It is shown that simplified droplet vaporization models that do not solve temperature gradients or flow within the droplet and do not solve gradients in temperature or species in the immediate surrounding of the droplet are able to reproduce droplet vaporization rates and droplet lifetime with about 15 accuracy compared to detailed models for typical Diesel operating conditions. Under high temperature 1200 K conditions the differences begin to increase. However, it is also shown that under such conditions as well as at even lower temperatures 900 K the vaporization process is mixing limited i.e., the droplet lifetime is not controlling but rather the characteristic time for mixing of ambient air with the vapor phase the liquid, vapor and air are in phase equilibrium. It is shown that droplets are not likely to react the critical state under typical engine conditions. With application to multidimensional spray models as focus, a new model for predicting the outcome of drop collisions has been developed. Such models are important because they predict the drop sizes in the spray following atomization.
- Combustion and Ignition