Use of Impinging Sprays to Reduce Engine Emissions

Achuth Munnannur and Prof. Rolf D. Reitz

Acknowledgement: S C Johnson Wax

•Spray - spray impingement has been found to be quite beneficial for enhanced atomization and mixing.•Application areas are diverse - rocket motors, internal combustion engines, household and agricultural sprays…..•Is of special interest to I C engines because spray-spray impingement can,•produce ultra-low NOx and low smoke (SAE 1999-01-0185)•possibly reduce HC emissions and fuel consumption (SAE 2001-01-1892)

Why Impinging Sprays?

• In this application, reliable modeling of drop-drop collisions is extremely important.

• The collision model used in current CFD codes (O’Rourke (1981)), including KIVA, is inadequate since it considers only a limited number of collision outcomes. Further, it is very dependent on gas phase mesh-size.

• The current project will improve the collision sub-model such that it considers all major regimes of binary droplet collisions, trying also to achieve adequate grid independency in collision calculations. The improved model will be used for studying the effect of impinging fuel sprays on engine emissions.

Major Modeling challenges

Modeling New Regimes(Drops cannot expel

intervening gas film)

(Kinetic energy of unaffected part vs.Surface energy)

(Reflexive energy vs. surface energy)

(Drops form a combined mass)

Separation processes modeled considering temporal evolution of a ligament that eventually breaks-up by capillary instability or retracts to form a single satellite.

Results from the new collision model

Ethanol droplets colliding at atmospheric pressure (Estrade et al. (1999))

Propanol-2 drop streams (Brenn et al. (2001)) – drops enter from top

Experiment Simulation

Results from the new collision model

Colliding steams of Stoddard Solvent (Hung (1998))

Collision angle 10°

Collision angle 20°

• Achieving adequate grid independence• Extensive validation of the model • Use of the model for simulations in engine

conditions including impinging spray applications

Future Work