1991-02-01

Calculation of Inhomogeneous-Charge Combustion in a Swirl-Assisted Lean-Burn Engine 910266

A multidimensional computational method is extended to include the methodology for modelling of partially-mixed inhomogeneous charge combustion and is applied to investigation of combustion and simultaneous mixing process of an inhomogeneous mixture in a lean-burn spark-ignition engine. The in-cylinder flow and charge mixture distribution pertain to a helical intake port with manifold fuel injection, and were obtained through complete simulation of the induction and compression processes. The engine compression ratio is 12:1 and the study pertains to the operating condition of 2500 rpm.
The results show that the flow and charge distribution at the time of ignition is predominantly characterised by the evolution of the induction flow. The effect of heat release on enhancement of charge mixing is marginal and the pre-ignition charge distribution is preserved throughout the combustion. The remnant of the induction vortical flow structure persists through a major part of the flame development, but the swirl component suppresses its interaction with the flame. The results indicate that combustion has a limited transitionary influence on the turbulence parameters, and the effect of bulk dilatation imposed by the expansion stroke is predominant. The flame interaction with the swirl and reverse-squish flows is indicated as the principal mechanism of rapid combustion.

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