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Technical Paper

The Prediction of Ignition Delay and Combustion Intervals for a Homogeneous Charge, Spark Ignition Engine

Correlations for the ignition delay and combustion energy release intervals in a homogeneous charge, spark-ignited engine are developed. After incorporation within a simplified engine cycle simulation, predicted values of these two combustion parameters are compared to experimental engine data. The correlations are based on four fundamental quantities-the turbulent integral scale, the turbulent micro-scale, the turbulent intensity, and the laminar flame speed. The major assumptions include: (1) The turbulent integral scale is proportional to the instantaneous chamber height prior to flame initiation. (2) Angular momentum is conserved in the individual turbulent eddies ahead of the flame front (i.e., a “rapid distortion” turbulence model). (3) The turbulent intensity scales with the mean piston speed. Two empirical constants scale the correlations to a given engine.