The Effect of Inlet Velocity Distribution and Magnitude on In-Cylinder Turbulence Intensity and Burn Rate—Model Versus Experiment

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Abstract
Steady flow measurements of velocity and mass flux distributions around the intake valve were used as input to a General Engine Simulation Model (GESIM) to assess the assumptions of uniform velocity and mass flux distributions and their effects on in-cylinder turbulence intensity and burn rate. In addition, an improved submodel for calculating the instantaneous velocity past the intake valve was developed and its effects on intake generated turbulence and burn rate assessed. Using the improved, inlet velocity submodel, a study was carried out for three different intake port configurations. Burn rate measurements were compared with model results for these configurations, which utilized the same engine head and block assembly. Model predictions, based on the standard port/valve discharge coefficient, indicated that velocity and mass distributions alone had a small effect on the in-cylinder turbulence intensity and burn rate. Significant differences in burn rate and turbulence intensity were predicted when the improved submodel for valve discharge coefficient was used. The new predictions agreed well with experimental measurements of burn rate. This implies that the increased mean velocities (which occur due to the restriction that creates the velocity and mass flow distributions) are the major cause for increased turbulence levels.

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