1990-10-01

An Experimental and Computational Evaluation of Two Dual-Intake-Valve Combustion Chambers 902140

Multi-dimensional computations were made of spark-ignited premixed-charge combustion in two engines having pent-roof-shaped combustion chambers and two intake valves per cylinder, one with a central spark plug and the other with dual lateral spark plugs. The basic specifications for the two engines were the same except for differences in the number of spark plugs and exhaust valves. The effects of swirl and equivalence ratio on combustion, wall heat transfer, and nitric oxide emission characteristics were examined using a global combustion model that accounts for laminar-kinetics and turbulent-mixing effects. The initial conditions on both mean-flow and turbulence parameters at intake valve closing (IVC) were estimated in order to simulate engine operation either with both intake valves active or with one valve deactivated. The predictions were compared with experimentally derived pressure-time, heat loss, and nitric oxide emission data.The model, consistent with experimental data, indicates that the dual lateral ignition engine responds more favorably to valve deactivation as charge dilution is increased, and shows flame convection to be the source of the dual lateral ignition engine's superior dilute performance. The results also indicate that when the effects of flame convection are considered, the model predicted top dead center (TDC) turbulence intensities are in good agreement with experimentally derived apparent TDC turbulence intensities for both engines with and without valve deactivation.

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