Up-Front Prediction of the Effects of Cylinder Head Design on Combustion Rates in SI Engines

Accurate prediction of engine combustion characteristics, especially burn rates, can eliminate a number of hardware iterations, thus resulting in a significant reduction in design and developmental time and cost. An analytical methodology has been developed which allows the determination of part-load MBT spark timing to within 2 crank-angle degrees. The design methodology employs the in-house-developed steady-state quasi-dimensional engine simulation model (GESIM), coupled with full-field measurement of the in-cylinder fluid motion at bottom dead center (BDC) in the computer-controlled water analog system (AquaDyne). The in-cylinder flow-field measurements are obtained using 3-D Particle Tracking Velocimetry (3-D PTV), also developed in-house. In this methodology, the in-cylinder flow measurement data are used to calibrate both the tumble and swirl models in GESIM. Once the relative magnitude of the angular momentum fluxes associated with each component is calibrated, GESIM can accurately predict MBT. This paper will present both the model and test results from several engines with varying port and chambers configurations, i.e. swirl, tumble or swumble head designs.