Abstract
An essential target in today´s gasoline engine development is the optimization of the fuel consumption at part load operation. A dethrottling of the intake system by diluting the charge either by lean operation or by increased residual gas concentration combined with high turbulence measures is a common method of resolution to improve the engine´s fuel economy.
Extensive CFD-simulations have been carried out to optimize the design of a gasoline engine with Twinport intake system and port deactivation. The simulation results showed the intense swirl flow that decays to a high turbulence at spark timing in the case of port deactivation. This causes an accelerated combustion what allows an ignition closer to TDC at higher temperatures. The predictions of the simulation could be confirmed at the test bench.
The possibility to ignite the mixture at higher temperatures and the improved and more homogeneous mixture preparation with deactivated port increases the speed of the initial flame and thus stabilizes the combustion and allows an enhanced residual gas recirculation of the engine process compared to the engine without port deactivation. Thus, a further decrease of the fuel consumption of 4 % could be achieved.
Consequently, with the map regulated port deactivation an affordable measure was found to provide both charge motion and turbulence at part load and the required inlet cross sections for an optimal full load performance.
Keywords:Fuel Consumption, Residual Gas Tolerance, Turbulence, Charge Motion, CFD-Simulation