首页|VARIABLE SWIRL AND INTERNAL EGR BY VVT APPLICATIONON SMALL DISPLACEMENT 2 VALVE SI ENGINES: ANINTELLIGENT TECHNOLOGY COMBINATION
VARIABLE SWIRL AND INTERNAL EGR BY VVT APPLICATIONON SMALL DISPLACEMENT 2 VALVE SI ENGINES: ANINTELLIGENT TECHNOLOGY COMBINATION
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During recent years several VVT devices have been developed in order to improveeither peak power and low end torque, or part load fuel consumption of SI engines.When the target of the VVT application was an improvement of part load fuelconsumption these VVT devices were often combined with devices for variablecharge motion such as port deactivation, valve deactivation or tumble flaps, in orderto allow acceptable combustion stability at part load with high EGR rates.This paper describes an experimental activity concerning the integration of acontinuously variable cam phaser (CVCP) and a special intake and exhaust portgeometry on a family of small displacement 4 cylinder 2 valve engines. The targetwas to achieve significantly lower fuel consumption under normal driving conditions,compared to a standard MPFI application, without the need for a separate variablecharge motion device.A hydraulic vane-type cam phaser is used to shift the single overhead camshaft toretarded positions at constant overlap. Thus high EGR rates in the combustionchamber are generated by re-aspiration of burnt gas from the exhaust port into thecylinder. This re-aspiration phase is used to generate increased swirl with the help ofa unique exhaust port design to enable stable combustion under high residual gasoperating conditions. The consecutive aspiration phase through the intake port createsan additional moderate swirl motion. In this way a conventional tangential intake portcan be adopted, allowing at the same time good combustion stability with high EGRrates, with a good trade-off between part load fuel consumption and full loadperformance. Late intake valve closure ("reverse Miller cycle") is combined withthese measures in order to further reduce pumping losses at part load.Using 1.2 and 1.4 dm dm3 4 cylinder 8V engines equipped with these devices the conceptwas developed on the engine test bed with respect to functionality, durability and cost.Two demonstration cars with these engines were prepared. ECU calibration wasperformed on the test bed and in the vehicles with given targets for driveability andemissions. EURO 4 exhaust emission limits were reached using a conventionalcatalyst aged for 100’000 km. Fuel consumption was reduced by 5% in the NEDCcycle due to the thermodynamic effects achieved with VVT, high residual gas content
EGRMillerSwirlVVTFIRE
R. Fiorenza、M. Pirelli、E. Torella、P. Pallotti、P. E. Kapus、B. Praesent、G.Kokalj、K. W. Pachernek
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