Browse Publications Technical Papers 2011-24-0026
2011-09-11

The HCCI Concept and Control, Performed with MultiAir Technology on Gasoline Engines 2011-24-0026

The introduction of MultiAir technology [8] has had a strong impact on engine performance, fuel consumption, emissions and control. This technology, intended at first for gasoline engines and applied only on intake valves, is aiming at the reduction of engine breathing losses and, as a consequence, reduction of pollutant emissions and fuel consumption, together with an improvement of maximum intake efficiency. Further positive effects of MultiAir technology have been a significant improvement of Low End Torque, engine driveability (“fun-to-drive” index) and other operating conditions (e.g. idle control).Current development of MultiAir technology is focusing on a better management of hot EGR (Exhaust Gas Recirculation), still acting only on the intake side, although with specifically designed valve lift profiles. This application of MultiAir technology is pushing gasoline engines towards new levels of performance improvements.A further potential evolution of MultiAir technology is the controlled use of HCCI (Homogeneous Charge Compression Ignition, usually called CAI, Controlled Auto Ignition) concept and process, like in this paper we try to explain.Many different research teams, all over the world, have carried out important works about general, physical and chemical aspects of CAI (see, only e.g., [9], [10] and [11]).The focus here, instead, has been to only theoretically investigate - by way of reliable, coherent and global engine simulation - the opportunity of CAI introduction through valve control devices that today production has made available.In the first part of this paper, the authors present a quick review of a specific, complete, in-cylinder engine model, previously developed and accurately tuned for standard production MultiAir gasoline engines.The second part introduces the proposed evolution of MultiAir technology: acting on both intake and exhaust valves, a further degree of freedom becomes available, and the HCCI is achievable through NVO (Negative Valve Overlap). The NVO is a well-known way ([3], [5]) to trigger the combustion conditions from conventional to controlled autoignition, and it could be managed with production MultiAir components and control techniques. Simulated results are then presented.

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