Controlled auto ignition (CAI) is a promising future combustion process concept by which fuel consumption as well as NOx emissions can be significantly reduced, but only within a limited engine map area. In combination with a supercharged combustion system tuned for enhanced lean burn capability, homogenous lean burn combustion enables a significant increase in compression ratio together with a significant reduction in fuel consumption. In this paper, various technology concepts for future combustion processes achieving a reduction of fuel consumption in gasoline engines through valve train variations are discussed. In order to reach the highest degree of flexibility, the investigations were conducted using an engine equipped with an electromechanical valve train (EMVT), featuring both part fuel injection and gasoline direct injection. It was shown that the electromechanical valve train is an excellent platform for developing the CAI process realised by port fuel injection (PFI) over a speed range between 1000 and 4500 rpm and over a load range between 1 and 6 bar BMEP, depending on the engine speed. The fuel consumption at part load operation was reduced by up to 18% compared to the conventional base engine. Tests performed with gasoline direct injection proved to extend significantly the maximum possible load range for CAI by 1 bar. Additionally, the reduction in fuel consumption was improved to 22% during CAI operation with direct injection. Due to the cycle-synchronous control of valve timings and injection and ignition offered by the EMVT, transitions between the CAI and SI (spark igntion) operating modes were realised without misfire or negative torque response. Based on these investigations the necessary variations in the valve train and the requirements for transient behaviour and thus for CAI. were identified.
Controlled auto ignition combustion process with an electromechanical valve train
Mit einem elektromechanischen Ventilsatz gesteuerter Sebstzündungsverbrennungsprozeß
2003
9 Seiten, 11 Bilder, 10 Quellen
Conference paper
English
Brennverhalten , Direkteinspritzung , elektromechanische Steuerung , Emissionsminderung , Kraftstoffeinsparung , Kraftstoffeinspritzung , Selbstzündung , Teillast , transientes Verhalten , Ventilsteuerung , Ventilverstellung , Verbrennungsmotor , Verdichtung , Verdichtungsverhältnis , Wirkungsgrad (thermisch) , variable Ventilsteuerung , CO2-Emission , NOx-Emission
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