Gasoline engine combustion development for EU 6c emission legislation

Abstract

CO2 legislation in Europe – with 130g/km as a fleet average starting in 2012 and the discussion of 95g/km in 2020 – requires a significant CO2 reduction of existing power trains. Diesel engines are known to be beneficial regarding CO2 emissions. However, higher costs limit their market share and thus impact on CO2 fleet emission reduction potential, especially in cost sensitive vehicle segments. In the area of gasoline engine development, downsizing has moved from a “mega” trend to a well established engine technology in Europe. Hyundai-Kia’s all-new Kappa T-GDI engine family is developed to be a downsizing concept replacing e.g. a 1.6l naturally aspirated engine in B and C-segment with the aim to reduce CO2 emissions. The associated low end torque benefit enhances “fun to drive” for the customer. With Euro 6 starting in 2014, not only CO2 and standard emissions like HC, CO and NOx will be in the focus of engine development, but also Particle Number (PN) and Mass (PM).

In order to achieve Euro 6c PN-emission targets, more than a 95% PN reduction over a Euro 5 calibration is required. A major portion of this required PN reduction can be achieved by increasing fuel pressure at part load to 150 to 200bar in combination with optimized cam and start of injection timing. In order to achieve the Euro 6c PN emission target, additional combustion development is required. Injector layout and spray targeting can be optimized by means of in-cylinder optical investigations and result in BSFC as well as PN reduction.

From a technical point of view, the upcoming Euro 6c legislation limit can be fulfilled either by combustion development or by after treatment. For a single vehicle, the Particle Number limit – including a safety margin – can be fulfilled by combustion development only and thus without a gasoline particle filter. The real challenge is to maintain this level for mass production as well as for the life time of the vehicle.