Transportation Engineering (Jun 2022)
Gasoline powertrain solutions with ultra low tailpipe emissions
Abstract
The introduction of Euro 6d legislation brought into law the regulation of particulate number and nitrous-oxide emissions under road-driving conditions. In line with these regulations, driving conditions involving highly dynamic, low ambient temperatures, and high vehicle loads are to be given particular attention. This leads to new challenges to the gasoline engine, the mixture preparation, and the exhaust-gas treatment. In the past, refinements made to the fuel-injection system have already resulted in significant progress being made in the reduction of particulate emissions. Supplemented by a latest-generation particulate filter, particulate emissions are now being continuously decreased. Gaseous emissions are reduced by combining innovative measures inside the engine itself with effective exhaust-gas treatment. The target of this investigation is the evaluation of innovative emission reduction measures in a demonstrator vehicle with a gasoline powertrain. For lower engine out emissions a fast heated air-fuel-ratio-sensor, new injection system with higher pressure, enhanced injection strategy with up to 7 injections per stroke, optimized calibration has been implemented. A gasoline particle filter, higher precious metal load of the three-way-catalyst, a second three-way-catalyst in underbody position and a burner for fast heat up of the exhaust system, leads to higher efficiency of the exhaust aftertreatment system. Among the development, particular emphasis is placed on minimizing the share of emissions during cold starts and the engine's warming-up phase. Emissions produced during the phase when engine and exhaust system are cold, are crucial to the total emissions during a trip. Innovative approaches, such as an expanded hybrid operating strategy and catalyst heating systems, are also assessed. The full integration of all emissions measures and precise adaptation in the interaction among these will open up further potential for reduction. The equipped with the measures pointed above can achieve values for particulate number and gaseous emissions amounting around 20% of the figures demanded by law. This low level of emissions achieved was confirmed and validated through challenging test cycles on a dynamometer at low temperatures and additionally in comprehensive road trails. The influence of such vehicles on air quality becomes negligible. True to its motto of “technology invented for life”, BOSCH is endeavoring to spur these developments on.
