System modelling and analysis for design and development of a lean exhaust after-treatment system

Abstract

A comprehensive system-level modelling methodology for vehicle exhaust and after-treatment system development is presented. Within the constraints required for a development vehicle equipped with a lean-burn direct-injection gasoline engine, system-level analysis was extensively applied to guide the design of the after-treatment system. The size and location of the lean nitrogen oxide (NO x) after-treatment device was determined to achieve the best trade-off between engine back pressure, catalyst light-off, and acceptable thermal ageing under high-speed and high-load conditions. In addition, various after-treatment architecture and layout concepts were efficiently evaluated and screened, requirements for after-treatment components and exhaust thermal management devices were defined, and promising technologies were recommended for further development and testing. Beyond immediate implementation in the development vehicle, several exhaust thermal management strategies (electrically heated converter, lambda split control, engine stop—start, and multiple warm-up) were explored. These technologies have been assessed individually and in combination to formulate effective thermal management strategies under fuel penalty constraints. While the specific applications described in this paper are for a lean-burn gasoline direct-injection development vehicle, the methodology is equally applicable to advanced powertrains with one or more after-treatment devices (diesel engines, alternative fuels, hybrid vehicles, etc.)