A Cold-Start Emissions Model of an Engine and Aftertreatment System for Optimisation Studies

Abstract

The minimisation of tail-pipe emissions and fuel consumption during cold-start can be viewed as a constrained optimisation problem involving many parameters. Examining this problem mathematically first requires an accurate and computationally practical model of the engine and exhaust system. This paper proposes such a model for use during the cold-start of a conventional spark ignition engine. This model uses as much physics-based modelling as is computationally practical for optimisation and control studies. It takes a given set of engine control inputs to simulate tailpipe CO, HC and NO emissions, and is both calibrated and validated using detailed measurements obtained on a transient engine dynamometer following the New European Drive Cycle (NEDC).

Cold start modelling of spark ignition engines

“…Potentially, a thermal mean value engine model may be useful for problems including cold start fuel consumption (Keynejad & Manzie, 2006), cold start emissions (Andrianov et al, 2010), and catalyst warm-up (Fiengo et al, 2003). These different problems have varying modelling requirements and therefore may benefit computationally from reduction in model complexity-for example if fuel consumption over cold start is the goal then the need to model gas composition, x, is minimal if the coupling between Eq.…”

Modelling and Fuzzy-Threshold Control of SI Engine for Emission Reduction during Cold Start Phase

“…Ch is the heat transfer coefficient between the combustion gas and the exhaust system, which is a function of the air mass flow (all of these functions has been stored in ECU in the form of lookup tables). The one-dimensional differential equations describing the TS -Tsub and mean temperature of the catalyst converter are based on [6], which equations are complex and require calibration of many parameters. Next, the mean temperature of the exhaust gas (Tg) is converted to the mean temperature of the catalyst converter by a calibration table.…”

“…To develop a control strategy aimed at reducing harmful emissions in the cold start phase, we need a suitable and controllable engine model in this phase. Several mean value and controllable models have been proposed to catch cold start operating condition by Farzad Keenezhad, Chris Manzi and their colleagues in [5][6][7]. These models have been presented for designing controllers to improve emissions, fuel consumption and performance of cold start condition.…”

“…These models have an experimental basis, but they have not including the effect of intake and exhaust valve overlapping (VO) on air pollution and volumetric efficiency. Moreover, the models of the exhaust path, particularly, the model of catalyst temperature, are very complicated and requires calibration of many parameters [6].…”

Optimal cold start calibration of spark ignition engines

“…Hafner and Isermann (2003); Fiengo et al (2003)) may be appropriate following light off, however models capturing catalyst dynamics (e.g. Andrianov et al (2010)) are likely to be required to enable accurate cold start emissions optimisation.…”