Modelling Analysis of Aftertreatment Inlet Temperature Dependence on Exhaust Valve and Ports Design Parameters

Upcoming emissions regulations will force to optimize aftertreatment system to reduce emissions looking for lack of fuel penalty. Despite advances in purely aftertreatment aspects, the performance of the diverse aftertreatment devices is very dependent on the operating temperature. This makes them rely on the engine design and calibration because of the imposed turbine outlet temperature. The need to reach target conversion efficiency and to complete regeneration processes requires controlling additional parameters during the engine setup. For that reason, exploring the potential of different solutions to increase inlet aftertreatment temperature is becoming a critical topic. Nevertheless, such studies cannot be tackled without considering concerns on the engine fuel consumption.

In this paper, the influence of several design parameters is studied by modelling approach under steady state operating conditions in a Diesel engine. An engine model has been setup with experimental data using GT-Power software coupled to an external heat transfer and friction losses turbocharger model to predict correctly turbine outlet temperature. The analysis covers parametric studies focused on the exhaust and intake valves diameter, valves timing as well as the use of multi-step openings. The exhaust ports total length and distribution into several branches are also explored. Differences in the potential of every proposal are also considered as a function of the engine operating range. Finally, discussions on the influence on turbine outlet temperature and fuel consumption are conducted to define general guideline criteria. These are affected by the need to look for solutions providing a suitable balance between exhaust temperature increase and minimized impact on engine fuel economy.