Virtual Performance and Emissions Mapping for Diesel Engine Design Optimization

Abstract

This paper builds upon recent publication (SAE Technical Paper 2011-01-1388, 2011, doi:10.4271/2011-01-1388) and outlines the on-going development of an advanced simulator for virtual engine mapping and optimization of engine performance, combustion and emissions characteristics. The model is further advanced through development of new sub-models for turbulent mixing, multiple injection events, variable injection pressures, engine breathing and gas exchange, as well as particulates formation and oxidation. The result is a simulator which offers engine design and performance data typically associated with 1D thermodynamic engine cycle simulations but with the “physics-based” model robustness usually associated with 3D CFD methods. This combination then enables efficient optimization of engine design with respect to engine performance, combustion characteristics and exhaust gas emissions. As a demonstration, a detailed method to parameterize (calibrate) the advanced PDF-based model is presented followed by application to three case studies: 1) a concept study of a heavy duty diesel engine, examining the impact of increased injection pressure and lower compression ratio to meet engine design constraints and Stage IV/Tier 4 exhaust gas emission limits for both NOx and PM, 2) examining the performance of both the proposed model and 3D-CFD to simulate heat release and exhaust gas emissions in a HSDI diesel engine, 3) performance of the model over a full loadspeed map in terms of combustion and NOx emissions. The results demonstrate the robustness of the model compared to experimental observations and equivalent performance compared to more human resource and CPU cost intensive 3D-CFD simulations.