Dynamic Optimization of Diesel Air-Path Control for Reduced Pumping Work

Abstract

One potential method to reduce fuel consumption in diesel engines with variable geometry turbines (VGT) and exhaust gas recirculation (EGR) is to reduce the transient engine pumping work through improved EGR-VGT control. Numerical dynamic programming is applied to investigate optimal EGR-VGT control policies for reduced pumping work on a three-state model of a 6.7-liter medium-duty diesel engine. Optimality is defined by a multi-objective cost function that penalizes pumping work, EGR rate control error, and boost pressure control error. Multiple dynamic programs, each with a different set of cost function weights, are performed over an acceleration in the Heavy-Duty Federal Test Procedure cycle to generate the optimal trade-off between the stated objectives. Additionally, a production-representative EGR-VGT controller is simulated, and the resulting suboptimal performance is compared to the optimal frontier to establish the potential fuel consumption benefit of improved EGR-VGT control.