Improving performance specifications of internal combustion engine dedicated to plug-in hybrid electric vehicles based on coupled optimization methodology

Abstract

In the context of heavy-duty application, this paper introduces a novel methodology for better defining the specifications of the internal combustion engine (ICE) in plug-in hybrid electric vehicles (pHEVs) with energy management-based evaluation. From mathematical modelling of reference engine static efficiency and maximum torque, parametric transformations are performed to explore alternative engine designs. A coupled optimization problem is formulated as a bi-level form with powertrain optimal energy management based on a combinatorial problem formulation solved by Branch&Bound algorithm in the inner loop and exhaustive evaluation of ICE designs in the outer loop. A detailed transmission losses model and limitations on engine torque response dynamics are included in the optimization problem. The number of engine ignition and shutdown phases are also considered in order to better simulate the powertrain. The results show potential fuel reduction of 2.4% on a regional delivery cycle with zero-emission zones, and are intended to be used as specifications to guide further detailed engine development dedicated to hybrid powertrains.