Development of a Comprehensive Model for the Concurrent Minimization of CO 2 and NOx Emissions of a 48 V Mild-Hybrid Diesel Car
Abstract:
Nowadays, demanding carbon dioxide (CO2) targets push for the
electrification of the powertrain since the internal combustion engine, as the
sole way to propel the vehicle, cannot reach those targets. In this context,
Mild-Hybrid Vehicles (MHV) with a low-voltage 48 V electric network proved to be
a cost-effective solution for the reduction of CO2 emissions.
However, the impact of the electrification on the powertrain thermal management,
on the aftertreatment light-off, and thus on tailpipe (TP) emissions must be
properly assessed. For this reason, a virtual testing approach for thorough
powertrain and vehicle virtual validation is required to reduce testing and
calibration efforts.
The aim of this research work is to bridge the gap between high-fidelity models
commonly used for the development of components and a system-level approach for
the evaluation of full vehicle technologies and architectures. This work means
to integrate detailed subsystem models in an inclusive vehicle model of a 48 V
diesel-powered Mild-Hybrid Large Multi-Purpose Vehicle (LMPV) passenger car,
featuring the engine, cooling circuit, aftertreatment system, dual-voltage
electric network, and electronic control unit (ECU).
After the validation of the main powertrain subsystems (e.g., engine and coolant
circuit), the virtual test rig has been coupled with an Energy Management System
based on the Equivalent Consumption Minimization Strategy (ECMS) to reproduce
the behavior of the MHV along the Worldwide Harmonized Light-Duty Vehicles Test
Cycle (WLTC) driving cycle.
Additionally, the Equivalent Emissions Minimization Strategy (EMS) has been
updated in an Equivalent Emissions Minimization Strategy (EEMS) to account for
the concurrent minimization of CO2 and nitrogen oxides (NOx).
Different calibration approaches have been undertaken with the aim to generate a
trade-off frontier for the optimization of fuel consumption and engine-out (EO)
and TP NOx emissions.
Promising results are obtained: the EEMS provided a fuel consumption improvement
of up to 6.1%, while EO and TP NOx emissions reduced up to 16.1% and 12.6%,
respectively.