This article details the development of a plug-in hybrid electric powertrain
system for a wheel loader. The work included both computer modeling and fired
engine testing. A methodical approach was utilized, which included identifying
system requirements, an architecture study, component sizing, and cost analysis.
After the optimal system was designed, the engine and hybrid motor were
installed in a powertrain test cell and evaluated over an in-use duty cycle. A
bespoke utility factor, relevant for wheel loader operation, was developed to
enable realistic fuel economy and emissions weighting between charge depleting
and charge sustaining operation. Finally, an exhaust heater was used to ensure
rapid warmup of the aftertreatment system. Compared to an internal combustion
engine–only baseline, the hybrid powertrain system resulted in a 48% reduction
in CO2 and an 84% reduction in NOX emissions when operated
over an 8-h shift, with daily recharging.
