Homogeneous charge compression ignition technology implemented in a hybrid electric vehicle: System optimal design and benefit analysis for a power-split architecture

Abstract

Homogeneous charge compression ignition technology can improve fuel economy by providing increased efficiency at low-load operation. This article examines the implementation of this technology in hybrid propulsion systems. To assess the benefits, a physics-based model for a spark ignition–homogeneous charge compression ignition dual-operation engine is developed, together with system and component models, and is used to optimize a crossover sport utility van with a power-split hybrid powertrain. Comparison of optimal designs for the pure spark ignition and dual homogeneous charge compression ignition cases indicates the reduction in the fuel consumption based on our modeling assumptions to be in the range 2.5–5%, depending on the test cycle. These benefits increase substantially when the acceleration performance requirements increase. An analysis method is presented to show how such engine-level changes affect the entire powertrain characteristics, and mode maps are developed to indicate when the benefits are expected.