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Pre-chambers are a means to enable lean burn combustion strategies which can increase the thermal efficiency of gasoline spark ignition internal combustion engines. A new engine concept is evaluated in this work using computational simulations of non-reacting flow. The objective of the computational study was to evaluate the feasibility of several engine design configurations combined with fuel injection strategies to create local fuel/air mixtures in the pre-chambers above the ignition and flammability limits, while maintaining lean conditions in the main combustion chamber. The current work used computational fluid dynamics to develop a novel combustion chamber geometry where the flow was evaluated through a series of six design iterations to create ignitable mixtures (based on fuel-to-air equivalence ratio, ϕ) using fuel injection profiles and flow control via the piston, cylinder head, and pre-chamber geometry.

This paper describes the simulation, design, and testing of a mechanically supercharged 2.4L I-4 gasoline direct injection engine with Miller cycle late intake valve closing and high geometric compression ratio. Engine downspeeding is also achieved through modified transmission gear ratios. A 3.3L naturally-aspirated V6 engine was chosen as the benchmark for comparison. Intended vehicle application is a mid-size passenger car or small/mid-size CUV. The CAE tool GT-Power was used for component selection and air path development. The powertrain simulation model was then exercised to show both improved fuel economy and performance compared to the V6 baseline engine. The design of a bespoke integrated supercharger with magnetic clutch, charge air cooler, and intake manifold was made and procured. A large new software aggregate was ported into an existing production ECU with modified internal circuitry.