Predicting the Behavior of a Hydrogen-Enhanced Lean-Burn SI Engine Concept

This paper explores the modeling of a lean boosted engine concept. Modeling provides a useful tool for investigating different parameters and comparing resultant emissions and fuel economy performance. An existing architectural concept has been tailored to a boosted hydrogen-enhanced lean-burn SI engine. The simulation consists of a set of Matlab models, part physical and part empirical, which has been developed to simulate a working engine.

The model was calibrated with production engine data and experimental data taken at MIT. Combustion and emissions data come from a single cylinder research engine and include changes in air/fuel ratio, load and speed, and different fractions of the gasoline fuel reformed to H₂ and CO. The outputs of the model are brake specific NO_x emissions and brake specific fuel consumption maps along with cumulative NO_x emissions and fuel economy for urban and highway drive cycles.

Model results closely match production engine performance data for naturally aspirated stoichiometric operation. Simulation of lean boosted operation with 20% gasoline reformate fraction and 20% downsized displacement predicts a 23% improvement in fuel economy. Furthermore, part load engine-out NO_x emissions are reduced by 83% compared to a baseline naturally aspirated stoichiometric production engine with 10% EGR dilution.