Control strategy for a hydrogen combustion engine with lean and stoichiometric combustion system

Abstract Hydrogen presents a promising opportunity for the reduction of CO 2 emissions in combustion processes. Due to its wide ignition limits, operation in lean mode is possible, which significantly reduces NO x emissions. However, this lean operation also leads to a reduction in the resulting torque. In contrast, stoichiometric operation increases maximum power output but leads to increased NO x emissions. In particular, a cost-effective three-way catalyst can be used in stoichiometric operation, enabling effective emission control. This investigation proposes an innovative approach that involves lean-burn operation at part load conditions and switching to stoichiometric operation at full load. The transition between these two modes has a considerable impact on overall NO x emissions. To optimize this process, new functions were developed that implement countermeasures such as lambda control, ignition timing adjustment, catalyst purging, and shortening the switching range through the use of variable valve timing and variable turbine geometry. The results show that nitrogen oxide (NO x ) emissions downstream of the three-way catalyst are kept below $${\text{c}}_{{{\text{NO}}_{x} }} = 100\,{\text{ppm}}$$ in the lean operating range and below $${\text{c}}_{{{\text{NO}}_{x} }} = 30\;{\text{ppm}}$$ in the stoichiometric operating range. By optimizing the transition between the two operating modes and using advanced emission control technologies, it is possible to reduce NO x emissions by 84% while maintaining power efficiency under different load conditions. In addition, the almost torque-neutral switching between the two operational modes ensures that the vehicle’s drivability is not impaired. By incorporating additional dosing of a urea-water solution in an active SCR system, a significant improvment in NO x reduction is attained, achieving levels comparable to those of diesel internal combustion engines. This dual-mode operation strategy improves the feasibility of hydrogen as a viable fuel alternative in future energy systems.