Investigation of boost pressure and spark timing on combustion and NO emissions under lean mixture operation in hydrogen engines

Abstract

Copyright © 2023 The Authors. Hydrogen may become a replacement for liquid fossil fuels, contributing to greenhouse gas emissions reductions by improving the thermal efficiency of boosted lean burn spark ignition engines. Single-zone engine combustion models are simple, but can yield useful results as a step in the design process for developing alternative fuel systems. The single-zone thermodynamic model is advanced by implementing a laminar flame speed sub-model to investigate combustion, an extended Zeldovich mechanism for nitric oxide emissions, and incorporating the Livengood-Wu integral model for knock characteristics. The results were validated using published experiments giving satisfactory predictions between simulation and experiment for spark timing variation, manifold air pressure, and equivalence ratios. A detailed analysis of boosted lean burn strategies showed that nitric oxide emissions increased with boosted pressure, hence emissions can be controlled through optimizing the excess air ratio and the start of combustion. Further techniques to achieve high thermal efficiency and to prevent knock for boosted lean burn hydrogen SI engine are discussed.