<div class="section abstract"><div class="htmlview paragraph">One challenge for the development of commercial vehicles is the reduction of CO<sub>2</sub> greenhouse, where hydrogen can help to reduce the fleet CO<sub>2</sub>. For instance, in Europe a drop in fleet consumption of 15% and 30% is set as target by the regulation until 2025 and 2030. Another challenge is EURO VII in EU or even already approved CARB HD Low NO<sub>x</sub> Regulation in USA, not only for Diesel but also for hydrogen combustion engines.</div><div class="htmlview paragraph">In this study, first the requirements for the combustion and after-treatment system of a hydrogen engine are defined based on future emission regulations. The major advantages regarded to hydrogen combustion are due to the wide range of flammability and very high flame speed numbers compared to other fossil based fuels. Thus, it can be well used for lean burn combustion with much better fuel efficiency and very low NO<sub>x</sub> emissions with an ultra lean combustion.</div><div class="htmlview paragraph">A comprehensive experimental investigation is performed on a HD 2 L single-cylinder engine. The hydrogen combustion characteristics are studied with variation of multiple operating parameters like EGR, air-fuel ratio, etc. A predictive hydrogen combustion and NO<sub>x</sub> model is then developed and validated using the test results.</div><div class="htmlview paragraph">As baseline for the numerical investigations of engine transient behavior in the cold cycle, an in-line six cylinder 12L HD diesel engine is developed. Cold WHTC and FTP cycles are simulated and the combustion, exhaust gas temperature and emission behavior are evaluated.</div><div class="htmlview paragraph">The effects of lean-burning combustion and exhaust after-treatment for engine NO<sub>x</sub> reduction as well as thermal management in transient cycles on exhaust after-treatment (EAT) system to fulfil future regulations are discussed. Multiple EAT architectures are investigated and the trade-off between fuel consumption and the end-of-pipe NO<sub>x</sub> is assessed. Challenges and potentials of hydrogen combustion for heavy-duty applications considering future regulations are addressed. Variation of engine operating parameters and the potentials of engine calibration for series development is demonstrated using predictive engine and EAT models.</div></div>
