Electrically assisted compressor in hydrogen fuelled internal combustion engine for better performance and ultra-low NOx emissions

To reach a carbon neutral future as quickly as possible, it is important to consider different alternative solutions. One alternative is the use of hydrogen as a fuel in the internal combustion engine (H2 ICE). This solution offers close to zero CO2 emission, and it can benefit from the existing combustion engine. However, it comes with its own challenges. One such challenge is the NOx emissions being strongly dependent on air-fuel ratio i.e., lambda in a spark ignited direct injection H2 ICE. This is a big challenge especially at transient operation since the airflow is limited because of the turbocharger lag. If the minimum air fuel ratio is limited to keep NOx emissions at a certain level, then transient performance is significantly deteriorated. In this paper, the benefits of an electrically assisted compressor combined with a variable geometry turbocharger are investigated and different layouts are analysed using a thermodynamical model. Variable geometry turbocharger is matched to cover the steady state operation of the engine, whereas electrical compressor assists during transient to keep air fuel ratio above a certain level.