Krishnan Unni, J., Bhatia, D., Dutta, V., Das, L. et al., "Development of Hydrogen Fuelled Low NOx Engine with Exhaust Gas Recirculation and Exhaust after Treatment," SAE Int. J. Engines 10(1):46-54, 2017, doi:10.4271/2017-26-0074.
Air pollution caused by vehicular tail pipe emissions has become a matter of grave concern in major cities of the world. Hydrogen, a carbon free fuel is a clean burning fuel with only concern being oxides of nitrogen (NOx) formed. The present study focuses on the development of a hydrogen powered multi-cylinder engine with low NOx emissions. The NOx emissions were reduced using a combination of an in-cylinder control strategy viz. Exhaust Gas Recirculation (EGR) and an after treatment method using hydrogen as a NOx reductant. In the present study, the low speed torque of the hydrogen engine was improved by 38.46% from 65 Nm to 90 Nm @ 1200 rpm by operating at an equivalence of 0.64. The higher equivalence ratio operation compared to the conventional low equivalence ratio operation lead to an increase in the torque generated but increased NOx as well. The back fire at higher equivalence ratios was prevented by cold EGR operation while maintaining conditions to prevent water condensation. The spark timing was varied between 2°-15° BTDC and the variation in torque with and without EGR was investigated. The spark timing was found to be advancing with increasing EGR concentration. In the present work, parameter optimization was carried out to generate a peak torque of 180 Nm @ 3600 rpm and a maximum power of 67 kW @ 3600 rpm. The NOx emissions were further reduced by catalytic after treatment. A NOx reduction of upto 20% was obtained due to unburned hydrogen in the exhaust stream. Further studies are being carried out to enhance the NOx reduction capability.