Assessment of Multiple Injection Strategies in a Direct-Injection Hydrogen Research Engine

Hydrogen is widely considered a promising fuel for future transportation applications for both, internal combustion engines and fuel cells. Due to their advanced stage of development and immediate availability hydrogen combustion engines could act as a bridging technology towards a wide-spread hydrogen infrastructure. Although fuel cell vehicles are expected to surpass hydrogen combustion engine vehicles in terms of efficiency, the difference in efficiency might not be as significant as widely anticipated [1]. Hydrogen combustion engines have been shown capable of achieving efficiencies of up to 45 % [2]. One of the remaining challenges is the reduction of nitric oxide emissions while achieving peak engine efficiencies.

This paper summarizes research work performed on a single-cylinder hydrogen direct injection engine at Argonne National Laboratory. Several injection strategies, composed of injection angle and combination of primary and secondary injection, were evaluated and compared to single injection strategy as a baseline. Due to the limitations in injector flow rates the study mainly focused on an engine speed of 1000 RPM. It was found that multiple injection strategies have the potential of reducing nitric oxide emissions by up to 85 % compared to single injection while maintaining constant engine efficiency. Further improvements to injector technology will be required to expand the operating regime of multiple injection strategies to higher engine speeds.