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Hydrogen engines are required to provide high thermal efficiency and low nitrogen oxide (NOX) emissions. There are many possible combinations of injection timing, ignition timing, lambda and EGR rate that can be used in a direct-injection system for achieving such performance. In this study, NOX emissions of natural aspirated 4 cylinders engine with management strategies involving the injection timing, ignition timing, lambda and the EGR rate were evaluated under a Japanese JE05 emissions test cycle. Finally, the paper projects the potential of direct injection hydrogen engine for obtaining high output power and attaining low NOX emissions of 0.7 g/kWh under the emission test cycle.

A development project for a hydrogen internal combustion engine (ICE) system for trucks supporting Japanese freightage has been promoted as a candidate for use in future vehicles that meet ultra-low emission and anti-global warming targets. This project aims to develop a hydrogen ICE truck that can handle the same freight as existing trucks. The core development technologies for this project are a direct-injection (DI) hydrogen ICE system and a liquid hydrogen tank system which has a liquid hydrogen pump built-in. In the first phase of the project, efforts were made to develop the DI hydrogen ICE system. Over the past three years, the following results have been obtained: A high-pressure hydrogen gas direct injector developed for this project was applied to a single-cylinder hydrogen ICE and the indicated mean effective pressure (IMEP) corresponding to a power output of 147 kW in a 6-cylinder hydrogen ICE was confirmed.

The planned development of a hydrogen ICE system for trucks is one of the technological candidates for air pollution reduction and global warming prevention for the large-sized (heavy-duty) trucks supporting Japanese freightage. This project is the first to develop a DISI multi-cylinder hydrogen ICE system aimed at combining high power output and low NOx generation.