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Diesel engines with relatively good fuel economy are known as an effective means of reducing CO₂ emissions. It is expected that diesel engines will continue to expand as efforts to slow global warming are intensified. Diesel particulate and NOx reduction system (DPNR), which was first developed in 2003 for introduction in the Japanese and European markets, shows high purification performance which can meet more stringent regulations in the future. However, it is poisoned by sulfur components in exhaust gas derived from fuel and lubricant. We then developed the sulfur trap DPNR with a sulfur trap catalyst that traps sulfur components in the exhaust gas. High purification performance could be achieved with a small amount of platinum group metal (PGM) due to prevention of sulfur poisoning and thermal deterioration.

The hydrogen combustion characteristics have been studied in a late-injection (near TDC) hot surface ignition engine. As a supplemental experiment, the mode of combustion was observed in a constant volume combustion chamber by the schlieren method. Consequently the combustion process, that was the flame propagation initiated by a hot surface through heterogeneous hydrogen jets, was not the same as that of a diesel engine. The experimental results in test engine showed the optimum number of injection holes and the effect of intake air swirl for better mixture formation. It was observed that the combustion was frequently accompanied by non-negligible combustion pressure vibrations at all engine operating conditions.