Effects of Hydrogen on Combustion in Ammonia–Diesel Dual Fuel Engine and Demonstration of Autothermal Catalyst to Reform Ammonia Into Hydrogen

Abstract

Abstract The authors conducted NH3 and diesel fuel dual fuel combustion experiments using both large and small single-cylinder diesel engines and investigated its combustibility and emission changes by adding H2. In addition, the small engine was operated by supplying reformed gas containing H2, which was produced using a device to reform NH3 into H2. Co-combustion of NH3 and diesel fuel with large and small single-cylinder engines showed similar trends in the change of emissions. In particular, N2O emissions tended to decrease when the NH3 energy fraction was higher in the cases of the large engine. The combustion-assisting effect of H2 was obtained when H2 was mixed into the charge air of NH3/diesel dual fuel mode with the large and small single-cylinder engines. The addition of H2 resulted in a reduction in unburned NH3 and a change in N2O emissions. Reduction in N2O emissions was achieved by increasing the amount of supply H2, particularly for the large engine. The small engine was operated by supplying reformed gas. This allowed unburned NH3 to drastically decrease. It was also found that N2O emission can be generated when NH3 remains in the reformed gas. The NH3 reforming system has achieved the target H2 flow rate, and the effectiveness of the proposed reforming system has been demonstrated. This research provided valuable insights for the design of an NH3 reforming system suitable for marine engines.