Effect of Intake Air Hydrogenation Coupled with Intake Air Humidification on Combustion and Emissions of Marine Diesel Engine

The purpose of this study is to investigate the effect of intake air hydrogenation coupled with intake air humidification (IAH) on the combustion and emission of marine diesel engines. A 3D numerical model of four-stroke turbocharged intercooled marine diesel engine was established by using commercial software AVL-Fire. The effects of hydrogen and water injected into the intake port on engine in-cylinder combustion and emission characteristics at 1350 r/min and partial load were studied. The novelty of this study is to combine different hydrogen-fuel ratios and water-fuel ratios, so as to find the optimization method that can reduce NO_x and soot emissions and ensure the thermal efficiency of the engine doesn’t decrease. The results show that by injecting a small quantity of hydrogen (the ratio of hydrogen mass to diesel mass is 1.40%) into the intake port of diesel engine as the activator of in-cylinder combustion, the indicated specific fuel consumption (ISFC) of diesel is reduced by 2% and NO_x emissions are reduced by 6.7%. However, the intake air hydrogenation will make in-cylinder combustion temperature higher, resulting in the limited effect of NO_x emissions reduction, so it is difficult to meet the requirements of emission regulations only by adopting intake air hydrogenation technology. Using the technology of intake air humidification, the low temperature combustion of diesel engine can be realized. When the water-fuel ratio is 1.0, NO_x emissions are reduced by 62.2%. Therefore, by coupling technology of intake air hydrogenation and intake air humidification, the method of improving fuel economy and reducing NO_x and soot emissions can be explored, so as to optimize engine performance and meet stricter emission regulations.