Abstract
The Shipbuilding Research Association of Japan started a project in 2003 to develop a direct water injection (DWI) system to decrease NOx formation through the reduction of flame temperatures at the combustion stage in marine diesel engines. In this project, it was decided that an 80% reduction in NOx emission must be achieved with a less than 3% increase in specific fuel consumption. To evaluate this system, high-speed photography of combustion was carried out using a visual test engine that had the same construction as a low-speed marine engine. Flame temperature decreases were visualized using the two-color method of digital photo data analysis. CFD calculations using KIVA code and StarCD were also made, and the behavior of sprays/flames and the temperature distribution in flames were successfully simulated. Furthermore, experiments to optimize the water injection system design, ensuring NOx reduction, were carried out using a constant volume combustion chamber simulating the engine running conditions.
