| dc.description.abstract | Natural gas is a promising alternative fuel for marine engines that must comply with strict international emissions regulations. The current standard for these engines is the low-pressure dual fuel arrangement usually associated with high levels of harmful hydrocarbon emissions. Alternatively, the high-pressure dual fuel arrangement has the potential to eliminate these emissions which makes it one of the best options to comply with the International Maritime Organization's emissions guidelines for ships. Direct injection of gaseous fuel into the cylinder requires a novel fuel injector. A prototype in development by L'Orange was modeled for this thesis using bond graph theory and the modeling and simulation program 20-Sim. The internal dimensions of this complex injector were modified to understand how further iterations of the design process may influence how the injector functions, specifically concerning mass flow into the cylinder during injection and pressure fluctuations within the injector. The largest volumes were confirmed to have the most significant influence on injector performance, indicating that if these components require significant re-sizing, more advanced simulations may be required to ensure adequate flow for different engine requirements. A safety shut-off device proposed by the manufacturer was also evaluated for effectiveness. Simulations indicate that this quick-closing device activated by a significant decrease in downstream pressure is not an effective safety system to prevent excessive fuel buildup in the cylinder during a failure of a needle stuck in the open position. | |
