With increasingly stringent emissions limitation of green-house gas and atmospheric pollutants for ship, the natural gas engine has played a significant role in marine engines because of its lower CO2, NOx and PM emissions than that of marine diesel engine. There are two types of marine natural gas engine for low-speed two-stroke engine. The one is that natural gas is injected just above the scavenging ports with low injection pressure. That causes the premixed combustion in the chamber of engine that leads to low NOx emission and high possibility of knocking, and the knocking results in lower power output compared to diesel engines. The other one is the direct injection of natural gas on the cylinder head with high-pressure injection, it can make a high power output that is similar with diesel engine, however the emission of NOx can not be decreased dramatically. The mixing characteristics of natural gas jet is the prerequisite of the combustion improvement for decreasing the NOx emissions. However, high-pressure natural gas injection causes the compressible and underexpanded jet, its effects on the mixing process have not been fully understood, especially, the injection pressure is up to 30 MPa with large injection quantity and critical surrounding gas conditions for the low-speed two-stroke marine engine.Therefore, this research is focused on the flow and mixing process of the natural gas jet with high-pressure injection under the in-cylinder conditions of low-speed two-stroke marine engine. A numerical model of the natural gas jet was constructed, and it was validated using the experimental data measured by shadowgraphy and Particle Image Velocimetry (PIV) methods based on a constant volume chamber. The natural gas jet penetration, air entrainment, and the distribution of velocity, density, equivalence ratio have been analyzed under different injection conditions. The effects of surrounding gas conditions including pressure, temperature, and swirl ratio on air entrainment and equivalence ratio distribution were studied in detailed. Finally, it revealed and summarized the mixing characteristics of the natural gas jet under the injection and surrounding gas conditions same with low-speed two-stroke marine engines.

A Numerical Investigation on Mixing Characteristics of Natural Gas Jets With High-Pressure Injection

Paper Proceedings: https://asmedigitalcollection.asme.org/ICEF/ICEF2021/volume/85512

ASME 2021 Internal Combustion Engine Division Fall Technical Conference (ICEF2021)

Supporting the need among researchers worldwide for additional online and multimedia content, ASME now offers the ASME Conference Video Collection. This platform will collect and provide long-term access to conference presentation videos, encompassing all technology areas within ASME's technical conference and events program. About 30,000-40,000 engineers across all mechanical engineering and related disciplines participate in ASME conferences each year. This includes authors of approximately 6,000 to 8,000 technical papers published by ASME, the majority of whom also submit video presentations for our virtual conferences. The video collection will be available as an add-on to existing product packages or as a separate subscription.