Abstract
Direct injection technology benefits the natural gas fuel engine with high efficiency together with low emission, and the gas fuel jet characteristic directly affects the combustion. In this work, the high-pressure methane jet characteristic especially the flow characteristic in the near nozzle zone under condition of injection pressure ratio of 10 was investigated based on a three-dimensional numerical model of methane jet adopting Large Eddy Simulation (LES) model. The results show that the primary vortex appears in the near-nozzle zone, and the Mach disk formed in this region promotes the formation of the primary vortex. The developing process of the primary vortex (0.02 ms∼0.06 ms) coincides with the entrainment ratio, the transient entrained air mass, Reynolds number, and Mach disk length-to-width ratio, which indicates that the primary vortex has a significant impact on the entrainment capacity and flow characteristics of the methane jet during the initial stage. When the primary vortex reaches its maximum size at 0.46 ms, the entrainment mass flow rate, Reynolds number, and the length-to-width ratio of the Mach disk in the near zone all reach their maximum values. The primary vortex developing causes influence on the Mach disk characteristics in the near-nozzle zone, especially on the Mach disk height and the length-to-height ratio. However, the impact on the Mach disk height is relatively small. Understanding the primary vortex developing characteristics is beneficial for the optimization design of nozzle structures for the development of more efficient new high-pressure DI natural gas fuel engines.
Get full access to this article
View all access options for this article.