ABSTRACT

This study aims at developing a CFD model for large marine two-stroke dual fuel engine with gaseous fuel direct injection at high pressure. For the gaseous fuel, the shock tube theory and the pseudo-diameter concept are employed to model the injection, jet penetration and air entrainment processes, whereas its non-premixed combustion is represented by a steady diffusion flamelet model along with a pilot fuel ignition kernel. Following this model validation, a large marine two-stroke dual fuel engine closed cycle is simulated for both the gas and diesel modes at 75% load, and the involved phenomena are comparatively assessed. The derived results demonstrate that the gas mode combustion takes place in lower maximum temperature and leaner conditions compared to the diesel mode, resulting in lower NOx emissions. This study is expected to benefit the development of future engine designs and the engine settings optimisation for reducing emissions and increasing efficiency.

摘要

本研究旨在开发一种高压气体燃料直喷大型船用二冲程双燃料发动机的 CFD 模型。对于气体燃料，采用激波管理论和伪直径概念来模拟喷射、射流穿透和空气夹带过程，而其非预混燃烧则由稳定扩散小火焰模型和引燃燃料点火核来表示. 在该模型验证之后，对一个大型船用二冲程双燃料发动机闭式循环在 75% 负载下的燃气和柴油模式进行了模拟，并对所涉及的现象进行了比较评估。推导出的结果表明，与柴油模式相比，气体模式燃烧发生在较低的最高温度和较稀薄的条件下，从而导致较低的 NOx 排放。