Nowadays, the ocean shipping carbon emission accounting for 2∼3% of global carbon emission. As a zero-carbon fuel with higher volumetric heat density than hydrogen, ammonia has the potential to serve for marine engines, thereby aiding in the decarbonization of ocean shipping. However, as a fuel with weak flammability, ammonia engine still faces the problem of how to organize its combustion. This study investigates the feasibility of utilizing ammonia as the main fuel for marine engines and its combustion characteristics. A centralized jet-flame controlled combustion strategy for two-stroke marine engine are proposed to better organize the ammonia combustion in large combustion chamber. Firstly, the relative injection direction of ammonia and diesel was researched, ammonia and diesel injected in an opposite direction has better performance as the ignition happens downstream of ammonia spray with better fuel-air mixture for ignition and flame transport from downstream to upstream preventing flame hitting liner to avoid extinguishing. Secondly, centralized jet-flame controlled combustion strategy was researched in engine model. There are two phases of this combustion strategy, premixed combustion and diffusion combustion. The ITE and unburn ammonia most related to the premixed ammonia which was influenced by ammonia injection timing. The unburn ammonia most related to diffusion combustion. Ammonia injection direction concentrating in the center and flame transport from downstream to upstream can preventing ammonia flame from hitting liner and better the diffusion combustion efficiency than existing ammonia-diesel injected in same direction mode. A replacement rate of up to 98% for ammonia can be achieved while maintaining an indicated thermal efficiency (ITE) ranging from 43.7% to 50.4%. Unburned ammonia can be optimized from 4.4% to 0.18%.

中文翻译：

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采用集中射流火焰控制燃烧策略的液氨对远洋航运推进动力脱碳的研究


如今，远洋航运的碳排放量占全球碳排放量的 2∼3%。作为一种体积热密度高于氢气的零碳燃料，氨有可能用于船用发动机，从而有助于远洋运输的脱碳。然而，氨发动机作为一种可燃性较弱的燃料，仍然面临着如何组织其燃烧的问题。本研究探讨了利用氨作为船用发动机主要燃料的可行性及其燃烧特性。提出了一种用于二冲程船用发动机的集中式喷射火焰控制燃烧策略，以更好地组织大型燃烧室中的氨燃烧。首先，研究了氨和柴油的相对喷射方向，氨和柴油相反方向喷射具有更好的性能，因为点火发生在氨喷雾的下游，具有更好的燃料-空气混合物用于点火和火焰从下游到上游的运输，防止火焰击中衬里以避免熄灭。其次，在发动机模型中研究了集中式喷射火焰控制燃烧策略;这种燃烧策略有两个阶段，预混燃烧和扩散燃烧。ITE 和未燃烧氨与预混氨最相关，后者受氨注入时间的影响。与扩散燃烧最相关的未燃烧氨。氨喷射方向集中在中心，火焰由下游向上游输送，可以防止氨火焰撞击内衬，比现有的同向注射氨柴油模式提高扩散燃烧效率。 氨的替代率高达 98%，同时保持 43.7% 至 50.4% 的指示热效率 （ITE）。未燃烧的氨可以在 4.4% 到 0.18% 之间优化。