Liquid Ammonia Direct Injection (LADI) fundamental physics and modelling of the aero-thermodynamic of transitional atomisation regime

本课题旨在发展直喷液氨（LNH3）的知识和技术，使之成为一种绿色、无碳的可替代发动机液体燃料。这是重型公路运输和电力生产部门向脱碳迈出的关键一步。根据国际能源协会的报告，LNH3被认为是“唾手可得”的无碳氢替代能源载体，原因如下b[1]。(1)由于LNH3在化肥行业的广泛应用，LNH3的大规模生产和运输基础设施已经广泛存在；(2)与氢气或天然气（LNG）相比，大量储存LNH3明显比氢气更安全、更经济，氨在9.90 atm的室温下液化（类似于丙烷，一种广泛应用于国内的燃料）；(3) LNH3具有非常高的氢密度，每100升kg H2（甚至高于液氢），是主要的氢载体。LNH3的热值低于柴油、汽油等化石燃料，因此产生同样的发电量需要更多的燃料。直喷技术的发展使先进的喷射策略成为可能，通过在较长时间内高精度和可调节的多次喷射，可以提供更多的燃料，同时通过增强蒸发和混合来改善混合物质量。特别强调了MAN和Wärtsilä公司最近开发的发动机，这些公司目前正在将用于船舶应用的氨往复式发动机商业化。问题：理论上，纯LNH3 di发动机作为电力和道路运输部门全面脱碳的可行解决方案是可以实现的。然而，目前存在技术障碍，阻碍了LNH3的广泛使用，以零碳排放发动机完全取代化石燃料。这主要体现在以下几个方面：(1)氨/空气混合物的反应性很低，与发动机工作条件极不相容；(2) LNH3喷射不同于化石燃料，呈现出高度非线性和非定常的行为，会引发严重的燃烧不稳定性和灾难性的发动机故障。在这个项目中，我们通过研究LNH3喷雾在di发动机中的应用来关注第二个问题。

This proposal develops the knowledge and technology for direct injection (DI) of liquid ammonia (LNH3), as green and carbon-free alternative liquid fuel for engine applications. This is a critical step toward the decarbonisation of heavy road transportation and the power production sector. According to the International Energy Association report, LNH3 is considered as "the low hanging fruit" carbon-free hydrogen alternative energy carrier for the following reasons [1]. (1) Mass production and shipping infrastructure of LNH3 is already widely available thanks to its widespread applications in the fertiliser industry; (2) Storage of LNH3, in large quantity, is significantly safer and more economical than hydrogen-compared to hydrogen or natural gas (LNG), ammonia is liquefied at room temperature at 9.90 atm (similar to propane, a fuel with widespread domestic applications); (3) With a very high hydrogen density of kg H2 per 100 litres (even higher than liquid hydrogen), LNH3 is a prime hydrogen carrier. The heating value of LNH3 is lower than fossil fuels, e.g., diesel and gasoline, hence, more fuel is required to produce the same power out. The evolution in DI technology has enabled advanced injection strategies, by which highly precise and modulated multiple injections over an extended period of time allows delivering more fuels while improving the mixture quality by enhancing the evaporation and mixing. Especial emphasis is made on the recent engines developed at MAN and Wärtsilä, companies that are currently commercialising ammonia reciprocating engines for marine applications [2]. Problem: In theory, pure LNH3 DI-engines, as a viable solution for full decarbonisation of power and road transportation sectors, is achievable. However, there are currently technological barriers that prevent the widespread use of LNH3 to completely replace fossil fuels with zero-carbon emission engines. This lays in the following facts: (1) the reactivity of ammonia/air mixtures is very low and quite incompatible with the engine operating conditions; (2) spray of LNH3 is different from fossil fuels and exhibits a highly non-linear and unsteady behaviour which trigger significant combustion instabilities and catastrophic engine failure.In this project, we focus on the second issue by investigating LNH3 sprays in DI-engine applications.