Experimental Investigation of High-Pressure Ammonia Spray and Combustion under Marine Engine-Like Conditions Using Optical Diagnostics

Ammonia could represent a viable alternative to the use of conventional fossil fuels in marine engines as it is carbon-free and can be produced using renewable energy sources. However, the use of ammonia as a marine fuel presents some critical issues, due to its high toxicity, its lower energy density compared to conventional fuels, and its low flammability limits, which make it difficult to burn under lean conditions. To address the latter issue in more detail, experiments were conducted in a constant volume optical chamber designed to inject and burn ammonia under conditions similar to those of 2-stroke Marine engines. The chamber, which mirrors the dimensions of a single-cylinder in a two-stroke marine engine, repre-sents a high-temperature and high-pressure cylinder. Two injectors have been integrated, one for am-monia injection and the other for the supply of conventional fuel to ignite ammonia. High-precision instruments, including pressure and temperature sensors, as well as a sapphire window for the use of optical methods, such as high-speed imaging, were installed on the chamber. This setup made it possible to collect both thermodynamic and optical data and facilitated the observation of com-bustion behavior under various boundary conditions. Various temperature conditions were investigated in the optical chamber and a sweep of the diesel pilot injection duration was performed. The vaporization of ammonia spray was measured and the combus-tion process was studied in detail to better understand the phenomena controlling the process. The findings from these experiments provide crucial insights for optimizing ammonia combustion for marine engines under various operating conditions.