A study on the laminar flame speed of ammonia-acetylene with enhanced oxygen content: Experimental and modeling investigation

The endeavor to decarbonize the maritime industry has spurred intensive exploration into ammonia as a potential solution, despite its inherent drawbacks such as low combustion speed and high ignition energy. Acknowledging the significance of employing a pilot fuel, a pivotal aspect in this context, the current work provides measurements on laminar flame speed (LFS) and Markstein length for ammonia/acetylene mixtures in enriched air (30 % O2) in a constant volume spherical chamber for the first time. With acetylene content ranging from 1 to 10 %-the conventional volume percentage as a pilot fuel-the research unveils compelling findings. The results show an expected increase in LFS with increasing acetylene content, but the Markstein length initially decreases followed by a modest increase, producing a clear plateau. To further bolster the investigation, a detailed assessment of recent kinetic mechanisms governing ammonia combustion, including the C2 submechanism, is conducted. This study also includes the evaluation of the Zeldovich number, which is used for flame dynamics analysis, and the theoretical computation of Markstein length, which is then compared to experimental data.