Abstract

Ammonia is a promising alternative fuel due to its potential to significantly reduce the demand for conventional fuels and decrease harmful pollutant emissions during combustion. However, using it as a fuel presents challenges such as low burning velocity, narrow flammability range, combustion instabilities, and emissions of nitrogen oxides. This study aims to improve ammonia combustion performance in internal combustion engines using a novel methodology. Experiments were conducted on a modified single-cylinder four-stroke optical compression-ignition research engine capable of running on compression-ignition and spark-ignition engine conditions. The study compared pure ammonia combustion with pure methanol combustion at the same operating conditions. Additionally, highly reactive hydrocarbon fuels were injected into the ammonia mixture to improve its combustion performance. The finding exhibited that injecting high-burning velocity fuel into ammonia improved its combustion performance significantly due to a faster heat release rate. Furthermore, the study explored the effect of multiple flames on pure ammonia combustion using a specialized metal liner equipped with four equispaced spark plugs. The results demonstrated that multiple flames inside the combustion chamber enhanced the burning rate of ammonia and improved engine performance significantly. Furthermore, different ammonia-hydrocarbon dual-fuel mixtures coupled with multiple spark plugs were studied, with findings showing that dual-fuel with multiple flames improved performance more effectively and reduced the additional fuel amount. Moreover, increasing hydrocarbon fuel fraction into ammonia increased NO_x emission due to both fuel bound and thermal NO_x, along with higher CO₂ and lower unburned hydrocarbon emissions were observed due to improved combustion performance. The study also examined ammonia-diesel dual-fuel combustion in compression-ignition engine conditions, revealing that increasing the diesel fraction into ammonia achieved promising stable combustion with lower emissions of incomplete combustion products. Additionally, high-speed natural-flame-luminosity imaging was performed to capture flame front propagations for various combustion cases.

Biography

Kalim Uddeen is a Ph.D. candidate in the Mechanical Engineering Program, in the PSE division under the supervision of Prof. James Turner. He received his Master of Science (MS) degree from the Indian Institute of Technology Guwahati (IITG), in India. He started his PhD at KAUST in 2019 and his research interest is focused on the application of alternative fuels in the internal-combustion engine.