The talks are on:
Kalim Uddeen
Ph.D. Student, supervised by Prof. James Turner
Abstract: Ammonia (NH3) is an attractive carbon-free fuel that has the potential to reduce the need for conventional hydrocarbon (HC) fuels and reduce emissions of undesirable pollutants such as CO, CO2, particulates, and unburned hydrocarbons (UHCs). However, ammonia has different combustion characteristics than conventional HC fuel. Ammonia is difficult to ignite and has a low combustion rate, resulting in large cyclic variations. In addition, nitrogen oxides (NOx) emissions in the exhaust tract are a major challenge when using ammonia as a fuel directly in engines. Therefore, this research work used dual fuel, and multiple spark-ignition approaches to achieve stable ammonia combustion with high engine performance. In this study, the effect of multiple spark ignition sites on the combustion of pure ammonia in an optical spark ignition engine (SI) was investigated. The experiment was conducted with four spark plugs mounted equidistantly on a special metal liner and one spark plug fitted at the top of the cylinder head. The multiple flames emitted from the different spark ignition sites were captured by natural flame luminosity (NFL) imaging. In the results, the conventional single spark ignition is compared with multiple ignition locations. It was found that single spark ignition resulted in lower in-cylinder pressure, longer combustion duration, and higher combustion instability due to the poor ammonia fuel combustion rate. However, firing multiple spark plugs significantly improved combustion stability, increased engine power, and shortened the combustion period under the same operating conditions. In addition, the flame kernels produced by multiple ignition sites resulted in higher NOx emissions in the exhaust tract due to the higher temperatures in the cylinder. In addition, this study also investigated the effect of three different air-fuel equivalence ratios of λ: 1.0, 1.2, and 1.4 on the combustion characteristics of ammonia fuel. The maximum NOx level was obtained for λ: 1.2 because the excess air in the mixture oxidizes the ammonia and provides abundant oxygen to generate more NOx.
Bio: Kalim Uddeen is a Ph.D. student in the mechanical engineering department at KAUST, supervised by Prof. James Turner. He received his Master of Science (MS) degree from the Indian Institute of Technology Guwahati (IITG), in India. The focus of his current research is to use low-carbon and alternative carbon-free fuels e.g. ammonia, hydrogen, methane, and its blends in a spark-ignition engine.
Seunghwan Bang
Ph.D. Candidate, supervised by Prof. Min Suk Cha
Abstract: Ammonia is considered as one of the promising hydrogen carriers toward a sustainable world. Plasma-assisted cracking of NH3 could provide cost- and energy-effective, low temperature, on-demand (partial) cracking of NH3 into H2. Here, we presented a temperature-dependent plasma-chemical kinetic study to investigate the role of both electron-induced reactions and thermally induced reactions on the decomposition of NH3.We employed a plasma-chemical kinetic model (KAUSTKin), developed a plasma-chemical reaction mechanism for the numerical analysis, and introduced a temperature-controlled dielectric barrier discharge reactor for the experimental investigation using 1mol% NH3 diluted in N2. As a result, we observed the plasma significantly lowered the cracking temperature and found that the plasma-chemical mechanism should be further improved to better predict the experiment. The commonly used rates for the key NH3 pyrolysis reaction (NH3+M ↔ NH2+H+M) significantly overpredicted the recombination rate at temperatures below 600 K. Furthermore, the other identified shortcomings in the available data are (i) thermal hydrazine chemistry, (ii) electron-scattering cross-section data of NxHy,(iii) electron-impact dissociation of N2,and (iv) dissociative quenching of excited states of N2.We believe that the present study will spark fundamental interest to address these shortcomings and contribute to technical advancements in plasma-assisted NH3 cracking technology.
Bio: Seunghwan Bang is a Mechanical engineering Ph.D. student supervised by Professor. Min Suk Cha. Before joining CCRC in 2019, he obtained his bachelor's and master’s degree in mechanical engineering from Yeungnam university, South Korea, in 2018. His research focus on the development of a comprehensive reaction mechanism to achieve the fundamental understanding of the plasma-assisted chemical process.