The talks are on:
Abstract: To mitigate global warming and achieve carbon neutrality by mid-century, variable renewable energy sources (VRES) must scale up to increase their shares in the total primary energy supply in the near future. Among the VRESs, ammonia (NH3) and hydrogen (H2) are attractive carbon-free fuels with zero carbon emissions in their combustion process. Considering the respective properties of NH3 and H2, cofiring NH3/H2 mixtures produces zero carbon emissions, while enhancing the combustion intensity of NH3 and diminishing the safety concerns regarding H2. Fundamental combustion chemistry studies are helpful to better understand the effects of NH3/H2 blending and the inherent mechanism behind engine performance. In this work, jet-stirred reactor (JSR) oxidation experiments on NH3/H2 are conducted. Speciation data of NH3, H2O, NO and N2O are measured using Fourier-transform infrared (FTIR) spectroscopy. A comprehensive kinetic model for NH3 and NH3/H2 is developed, based mainly on the evaluation of kinetic parameters, and validated against the present JSR experimental data and those available in the literature. Based on this model, the blending effects of H2 on NH3 oxidation under present conditions are revealed, including both fuel conversion and NOx formation.
Bio: Xiaoyuan Zhang is currently a postdoc fellow led by Prof. Mani Sarathy. She received her PhD degree in Power Engineering and Engineering Thermophysics from Shanghai Jiaotong University (SJTU), China. Her current research interests are FGMech model development for real fuels, including gasolines, jet fuels, biodiesels and heavy oils, and the reaction kinetic studies on various fuels, including ammonia.
Abstract: Combustion of the promising but weakly-reactive ammonia (NH3) under oxygen-enriched and elevated pressure conditions is critical for adopting this non-carbon fuel in the energy system for decarbonization. However, ammonia's fundamental turbulent combustion characteristics like turbulent flame speed (ST), which is more related to the practical combustion stability in controlled turbulent engine environments, gains sparse research. Thus, this work aims to 1) investigate the turbulent combustion characteristics of ammonia and how the oxygen-enrichment can facilitate the replacement of methane by ammonia in terms of chemical kinetics interacted with turbulence flow dynamics; 2) chase new general correlations of turbulent flame speed to represent the self-similar propagation of turbulent spherical flame. In this study, the turbulent flame speed of stoichiometric ammonia/oxygen/nitrogen mixtures under oxygen enrichment conditions was investigated at elevated pressures using a fan-stirred constant volume combustion chamber. The self-similar propagation characteristics of ammonia flame were found and the flame surface wrinkling as well as stretch sensitivity analysis were performed to explain the acceleration mechanism. Finally, the interaction between Darrieus-Landau instability, thermal-diffusion instability and turbulence were accounted for and a general correlation regardless of different turbulent intensity, measurement method, initial temperature, pressure and fuels was produced.
Bio: Shixing Wang received a Ph.D. in Thermal power engineering from Zhejiang University in China in 2020. He interned in CCRC from 2019 to 2020 as a visiting student. He joined CCRC as a post-doctoral fellow in Prof. William L. Roberts' group from Mar, 2021. His research interest lies in the advanced and clean renewable fuel utilization, ammonia combustion, high-pressure laminar and turbulent combustion, and chemical kinetic modeling.