University of Hertfordshire

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Description

Alternative carbon-free fuels as well as optimised combustion systems have recently drawn a lot of attention in engine research to further reduce emissions of criteria pollutants and greenhouse gases (GHGs) in transport. There have been proposals to replace these systems with electric drives, however, the transport sector produces about 10% of the world's GHG emissions and replacing combustion engines with "zero emission" alternatives has only a limited potential in reducing global GHG emissions. On the other hand, the proposed alternatives are facing a number of obstacles, for instance, electric vehicles powered by batteries have tremendous cost and weight; they are hoped to be charged by renewable electricity, which currently represent only a minuscule fraction of the world's energy supply. Since around 80% of useful energy such as heat, propulsion energy and electricity is produced via combustion processes and due to the high energy density and storability of fuels, combustion will remain for several decade the technologically, economically and ecologically best solution for many applications in transport and power generation.

The UK's long-term emissions target is currently for at least an 100% reduction in GHG emissions by 2050 compared to 1990. In order to minimise the effects on climate change, alternative carbon-free fuels as well as highly efficient combustion systems have recently drawn a lot of attention in engine research. Ammonia (NH3) has been identified as one of the most promising hydrogen energy carriers, and will play an important role during the process of decarbonisation of the transport. Ammonia is carbon-free, has no direct greenhouse gas effect, and can be synthesised with an entirely carbon-free process from renewable power sources. The greatest advantage of ammonia is that it has a high energy density (22.5 MJ/kg, comparable to some fossil fuels) which makes it an effective fuel and energy storage option. Analyses of the feasibility of ammonia as a sustainable fuel in internal combustion engines, concluded that to make ammonia a viable fuel in engines, it needs to be mixed with other fuels (e.g., hydrogen) as combustion promoters due to ammonia's low flame speed and high resistance to auto-ignition.

Gas turbines are high-efficiency candidates for use of ammonia enabling development of combined cycles to power isolated communities while serving as sources of heat and chemical storage. Although, recent studies have shown that ammonia/hydrogen blends could be burned efficiently with low emissions and high efficiencies in gas turbines, they require optimisation study in terms of choice of fuel composition and development of advanced injection strategies to achieve acceptable NOx levels with high thermal efficiencies.

The computational optimisation of fuel composition and combustion system in an ammonia based engine requires development of reduced reaction mechanism for fuel blends under engine relevant conditions. While computational fluid dynamics (CFD) simulations in combination with reaction mechanisms can capture complex phenomena with high accuracy, they have high computational cost and, therefore, are not efficient for the optimisation studies. Zero-dimensional (0D) phenomenological models, on the contrary, are relatively computationally inexpensive and, once validated, can be utilised as a reliable auxiliary design tool in analysis of combustion engines. The aim of the proposed project is to develop a computationally cost-effective numerical tool for Co-Optimisation of fuel blend and combustion system in a systematic way, and to examine how the conflicting requirements can be met by adding gaseous fuels (e.g., methane, hydrogen and syngas) to Ammonia so that engine can be operated stably and reliably with improved thermal efficiency and minimal NOx emissions. The developed tools will be handy in combustion study and optimisation of ammonia-based gas turbine engines.
StatusActive
Period1/11/2031/10/22

ID: 22436625