Flame Stability and Emissions in Methane/Hydrogen Combustion
Designing for Fuel Flexibility
S.J. Link (TU Delft - Flight Performance and Propulsion)
G. Eitelberg – Promotor (TU Delft - Flight Performance and Propulsion)
A. Gangoli Rao – Promotor (TU Delft - Flight Performance and Propulsion)
F. De Domenico – Copromotor (TU Delft - Flight Performance and Propulsion)
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Abstract
Human civilization must transition tomore sustainable energy sources to meet the goals of the Paris Agreement, which aims to limit the global temperature increase to well below 2 ◦C above pre-industrial levels. However, hard to abate sectors such as aviation and heavy industries will continue to rely on combustion for the foreseeable future. For these industries, the development and deployment of alternative fuels are essential. One of the most promising alternative fuels is hydrogen (H2), primarily because it enables carbonfree combustion. Nevertheless, significant challenges remain regarding its production, storage, and transportation, leading to uncertainties in its large-scale availability. As a result, there is growing interest in fuel-flexible combustion systems that can operate efficiently on traditional carbon-based fuels, hydrogen, or any mixture of the two, while maintaining combustion stability and lowemissions across the full fuel range. Hydrogen differs significantly from carbon-based fuels such as methane (CH4) in its combustion characteristics. It has a much higher flame speed and higher adiabatic flame temperature at the same equivalence ratio. These properties can pose serious design challenges such as increased risk of flashback and elevated NOx emissions.
In swirl-stabilized combustion, injecting non-swirled air axially on the centreline can be a very efficient way to stabilize flames with high hydrogen content. This work investigates the emissions and flame stability of a fuel flexible swirl-stabilized combustor that can operate on fuel mixtures ranging from 100% CH4 to 100% H2. In this set-up, fuel is injected in a jet in cross-flow configuration just downstream of the swirler exit. A mixing tube is placed between the injection point and the combustion chamber to allow for fuel-air mixing. The objective of this thesis is to identify the dominant parameters that govern emissions and stability in fuel-flexible combustion systems. To support this aim, several research questions are formulated and addressed in dedicated chapters…