Experimental investigation of conventional domestic burners fueled with increasing hydrogen content up to pure hydrogen operation
Session chaired By Pr. Aimee Morgans
The necessity to reduce the carbon footprint of energy production has sprung the development of renewable electricity production via windmills and photovoltaic panels. Because these sources are intermittent, long-term storage in the form of hydrogen via the electrolysis of water is seen as a promising technology. The objective of this work is to use ‘green H2’ for heat production in domestic heaters. Because of the peculiar properties of hydrogen, its combustion characteristics are quite different from other fuels, e.g. flame speed, flammability limits, ignition energy, etc. It is therefore investigated how two existing burners, developed for pure methane combustion, can safely burn a mixture with increasing hydrogen content. The burners, presented as B1 and B2 in Fig. 1, are characterized by different porosity, hole pattern and internal structure, providing versatility of results which are not restricted to unique and specific configuration. Since two fuels are simultaneously used, two parameters are needed to univocally defined the mixture: global equivalence ratio (Fg) and hydrogen power percentage (PH2), which fix the relative amount of hydrogen and methane in fuel. A methodical approach is used to generate constant power maps in which both burners are tested from pure methane to pure hydrogen combustion, following step of 10% in PH2. For each fuel blend a well-defined range of Fg is investigated. Results exhibit the following trends: the increase of PH2 shifts blow-off towards leaner mixtures, while it simultaneously reduces the upper equivalent ratio achievable due to limit wall temperature or flashback occurrence. It is worth mentioning that both burners can be run with pure hydrogen, achieving flame stabilization at equivalence ratio well below 0.5. The burnt gas temperature is therefore quite low, which is notably favorable to limit NOx emissions.
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