Effects on the performance of domestic gas appliances operated on natural gas mixed with hydrogen

As an environmentally friendly fuel, hydrogen is one of the research hotspots of renewable energy currently, but transportation and utilization of pure hydrogen remain to be improved due to vast investments and high risk. Therefore, as a transitional program before the implementation of large-scale applications, mixing hydrogen into natural gas pipeline is an effective and feasible method. The paper studied the influence of natural gas mixed with hydrogen at 0%, 5%, 10%, 15% and 20% by volume on the performance of domestic gas appliances including domestic gas stoves and gas water heaters. The experiments show that the flame length shortened with increasing proportion of hydrogen. Flashback can be obviously observed when hydrogen addition reaches to 23% in gas water heaters. It is concluded that the measured heat inputs of domestic gas appliances decrease gradually with the increase of hydrogen addition, but the thermal efficiency increases. The increasing proportion of hydrogen mixed with natural gas promotes the emission reduction of CO and NOx for most test samples. When hydrogen addition fraction is up to 20%, annual CO2 emission reduction can reach 9.33% in gas water heaters, but when the hydrogen is produced by water electrolysis, the annual fuel cost will increase 32.7% on average. •Flashback in gas water heaters can occur when hydrogen is more than 23%.•The air entrainment capacity increases with the increase of hydrogen proportion.•Hydrogen addition can improve the thermal efficiency of domestic gas appliances.•20% hydrogen addition achieves 9.33 % annual CO2 emission reduction.