Flame Visibility in Hydrogen Appliances

One of the benefits of the direct use of hydrogen is its ability to be burned in a similar way to natural gas, using appliances with which the community is already familiar. This is particularly true for applications where electrification is neither practicable nor desirable. One common example is domestic cooking stoves, where the open flame offers numerous real and perceived benefits to the chef. Similarly, many commercial and industrial appliances rely on the unique properties of combustion to achieve a desired purpose that cannot readily be replaced by an alternative to an open flame. Despite the enormous decarbonisation potential of the direct replacement of natural gas with hydrogen, there are some operational constraints due to the different burning characteristics of hydrogen. One of the challenges is the low visible light emission from hydrogen flames. The change in visible radiation from the combustion of hydrogen compared with natural gas is a safety concern, whereby visual observation of a flame may be difficult. This paper aims to provide clarity on the visual appearance of hydrogen flames via a series of measurements of flame visibility and emission spectra, accompanied by the assessment of strategies to improve the safe use of hydrogen.