Objective Adding hydrogen to natural gas alters its combustion characteristics,prompting this study to investigate the thermal venting process of hydrogen-blended natural gas.The aim is to ascertain the appropriate operating conditions for existing elevated flare systems under hydrogen transportation scenarios,ensuring the safety of the natural gas pipeline system during hydrogen blending.Methods By integrating hydrogen blending combustion experiments and numerical simulations of CFD,in this study,the combustion characteristics and changes of thermal radiation radius changes during the diffusion combustion of natural gas blended with 0 to 20 mol%hydrogen are explored,the mechanisms by which hydrogen blending influences the thermal radiation radius is revealed,and it is defined establishes that the thermal radiation radius analysis model in API-521 is suitable for calculating hydrogen-blended natural gas.Results At equal volume flow rates,hydrogen blending has been observed to reduce the heat release,thus shortening the flame length.In the presence of side winds,the flame tilt angle remains almost the same,reducing the radius of the heat radiation.At equal mass flow rates,hydrogen blending has been observed to increase the heat release,thus increasing the flame length.Concurrently,the flame tilt angle becomes larger,which results in a tiny change in the radius of the heat radiation.Additionally,the higher wind speed leads to a bigger radius of heat radiation.Conclusions Under the condition that the safety thermal radiation radius is constant,the volumetric flow rates when the hydrogen is added can be increased by approximately 19%to 23%at most when the hydrogen is added,thereby enhancing the emission efficiency of the flare system.The mass flow rates of flares when hydrogen is added are almost the same.
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