Hydrogen,　as　a　carbon-free　fuel,　is　significantly　for　replacing　fossil　fuels　and　reaching　the　ultimate　goal　of　carbon　neutrality,　and　is　commonly　expected　to　play　a　major　role　in　future　energy　supply.　Blending　hydrogen　into　natural　gas　pipeline　networks　for　end-user　consumption　as　a　means　of　delivering　pure　hydrogen　to　the　market　which　not　only　improves　the　utilization　rate　of　hydrogen　energy,　but　also　reduces　the　cost　of　hydrogen　transportation.　A　three-dimensional　model　of　the　blending　the　natural　gas　and　hydrogen　with　SMX　mixing　elements　is　developed　to　obtain　homogeneous　mixed　gas　injected　into　the　natural　gas　pipeline　network.　The　Reynolds-averaged　Navier-Stokes　(RANS)　method　is　employed　to　investigate　the　flow　physics　in　the　static　mixer,　which　was　verified　by　experiments.　The　numerical　results　are　in　good　agreement　with　the　experimental　data.　Based　on　the　static　mixer　model,　the　coupling　relationship　between　mixing　performance　and　the　crucial　parameters　including　the　number　of　mixing　elements,　operating　conditions　and　hydrogen　blending　volume　fraction　is　analyzed　in　detail,　and　a　compromise　design　scheme　is　proposed　under　the　studied　conditions　to　improve　the　mixing　performance　of　natural　gas　and　hydrogen.&　COPY;　2023　Published　by　Elsevier　Ltd　on　behalf　of　Institution　of　Chemical　Engineers.