Using　syngas　as　a　primary　fuel　for　internal　combustion　engines　with　spark　ignition　is　a　bridge　technology　for　transitioning　from　carbon-based　to　hydrogen-based　energy　sources.　There　are　two　different　ways　of　syngas　delivery　into　combustion　chamber:　port　injection　or　direct　injection.　In　this　study,　the　combination　of　these　methods　is　considered　for　integration　benefits　of　each　injection　technology　and　promotion　of　syngas　utilization　in　rotary　engines.　In　the　novel　concept　of　syngas　dual　injection,　part　of　the　fuel　is　delivered　by　a　port　injector　during　the　induction　stroke,　while　another　part　is　directly　injected　during　the　compression　stroke.　The　ratio　of　fuel　mass　delivered　by　port　and　direct　injection　is　changed　within　the　range　of　0.0　(direct　injection　only)　to　1.0　(port　injection　only)　and　chosen　as　a　key　parameter　of　concentration　stratification.　This　study　aims　to　investigate　the　optimal　fuel　injection　strategy　with　numerical　simulation　of　mixture　formation,　ignition,　and　combustion　processes.　It　was　shown　that　dual　injection　strongly　influences　turbulence　intensity　and　mixture　heterogeneity.　The　turbulence　lengthscales　generally　increase　with　dual　injection　ratio　growth.　The　direct　injection　case　demonstrates　maximum　performance　characteristics.　However,　the　case　with　a　small　portion　of　directly　injected　fuel　(10%–25%)　increases　fuel　conversion　efficiency　by　5%–7%　and　decrease　fuel　consumption　by　4%–6%　with　lower　level　of　CO　emission.　The　results　show　that　the　dual　injection　strategy　provides　flexibility　in　controlling　the　combustion　process　and　emission　reduction.　©　2023　Elsevier　Ltd