To　achieve　more　efficient　and　robust　combustion,　split　direct-injected　hydrogen　as　a　new　injection　strategy　for　rotary　engines　was　used　to　clarify　the　influences　of　various　injection　parameters,　including　hydrogen　amount　for　each　pulse,　the　dwell　between　pulses,　and　secondary　injection　pulse-width,　on　combustion　performance　and　emissions　formation　by　CFD　modeling.　The　results　of　this　investigation　confirmed　the　benefit　of　split　direct-injection　as　a　useful　means　to　govern　mixture　stratification　which　enabled　the　combustion　more　effective　and　rapid　compared　to　single-injection　mode.　Enhanced　combustion　could　be　achieved　by　increasing　the　mass　fraction　of　post-injection　with　an　optimized　dwell　between　injections.　Further　investigation　on　secondary　injection　pulse-width　demonstrated　that　engine　performance　was　substantially　improved　with　a　wider　second　injection　pulse.　From　one　side,　as　the　secondary　injection　pulse-width　was　increased,　the　surrounding　mixture　distribution　of　the　spark-plug　location　was　richer,　which　was　confirmed　as　a　beneficial　inhomogeneous　circumstance　of　hydrogen　to　accelerate　the　burning　rate.　From　another　side,　strong　tumble　level　and　turbulence　intensity　were　of　significant　importance　for　facilitating　the　combustion　process　and　getting　optimal　thermal　efficiency.　For　emissions　formation,　split　direct-injected　hydrogen　made　a　near-zero　HC　and　CO　emissions　at　the　price　of　a　comparable　increase　of　NOx　emissions.　(c)　2020　Elsevier　Ltd.　All　rights　reserved.