This　paper　explores　the　combustion　and　emission　characteristics　of　TJI　ammonia/hydrogen　(NH3/H2)　dual-fuel　engines　through　experiments　and　numerical　simulations.　The　NH3/H2　engine　operates　at　1600　rpm　with　a　manifold　absolute　pressure　of　60　kPa.　Two　independent　hydrogen　supply　systems　enable　hydrogen　port　injection　(HPI)　and　hydrogen　direct　injection　(HDI).　The　results　indicate　that　HDI　yields　higher　power　output　compared　to　HPI.　The　strong　injection　ignition　ability　of　the　pre-chamber　(PC)　realizes　the　stable　combustion　of　the　NH3/H2　engine　under　different　ammonia　volume　share　(AVS)　conditions.　With　the　increase　of　AVS,　the　mixture　of　HDI　in　PC　is　stratified　and　the　jet　velocity　is　significantly　reduced.　Power　output　under　HDI　conditions　decreases　with　increasing　AVS.　At　an　AVS　of　10　%,　the　brake　mean　effective　pressure　(BMEP)　and　brake　thermal　efficiency　(BTE)　reach　maximum　values　of　3.67　bar　and　30.25　%,　respectively.　The　BMEP　and　BTE　increase　and　then　decrease　with　increasing　AVS　under　HPI　conditions.　An　AVS　of　40　%　achieves　peak　power　and　efficiency.　The　CA10-90　is　always　shorter　than　CA0-10　in　the　combustion　process.　At　an　AVS　of　20　%,　NO　emissions　peak　and　then　decrease　with　increasing　AVS,　but　higher　AVS　increases　unburned　NH3　and　N2O.　Experimental　results　show　that　spark　timing　(ST)　has　relatively　low　sensitivity　to　H2-dominated　TJI　NH3/H2　combustion.　With　the　increase　of　AVS　to　60　%,　the　delayed　ST　will　lead　to　a　rapid　decrease　in　power　output　and　a　sharp　deterioration　in　combustion　stability.　When　the　ST　is　postponed　from　12　°CA　BTDC　to　4　°CA　ATDC,　and　AVS　is　60　%,　the　COVPmax　of　the　TJI　engine　increases　rapidly　from　1.9　%　to　13.9　%.　©　2024　Elsevier　Ltd