Effects　of　the　coolant　swirl　ratio　(SR)　and　density　ratio　(DR)　of　simulated　upstream　slot　purge　flow,　which　is　used　to　simulate　the　rotation　effect,　and　the　mid-passage　leakage　blowing　ratio　M　on　the　turbine　blade　platform　cooling　and　suction　side　surface　phantom　cooling　performance　are　numerically　investigated　using　three-dimensional　Reynolds-Averaged　Navier-Stokes　(RANS)　equations　coupled　with　the　SST　k-ω　turbulence　model.　Simulations　with　four　slot　injection　swirl　ratios　(SR)　of　0.4,　0.6,　0.8　and　1.0,　three　platform　blowing　ratios　M　of　0.5,　1.0,　1.5　and　three　coolant　density　ratios　(DR)　of　1.0,　1.5,　2.0　under　four　different　mass　flow　ratios　(MFR)　that　range　from　0.5%　to　1.25%　are　conducted.　The　calculated　results　indicate　that　at　low　mass　flow　ratio　(MFR　=　0.5%　and　1.0%)　the　best　and　worst　platform　cooling　performance　appear　at　SR　=　0.4　and　0.8,　respectively.　But　at　MFR　=　1.25%,　the　swirl　ratio　has　positive　effect　on　the　cooling　effectiveness　after　eliminating　the　mainstream　ingestion.　In　addition,　the　phantom　cooling　effectiveness　also　increases　with　the　increase　of　the　relative　motion　between　coolant　and　blade　with　the　movement　of　separation　vortex　toward　suction　side.　With　the　increase　of　DR　(changes　simultaneously　in　slot　and　midpassage　gap),　the　uncooled　area　near　the　leading　edge,　which　is　usually　referred　to　as　the　hot　ring,　is　enlarged　at　high　swirl　ratio　and　the　platform　cooling　effectiveness　decreases　for　the　fore　portion.　Similarly,　the　density　ratio　has　negative　effect　on　the　phantom　cooling　effectiveness　for　all　the　cases.　As　for　the　mid-passage　gap,　its　coolant　blowing　ratio　M　has　a　significant　impact　on　the　downstream　portion　platform　cooling　by　acting　partly　as　an　endwall　fence.　With　the　increase　of　blowing　ratio　M,　the　leakage　coverage　on　the　platform　increases　firstly　and　then　decreases　at　low　density　ratio　(DR　=　1.0　and　1.5)　but　increases　continuously　at　DR　=　2.0.　As　a　result,　the　platform　cooling　effectiveness　reaches　its　highest　at　M　=　1.0　and　1.5　for　DR　=　1.0　and　2.0,　respectively.　The　phantom　cooling　effectiveness　increases　slightly　when　increasing　M　from　1.0　to　1.5,　but　has　nearly　no　difference　for　further　increasing　M.　©　2018　Elsevier　Ltd