Aiming　at　the　recovery　of　exhaust　energy　for　a　diesel　engine,　a　set　of　ORC　(organic　Rankine　cycle)　system　is　designed.　The　characteristics　of　the　exhaust　gas　under　various　operating　conditions　are　studied　through　experiment.　Based　on　experimental　results　and　theoretical　calculation,　effects　of　eight　kinds　of　zeotropic　mixtures　on　the　performance　of　ORC　system　for　exhaust　energy　recovery　are　discussed　for　vehicle　engine　under　various　operating　conditions.　Variation　of　net　power　output,　thermal　efficiency,　exergy　efficiency　of　ORC　system　and　mass　flow　rate　of　zeotropic　mixture　under　various　operating　conditions　of　engine　is　investigated.　Two　concepts　-　WHRE　(waste　heat　recovery　efficiency)　and　POIR　(power　output　increasing　rate)　are　-　defined　and　studied.　The　results　show　that　when　the　evaporating　pressure　is　2.0　MPa,　the　net　power　output　of　ORC　system　can　reach　up　to　24.65　kW.　Using　this　ORC　system,　the　maximum　WHRE　is　8.5%　and　engine　power　output　can　be　increased　by　10.63%.　Crown　Copyright　(C)　2013　Published　by　Elsevier　Ltd.　All　rights　reserved.