Axialturbomachinemodellingwitha1Daxisymmetricapproach:ApplicationtogascoolednuclearreactorOriginalResearchArticle

Thisworkconcernsthedesignandsafetyanalysisofdirectcyclegascooledreactor.Theestimationofcompressorandturbineperformancesintransientoperationsisofhighimportanceforthedesigner.Thefirstgoalofthisstudyistoprovideadescriptionofcompressorbehaviourinunstableconditionswithabetterunderstandingthanthemodelsbasedonperformancemaps(“traditional”0Dapproach).Asupplementaryobjectiveistoprovideacoherentdescriptionoftheturbinebehaviour.Theturbomachinemodellingapproachconsistsinthesolutionof1DaxisymmetricNavier–Stokesequationsonanaxialgridinsidetheturbomachine:mass,axialmomentum,circumferentialmomentumandtotal-enthalpybalancesarewritten.Bladeforcesaretakenintoaccountbyusingcompressororturbinebladecascadesteadycorrelations.Aparticularefforthasbeendevelopedtogenerateortestcorrelationsinlowmassflowandnegativemassflowregimes,basedonexperimentaldata.Themodelistestedonopenliteraturecasesofthegasturbineaircraftcommunity.Forcompressorandturbine,steadysituationsarefairlydescribed,especiallyformediumandhighmassflowrate.Thedynamicbehaviourofcompressorisalsoquitewelldescribed,eveninunstableoperation(surge):qualitativetendencies(roleofplenumvolumeandroleofthrottle)andsomequantitativecharacteristics(frequency)areinagoodagreementwithexperimentaldata.Theapplicationtotransientsimulationsofgascoolednuclearreactorsisconcentratedonthehypothetical10in.breakaccident.Theresultspointouttheimportanceofthelocationofthepiperuptureinahypotheticalbreakevent.Insomedetailedcases,compressorsurgeandbackflowthroughthecircuitcanoccur.Inordertobeusedinadesignphase,asimplifiedmodelofsurgehasalsobeendeveloped.Thissimplifiedmodelisappliedtothegasfastreactor(GFR)andcomparedquitefavourablywith1Daxisymmetricsimulationresults.