chapter9SteamPowerCycle

9-1TheRankineCycle9-1-1.VaporCarnotcycleTs1234Therearesomeproblems:Compressorturbine

9-1-2.Rankinecycle

Trainedasacivilengineer,WilliamRankine(1820-1872)wasappointedtothechairmanofcivilengineeringandmechanicsatGlasgowin1855.Heworkedonheat,andattemptedtoderiveSadiCarnotslawfromhisownhypothesis.HewaselectedaFellowoftheRoyalSocietyin1853.AmonghismostimportantworksareManualofAppliedMechanics(1858),ManualoftheSteamEngineandOtherPrimeMovers(1859).

9-1-3.TheefficiencyofRankinecycleqabsorb=h2-h1qexhaust=h3–h4

Usually,Theproperties:p1,t1andp2areavailableforapowerplant,then:h1:Fromp1,t1,geth1,s1h2:Fromp2,gets2’,s3”h2’,h2”So,xcanbeknownh3:Fromp2,geth2’,s2’.h3=h3’s3=s3’h4:Fromp1,s1=s4geth4

9-2TheInfluenceofSteamProperty9-2-1.ExhaustPressureTodecreasetheexhaustpressurecanincreasetheefficiencyofRankinecycle.Butthedrynessfractionwillincreasetoo.Thiscanleadsomedamagetosteamturbine

9-2-2.InlettemperatureTodecreasetheinlettemperaturecanincreasetheefficiencyofRankinecycle.Butthisincreasedependsonboilermaterial

9-2-3.InletpressureToincreasetheinletpressurecanincreasetheefficiencyofRankinecyclegreatly.Butthisincreasealsodependsonboilermaterial

boilercondenserFeedwaterpumpSteamturbine9-3-1EquipmentsofReheatCycleReheater9-3ReheatCycle

9-3-2EfficiencyT-sdiagramEfficiency

Theproperties:p1,t1,pm,tn(equalst1usually),p2areavailableforareheatpowerplant,then:h1:Fromp1,t1,geth1,s1hm:Fromp2,s2=s1,gethmhn:Frompm,tn,gethnh2:Fromp2,gets2’,s3”h2’,h2”So,xcanbeknown

h3:Fromp2,geth2’,s2’.h3=h3’s3=s3’h4:Fromp1,s1=s4geth4

9-4RegenerativeCycle9-4-1I