09第九章-压气机的热力过程课件1.ppt

1、P1,T1不变，dm0P2,T2不变，dm0dm=012pp2112341Spdvwt211,lnppTmRwgTs)(121,TTmRKKwgss)(121,TTRmnnwgns例例1：理想的活塞式压气机吸 入20,1.011tMPap空气hm31000并将其压到MPap6.02,设压缩指数为n=1,n=1.25,n=k=1.4过程可逆，求压气机功耗。分析：(1)n=1，等温压缩：(2)n=1.25，多变压缩：(3)n=1.4，绝热压缩：KWppvpwTt77.49ln1211,KWppvpnnwnnnt86.591111211,KWppvpkkwkkSt08.651111211,可见，等温

2、压缩耗功最省，绝热压缩耗功最多，多变压缩介于两者之间*当压缩气体不能按理想气体计算时当压缩气体不能按理想气体计算时，则qhhwwnett21若过程可逆，则12121ssThhwnet21,hhwRnet（等温）（绝热）若过程不可逆，则qhhwInet21,定义InetRtnetcotww,等温效率为可逆等温压缩的耗功与不可逆放热压缩的耗功之比。等温效率用于评价活塞式压气机性能的主要参数。CtmvMPap0131140052.01.0322013.0,565.0mvMPapkgRTpvm058.025.1lnln2112vvppnKvvTTn44212112KjTTCnKnmTTmCmqQvv2

3、1.3)(1)(1212KjTTnRmw58.8)(121Kjwnwt7.10)58.8(25.141VVVechVVVVV131heVVv111144441ccchchchhhevVVVVVVVVVVVVVVV升压比而12112143344,PPPPPPVVVVnnc11111112vncncPP125011111112111121,面积nnnnntppvpnnppRTnnw350431250112341,面积面积面积ntwnnnnntppvpnnppvpnnw1434411211,11113241,pppp14344,1135043nnvntppvpnnwc面积nnennntppvpnnp

4、pvvpnnw1121112411,1111nnppTT11212)(461312,面积Ttw461123,”面积ntw3452212561,面积面积stw33TT 2,1,2,1,2,ttttntwwwww1111123222,112111,nntnntppvpnnwppvpnnwnnnnntppppvpnnw12311211,21TRvpvpg2211ntw,02,dpdwnt2312312,ppppppp或写成 11112312,ppppppppnnn压缩终压压缩终压气体初压气体初压 432342312134341232311212321;,;TTTppppppppTTppTTppTTTTTnnnnnn于是又而11,1iiiigntTTTTRnnw进气温度进气温度排气温度排气温度ntttwww,2,1,tntwnw,nTTCww,定温压气耗功实际压气耗功201.011tMPapTC,TC,5314ppKppTTTTnn4041121432KgKjTTRnnwnwtnt/478404293287.0125.125.131321,1KppTTnn6.7691.05.1229325.1125.111414,215.121.0ln293287.0lntTTCntTTCTwwwwppRTwkgkJTTRnnwt/683)6.769293(287.0125.125.1)(141