上游充通大￥ SHANGHAI JIAO TONG UNIVERSITY a Engineering Thermodynamics I Lecture 47 Chapter 9 Gas Power Systems (section 9.10) Spring,5/15/2018 强 Prof.,Dr.Yonghua HUANG VVAMA http://cc.sjtu.edu.cn/G2S/site/thermo.html SHANG 1日 ERSITY
Engineering Thermodynamics I Lecture 47 Spring, 5/15/2018 Prof., Dr. Yonghua HUANG Chapter 9 Gas Power Systems (section 9.10) http://cc.sjtu.edu.cn/G2S/site/thermo.html
Non-adiabatic compression 2 Assumptions: SSSF A) -△KE=△PE=0 PiV"=P2V2 -0-w+学e-a++g dt 0=Qc-Wc+m(h-h2) →wc-qc=h1-h2 p 2c For an internally reversible,steady flow process: P2 2 cooling wc=Jvdp adiabatic Note:Compressor cooling decreases v, therefore also decreases wc! →Try to exchange heat P1 from the compressor V to environment! 上游充通大率 May15,2018 2 SHANGHA BAO TONG LINIERSITY
May 15, 2018 2 Non ‐adiabatic compression 2 2 CV in out in out in out C C 12 CC12 v v 2 2 dE Q W m h gz m h gz dt 0 Q W mh h w q hh Assumptions: ‐ SSSF ‐ KE = PE = 0 1 2 . W C . Q C CV v 1 2s p p 2 p 1 2c cooling adiabatic For an internally reversible, steady flow process: 2 C 1 w vdp Note: Compressor cooling decreases v, therefore also decreases w C! Try to exchange heat from the compressor to environment! n n 11 2 2 p v pv
Continue Non-Adiabatic Compression Limiting Cases: 1.Adiabatic: S2=S1 (no heat transfer) 2.Isothermal: T2=T(infinite heat transfer) 》 For an adiabatic,reversible process with an ideal gas: 2t22s p---g where k=C 1<n<k pyk=constant Cv For an isothermal process with an ideal gas: (isentropic) n=1 N pv constant (isothermal) 》 Between the limits of isentropic and p---- isothermal compression,we can assume a polytropic process that satisfies: py"constant,where n is the polytropic exponent 上游充通大粤 May15,2018 3 SHANGHAI BAO TONG LINIERSITY
May 15, 2018 3 Continue Non ‐Adiabatic Compression Limiting Cases: 1. Adiabatic: s 2 = s 1 (no heat transfer) 2. Isothermal: T2 = T1 (infinite heat transfer) » For an adiabatic, reversible process with an ideal gas: » For an isothermal process with an ideal gas: » Between the limits of isentropic and isothermal compression, we can assume a polytropic process that satisfies: k p v c pv constant where k c pv constant n pv constant , where n is the polytropic exponent v 1 2s p p 2 p 1 1 < n < k 2t 2 n = k (isentropic) n = 1 (isothermal)
Continue Non-Adiabatic Compression For any internally reversible process:w=-vdp For a polytropic process n1 -n n≠1 For an ideal gas “=nR(c,-T) n n≠1 国 For an isothermal process n=1 Wc=-PiVi In(p2/P)=-piVi In(Vi/V2) n=1 For an ideal gas We=-RTIn(p2/p) n=1 上游充通大率 May15,2018 4 SHANGHA BAO TONG LINIERSITY
May 15, 2018 4 Continue Non ‐Adiabatic Compression For any internally reversible process: For a polytropic process For an isothermal process ܹୡ ൌ െ ݀ݒ න ଶ ଵ C 2 2 11 n w pv pv n 1 n 1 For an ideal gas C 21 n w RT T n 1 n 1 n 1 w p v ln(p / p ) p v ln(v / v ) n 1 C 11 2 1 11 1 2 For an ideal gas w RT ln p / p n 1 C 21 n 1
Two-stage Compression with Intercooling 2 Intercooler / T P2 P2 2s Px Pi 2s T Ti 1 1 2t xt=y S S 上游充通大率 May15,2018 5 SHANGHA BAO TONG LINIERSITY
May 15, 2018 5 Two ‐stage Compression with Intercooling s T 1 xt=y 2 2s x xs 2t T 1 p 2 p x p 1 qI air x Intercooler w c 2 y 1 1 1 2 . W C . Q C CV s T 1 2 2s T 1 p 2 p 1