上海交通大学：《热力学 Thermodynamics（I）》课程教学资源（课件讲义）Lecture 46_Diesel cycle and dual cycle

上游充通大￥ SHANGHAI JIAO TONG UNIVERSITY Engineering Thermodynamics I Lecture 46 Chapter 9 Gas Power Cycles Spring,5/15/2018 Prof.,Dr.Yonghua HUANG 强 LA http://cc.sjtu.edu.cn/G2S/site/thermo.html SHANG 1日 ERSITY

Engineering Thermodynamics I Lecture 46 Spring, 5/15/2018 Prof., Dr. Yonghua HUANG Chapter 9 Gas Power Cycles http://cc.sjtu.edu.cn/G2S/site/thermo.html

Diesel and Dual Cycles Air Standard Diesel Cycle for CI Engines: k p 3 s=const Qin p=const 4 v=const s=const Qout 1 V1=V4 ---。。-1 S1=S2 S3=S4 Define:ir ="cutoff ratio"compression ratio r= V2 上游充通大率 May15,2018 2 SHANGHA BAO TONG LINIERSITY

May 15, 2018 2 Diesel and Dual Cycles Air Standard Diesel Cycle for CI Engines: qout s T 1 2 4 3 s 1=s 2 s 3=s 4 qin qout V p 1 2 4 3 V 1=V 4 qin V 2 V 3 3 1 BDC c 2 2 TDC V V V Define : r " " compression ratio r V V cutoff ratio V   

Continue Diesel Cycle qin s=const Diesel Cycle Energy Balances: const ·Assuming: V, V3 ·w=0 only during heat transfer4→1；AKE=APE=0 Air is ideal gas,constant specific heats du=0 Wnet W23 W34-W12=qin -lqoutl . during process2→3，wist0(change in volume) qin-W23=(u3-u2) 今qin=(u3-u2)+W23=(u3-u2)+p23(V3-V2) =h3-h2 dout u4 -u1 上游充通大 May15,2018 3 SHANGHAI BAO TONG LINIERSITY

May 15, 2018 3 Continue Diesel Cycle Diesel Cycle Energy Balances: • Assuming: • w = 0 only during heat transfer 4 1; KE = PE = 0 • Air is ideal gas, constant specific heats wnet = w23 + w34 – |w12| = qin – |qout| • during process 2 3, w is ≠0 (change in volume) qin – w23= (u 3 – u 2)  qin = (u 3 – u 2) + w23 = (u 3 – u 2) + p23 (v 3 – v 2) = h 3 – h 2 qout = u 4 – u 1 d 0 u   V p 1 2 4 3 V1=V4 qin V2 V3

Continue Diesel Cycle Tt p=const 3 Diesel cycle efficiency: v=const For m-constant:=V3 and r=VL V2 V2 Qout n%-w-99-19-1-u=u=1-cc,-p S1=S2 3S4S Qin Qin Qin h3-h2 c(T3-T2) or1→2是-（) =rk-l For a constant pressure process2-→3：p2=P3→ → V2 V3 T V2 上游充通大率 May15,2018 4 SHANGHAI BAO TONG LINIVERSITY

May 15, 2018 4 Continue Diesel Cycle Diesel cycle efficiency: 3 1 c 2 2 v v For m=constant: r and r v v   s T 1 2 4 3 s1=s2 s3=s 4 qin qout net v 4 1 in out out 4 1 th in in in 3 2 p 3 2 w c (T T ) qq q u u 11 1 q q q h h c (T T )            4 1 3 2 41 1 th 32 2 T T T T 1 (T T ) T 1 1 k(T T ) T k 1                                k 1 2 1 k 1 1 2 T v For isentropic process 1 2: r T v           2 3 33 23 c 2 3 22 RT RT T v For a constant pressure process 2 3: p p r v v Tv     

Continue Diesel Cycle s=const Continue Diesel cycle efficiency: s=const For isentropic process3-→4： 1V2 V3 Vi=V,V k- Then, 1-1 =1- k。-) (const.k) ≥1 Thus,for a given r:nth.Diesel snth.ot! 上游充通大率 May15,2018 5 SHANGHAI BAO TONG LINIERSITY

May 15, 2018 5 Continue Diesel Cycle Continue Diesel cycle efficiency: k 1 k1 k1 k1 2 k 1 2 3 4 1 1 1 22 k1 k1 4 3 3 3 3 13 k1 k1 k 4 33 33 3 k c 1 22 22 2 For isentropic process 3 4: T V T V V V T TV T V V V V TV T TV VV V r T TV VV V                                    k 1 2 1 1 2 T v T v         (const. k) 4 1 3 2 k c k 1 th 2 1 c 1 T T T T 1 T Then, 1 T k 1 1 r 1 1 r k(r 1)                                    V p 1 2 4 3 V1=V4 qin V2 V3 Thus, for a given r : !   th,Diesel th,Otto