流体机械习题2.1压缩机设计昆明理工大学

--#、确定各级直径总压比己=1==—=62.75总P0.4S1按等压比分配：5=4几=4.62.75=2.8146假设此压缩机冷却完善，k\i=L：.4M-IQPb2 卜0 -1s4假设此压缩机冷却完善，级次IIIinWPs(MPa)0.41.12583.1685648.917924Pd(MPa)1.12583.1685648.91792425.1£2.81462.81462.81462.8146——d]—H—H—H——-di -'d2 匕3 Fd4二二二「M-0所以T=T=T=T=25℃si s2s3s4由图2-114可得:=—(d2-d2)sTOC\o"1-5"\h\zsi 4 i=—(D2-d2)ss2 4 2兀=-D2ss3 4 3兀=-D2s

s4 4 4有已知条件带入〔1〕式得V=—(d2—d2)ss1 4 1兀=-4(0.1752—0.0352)x0.095=2.193X10—3m3又有公式〔2-38〕V二six二psiT九九ZXfV二six二psiT九九ZXfX 隼，ciXTns1vi“其中九s1Z

九二1、―si-=1、

ciZs1n二九九九九)

v1v1p1t1l1所以nV1q

V-

nVs11.5980义2.193x10一3=0.698容积系数计算：(1)压力系数取九=0.97p取九=0.97p1九二0.99p2九二0.99p3九p4=1.0(2)温度系数取九=0.95

取九=0.95

t1九二0.96t2九二0.97t3九二0.98t4(3)泄露系数(3)泄露系数〔无油润滑〕九=0.95九九=0.95九l1 l2=0.96九二0.97l3九l4=0.98(4)膨胀指数〔由表2-1得〕级次IIIinWPs(MPa)0.41.12583.1685648.917924Ps(bar)411.25831.6856489.17924m1.2251.3081.41.4由公式n=入入入入v1 v1p1t1l1,14=1-a&m1—1)v111v1贝”「HL两粽标=0.797pltl11TOC\o"1-5"\h\z1-X 1-0.797 0cot= ^4-= =0.1521-L -J—己叫—12.81461.225—1i1分别取a=0.130、a=0.135、a=0.1452 3 4确定各级气缸直径:(II)级直径=A•s=—G)2-d^)ss2 P2 4 2_qPT 1v-X-X-X- s2npTXXXXs2siv2p2t212联立以上两式可得：九九九Sp2t212A•九二&x%-xLp2v2npT九九九Sp2t212带入数据可得:人、q p T 1A•人=fX—+XT~X 〃2i，2np T 九九九ss2sip2tl121.5 0.4 1 1_ x X1x —9801.1258 0.99x0.96x0.96x0.095=6.274x10-3X=l-a-1) A=-G)2-J2/TOC\o"1-5"\h\zv2 2 2, p24 2联立以上三式得：A•九=—G)2-rf2)1-a -1)p2y2 4 2 2 2~即6.274x10-3=1⑷2—0.0352)1-0.130(2.8146京—1)4 2 [解之得d=0.103m=103mm2查表取气缸直径。=105mmo2则实际行程容积为:

V'二A・s=三(D2—d2)s=三(0.1052—0.0352)X0.095=7.308x10-4m3s2p2 4 2 4活塞有效面积：兀一-4(0.1052-0.0352)=7.693x10-3m2[III）级直径A•九=qx

p3A•九=qx

p3v3nP—s1p.s3Tx7xTs11.5 x0.4x1x九九九sp3131319803.1686 0.99x0.97x0.97x0.095=2.1835x10-3又A•九=：D21-a化与一1)p3v3 4 3 3 3带入数据得2.1835x10-3=—(D2)|1-0.135(2.8146=-1)43L解之得d=0.057m=57mm3查表圆整取d=60mm3则实际行程容积为:TOC\o"1-5"\h\z— —L _L_V'=A'・s=-D2・s=—0.062x0.095=2.685x10-4m3s3 p3 43 4活塞有效面积：— —八A'=—D2・s=—0.062=2.826x10-3m2p3 43 4(W)级直径qqA•儿=fxp4v4nTOC\o"1-5"\h\zp T—s1x-s4xp Ts4 s11九九九s

p414141.5 0.4 1 1 x x1x 9808.9179 1.0x0.98x0.98x0.095=7.5246x10-43又A•九二一Dd2)|1-a(己m4-1)p4 v444 44带入数据得7.5246x10—4C(D2)1-0.145(2.8146114-1)解之得D=0.034m=34mm4查表得D=36mm4则实际行程容积为：兀 兀八TOC\o"1-5"\h\zV'=A・s二—D2.s=—0.0362x0.095=9.665x10-5m3s4p4 4 4 4活塞有效面积：\o"CurrentDocument"兀 兀/A'=—D2・s=-0.0362=1.017x10-3m2p444 4由公式九’二九,与a= 计算出新的九,与a,，结果如下表:vvA' g，1 vp 彳m—1级次IIIIIIW气缸实际直径D〔m〕0.1750.1050.060.036有效实际面积Ap(m2)2.193x10-37.308x10-42.685x10-49.665405气缸直径D〔m〕0.1750.1030.0570.034有效面积Ap(m2)2.193x10-36.998x10-42.423x10-48.62x10-5九v0.7972.3976.78218.487实际九'v0.7972.2956.12116.490a0.1530.1300.1350.145实际a'0.1530.1530.2080.238实际V，s2.193x10-37.308x10-42.685x10-49.665x10-5三、计算活塞力由课本P22图2-14分别取:

5 =0.029 5 =0.021 5 =0.019 5=0.017s1 s2 s3 s45 =0.058 5 =0.043 5 =0.027 5=0.014d1 d2 d3 d4各级进、排气压力和实际压力比级次公称压力压力损失实际压力/MPa实际压力比£psPd5,s5,dP'sP'dI0.41.12580.0290.0580.38841.19113.067ii1.12583.168560.0210.0431.10223.30482.998m3.168568.91790.0190.0273.10849.15872.946w8.917925.10.0170.0148.766325.45142.903P'、P，由公式4一P"5s)sd P'=P(1+5')ddd压力比由自=条计算得出，结果如上表。s止点气体力计算：列次内止点(kN外止点(kNi-w16.27-19.23ii-m16.06-17.99I-W内止点气体力：F=P；A-P.-（D2—D2）-P；A=16.27kN（拉应力）

31d1I平4Iwsww外止点气体力：f=P'・A-P二（）‛•A=-19.23kN〔压应力〕c1siI平4Iwwwii-m内止点气体力：F=PA-P•—（D2-D）-PA=16.06kN（拉应力）32 di ii 平4 ii m sm m外止点气体力：F=PA-P―-（D2-D）-P；A=-17.99kN（压应力）c2 si ii 平4 ii m m m

四、确定各级排气温度因假设冷却完善，故：级次IIIinWr(K)s298.15298.15298.15298.15r(K)d391.21389.09387.44386.06上表由T"m？(n=L32)计算得出各级排气温度。disi五、计算轴功率并选配电机各级指示功率为1 . n,1N=-n''PV'-j{《"，)-1}

j60Vjsjsn—1计算结果如下表：j总的指示功率为计算结果如下表：Ni1Ni2Ni3Ni4Ni14283W13498W13008W12447W53237WN=24Ni ijj=1取机械效率叩=0.94，轴功率为：mN53237N=t= =56635(W)=56.635(kW)zn0.94m取电机功率余度10%,56.635X1.1=62,3(kW)，则选择电机功率为65kWo

六、变工况热力计算1、确定与容积有关的系数级次压力系数九.pj温度系数九.t泄露系数lj九二九九九0j pj tjijI0.970.950.950.8754II0.990.960.960.9124in0.990.970.970.9315w1.000.980.980.96042、设想容积的计算级次Ts入0入k设想容积I298.150.875411.919x10-3II298.150.912416.668x10-4n298.150.931512.501x10-4w298.150.960419.282x10-53、压力比及容积系数级次P=PV1/MPasj s1V0sP/MPdj自j「）九二1—a匕mj-1vj jj1 7I0.41.1512.8780.790II1.1513.0702.6660.829n3.0708.2712.6940.786w8.27131.13.7600.6254、各级压力比复算

次数级次ccV0入，.P=P —S1X—T1/MPsj s1V0九sS vjP/MPdj自j九vj一P」,V=—vV0九/m3jPsjvjs1V/Vminmax1I0.41.20803.010.771.49x10-387.1%II1.20803.05252.530.841.70X10-3III3.05258.55302.800.771.48x10-3W8.553031.13.640.821.64x10-32I0.41.11282.78