工程熱力學(xué)第九章 習題解答

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9-1

???13.5?T?c，p0?p1?0?T0?T1?2cp?T1?21?T??p1?0?

?T1?1002?298K，c1?100m/s，T0?293?2023?298?p0?0.1???293?3.5?0.106MPa

3002?337.6K，c1?300m/s，T0?293?2023?337.6?p0?0.1???0.164MPa

293??5002?416.8K，c1?500m/s，T0?293?2023?416.8?p0?0.1???0.343MPa

293??10002?788K，c1?1000m/s，T0?293?20233.53.5?788?p0?0.1???293?9-2

3.5?3.190MPa

?p?T2?T1?2??p1???1??0.2??473???0.3?1.4?11.4?421.2K

c2?2cp?T1?T2??2?1010?473?421.2??323.5m/s

v2?RT2287?421.2??0.6044m3/kg6p20.2?10?21?0.6044mv??1.868?10?3m2c2323.5f2?工程熱力學(xué)41

9-3

pc??p1?0.528?2.5?1.32MPa?pB∴p2?pB?1.5MPa

?p??1.5?T2?T1?2??353??305.1K??2.5??p1?RT287?305.13v2?2??0.0584m/kg6p21.5?10c2?2cp?T1?T2??2?1010?353?305.1??311m/s

??1?1.4?11.4f2c21?10?4?311??m??0.533kg/s

v20.05849-4

pc??p1?0.528?2.5?1.32MPa?pB∴p2?pc?1.32MPa

?p??1.32?T2?T1?2??353??294.1K??2.5??p1?RT287?294.13v2?2??0.0639m/kg6p21.32?10??1?1.4?11.4c2?cc??RTc?1.4?287?294.1?343.8m/sf2c21?10?4?343.8??m??0.538kg/s

v20.06399-5

pc??p1?0.528?0.7?0.37MPa（1）p2?0.5MPa?pc，采用漸縮噴管

??1?1.4?11.4?p2??0.5?T2?T1???1220??1108K?p0.7???1?RT287?1108v2?2??0.636m3/kg6p20.5?10c2?2cp?T1?T2??2?1010?1220?1108??475.6m/s

f2??20.5?0.636mv??6.68?10?4m2c2475.642

工程熱力學(xué)

（2）p2?0.12MPa?pc，采用漸縮漸擴噴管

?p??0.12?T2?T1?2??1220??737K??0.7??p1?RT287?737v2?2??1.763m3/kg6p20.12?10c2?2cp?T1?T2??2?1010?1220?737??987.8m/s

??1?1.4?11.4f2??20.5?1.763mv??8.92?10?4m2c2987.8RT1287?373??0.714m3/kg6p10.15?10f1c10.1?100??14.01kg/sv10.714f2c20.1?171.4??1.223m3/kg?m14.019-6

（1）v1???m（2）v2?p2v20.14?106?1.223T2???596.8K

R287（3）9-7

?p?T2?T1?Q??H?mc?14.01?1.01??596.8?373??3167kW

pc??p1?0.528?0.5?0.264MPa?p2，采用漸縮漸擴噴管

?p??0.1?（1）T2?T1?2??600??379K?p0.5???1?RT287?379v2?2??1.088m3/kg6p20.1?10c2?2cp?T1?T2??2?1010?600?379??668.1m/s

??1?1.4?11.4f2??21.5?1.088mv??0.00244m2c2668.143

工程熱力學(xué)

（2）T2??T1??n?T1?T2??600?0.95?600?379??390K

v2??RT2?287?3903??1.119m/kg6p20.1?10c2??2cp?T1?T2???2?1010?600?390??651.3m/s

f2???2?1.5?1.119mv??0.00258m2c2?651.39-8由題意得：T1?300K，p1?784.6kPa

p2??p1?0.528?784.6?414.3kPa

?p??0.4143?T2?T1?2??300???249.96K?p0.7846???1?c2?2cp?T1?T2??2000??300?249.96??316.4m/sRT2287?249.963??0.1732m/kg6p20.4143?1011f2??d2??3.14?0.032?7.07?10?4m2

44f2c27.07?10?4?316.4??m??1.292kg/s

v20.1732??mRT?1.292?287?300?3600?4083.5m3/hVp98070??11.36?1cp??1000?264.7J/kg?K9-9R??1.36v2???1?1.4?11.4????0.535???????1??1.36?1?（1）pc??p1?0.535?1?0.535MPa

1.36?1?pc?Tc?T1???1000?0.5351.36?847.4K

?p1?RT264.7?847.43vc?c??0.4193m/kg6pc0.535?10?2????1?2?1.361.36?1??1?cc??RTc?1.36?264.7?847.4?552.3m/s

?mv5?0.4193fmin?c??0.00380m2

cc552.3工程熱力學(xué)

44

?p??0.1?（2）T2?T1?2??1000???543.6K?p1???1?T2??T1??n?T1?T2??1000?0.95?1000?543.6??566.4K

v2??RT2?264.7?566.43??1.50m/kg6p20.1?10?2?5?1.50mv??0.00805m2c2?931.21f2?fmin?0.398m?tg5??1?1.36?11.36c2??2cp?T1?T2???2?1000?1000?566.4??931.2m/s

f2??（3）取頂錐角??10?，漸擴部分長度l：

l?d2?dmin2tg????2c9-10由M?得：

a2cp?T0?T1??RT1?T1?p1?p0???T0??2000??350?T1?1.4?287?T11.41.4?1?0.6?T1?326.4K

???1?326.4??0.65????350??0.51MPa

c1?2cp?T0?T1??2000??350?326.4??217.3m/s

pc??p0?0.528?0.65?0.3432MPa>0.28MPa∴p2?0.3432MPa

T2?T0???1??350?0.5281.4?11.4?291.6K

c2?2cp?T0?T2??2000??3