流体力学泵与风机 - 课后题答案

流体力学泵与风机部分习题答案

2-15

解：（1）当?1为空气 p1?p2 pB???z?h??pA ?p?pA?pB???z?h?

?0.3 ?9.8?1000 ?2940pa?2.94kpa （2）当?1为油 p1?p3 pA?p1???h?H?z?

pB?p3???1h??H?

?p?pA?pB?p1?p3??h??H??z??1h??H

??h??z??1h

?9.8?1000?0.1?9.8?1000?0.2?9000?0.1 ?2040pa?2.04kpa 2-16 解：p1?p2

p1?pM??水?H?h1?h2? p2?pa??油h1??汞h2

pM??水?H?h1?h2??pa??油h1??汞h2

?980?9.8?1000??1.5?0.2?h1??7850?h1?13.6?9.8?1000?0.2 ?980?9800?1.5?9800?0.2?9800h1?7850h1?26656 1950h1?26656?980?14700?1960

h1?5.63m 2-28

解：p???h1?h2?

1

P?1212??h1?h2??h1?h2?sin450b???h1?h2?3?2sin450h2sin450b

2sin450 ??9.8?1000??3?2??52?1?9.8?1000??3?2??1

?9.8?1000?1lD?22?34650N?34.65kN

??h1?h2??h1?h2?sin450blD1???h1?h2?Ph2sin450blD2

9.8?1000?22?232?9.8?1000?22?2252?2.45m

2 ?9.8?1000?2-32 解：P??h1h2sin450b?12?h2222h2sin450b

?9.8?1000?1??2?12?9.8?1000?2?222?2

?9.8?1000?82?110857.6N?110.8576kN h2?2h2???h?h??1??1?h2h22?13????h1b??h2b0000sin45sin452sin45sin45lD?

P9.8?1000?42?22?9.8?1000?42?732 ?9.8?1000?82131372 lp?2?2?2 ?666G?lG?P?lP?T?lT 19.62?1?9.8?1000?82?T?9.81?274.43762?T?2

?101.31kN

2-41

解：h?r?sin45? Px???h?h?1202

?b

2?2?12?4

? ?9.8?1000 2

?39200N?39.2kN Pz??V

????r2??45360?100?r?sin45?r?cos45?b 2? ?9.8?1000??3.14?22???18?2?2?1???4 2? ?22344N?22.344kN P?39.2?22.344PzPx22?45.1kN

22.34439.2?arctan0.57?30

0??arctan

?arctan3

3-3

解：（1）Q??4d3?v3?22?4?0.025?10?0.0049m/s ?Q?4.9kg/s

223?d??d3??v3?0.625m/s v2??3?v3?2.5m/s （2）v1???d??d??1??2?3-5

解：Q?10000m3/h?2.778m3/s

v?Q?20m/s

2?4d所以，d?4Qv??0.177

所以，d?0.45m?450mm 此时，v?Q?4?24Qd?d2?11.1120.63585?17.4m/s

3-6

?解：A1?A2?A3?A4?A5?4d52??20d

21??1?22A1?A1??d??d

220401??1?22A2?A2??d??d

220401??1?22A3?A3??d??d

220401??1?22A4?A4??d??d

220401??1?22A5?A5??d??d

22040?4d1?2140340540740?d d1?2110310d r1?12103210521072104

d

?4d2?2?d d2?2d r2?d

?4d3?2?d d3?2510710d r3?d

?4

d4?2?d d4?2d r4?d

?4d5?29402?d d5?310d r5?3210d

G??Q???d22?u1?u2?u3?u4?u5????d2?u1?u2?u3?u4?u5?

40203-7

解：干管前端的质量流量为：

2Q?1??1v1A1?2.62?25??d14

?2.62?25??24??0.05??0.128544kg/s

QQ?1?2?Q?3?2?0.064272kg/s

vQ?20.0642722???22.247m/s

2A?22.3??4??0.04?2vQ?33???0.064272?18.05m/s

3A32.24??4??0.045?23-10

解：将基准面建立在B点经过的水平面上，列能量方程：

2zp1?1v1?22v21???2g?z2?p2??2g

2其中，z11?1.2m

p??1.5m v1?2m/s v2?d1d2v1?4.5m/s221.2?1.5?2.522g?0?p2??42g

252

p2??1.2?1.5?22g?4.2g?1.871

3-11

解：将2点所在的水平面作为基准面，列能量方程： 22 z11?p???1v12g?zp22????2v22g

5

?1??2?1

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