??? (Pump)

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??? (Pump)

• Aquacultural Engineering
• W 10 -11

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What are pumps

• ???????????????
• ????????????(energy gradient)??,?????(total
  energy)????????
• ?????????????????????????
• ?????????????????,?????????(do work)????(load)?

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Purposes of this chapter

• ???????????????????????????
•  
• ?????????????????
•  
• ????????????????????????????

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DEFINITIONS

• ????(Free water surface)
• ??????????????????
• ?????) Net positive suction head (NPSH)
• ????????????????????

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a positive NPSH.

• NPSH hb hv - hf hh (11.1)
• hb ???? (Pa)

• hv ????? (Pa)
• hf ???????????????????? (Pa)
• hh ?????????? (Pa)

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??????????

• NPSH hb hv hf hh (11.2)

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???????????

• NPSH hb hv hf hh P1 (11.3)

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????(Pressure head)

• ????????????????? ?h P2 V22/2g hf ? NPSH
  (11.4)
• h ?????????????????????
• g ?????
• P2 ??????????
• V22/2g ???????????????
• hf ???????????
• NPSH ????? (???????????, ??????????)

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• The total pressure head(h ?????)
• ???????????
• Brake power (BP)(????)
• ???????? ??????????
• Pump output power (POP)(?????)
• ???????????? POP CQh (11.5)
• ??? 1 g/ml ???? POP (watts) 9800Q (m3/sec) h(m)
  

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• Efficiency of a pump (e)
• e output/input POP/BP (11.7)

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PUMP CLASSIFICATION
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CENTRIFUGAL PUMPS

• ???????????
• ???????????(shaft), ???? (impeller)??
• ???????(vanes)??????????????
• ????????????????, ?????
• ?????????????, ???????????????????, ??????????

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• ??????????????????? 
• ???????????, ??????, ????????????????( static
  pressure head)
• ????????????????????????????
• ????????????????????

15

• ????????(stuffing box) ???????, ???????, ????????
•  

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Pump bearing (??)

• ?????????, ???????????
•  
• ???????????????

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Volute (??) Centrifugal Pumps
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Diffuser (???) Centrifugal Pumps
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Open impellers
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Semienclosed impellers
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Enclosed impellers
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Performance Characteristics

• ??????????????, ??????? ???????(head),
  ??(efficiency), ???(discharge)?????(power
  requirements)?????????

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Deep Well Turbine (????????)

• multistage centrifugal pumps, either volute or
  diffuser type

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ROTARY PUMPS

• Rotary pumps consist of a casing and rotating
  member(s) that force the fluid from the low to
  high pressure side.

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Propeller (??) Pumps

• Propeller pumps are best used for conditions of
  low head and high discharge

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• Single-stage propeller pumps are limited to heads
  of 7 to 8 m, whereas multistage pumps are built
  for heads up to about 40 m.
• Pump discharges are available up to several
  thousand cubic meters per minute.
• Propeller pump speed is limited by cavitation at
  the propeller tips.
• Since the tip velocity increases with diameter,
  the larger the propeller diameter, the slower it
  must turn.
• Large pumps commonly operate in the 100 to 300
  rpm range, too slow for direct coupling to an
  electric motor.

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Flexible Tube Pumps
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• Low volume pumps.
• Generally used as metering pumps for metering
  corrosive liquids 
• Provide adjustable and accurate flow rates and
  are particularly applicable for corrosive
  liquids.
• Pressure capabilities of flexible tube pumps are
  relatively low, the maximum pressure depending on
  flexible tube strength.

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RECIPROCATING PUMPS

• Piston (??) Pumps - theoretical suction lift of
  10.3 m and a practical limit of 7 or 8 m

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• Diaphragm (??) Pumps

• ?????????????
• ?????

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• Airlift Pumps (???) hm?m hs?1

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• ???????????,?hm hs gt h1 ,?????????
• ?hm?m????hs?1???,???????????????

• ?????????h1 ho,??????????hs???????Qa??? (by
  Andeen, 1974) ? ho Qa/(1 - Qahs)

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• ????? (by Todoroki et al., 1973)
• ?? 25 - 100 mm??? 4 - 42 m?????0.4 - 0.8
• Qam 0.35 (1 Ms) A(gd)1/2/(1.2 Ms 0.2)
• Qam ?????????,cm3/s
• Ms hs/hm
• A ??????,cm2
• g ?????,cm/s2
• d ?????,cm

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• ??????????? (slip) ????????,????slip??,??????,????
  ????
• ?????????????slip????
• ????,????????????,?????????????10???????,?-?????,
  ????????????????10,??????????0.1 hs?

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• ?????by orifice
• Rb (St)(Ro)/g(?e - ?g)1/3
• Rb bubble radius (cm)
• St surface tension (g-cm/s2)
• Ro orifice diameter (cm)
• g acceleration of gravity (cm/s2)
• ?e density of liquid (g/cm3)
• ?g density of gas (g/cm3)

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??????

• ??????1 liter ???????? (m3)
• Q 0.8 h1/C log (hs 10.36)/10.36

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Fitting a pump to the system

• ??????,??????,???????????????????????????????????
  ?????????????????
• ??????????,??????????,?????????????????,?????????
  
• ??NPSH??????,?????? (cavitation),????????????
• ?????? ???? ?????? ????

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???

• ???????????????????,????????,?????????????,?????
  ???

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• ??????-????,
• ?????????,?A???????
• ?????????????,
• ????????????A???????,?????????B,
• ??????C?????

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???????????

• ?????
• ????
• ?????
• ?????????
• ????????
• ????
• ??????????
• ????

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??????

• ?????(engine)
• ?????? (POP) ?Qh
•  
• ?????????? (BP) ?Qh /e