Hydraulic Pumps Std

8/3/2019 Hydraulic Pumps Std

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HYDRAULIC PUMPSthe source of hydraulic power

Text Ch #4

Archimedean Screw3rd C BC

References:

W. Peng,Fundamentals of Turbomachinery, Wiley, 2008, CH #4Esposito, Fluid Power w/ Applications, Printice Hall, 1988.Lindeburg, M.E. Reference Manual, NSPE, 9th ed

Volk, Pump Characteristics and Applications, Marcel Dekker, 1996Logan, Turbomachinery, Marcel Dekker, 1993.

Video, History Channel, Modern Marvels: Pumps

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HYDRAULIC PUMPSTwo very broad classifications

Positive Displacement Pumps (PDP)Energy added intermittently to the fluid

Reciprocating action pumps(pistons, plungers, diaphragms, bellows)

Rotary action pumps(vanes, screws, gears, lobes)

Kinetic PumpsEnergy added continuously to the fluidCentrifugal pumps (impeller)

Axial pumps (propeller)

Jet pumps

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POSITIVE DISPLACEMENT PUMPS

High Pressure (0-100k+ psi)Low FlowSmall, CompactHigh ViscositySlurriesTwo-Phase flowsHigh efficiency = (actual flow) / (theoretical flow) > 90%

PISTON PUMP

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GEAR PUMP

LOBE PUMP

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SCREW PUMP

VANE PUMP


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Kinetic Pumps

CENTRIFUGAL PUMP

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AXIAL FLOW PUMP

JET PUMP

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PUMP TERMINOLOGY: Head Pressure

PRESSURE = HEAD x DENSITY

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P = h x Many different types of head pressures:

hf= friction head = fLeV2 / 2Dgc

Flow resistance due to pipe friction, fitings, valves, entrances, exits, etc.

hv = velocity head = V2 / 2gc

ha = atmospheric pressure head = pa / (converted to fluid being pumped1 atm = 33.9 ft of water)

hp = pressure head = P / pressure converted to feet of fluid being pumped

hvp = vapor pressure head = Pvp / fluid vapor pressure converted to feet of fluid being pumped, steam tables can be used forwater, figures and tables available for other fluids. Fig L 4.9 vapor pressures of

hydrocarbons.

hs = static suction headvertical distance in feet above the pump centerline to the free level of the fluid source.

If free level of fluid is below pump, referred to as the static suction lift.

hsd = static discharge headvertical distance in feet above the pump centerline to the free level of the discharge.

hts = total static headvertical distance in feet between the free level of the supply and discharge reservoirs.


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hs

STATIC SUCTION HEAD

hs

STATIC SUCTION LIFT


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hsd

STATIC DISCHARGE HEAD

hts

TOTAL STATIC HEAD


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H = Total (dynamic) head= (total discharge head) (total suction head)= Hd Hs

= ( hsd + hvd + h f, dis ) (hs h f,suction)

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hs

H

Q


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PUMP PERFORMANCE CURVE

H (m)

Q (m3/s)

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PERFORMANCE & SPECIFIC SPEED & PUMP SELECTION

NQ Ns ~

H

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COMPRESSORS

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Centrifugal pump

Axial inlet-radial/mixed outlet V2

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R2

R1 V1

V1 W1 V2 W2

U1 U2

Vu2

E = Vu1U1 Vu2U2 = gH


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EXAMPLE

V2

W2

U2

Position 1= into eye of impeller

Position 2 = exit of impeller

= (2)/60 (4800) = 502.7 rad/s

1. U2 = R2 = (502.7rad/s)(0.15m) = 75 m/s

2. E = U2Vu2 U1Vu1 = (75.4)(75.4) m2/s2 0 = 5685 J/kg

U21. Impeller tip speed U2 (m/s)2. Energy Transfer (J/kg)3. Power input (kW)

FIND:

No tangential component torelative exit velocity

Sp.Gr. oil = 0.81Q = 63 l/s @ 4800 RPMImpeller Diameter = 30 cmCentrifugal Oil Pump

Q = (63 l/s) = 0.063 m3/sm-dot = Q (density) = (0.63)(810) = 51 kg/s

3. P = (m-dot)E = (51)(5685) = 290 kW

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Radial Flow Hydraulic Turbine (for comparison)Radial inlet-Axial outlet

W1

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V1

U1R1

Vu1

R2

W2 V2

U2

V1

E = Vu1U1 Vu2U2 = gH

V2


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Q

Variable SpeedMOTOR N(rpm)

H

VALVE

CentrifugalPUMP

H

Q

bhp

NPSHR


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Centrifugal PumpsHead Capacity Curves

H(ft, m)

Q(gpm, m3)

N (rpm, rad/s)

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EXAMPLE: Sun Valley, Idaho Guest LodgeWater from a hot springs (T~150 F) is to be pumped uphill to a guest lodge for space heating, swimmingpool, atrium and winter waterfall. The pump performance curve is attached. Suction line losses are

negligible and delivery line losses are estimated to be ~150 ft-H2O.

9000 ftLODGE

Is cavitation a concern?

of the pump?

What is the power requirement (hp)

(gpm) that can be delivered to the lodge?

What is the maximum water flow rate7500 ft

PUMP

7493 ft

150 oF


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Bernoullis EquationConservation of energy, SFEE

Z1 + P1/g + V12

/2g HL HT = Z2 + P2/g + V22

/2g

Pressure rise across ideal pump impeller

H = (P1 P2) /g + (V22

V12

) / 2g

Z = elevation headP/g = pressure headV2/2g = velocity headHL = friction loss head

HT = turbine head


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Boat Propeller

Saturation pressure(cavitation)


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PUMP WIND TURBINE


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32o

~150o

212o

FTsat

SATURATION TEMPERATUREAND VAPOR PRESSUREOF PURE WATER

14.7 psia

P

5 psia


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CAVITATION DAMAGE ON MARINE PROPELLERJ. Crepeau, visit to San Francisco

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Hydraulic Pumps Std