Hydraulic Pumps Std
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Transcript of 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