Fluid Power Engineering

1. PRESENTATION
ON
CENTIFUGAL PUMPS
FLUID POWER ENGINEERING
SUBMITTED BY:
HIMANSHI GUPTA (140120119057)/ ME/A2
PRACHI SHARMA(140120119216) / ME / A2
(2151903)
GA N D H IN A GA R IN STITU TE OF
TEC H N OLOGY

2. CENTRIFUGAL
PUMPS

3. PUMP:
• The hydraulic machine which converts the
mechanical energy into hydraulic energy (form of
pressure energy).
CENTRIFUGAL PUMP:
• The hydraulic machine which converts mechanical
energy into pressure energy by means of centrifugal
force acting on the fluid.
• Purpose:
• To increase pressure energy
• To impart kinetic energy
• To lift and circulate
• To exhaust or extract liquids

4. CLASSIFICATION OF PUMPS
1) Positive displacement pump
i. Reciprocating pumps
a) Piston pumps
b) Plunger pumps
c) Bucker pumps
ii. Rotory pumps
a) Gear pumps
b) Vane/lobe pumps
c) Screw pumps
2) Roto-dynamic pump
a) Radial flow pump
b) Axial flow pump
c) Mixed flow pump
3) Other type of pumps
a) Jet pump
b) Air lift pump

5. MAIN PARTS OF
CENTRIFUGAL PUMP
Impeller
Casing
• Volute casing
• Vortex casing
• Casing with guide blades
Suction pipe with a
foot valve and a strainer
Delivery pipe

6. CLASSIFICATION OF
CENTRIFUGAL PUMPS
1) According to shape of impeller and casing
a) Volute or spiral casing type pump
b) Vortex (whirpool) casing type pump
c) Diffuser type pump
2) According to type of impeller
a) Closed or shrouded impeller
b) Semi-open impeller
c) Open impeller
3) According to working head
a) Low head centrifugal pump
b) Medium head centrifugal pump
c) High head centrifugal pump

7. 4) According to number of stages
a) Single stage centrifugal pump
b) Multi-stage centrifugal pump
• Impeller in series
• Impeller in parallel
5) According to direction of flow through impeller
a) Radial flow pump
b) Axial flow pump
c) Mixed flow pump
6) According to number of entrances to the impeller
a) Single suction pump
b) Double suction pump
7) According to specific speed of pump
a) Low specific speed pump
b) Medium specific speed pump
c) High specific speed pump

8. VELOCITY DIAGRAM AND
WORK DONE BY IMPELLER
• Centrifugal pump acts as a reversed of an
inward radial flow reaction turbine.
• Assumptions made for analysis are:-
1. Liquid enters the impeller in radial direction
2. No energy loses in impeller due to friction
and eddy formation
3. Liquid enters without shock

9. VELOCITY DIAGRAM

10. WORK DONE BY CENTRIFUGAL
PUMP
• u1= ω R1, u2 =ω R2
• Mass of water striking /sec = (ρ a V1 )
• Momentum of water striking the vanes at
Inlet = (ρ a V1 ) Vw1 , Outlet = (ρ a V1 ) Vw2
• Angular Momentum of water striking the vanes at
inlet = (ρ a V1 ) Vw1 x R1 (Vw1= V1 cos α )
at Outlet = (ρ a V1 ) Vw2 x R2 (Vw2= V2 cos β)

11. • T = Rate of change of Angular Momentum
= (ρ a V1 ) Vw1 x R1 – (ρ a V1 ) Vw2 x R2 )
= (ρ a V1 ) (Vw1 x R1 )–(Vw2 x R2 )
• Work done/sec = T x ω
= (ρ a V1 ) (Vw1 x R1 )–(Vw2 x R2 ) x ω
= (ρ a V1 ) (Vw1 x R1x ω )–(Vw2 x R2x ω )
= (ρ a V1 ) (Vw1 x u1)–(Vw1 x u2)
WORK DONE BY CENTRIFUGAL
PUMP

12. • Work done/sec/unit weight of water/sec
= (ρ a V1 ) (Vw1 x u1)–(Vw2 x u2) x
1
ρaV1 𝑔
• Work done/sec/unit weight of water/sec
= –
(Vw1 x u1)− (Vw2 x u2)
𝑔
• Work done/sec/unit weight of water/sec
= -
(Vw1 x u1)− (Vw2 x u2)
𝒈
= -
− (Vw2 x u2)
𝒈
(Vw1 = 0)
WORK DONE BY CENTRIFUGAL
PUMP

13. HEADS OF CENTRIFUGAL PUMP
where :
Vs = Velocity of fluid in the suction pipe.
Vd = Velocity of fluid in the delivery pipe
hs = Suction head.
hd = Delivery head.
hfs = head losses in the suction pipe.
hfd = head losses in the delivery pipe.
hst = static head

14. EFFICIENCIES OF A CENTRIFUGAL
PUMP
1- Hydraulic Efficiency (ζh)
)(
)('
e
h
HHeadEuler
HHeadTotalsPump

22UV
gH
w
h 
2- Manometric Efficiency(ζm)
)(
)('
e
m
m
HHeadEuler
HHeadManometricsPump

22UV
gH
w
m
m 
3 -Volumetric Efficiency (ζv)
QQ
Q
v


The normal value lies between 97% to 98%

15. 4- Mechanical Efficiency (ζ)
It is due to losses in the shaft, coupling, and other
losses as vibration
shafttheatPower
impellerthetoinPower

ShaftPower
UVQQ w)( 22



The normal value is 95% - 98%
5 - Overall Efficiency (ζo)



.T
QH
P
P
in
out
o 
hQQ
QH
P
P
P
P
P
P
lin
t
in
t
t
out
o


)(


hvmo   The normal value is 71% - 86%

16. LOSSES IN CENTRIFUGAL PUMP
1) Hydraulic losses
2) Mechanical losses
3) Leakage losses

17. TYPES OF IMPELLERS
• There are three main categories of impeller due type of
impeller’s vane, which are used in the centrifugal pumps as;
1. Radial vanes, Fig. (a).
2. Backward vanes, Fig. (b).
3. Forward vanes, Fig. (c).

18. MINIMUM SPEED FOR STARTING A
CENTRIFUGAL PUMP
• When a centrifugal pump is started, it will start
delivering liquid only if the pressure rise in the
impeller is more than or equal to the manometric
head.
• Flow will commence only if ≥Hmano
• For minimum speed ,we must have:
= Hmano ……………(1)
2 2
2 1
2
u u
g

2 2
2 1
2
u u
g

2 22 2
mano mano
mano
wW
H gH
V uV u
g
  
 
 
 

19. 2 2
1
1
60
w
mano mano
V u
H
g
D N
u


 
  
 
 2
2
60
D N
u


Substitute the value in eqn. 1
2 2
22 1 21
2 60 60 60
w
mano
VD N D N D N
g g
  

      
         
       
   2 2
2 1 2 2
120
mano w
N
D D V D

   
 
2 2
min 2 2
2 1
120 mano wV D
N
D D


  



20. CAVITATION IN CENTRIFUGAL
PUMP
• Cavitation begins to appear in centrifugal pumps when the
pressure at the suction falls below the vapour pressure of the
liquid. The intensity of cavitation increases with the decrease in
value of NPSH.
• In a centrifugal pump , the pressure is lowest at the inlet of the
impeller and hence vapour bubbles are formed in the suction
region.
• These bubbles are carried along with the flowing liquid to higher
pressure region near the exit of impeller where these vapour
bubbles collapse.
• Due to sudden collapsing of bubbles on metalic surface the high
pressure is created, which cause pitting action on metalic surface
and produces noise and vibrations.

21. CAVITATION
• Factors responsible for cavitation
i. High impeller speed
ii. Small diameter of suction pipe and inlet of impeller
iii. Too high specific speed
iv. Required NPSH > Available NPSH
v. High temperature of flowing fluid
• The harmful effects of cavitation are:-
i. Pitting and erosion of surface
ii. Sudden drop in head, efficiency
iii. Noise and vibration.

22. CAVITATION
Thomas cavitation factor is used to
indicate the onset of cavitation.
2
2
atm v s
mano mano
s
s s fs
atm
H H HNPSH
H H
V
H h h
g
H

 
 
  
 atmospheric pressure head

23. Thank You 