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POSITIVE PUMPS AND COMPRESSORS: A COMPREHENSIVE
ANALYSIS
Rizayev Abdumalik Nabiyevich
1.a
, Baratova Shahnoza
2.a
Tashkent State Transport University, Professor
1.a
;
Tashkent State Transport University, student
2.a
ANNOTATION: This article analyzes in detail the kinematics of fluid motion
inside the impeller of centrifugal pumps. The absolute, relative and peripheral velocity
components of the flow, velocity triangles, flow angles and their effect on efficiency are
considered. Flow disturbances, separation zones, twisting motions (vortices) and
methods for eliminating them are also covered. Based on kinematic analysis, the
possibilities of determining theoretical pressure using the Euler equation and other
hydraulic formulas, and evaluating flows using computer modeling (CFD) are also
considered. The article is intended for engineers and technical specialists involved in
pump design, hydraulics and energy efficiency.
Key words: Positive displacement pumps, positive displacement compressors,
volumetric efficiency, reciprocating pumps, rotary pumps, lobe pumps, diaphragm
pumps, gear pumps, scroll compressors, screw compressors, piston compressors, fluid
transfer systems, high-pressure applications, flow control, pump-compressor
comparison.
INTRODUCTION
Centrifugal pumps are widely used in industry, utilities, water supply and heat
energy systems. The efficiency and stability of such pumps directly depend, first of all,
on the kinematics of internal flows - in particular, the flow in the impeller. This article
discusses the speed conditions, directions of flows inside the pump, the causes of
failures and methods for their calculation.
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From the center escape of the pump work principle
Pump worker wheel using an electric motor turns into . Liquid wheel from the
center ( entrance (through the eye ) and rotation under the influence to the periphery (
external) diameter ) moves . Centrifugal power liquid particles additional kinetic
energy gives , this energy later pressure to the energy turns .
Worker on the wheel currents types
Liquid worker on the wheel movement as follows classification possible :
Login flow
– in the axial direction , usually one kind pressure under
Radial flow
– vanes between , wheel to the cycle related
Peripheral ( tangential ) motion
– rotation because of to the surface
comes
Spiral ( vortex ) flow
– on the periphery it will be , this energy to their
losses reason will be
The flow cinematic analysis
1. Speed components
Worker on the wheel every one liquid of a particle movement 3 main speed
from vector consists of :
Character
Description
c
⃗
\vec { c } c Absolute velocity – of the fluid general speed
u
⃗
\vec { u } u Rotational ( peripheral ) speed – working wheel rotation because of
w
⃗
\vec { w } w Relative velocity – of the fluid to the wheel relatively speed
They between dependency following vector equation with is expressed as :
c
⃗
=u
⃗
+w
⃗
\ vec {c} = \ vec {u} + \ vec {w} c = u + w
2. Speed triangles
Liquid entrance and exit at points every kind speed triangles has :
At the entrance (r₁):
stream mainly in the axial direction
At the output ( r ₂):
peripheral component increases
Exit triangular
according to Aylor equation through of the pump giving
pressure is defined as :
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H= 1g( u2cu2−u1cu1)
Here :
uu u – rotation speed
cuc_ { u } cu – peripheral component
HH H – theoretical pressure ( pressure )
gg g – free fall acceleration
Flow corners and their importance
Worker wheel of the wings corners stream direction determines :
Incoming angle ( β 1\beta_1 β 1 )
– liquid to the wing how enters
Outgoing angle ( β 2\beta_2 β 2 )
– liquid wingtip how abandonment will
Flow compatibility
( i.e. , flow angle and wings angle compatibility ) – energy
their losses reduces . On the contrary without
divorce
or
turn flow
appearance will be
.In the stream disorders and losses
1. Divorce zones
Wings along stream enough undirected if , the current from the wall separates
– this
cavitation
,
energy loss
, and to
the noise
take is coming .
2. Turbulent flow
Big diameter and fast rotating on wheels stream It becomes turbulent . It is
viscous. losses
increases .
3. Slowing down zones
The wheel back in part stream speed decreases – this and
working being
released pressure
reduces .
Hydraulic efficiency and stream kinematics impact
Pump general efficiency :
η = Useful powerTotal power \eta = \ frac { Useful power }{ General power }
η = Total power Useful power
Kinematic malfunctions :
Wrong wing corners
The flow turn
Vortex and turbulences
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this factors
useful power reduces
, so
efficiency
reduces .
Flow kinematics calculation methods
1. Analytical methods
Closed formulas using calculation ( e.g. , Euler) equation , Bernoulli equation
).2. Graphic methods
Speed triangles on the graph build and geometric analysis .
3. Computer modeling (CFD)
Accurate 3D model ( pipe , wheel )
Speed fields , pressure gradients
Cavitation and stream turn zones determination
Practical example ( simplified )
Rotation
speed
:
n=2900
rpm
/
min
=
2900
Rotation corner speed :
ω =2 π n60=2 π
⋅
290060≈303.5 rad /s
Peripheral speed :
u=r
⋅
ω =0.1
⋅
303.5=30.35 m/s
Outgoing
cuc_u
cu
=
22
m/s
Theoretical pressure :
H=19.81( u
⋅
cu )= 19.81(30.35
⋅
22)≈68.1 m
Conclusion
From the center escape pump worker on the wheel of the stream kinematics of
liquid how movement , to him how much energy to be given and pump efficiency
determines . Speed components correct analysis , flow direction optimization and
cavitation of violations prevent to take through of the pump work deadline extends and
energy is saved . Therefore , this issue not only theoretically , maybe important
practical importance has .
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