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5 June 2014 1
5 June 2014
CONSTRUCTION. Classification
HYDRAULIC MACHINES
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CONSTRUCTION
THE MAIN COMPONENTS OF TURBOMACHINES. THEIR
ROLE
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Buidings.
The blades of the impeller areusually placed between two paralleldisks; one is fixed on the shaft (the
crown) and the other one thatcontains the inlet of the fluid (thering).
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The principle of operation
The fluid passes through the suctionpipe, gets into the rotor where akinetic energy is inculcated upon it,
which afterwards is converted intopotential energy in the spiral roomand in the discharge pipe. Some
centrifugal pumps are equipped witha stator with blades that have therole to convert the kinetic load into
pressure load and to direct the fluid.
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The components of centrifugal
pump
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the classification of turbo pumps and
the shape of the meridian suction of
their rotor
Hydrodynamic pumps or turbo pumps may be classified by thespecific rotation
or dynamic rapidity, that can beconsidered as the rotation of a pumpgeometrically similar with the given
one, which absorbs a power of 1 H.P.at a load of 1m:
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Classification
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Specific rotation ns androtation n measured with the
tachometer, obviously cannothave the same dimension.In order to classify the turbopumps we can also use theircharacteristic rotation orkinematic rapidity:
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The turbopump theory
Hypotheses:
a) Between two consecutive
blades of the rotor of thecentrifugal pump, the flow ofthe fluid is stationary, in theshape of some streamlines thattake the curvature of the blade.
b) Inside the pump we don’thave hydrodynamic losses.
c) The rotor consists of aninfinite number of blades withnegligible thickness.
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The speeds
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The fundamental equation of turbo
machines, applied in the case of centrifugal
pumps can be obtained in several ways: a) by applying the theory of variation
for the moment of movementquantity (impulse)
b) by applying Bernoulli’s equationfor the relative movement betweenthe points 1 and 2.
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The fundamental equation of
turbo machines
a) by applyingthe theory of
variation for themoment ofmovementquantity
(impulse)
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The fundamental equation of
turbo machines
b) by applyingBernoulli’s
equation for therelativemovementbetween the
points 1 and 2.
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The fundamental equation of
turbo machines
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CONSTRUCTION OF THE ROTOR(IMPELLER)
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Construction of hydraulic machines
The cinematics of movement in turbomachines
kjit
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The cinematics of movement inturbomachines
a. The representation of parameters’movement in the rotor in the fixed referencesystem
b. The representation of parameters’movement in the rotor in the mobile referencesystem
O1 x 1y 1 z 1
Oxyz
k jit x
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CONSTRUCTION
The relationship between kinematic elements
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CONSTRUCTIONc. Customize cinematic parameters of flow to movement in the rotor case
taking into account the following assumptions:
- It is acceptable that the z axis is along the machine axis, and the distancebetween the origins of the two systems is constant
- The reference cell is rotating rotor machine
- the fluid is considered ideal
- fixed reference system and the mobile is convenientlychoose
•accepted to represent the cylindrical coordinate system(R, , z);
- accepted to represent the cylindrical coordinate system(R, , z)
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Following expressions are obtained
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The hypothesys of potential absolutemovement
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d. Velocity triangles
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Velocity trianglesInlet and outlet
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Correlation between functional user request parameters (flow rate Qn, headHn ) and constructive parameters of the machine.It has adopted a number of simplifying assumptions about themachine and fluid
Peculiarities of functioning of hidropneumatice specific machines of a certainfluid transported or of a specific sense of energy transfer:
differences that may arise in the case of liquids and gases transports
differences that may arise in the event of a transfer of energy in forcing andworking machines
The laws governing the flow in turbomachines
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Flow rate and load of turbomachines in the
assumptions: the ideal, ideal fluid machine
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It is observed that, for the sake of axial symmetry
mişcarea are simetrie axială, adică v rm1, v rm2 şi
the movement has axial symmetry, i.e. Vrm1, vrm2 and the density,It cannot change over the surfaces S1, S2
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Theoretical flow of theoretical rotor
If fluid considered compression connectors (blowers and compressors)
rs)
If the fluids are considered incompresibile
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Theoretical load (head) of the rotor in theory
Observations:-the movement of the fluid in the impeller is considered permanent
- The absolute speed are expressed
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-These cross-sectional surfaces S1, S2, have axial symmetry,and their normals n1, n2, passing through the axis of the machine
-The fluid is ideal, that means the relative movement is tangent to the surface
-SI, SE, zSz
- the forces of gravity for reasons of symmetry, have the application directlyon the rotor axis
e pressure orces e u ac s on mpe er crowns e ro ors are equa an
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p p qopposite forces sign with these areas acting on the fluid, producing hydraulictorque
The expression of angular momentum theorem becomes
The components of the moment after the R and φ directions are taken fromshaft of machines, so the Mz is received from your machine, and drivethen, rotary, the fluid conveyed
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Control surface has axial symmetry
Using cylindrical coordinates for expressions of cinematical parameters
For reasons of symmetry, axial surfaces S1 and S2,the values of the density and speed remain constant
So
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Taking into account the hypothesis ofideal fluid
But so:
The Basic Law of the turbomachines (turbop
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Conclusionsfrom the fundamental theorem of turbomachines expressions
1. Conclusions on the basisof the expression
2. Conclusions on the basis
of the expression
CONSTRUCTIA MASINILOR HIDRAULICE
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CONSTRUCTIA MASINILOR HIDRAULICE
The extent of reaction
We distinguish the following types of machines depending on the degree ofreaction
R = 1 - pure reaction machines
- reaction machines
- action machines
- Pure action machines