MAJOR ASSINMENT A PRESENTATION ON

Numerical Modelization of the Flow in Centrifugal Pump

SUBMITTED BY-NAME-ANKIT KR. VERMAB.TECH (ME) 6thSEMESTERUID-K10715

SUBMITTED TO-MR. ADITYA MISHRA(ASST. PROF. OF MECHANICAL DEPARTMENT)

WHAT IS CENTRIFUGAL PUMP ?• Convert the mechanical energy into hydraulic

energy by centrifugal force on the liquid• Constitute the most common type of

pumping machinery• Used to move liquids through a piping system• Has two main components: 1. Stationary componets, casing, casing cover

and bearings2. Rotating components, impeller and shaft

• Classified into three categories ; Radial Flow, Mixed Flow, Axial Flow

WORKING MECHANISM OF A CENTRIFUGAL PUMP

• Simplest piece of equipment in any process plant

• Energy changes occur by virtue of impeller and volute

• Liquid is fed into the pump at the center of a rotating impeller and thrown outward by centrifugal force

• The conversion of kinetic energy into pressure energy supplies the pressure difference between the suction side and delivery side of the pump Liquid flow path inside a

centrifugal pump

PUMP SELECTION

The amount of fluid

The properties of the fluid

Type of power supply

Cost and mechanical efficiency of the pump

BACKGROUND

• Centrifugal pumps are used in a variety of applications, such as, water supply and irrigation, power generating utilities, flood control, sewage handling and treatment, process industries, transporting liquid-solid mixtures.

• Conventional design method of centrifugal pump are largely based on the application of empirical and semi-empirical rules along with the use of available information in the form of different types of charts and graphs as proposed by successful designers .

INTRODUCTION OF CFD MODEL

• Computational fluid dynamics (CFD) is being increasingly applied in the design of the centrifugal pumps. 3-D numerical computational fluid dynamics tool can be used for simulation of the flow field characteristics inside the turbo machinery

• To overcome the difficulties of Conventional design method , some simplifications in the geometry are often considered many hydrodynamic models are reported in two (2D) and three dimensional (3D) by using the CFD code.

CFD in the turbomachineryIMPELLER 3D FLOW SIMULATION

A 3D CFD flow simulation was carried out on an isolated impellerof a mixed-flow centrifugal pump with specific speedof 32 (impeller NS32).

Simulation parameters and boundary conditions

3D VIEW

Turbulence models

.

• Figure 6 shows the influence of the three turbulence models on the calculated pump head. The calculated head H varies very slightly (less than 0.02%). The same tendency is observed in Figures 7 and 8, where no significant influence of the turbulence model on the meridional velocity field and velocity profile near the wall is observed

Influence of turbulence model on the meridional velocity field

Static pressure field of pump NS32 at the best efficiency point (Q/Qbep = 1) for different relative positions of impeller-volute

tongue.

NON UNIFORM PREESUR DISTRIBUTIONThe non uniform pressure distribution around the impeller periphery is the origin of periodic loads causing the radial thrust. This fundamental parameter affects the life cycle of thepump shaft and bearings as well as the vibration behavior of the machine. The pressure distribution around the impeller periphery is shown in Figure for α = 0◦ and different flowrates.

Radial thrustThe radial thrust can be determined from the pressure distributionsby carrying out the integration of the elementary forces around the impeller periphery

CONCLUSIONS

• In this research work, an integral procedure for the optimization of centrifugal pumps has been developed based on 3D quasi-unsteady flow simulation using CFX-TASC flow and CFX 5.5 codes.

• The sensitivity study performed on the isolated impeller has shown two relevant aspects.

• (i) The numerical solution is stabilized with grids containing more than 40 000 nodes.

• (ii) All turbulence models used (k − ε, k ω, k − ω, SST) gave almost identical results, for the same simulating conditions.

• The impeller-volute assembly requires the addition of two extended computational domains; one at the impeller inlet and the other at the volute outlet. The Frozen-Rotor interface model (quasi-unsteady) is considered for the study of the impeller-volute assembly since it represents the best accuracy of computing time tradeoff.

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