perfomance analysis of mixed flow pump

International Journal of Emerging Trends in Engineering and Development Issue 3, Vol.1 (January 2013)

Available online on http://www.rspublication.com/ijeted/ijeted_index.htm ISSN 2249-6149

Page 647

“PERFORMANCE ANALYSIS OF MIXED FLOW

PUMP IMPELLER USING CFD”

P.G. STUDENT

PREPARED BY

MR. MEHTA MEHUL P.

ENROLLMENT NO: - 110300721001

Mob. +918866801327

THE DEGREE MASTER OF ENGINEERING

IN MECHANICAL ENGINEERING

BRANCH OF THERMAL ENGINEERING

GUJARAT TECHNOLOGICAL UNIVERSITY, AHEMDABAD.

UNDER THE GUIDANCE OF

MR. PRAJESH M. PATEL

ASST.PROFFSSOR, MECHANICAL DEPARTMENT,

L.D.R.P.-I.T.R COLLEGE OF ENGINEERING AND TECHNOLOGY

DIST.GANDHINAGAR

ST. GUJARAT, INDIA



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ABSTRACT

To improve the efficiency of mixed flow pump, computational fluid dynamics (CFD)

analysis is one of the advanced tools used in the pump industry. From the CFD analysis, the

velocity and pressure in the outlet of the impeller is predicted. These outlet flow conditions

are used to calculate the efficiency of the impeller. The optimum inlet and outlet vane angles

are calculate for the existing impeller by using the empirical relations. In the first case outlet

angle is increase, and second case inlet angle is decrease obtain from the CFD analysis, it is

reduce outlet recirculation or it is increase outlet recirculation flow cause to improve

efficiency. Thought that the calculation results by numerically simulation software Fluent can

truly reflect the flow in the impeller of a mixed flow pump on the premise that the turbulent

model and boundary conditions are similar to the actual situations.[1] By change the outlet

angle the head of the impeller is improve. Finally, from CFD analysis the calculated

efficiency of the impeller with optimum vane angle can be improved by changing the inlet

and outlet angle. The Head created by this analysis would be higher.

KEY WORDS- Mixed flow pump, computational Fluid Dynamics (CFD) analysis,of

impeller. With using software

CORRESPONDING AUTHOR: (AUTHOR-1 P.G. STUDENET) MEHTA MEHUL P.

(AUTHOR-2 UNDER GUIDANCE) PRAJESH M. PATEL

INTRODUCTION

A pump is a device used to move fluids liquids by mechanical action. Pumps can be

classified into three major groups according to the method they use to move the fluid: direct

lift, displacement, and gravity pumps. A few types of pump in Radial flow pump, mixed flow

pump, axial flow pump. A wide variety of pump types have been constructed and used in

many different applications in industry. From the CFD analysis software and advanced post

processing tools the complex flow inside the impeller can be analyzed.

Pumps must have a mechanism which operates them, and consume energy to perform

mechanical work by moving the fluid. The activating mechanism is often reciprocating or

rotary. Pumps may be operated in many ways, including manual operation, electricity, an

engine of some type, or wind action.



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Mixed Flow Pump

In this pump, addition of energy to the liquid

occurs when the flow of liquid in axial as well as

radial direction. In this type of pump liquid through

impeller is as combination of axial and radial

direction as shown in fig 1. The head is developed

partly by the action of centrifugal force and partly by

the propelling force. These pumps mostly suitable for

irrigation purpose where large quantity of water at a

lower head.

Fig: - 1 Mixed flow pump

Types of BladeS

Backward-curved blades, β2<90° When β2<90°, Cotβ2 is positive and hence with increase in mass flow rate, the head

decreases. The head capacity characteristic has a negative slope.

Radial Blades β2=0

For radial vanes β2=0 and cotβ2 =0, so head does not vary with flow rate.

Forward-Curved Blades, β2<90°

For forward curved blades β2<90° and cotβ2 is negative. Hence, with increase in mass flow

rate head also increases, the head capacity characteristic has a positive slope.

As shown from Figure 2 for forward blades impeller, the fluid leaves the impeller

with relatively high speed which means that the major part of the energy gained is kinetic

energy, this type of impeller requires a very good diffuser to convert this kinetic energy to

pressure energy. In practice, it is difficult to construct this kind of diffuser; also it is usually

more efficient to convert pressure energy to kinetic energy rather than converting kinetic

energy to pressure energy.



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Fig.2 Types of Impeller blade base on curvature of blades

“The pumps are divided into two basic groups, depending on the way in which the

liquid is transferred from suction side to the delivery side of the casing as positive

displacement pumps and impeller or rotodynamic pumps”. The rotodynamic pump and

impeller pump terms are firstly introduced by H. Addison, Based on the direction of the flow,

the rotodynamic pumps are in the category of cased pumps. The moving element in

rotodynamic pumps is the impeller which is the rotor mounted on the rotating shaft and

increases the moment of momentum of the flowing liquid in the impeller. The turbine pumps

are first used as lifting water from the small diameter water supplies and irrigation wells.

However they are used in wide range of applications other then lifting water from irrigation

wells such as used in circulation systems in the steel industry for cooling, water extraction

from boreholes and rivers, sea water services, deep sea mining, extraction water from

geothermal wells, city water district systems and etc. Moreover, the main advantage of using

the vertical turbine pumps is the ability to assemble the stages in series connection thus

increasing the pressure rise across the pump easily.

The pumps are classified by their specific speed. Non-dimensional specific speed or type

number, N, of the pump is defined as.

𝑁 =𝜔 𝑄

1

2

(𝑔.𝐻)3/4

Where, ω is in rad/s, Q is in m3/s, g is in m/s

2 and H is m.

The mixed flow pumps by means of specific speed range are located between the

radial pumps and axial flow pumps. The overlapping region between the radial and mixed

flow pumps are named as Francis type. The specific speed range of the mixed flow pumps are

given differently in the literature because of the overlapping regions of the mixed flow range

with axial flow pumps and radial pumps. The range for the mixed flow pumps by means of

specific speed is given in References. The mixed flow pumps discharges relatively low heads

however the usage of mixed flow pumps as vertical turbine type assembly allows series

connection. Thus the head of the pump assembly may be increased by series connection of

the stages for the desired flow rate. The pump efficiency concerns are playing a major role in

the usage of mixed flow type vertical turbine pumps. The Francis type and mixed flow type

pumps have better efficiency characteristics among the other types.



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The development of the mixed flow type turbine type pumps are highly related to the

demands of the market. The different application types developed during the years. However

the concerns about energy consumption are the most important factor in the development of

all type of pumps. The improvements in manufacturing techniques such as casting, surface

finish on the impellers, rapid prototyping and precise measuring devices lead the industry to

produce pumps with better efficiencies.

The vertical turbine type mixed flow pumps are mainly composed of four

subassemblies. These subassemblies are the driver, discharge head, column assembly and the

pump assembly. The pump assembly is also composed of several parts which are shown in

Figure. The power is transmitted from the electric motor or any other type of driver such as

diesel engine to the pump.

Fig 3: - Parts of the mixed flow Pump Assembly

Assumptions for Velocity Diagram of Pump Impeller:

Liquid enters the impeller eye in radial direction.

No Energy losses in impeller due to friction & eddy formation.

Liquid enters without shock.

Uniform velocity distribution in the passage between two adjacent vanes.



52

Figure: - 4 Velocity Diagram

Now,

𝑈1 = 𝜋 𝐷1𝑁

60

𝑈2 = 𝜋 𝐷2𝑁

60

Mass Flow Rate,

𝑄 = 𝜋𝐷1

2𝑉1

4

𝑉1 = 4 𝑄

𝜋 𝐷12

From Inlet Velocity Triangle,

Inlet Blade Angle,

tan𝛽1 = 𝑈1

𝑉1

And

𝑉𝑟1 = 𝑉12 + 𝑈1

2 = 𝑉𝑟2

From Outlet Velocity Triangle,

𝑄 = 𝜋 𝐷2 𝐵2 𝑉𝑓2

𝑉𝑓2 = 𝑄

𝜋 𝐷2𝐵2

𝑉𝑟22 = 𝑉𝑓2

2 + (𝑈2 − 𝑉𝑤2)2

And,

𝑉2 = 𝑉𝑤22 + 𝑉𝑓2

2

Outlet Blade Angle,

tan𝛽2 = 𝑉𝑓2

𝑈2 − 𝑉𝑤2

Head Generated by Impeller,

𝐻 =𝑉𝑤2 𝑈2

𝑔− 𝑉2

2

2𝑔

Overall Efficiency of Impeller,



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𝜂𝑜 = 𝜌 𝑔 𝑄 𝐻

𝑃𝑜𝑤𝑒𝑟

Submersible pumps are found in many applications. Single stage pumps are used for

drainage, sewage pumping, general industrial pumping and slurry pumping. They are also

popular with aquarium filters. Multiple stage submersible pumps are typically lowered down

a borehole and used for water abstraction, water wells and in oil wells. Special attention to

the type of ESP is required when using certain types of liquids.ESP's commonly used on

board naval vessels cannot be used to dewater contaminated flooded spaces. These use a 440

volt A/C motor that operates a small centrifugal pump. It can also be used out of the water,

taking suction with a 2-1/2 inch non-collapsible hose. The pumped liquid is circulated around

the motor for cooling purposes. There is a possibility that the gasoline will leak into the pump

causing a fire or destroying the pump, so hot water and flammable liquids should be avoided.

So, the main applications of the submersible pump are,

- Domestic & Community water supply

- Industries

- High rise buildings

- Agriculture

- Dairies

- Fire fighting systems

- Cooling water circulating systems

Fig: - 5 Types of pump

MA Xi-jin and ZHANG Hua-chuan in predicated the hydraulic performance of a

three-level Circulating mixed flow pump of a nuclear power station by CFD software.

Meanwhile, they conducted performance test on clear water rig. The numerically simulation

results were in good coincidence with the Experimental results. [2]The Mixed flow of the

liquid occurs when the flow is in axial as well as radial direction. In this type of pump liquid



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through impeller is as combination of axial and radial direction. The head is developed partly

by the action of centrifugal force and partly by the propelling force. There are three types of

blade used in mixed flow pump: forward curved blade, Backward curved blade, axial curved

blade. Mixed flow pumps are widely used for water transportation or as cooling water pumps

in power stations.

To increase the flow rate of the pump without changing the head, the blades of the

newly designed Axial pump impeller. Excellent impeller blade with similar specific speed,

the blade was designed into “C” type curved section to reduce the Occurrence of vortexes at

the head of the blade. Properly reduce the blade outlet structure Angle β2K to eliminate or

weaken the effect of vortex, and increase the flow rate in. [3] Mixed flow pump can we used

in following application like Domestic & Community water supply, Industries, High rise

buildings, Agriculture, Dairies, Firefighting systems, cooling water circulating systems. Not

many CFD studies or measurements concerning the complex flow in all types of centrifugal

pumps have been reported [4, 5].

LITERATURE SURVEY

Paper-1

1kiran patel, 2Professor N. Ramakrishnan in his studies of CFD analysis of mixed

flow pump derived that the Head predicted by CFD analysis is higher than the test result at

rated point. It also concluded that Power predicted by CFD analysis is higher at rated point to

compare with the test result.

Fig: - [6.] Head versus Capacity Curve

Power predicted by CFD analysis is 5 to 10% higher at rated point. To compare with

the test result, disc-friction power loss calculated using NEL method [6] the volumetric

efficiency is determined. Pump efficiency considering disc friction loss and leakage-loss is

predicted and it was found within +5% ranges, at duty point. Efficiency predicted by CFD

analysis is higher than the test result. Leakage-loss is predicted using. Efficiency is improved

admin

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by 1% after matching stator angle and changing hub curve profile. Stator blade loading at hub

and shroud has improved.

Fig: - [7] Efficiency versus Capacity Curve

Paper-2

A Manivannan Department of Mechanical Engineering, PSG College of

Technology Coimbatore, INDIA in his studies of CFD analysis of mixed flow pump

derived that the mixed flow pump the best efficiency point of the pump is found to be 11 lps.

The existing impeller, the head, power rating and efficiency are found out to be 19.24 m, 9.46

kW and 55% respectively.

Fig: - 8 Head developed by the existing and modified impellers

The impeller 1, the percentage increase in the head, power rating and efficiency are

3.22%, 3.9% and 7.27% respectively.



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Fig: - 9 Efficiency of the existing and modified impellers

The impeller 2, the percentage increase in the head, power rating and efficiency are

10.29%, 7.61% and 10.91% respectively. Viscous flow analysis of mixed flow pump

impeller.[7] The impeller 3, the percentage increase in the head, power rating and efficiency

are 13.66%,12.16% and 18.18% respectively.

Paper 3:-

Mandar TABIB*, Graeme LANE, William YANG and M Philip SCHWARZ in

his studies of CFD analysis of mixed flow pump derived that the computational simulation of

the mixed flow pump impeller was implemented.

A CFD code, the ANSYS® CFX® 12.1, was used to obtain the head and pressure,

velocity streamlines. The analysis results show the head of 7.45m and the head achieved by

the experimental work in industries was 8.08 m. The efficiency find by experimental result

was 53.27 % and by CFD analysis 49.6 %.In the CFD analysis high values were obtained for

the head, comparing to the manufacturer experimental head. Because in CFD analysis there

is no influence from the diffuser, so the friction losses are smaller, affecting the pressure

fields and increasing the head values. This fact represents the necessity to introduce the

friction losses due to coupling between the diffuser and impeller. Result shows pressure in

the impeller channels increases from the entrance to the discharge in successive ranges.



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Fig: - 10 The boundary condition applied to the pump impeller

Paper 4:-

1VASILIOS A. 2 GRAPSAS, JOHN S. ANAGNOSTOPOULOS AND IMITRIOS

E. PAPANTONIS in his studies of CFD analysis of mixed flow pump derived that the mixed

flow pump

The numerical results are compared to the measurements, showing good agreement

and encouraging the extension of the developed computation methodology for performance

prediction and for design optimization of such impeller geometries. A numerical

methodology for the calculation of the flow field in centrifugal pump impellers with 2D

curvature is developed and validated against corresponding experimental data taken at a

Laboratory test rig. The flow is calculated using a two dimensional approach in order to

achieve a fast simulation and the agreement between the numerical results and the

measurements is satisfactory. studied the pressure fluctuation in a vaned diffuser downstream

from a centrifugal pump impeller.[8] This is quite encouraging result in order to apply the

present numerical model to further flow analysis, as well as, for design optimization purposes

in these pump types.

Paper 5:-



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aMaitelli, C. W. S. de P.1; bBezerra, V. M. de F.; cda Mata, W. in his studies of

CFD analysis of mixed low pump derived that the mixed flow pump calculation of the flow

in a centrifugal pump impeller using Cartesian grid.[9]

In this paper a computational simulation of the centrifugal pump internal flow was

implemented. A CFD code, the ANSYS® CFX® 11.0, was used to obtain the head

performance curve and to evaluate the interface connection between the pump parts: the

impeller and the diffuser. Boundary conditions were adjusted in the software to characterize

the three-dimensional problem. Although the simplifications were done in the model, in order

to adjust the geometry to the software limitations, numerical analysis using a CFD code,

ANSYS® CFX® 11.0 presents results in agreement with the references. Three-dimensional

simulation of the entrance-impeller interaction of a hydraulic disc pump.[10] The results

obtained for the pressure fields, and therefore to the head performance curve, were

satisfactory in the three conditions tested.

Fig: - 10 Results obtained in the simulations and manufacturer head curve.

Paper 6:-

Jidong Lia, Yongzhong Zenga*, Xiaobing Liua, Huiyan Wanga in his studies of

Optimum design on impeller blade of mixed-flow pump based on CFD analysis

Under filing of impeller blades at the trailing edge improved the performance of the

pump that is designed in this study, as stated in References. Best efficiency point of the pump

that is designed in this study moves from 53 l/s to 56 l/s and system efficiency increases 2%

for the best efficiency point. The disturbance on the trailing edge of the blade caused by

offsetting the designed surface in order to give thickness the blade is reduced, when under

filing is performed in the impeller blades, While making the comparison of the CFD results;

the convergence of the analyses should be obtained. If the instable analyses are faced by

means of convergence, the number of elements should be increased and the analyses should



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be rerun for the stability. The integration of the CFD software to the design process is a

continuous procedure. The code should be verified in each case study by comparing the CFD

results with actual test results. The specific methods were to increase the blade inlet structure

angle β1K at the blade the affect of vortex, and increase the flow rate in. [11] the test results

are compared with the CFD results and hydraulic design of the pump. Selecting the suitable

blade and vane thicknesses, blade swirl and vane swept angles are important from the

manufacturing point of view.

Paper 7:-

Michal Varcholaa, Peter Hlbocanb, b* in his studies of Geometry Design of a

Mixed Flow Pump Using Experimental Results of on Internal Impeller Flow research of the

velocity and pressure flow field in the impeller of the mixed flow pump.[12]

A subject of this paper is a numerical solution of a mixed - flow pump geometry with

respect to a distribution of a static ressure in the channel of the pump. The distributions of

pressure and velocity fields were obtained through experiments. The blade's design was

obtained according to the pressure distribution in the impellers’ channel. The hydraulic

projection of an impeller is very sensitive in terms of the overall efficiency as well as the

position of the best efficiency point. Or said in a different way, the match of optimal flow-

rate and the specific energy measured and calculated. The pump designed through the

described procedure, achieved its peak efficiency at the calculation point, which justifies the

validity of the procedure. It can be said that the method used for projection of a blade cut

based on the characteristic pressure distribution in the channel of the impeller, seems to be

perspective for the prime projection of geometry of the diagonal pump.

MY COMMENTS:-

____________________________________________________________ From the above review it is conclude that the following scope of work.

CFD ANALYSIS OF MIXED FLOW IMPELLER

IMPELLER & BLADE MATERIAL CAN BE CHANGE

NUMBER OF BLADE INCRESES

NUMBER OF BLADE DECRESES

BLADE INLET ANGLE CAN BECHANGE

BLADE OUTLET ANGLE CAN BE CHNGE

CFD SOFTWERE RESULTS CAMPARE WITH THE ACTUAL TESTED

RESULTS AMD GET MAXIMUM HEAD

CONCLUSION:-

I have studied all the research papers. After I have found the solution how to

improve mixed flow pump efficiency and head. I will do mixed flow pump impeller

in modeling and meshing. Also, I will modify the impeller with number of blade

increase or decrease also change to be blade inlet and outlet angle. I will do CFD

Analysis of all this readings in CFX software. So I will get a different reading of

different parameters. According to all this reading, I will get best result of these



Page 660

different parameters. With this performance I can improve the mixed flow pump

efficiency and head. I will do CFD Software Results Compare with the Actual Tested

Results and Get Maximum Head and efficiency.

Nomenclature

C1 - axial velocity (m/s)

D1 - inlet diameter (m)

Q - Discharge (m3/s)

U1 - circumferential velocity (m/s)

β1 - inlet blade angle (Deg)

ω - Angular velocity (deg/s)

REFERENCE: -

___________________________________________________________________________

[1] Yun Chuan-yuan. Numerical Calculation of Turbulent Flow, Performance Experiment

Mixed-flow Pump Impeller. Transactions of the Chinese Society for Agricultural Machinery.

V01.39, No.3 2008. 52-55

[2] MA Xi-jin, ZHANG Huachuan, ZHANG Kewei. Numerical Simulation and Experiment

Analysis of Thirdly Circulating Feed-water Mixed-flow Pump in Nuclear Power Station.

FLUID MACHINERY. Vol.37, No.09, 2009 6-9

[3] JIA Rui-xuan, XU Hong. Optimal design of low specific speed mixed-flow pumps

impeller.Journal of Drainage Irrigation Machinery Engineering. Vol. No.02, 2010 98-102

[4] S. Cao, G. Peng, and Z. Yu, Hydrodynamic design of rot dynamic pump impeller for

Multiphase pumping by combined approach of inverse design and CFD analysis, ASME

Transactions, Journal of Fluids Engineering, Vol.127, 2005, pp. 330-338.

[5] J. Anagnostopoulos, CFD Analysis and design effects in a radial pump impeller, WSEAS

Trans. on Fluid Mechanics, Is. 7, Vol. 1, 2006, pp. 763-770.

[6] T.E.Stirling : “Analysis of the design of two pumps using NEL methods” Centrifugal

Pumps-Hydraulic Design-I Mech E Conference Publications 1982-11, C/183/82.

[7] Miner S.M. 2001, 3-D viscous flow analysis of a mixed flow pump impeller,International

Journal of Rotating Machinery, Vol. 7, No. l, pp. 53-63.



Page 661

[8] A. Furukawa, H. Takahara, T. Nakagawa, Y.Ono, Pressure Fluctuation in a Vaned

Diffuser Downstream from a Centrifugal Pump Impeller, Intl. J. of Rotating Machinery, Vol.

9, 2003, pp. 285-292.

[9] J. S. Numerical calculation of the flow in a centrifugal pump impeller using cartesian grid.

In: 2nd Wseas Int. Conference on Applied and Theoretical Mechanics, 2006, Veneza, Itália,

Proceedings 2nd WSEAS, Veneza, 2006, p. 124-129.

Available at: <http://www.fluid.mech.ntua.gr/lht/PYTHAGORAS/dimosieuseis/D-9.pdf>.

[10] J. L.; Carrilo L. P.; Espinoza H. Three-dimensional simulation of the entrance-impeller

interaction of a hydraulic disc pump, Rev. Téc. Ing. Univ. Zulia, v. 29, n. 1, p. 49-57, 2006.

Available at:

<http://www.scielo.org.ve/scielo.php?script=sci_arttext&pid=S025407702006000100007&ln

g=es&nrm=iso&tlng=es>.

[11] JIA Rui-xuan, XU Hong. Optimal design of low specific speed mixed-flow pump

impeller. Journal of Drainage and Irrigation Machinery Engineering. Vol. No.02, 2010 98-

102

[12] Paciga A.- Strýek O.- Gan�o M.-Varchola M.: Experimental research of the velocity

and pressure flow field in the impeller of the mixed flow pump. Research report.

Experimentálny výskum rýchlostného a tlakového po�a v obežnom kolese diagonálneho

erpadla, Výskumná správa Hz-14/70 ES SVŠT Bratislava 1973 .(In Slovak)

perfomance analysis of mixed flow pump

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