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Int. J. Mech. Eng. & Rob. Res. 2014 Karthik V and Rajeshkannah T, 2014

EXPERIMENTAL INVESTIGATION OF ACENTRIFUGAL BLOWER BY USING CFD

Karthik V1* and Rajeshkannah T1

*Corresponding Author: Karthik V,[email protected]

As the diffusion of flow process is highly complex in centrifugal blower operation, it is necessaryto design and develop the geometry of impeller and casing to reduce the flow losses significantly.In the present study, the methodology to find near optimum combination of blower operatingvariables for performance enhancement were analyzed using Computational Fluid Dynamics(CFD). Taguchi Orthogonal Array (OA) based Design of Experiments (DoE) technique todetermine the required experimental trials. The experimental results are justified by Analysis ofVariance (ANOVA) and confirmed by conformation experiments. The parameters chosen fordesign optimization are Impeller outlet diameter, Impeller wheel width, Thickness of blade, Bladewidth and Impeller inlet diameter. The levels for the parametric specification are chosen fromthe ranges and blade types where the blower will get the best efficiency. CFD results werevalidated by the fine conformity between the CFD results and the experimental results.

Keywords: Centrifugal blower, CFD, Taguchi, Impeller

INTRODUCTIONCentrifugal blowers are widely used in differentindustrial applications, which are proficient ofas long as restrained to high-pressure rise andflow rates. Centrifugal blowers are mainly twomain parts, namely, the casing and the impeller.Many experimental studies have beenreported on the performance of centrifugalpump impeller. The performance of centrifugalblower is mainly on design parameters ofimpeller. Changing some geometric

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Int. J. Mech. Eng. & Rob. Res. 2014

1 Department of Mechanical Engineering, Anjalai Ammal Mahalingam Engineering College, Kovilvenni 614403.

characteristics of the centrifugal pump impellerthe blower has more efficiency taking withenergy crises into consideration. In this paper,an experimental study has been carried out tostudy the performance characteristics ofcentrifugal blower. In order to improve theperformance the effects that the pertinentdesign parameters has been carried out fordifferent cases of primary geometry of theimpeller including the Impeller outlet diameter,Impeller wheel width, Thickness of blade,Blade width and Impeller inlet diameter.

Research Paper

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MODEL CONSTRUCTIONFor this study, the three-dimensional blowermodel Figure 1 was first created with theexisting model. The parameters of the existingmodel blowers are listed in Table 1. The designof impeller mainly include: Impeller outerdiameter, Impeller width, Blade Thickness,Blade width and Impeller inlet diameter.

Experimental Part for ExistingModel1. To determine the discharge (Q)

2. To determine the area of orifice (a0)

3. To determine the area of pipe (a1)

Diameter of the orifice = 7.5 cm = 0.075 m

Area of the pipe = 15 cm = 0.15 m

Coefficient of discharge = 0.6

Parameters Dimensions (mm)

Impeller outer diameter 390

Impeller inner diameter 225

Impeller width 75

Blade thickness 2

Blade width 75

Table 1: Parameters of the Existing Model

1. To calculate area of orifice

a0 = (/4)*d02

= (/4)*(0.752)

= 0.0044 m

2. To calculate area of pipe

a0 = (/4)*d02

=(/4)*(0.152)

= 0.0177 m

3. To calculate discharge

Q = {(cd*a0*a1)[(2*g*h)]}/ {(a12 – a0

2)}

Trial 1: (1/4 open)

Q = {(0.6*0.0044*0.0177)[(2*9.81*0.045)]}/{(0.0172 – 0.00442)}

= 0.166*0.939*60

= 9.76 m3/min

Trial 2: (1/2 open)

Q = {(0.6*0.0044*0.0177)[(2*9.81*0.18)]}/{(0.0172 – 0.00442)}

= 0.166*1.879*60

= 19.53 m3/min

Trial 3: (3/4 open)

Q = {(0.6*0.0044*0.0177)[(2*9.81*0.21)]}/{(0.0172 – 0.00442)}

= 0.166*2.029*60

= 21.10 m3/min

Trial 4: (full open)

Q = {(0.6*0.0044*0.0177)[(2*9.81*0.22)]}/{(0.0172 – 0.00442)}

= 0.166*2.077*60

= 21.60 m3/min

Figure 1: Three Dimensional Blowerfor Existing Model

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S. No. Gate Valve Discharge (m3/min)

1. Close 0

2. 1/4 9.76

3. 1/2 19.53

4. 3/4 21.1

5. Full open 21.6

Table 2: Experimental Resultsfor Existing Model

Output Parameters CFD Results

Discharge (m3/min) 10.3

Pressure (pa) 1385

Table 3: CFD Results for Existing Model

TAGUCHI METHODDr. Taguchi of Nippon Telephones andTelegraph Company, Japan has developed amethod based on OA experiments which givesmuch reduced variance for the experiment withoptimum settings of control parameters.Taguchi Technique is applied to plan theexperiments, in a three step approach namelysystem design, parameter design andtolerance design. In System Design, the mostinfluenced process parameters were identified

taking with minimum trials into consideration.Secondly, Signal-to-Noise (S/N) ratio toanalyze experiment data, for determiningquality characteristics implemented inengineering design problems. Thirdly,estimates individual parameter contributions.This study is to maximize discharge, pressureand efficiency considering power consumptionwithin optimal levels of process parameters;the higher the better quality characteristic isselected. A standard Taguchi L9 (3 3)Orthogonal Array (OA) is chosen for thisinvestigation as it can operate threeparameters, each at three levels. The threemost influenced identified parameters (A)

Figure 2: CFD Results for Existing Model

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Impeller width; (B) Blade Thickness; and (C)Blade width which affect the performance ofblower. Sufficient details of the effect of differentparameter values on experimental results canbe obtained by choosing three levels for eachparameter to investigate. The test run isdesignated by replacing the level number 1,2, 3 of parameters A, B, and C in L9 OA withthe chosen parameters level values in Table4. Each row of the array represents a test runparameter setting condition.

Impeller width (A) 70 75 80

Blade thickness (B) 1.8 2 2.2

Blade width (C) 70 75 80

Table 4: Parameters and Levels

ParametersLevels

1 2 3

1 70 1.8 70 15.3 1650

2 70 2 75 17.1 2070

3 70 2.2 80 16.56 1780

4 75 1.8 75 17.1 1650

5 75 2 80 17.1 1650

6 75 2.2 70 13.8 1100

7 80 1.8 80 19.62 1650

8 80 2 70 17.1 1350

9 80 2.2 75 17.88 1560

Table 5: Trials and Results

TrialParameters Discharge

(m3/min)Pressure

(pa)A B C

Mean of S/N RatiosImpeller Width (A)

70 mm = (15.3 + 17.1 + 16.56)/3

= 16.32

75 mm = (17.1 + 17.1 + 13.8)/3

= 16

80 mm = (19.62 + 17.1 + 17.8)/3

= 18.2

Blade Thickness (B)

1.8 mm = (15.3 + 17.1 + 19.68)/3

= 17.34

2 mm = (17.1 + 17.1 + 17.1)/3

= 17.1

2.2 mm = (16.56 + 13.8 + 17.8)/3

= 16.05

Blade Width (C)

70 mm = (15.3 + 13.8 + 17.1)/3

= 15.4

75 mm = (17.1 + 17.1 + 17.88)/3

= 17.36

Signal-to-Noise RatioThe Signal-to-Noise ratio (S/N) ratiorepresents both the average and variation ofthe experimental results to analysis the test runresults using Taguchi Methods. The S/N ratiois also used in Analysis of Variance (ANOVA).The S/N ratios in Taguchi Methods are, e.g.,smaller-the-better, larger-the-better, nominal-the-best and operating window. The standardS/N ratios can be made to order to fit explicitapplications. Depends on the physicalproperties of the problem proper S/N ratio isselecting. The performance improvement is theobjective function, so that the larger-the-betterS/N ratio is chosen in this study. Where, S/NLTB

is larger-the-better Signal-to-Noise ratio, MSDis the mean square deviation around the target,yi is the individually measured response value(experiment result), n is the number ofmeasurements taken in one test run. Table 5shows the results of each test run.

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Figure 3: Responses for Parameters A, B, C by S/N Ratios

Figure 4: CFD Results for Designed Model

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80 mm = (16.56 + 17.1 + 19.62)/3

= 17.76

Parameters Optimized Dimensions (mm)

Impeller width 80

Blade thickness 1.8

Blade width 80

Table 6: Optimized Result

Conference on Advances inComputational Modeling and Simulation,Vol. 31, pp. 110-114.

3. Pham Ngoc Son, Jaewon Kim E and AhnY (2011), “Effects of Bell MouthGeometries on the Flow Rate ofCentrifugal Blowers”, Journal ofMechanical Science and Technology,Vol. 25, No. 9, pp. 2267-2276.

4. Shojaeefard M H, Tahani M, Ehghaghi MB, Fallahian M A and Beglari M (2012),“Numerical Study of the Effects of SomeGeometric Characteristics of aCentrifugal Pump Impeller that Pumps aViscous Fluid”, Computers & Fluids,Vol. 60, pp. 61-70.

5. Sun-Sheng Yang, Shahram Derakhshanand Fan-Yu Kong (2012), “Theoretical,Numerical and Experimental Prediction ofPump as Turbine Performance”,Renewable Energy, Vol. 48, pp. 507-513.

6. Taguchi G (1992), Taguchi Methods-Research and Development, ASI Press,Dearborn, MI.

7. Zhang Bin, Wang Tong, Gu Chuan Gangand Shu Xin Wei (2011), “BladeOptimization Design and PerformanceInvestigations of an Ultra-Low SpecificSpeed Centrifugal Blower”, ScienceChina Technological Science, Vol. 54,pp. 203-210.

Output Parameters CFD Results

Discharge (m3/min) 17.1

Pressure (pa) 1650

Table 7: CFD Results for Designed Model

CONCLUSION• Comparing the discharge of existing model

by experimental is less than 5.24% from theCFD analysis.

• Comparing the pressure of existing modelby experimental is less than 2.52% from theCFD analysis.

• Comparing the discharge of existing modelby CFD analysis is more than 39.7% fromthe designed model by CFD analysis.

• Comparing the pressure of existing modelby CFD analysis is more than 16% to thedesigned model by CFD analysis.

REFERENCES1. Chen-Kang Huang and Mu-En Hsieh

(2009), “Performance Analysis andOptimized Design of Backward CurvedAirfoil Centrifugal Blowers”, HVAC &Research, Vol. 15, pp. 461-488.

2. Jie Jina Ying Fan, Wei Han and Jiaxin Hu(2012), “Design and Analysis on HydraulicModel of The Ultra-Low Specific-SpeedCentrifugal Pump”, International

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