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International Journal of Engineering Research and Applications (IJERA) is an open access online peer reviewed international journal that publishes research and review articles in the fields of Computer Science, Neural Networks, Electrical Engineering, Software Engineering, Information Technology, Mechanical Engineering, Chemical Engineering, Plastic Engineering, Food Technology, Textile Engineering, Nano Technology & science, Power Electronics, Electronics & Communication Engineering, Computational mathematics, Image processing, Civil Engineering, Structural Engineering, Environmental Engineering, VLSI Testing & Low Power VLSI Design etc.

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  1. 1. Shalin P Marathe, Mr.Rishi R Saxena, Mr. Chetan H Solanki / International Journal ofEngineering Research and Applications (IJERA) ISSN: 2248-9622 www.ijera.comVol. 3, Issue 3, May-Jun 2013, pp.1466-14691466 | P a g eNumerical Analysis On The Performance Characteristics Of TheCentrifugal PumpShalin P Marathe M.E. (CAD/CAM), Mr.Rishi R Saxena AssistantProfessor, Mr. Chetan H Solanki Assistant ProfessorMechanical Engineering DepartmentSardar Vallabhbhai Patel Institute of Technology, VASAdABSTRACTThe research is based on the performanceof the centrifugal pump having the backward, radialand forward bladed type of impeller. The impeller ismodeled using Creo Parametric 1.0 having 70 and80 degree outlet blade angle for the backward typeand outlet blade angle 90 for radial and 100 degreefor forward type impeller respectively. Numericalsimulation is carried out using ANSYS CFX andstandard k- turbulence model is adopted for theanalysis purpose. Cavitation is clearly predicted inthe form of water vapor formation inside thecentrifugal pump. The performance of the pump isaffected by the cavitation and hence cavitationnumber (σc) is a measure of the cavitationphenomenon for the centrifugal pump, it isdetermined by analytical calculations. From thenumerical results it has been found that the pumpworking on low head gives the best performancewhen it is operated with the backward bladed typeimpeller.KEY WORDS: ANSYS CFX, Cavitation,Cavitation number, Centrifugal pump, numericalsimulation, Turbulence Model k- Є.I. INTRODUCTIONA centrifugal pump is a rotodynamicmachine that uses a rotating impeller and casing, toincrease the pressure energy of a fluid in order totransfer the fluid from one place to another as shownin the figure 1. They are widely used for chemicalindustries, sectors of liquid transportation,petrochemical industries. The performance of thecentrifugal pump is affected mainly due to the lowerpressure developed inside the casing which will leadto the cavitations. Cavitation is the phenomenon offormation of bubbles in the low pressure regionsinside the centrifugal pump and as this bubblestravels from low pressure regions to high pressureregions, they collapse and it creates very high noise.Due to the cavitation pitting action is generated onthe blade of the impeller as shown n the figure 2Cavitation depends upon the factors like NPSH,temperature of the fluid, discharge of the pump so itmust be avoided. S R Shah[1]observed that asdischarge increases, the efficiency increases, reachesmaximum at rated conditions and then decreaseswhen discharge increases beyond rated conditions.SHI Weidong[2]found that the oversize impelleroutlet width leads to poor pump performances andincreasing shaft power. W.G.Li [3]stated that theblade discharge angle has a strong but equalinfluence on the head, shaft power and efficiency ofthe centrifugal oil pump for various viscosities ofliquids pumped , The rapid reduction in thehydraulic and mechanical efficiencies is responsiblefor the pump performance degradation withincreasing viscosity of liquids. E.C.Bacharoudis etal [4]found that the outlet blade angle increases theperformance curve becomes smoother and flatter.But pump performance goes down when the pumphandles high viscosity working fluids is that highviscosity results in disc friction losses over outsideof the impeller and that was found by M.H.S.Fard etal [5].Figure 1 CentrifugalpumpFigure 2 Impellereffected by cavitationS.Rajendran[6]found a continuous pressure rise fromleading edge to trailing edge of the impeller in acentrifugal pump due to the dynamic headdeveloped by the rotating pump impeller. Nearleading edge of the blade low pressure and highvelocities are observed due to the thickness of theblade. Near trailing edge of the blade total pressureloss is observed due to the presence of trailing edgewake.Mr. Ashok Thummar[7]found that as the total headincreases the overall efficiency increases but it alsofollow the same nature as that of powerconsumption. And finally it is also investigated thatas the discharge and the rotational speed of thepump increase simultaneously all the losseshydraulic as well as mechanical increase during theoperating range.
  2. 2. Shalin P Marathe, Mr.Rishi R Saxena, Mr. Chetan H Solanki / International Journal ofEngineering Research and Applications (IJERA) ISSN: 2248-9622 www.ijera.comVol. 3, Issue 3, May-Jun 2013, pp.1466-14691467 | P a g eII. GEOMETRIC AND NUMERICALMODELINGGeometric modeling of the impeller having differentblade angles and the casing are modeled in themodeling tool Creo Parametric. The figure 3 and 4shows the Creo model of the Impeller and the casingof the centrifugal pump.For reliable and long time efficient operation of thecentrifugal pump, its behavior should be studiedbefore putting it to the actual operation. ANSYSCFX is the simulation tool that is widely used toinvestigate the complex flows inside the centrifugalpump. The user can give the boundary conditionclose to real. For the simulation of the centrifugalpump the k- turbulence model is implemented inthe CFX.Figure 3 Creo model of ImpellerFigure 4 Creo model of casingAuto mesh is used to mesh the model of thecentrifugal pump. Figure 5 shows the meshed modelof the centrifugal pump, it indicates that thetetrahedrons are used asFigure 5 Meshed models of centrifugal pumpthe elements. The number of nodes and the elementsgenerated are 77542 and 419333 respectively.A steady state analysis is carried out taking 1atmospheric as the reference pressure. The wholedomain is given the rotation of 2900 rpm along theZ direction. Two fluids are selected in order todetermine the formation of vapors inside the pump.At inlet and outlet pressure conditions are providedand the discharge of the pump is determined fromthe simulation. The K-epsilon model is selectedbecause it is one of the most common turbulencemodels and in the standard k-epsilon model the eddyviscosity is determined from a single turbulencelength scaleIII. NUMERICAL RESULTS ANDDISCUSSIONSAfter the completion of the solver part ofthe simulation, results like pressure contours and thewater vapor formation contours are generated for the20 lps discharge, for all the configurations of theimpellers. Figure 6 shows the formation of watervapor inside the centrifugal pump for 70, 80, 90, and120 degree blade impeller. It is clear from thecomparison that as the blade angle increase from the70 degree to the 120 degree the formation of watervapor increases. So the impeller having 70 degreewill be more preferable than the 80, 90 and 120degree regarding the cavitationFigure 7 shows the comparison of the stream linecontours for the different blade configuration of theimpeller. It indicates the turbulence generated insidethe casing of the pump. As the angle is changedfrom 70 to 120 degree more turbulence is observedinside the pump casing. And high value ofturbulence will lead to the low pressure zones andthat will lead to the cavitations generation.Figure 8 shows the pressure contour at 20 lps acrossthe pump. Gradual increase from the inlet section tothe outlet section were found in all the differentconfigurations. But more low pressure zones wereidentified in the forward bladed pump compare to(a) 70 degree bladedimpeller(b) 80 degree bladedimpeller(c) 90 degree bladedimpeller(d) 100 degree bladedimpellerFigure 6 Water vapor contour at 20 lps
  3. 3. Shalin P Marathe, Mr.Rishi R Saxena, Mr. Chetan H Solanki / International Journal ofEngineering Research and Applications (IJERA) ISSN: 2248-9622 www.ijera.comVol. 3, Issue 3, May-Jun 2013, pp.1466-14691468 | P a g ethe 70 degree bladed impeller. And as the bladeangle increases the area occupied by the lowpressure zone increases.Figure 7 Streamline contours at 20 lpsFigure 8 Pressure contours at 20 lpsCentrifugal pump performance depends upon theblade configurations of the impeller. Head-Discharge characteristics of the centrifugal pump ispredicted from the analysis as shown in the figure 9(a) and figure (b), it shows the ideal results for thesame. It shows the good agreement of the idealresults and the simulation results It indicates that asthe exit blade angle increases the head and thedischarge produced by the pump increases.Development of power inside the pump varies as theexit blade angle changes. Figure 10 (a) and (b)shows the power and discharge produced by thepump for different blade configuration. A fairlygood matching is found between simulation resultsand ideal results. For higher exit blade angle, thepower and discharge developed by the pumpincreases.(a)(b)Figure 9 Head-Discharge characteristics of differentbladesCavitation Number shows indication of thecavitation for the centrifugal pump. Figure 11 showsthe effect of discharge on Cavitation Number for thedifferent blade configuration and it clearly indicatesthat as the exit blade angle increases the value of theCavitation Number increases and that will lead tothe cavitation.(a)05101520250 0.0005 0.001 0.0015 0.002HeEulersHead(m)Discharge Q (m3/sec)OUTLETANGLE 70OUTLETANGLE 80outletangle 90OUTLETANGLE1000501001502002503003504004500 0.0005 0.001 0.0015 0.002PowerP(W)Discharge Q (m3/sec)OUTLETANGLE70Outletangle90OUTLETANGLE100(a) ) 70 degree bladedimpeller(b) 80 degree bladedimpeller(c) 90 degree bladedimpeller(d) 100 degree bladedimpeller(a) ) 70 degree bladedimpeller(b) 80 degree bladedimpeller(c) 90 degree bladedimpeller(d) 100 degree bladedimpeller
  4. 4. Shalin P Marathe, Mr.Rishi R Saxena, Mr. Chetan H Solanki / International Journal ofEngineering Research and Applications (IJERA) ISSN: 2248-9622 www.ijera.comVol. 3, Issue 3, May-Jun 2013, pp.1466-14691469 | P a g e(b)Figure 10 Power-Discharge characteristics ofdifferent bladesFigure 11Cavitation Number vs Discharge fordifferent blade configurationsSo regarding the cavitation backward blade impellerhaving exit blade angle 70 degree will be morepreferable.IV. CONCLUSIONSThe results obtained from the analysisshows that the characteristic curve for differentoutlet blade angles are completely matched with thenumerical results and it can be concluded from theresults that for low head operating conditions, theimpeller with backward bladed works efficientlyand the problem of the cavitations, which reducesthe performance of the pump is less.REFERENCES[1] S.R.Shah , S.V.Jain , V J Lakhera- “CFDBased Flow Analysis Of Centrifugal Pump “In Proceedings Of The 37th National & 4thInternational Conference On Fluid MechanicsAnd Fluid Power December 16-18, 2010, IITMadras, Chennai, India.[2] SHI Weidong, ZHOU Ling*, LU Weigang,PEI Bing, and LANG Tao-" NumericalPrediction and Performance Experiment in aDeep well Centrifugal Pump with DifferentImpeller Outlet Width"- CHINESEJOURNAL OF MECHANICALENGINEERING Vol. 26,No.-2013[3] Wen-Guang LI “Blade Exit Angle Effects onPerformance of a Standard IndustrialCentrifugal Oil Pump”- Department Of CivilAnd Environmental Engineering Cvng 1001:Mechanics Of Fluids.[4] E.C. Bacharoudis, A.E. Filios, M.D. MentzosAnd D.P. Margaris- " Parametric Study Of ACentrifugal Pump Impeller By Varying TheOutlet Blade Angle” In The Open MechanicalEngineering Journal, 2008, 2, 75-83.[5] M.H.S.Fard And F.A.Bhoyaghchi –” StudiesOn The Influence Of The Various BladeOutlet Angles In A Centrifugal Pump WhenHandling Viscous Fluid" In American JournalOf Applied Science 2007.[6] S.Rajendran and Dr.K.Purushothaman-"Analysis of a centrifugal pump impellerusing ANSYS-CFX".International Journal ofEngineering Research & Technology (IJERT)Vol. 1 Issue 3, May - 2012 ISSN: 2278-0181[7] Mr. Ashok Thummar, Mr. Vijay F. Pipalia,Tushar V. Javiya -"Experimentalinvestigation of open well centrifugal pumpperformance". International Journal ofAdvanced Research in Science, Engineeringand Technology, Vol.01, Issue 03, pp. 01-0810152025308 13 18 23CAVITATIONNUMBERDISCHARGE (LPS)70 DEGREE80 DEGREE90 DEGREE100DEGREE