Experimental and Numerical Study of Efficiency Improvement by Surface Coating on the Impellers and Diffusers of Mixed Flow Submersible Borewell Pumps

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1 Journal of Scientific & Indutrial Reearch Vol. 75, May 2016, pp Experimental and Numerical Study of Efficiency Improvement by Surface Coating on the Impeller and Diffuer of Mixed Flow Submerible Borewell Pump C Murugean 1 * and R Rudramoorthy 2 *1 Aquaub Engineering, Thudiyalur Pot, Coimbatore , Tamil Nadu, India. 2 PSG College of Technology, Coimbatore , Tamil Nadu, India. Received 7 May 2015; revied 6 July 2015; accepted 12 January 2016 Thi tudy focue on the effect of urface coating on the impeller and diffuer in improving the efficiency of mixed flow ubmerible borewell pump. It conit of two part. In the firt part, a 3 tage pump wa contructed with uncoated bronze impeller and cat iron diffuer having a urface roughne value of 2.5µm Ra and teted for pump performance. Then the ame 3 tage pump wa teted with impeller, diffuer coated with a polymeric coating having a urface roughne of 0.2µm Ra and ceramic enamel having a urface roughne of 0.8µm Ra. Experimental reult howed coniderable improvement, upto 4.5% in pump efficiency. In the econd part, performance of the 3 tage pump wa imulated uing CFD tool Any Fluent for a urface roughne of 2.5µm Ra in the cat iron diffuer paage and bronze impeller paage. The ame model wa imulated with reduced urface roughne value viz. 0.2µm Ra urface roughne of polymeric coating and 0.8µm Ra urface roughne of ceramic enamel coating. The preure and velocity ditribution were analyed and input power calculation were made. Simulation reult alo how that the pump efficiency ha improved and found matching with experimental reult. Keyword: Surface coating, Surface Roughne Average, Ra, CFD, Pump Efficiency Improvement, Mixed flow ubmerible borewell pump, Ceramic Enamel, Polymeric. Introduction The mixed flow ubmerible pump are ued to pump water from higher depth of bore well.thee pump are ued in the borewell dug in the alluvial oil formation mainly in the delta region of the river.the population of thee pump are increaing in the lat two decade all over the world. Thi tudy focue on the efficiency improvement due to urface coating on the impeller and diffuer paage way. The ubmerible pump of mixed flow type i hown in Figure 1. The inlet bracet (1) i ued to guide the water entry to the firt tage mixed flow impeller (2). The rotating blade ytem in the impeller impart energy to the water and water come out with high velocity in a conical piral pattern. The diffuer (3) blade paage collect the water, diffue it velocity and direct the water to the next tage impeller. The velocity of the water at the econd tage i ept ame a that of the firt tage, but the preure energy i higher which i gained at the firt impeller. Thi proce repeat in all the ubequent tage and the energy i added in all the tage by the wor done at Author for correpondence cmurugean1960@yahoo.co.in the impeller paage. The dicharge caing (4) i at the end of the tage. It collect the water and direct it to the column pipe (5) which i tranferring the water to the ground level. Alo column pipe i upporting the entire pumpet i.e pump coupled with the motor and the axial down thrut caued by the pump impeller during running. In the lat decade, variou tudie were conducted on the impeller and volute interaction of centrifugal radial flow pump and the reult were publihed. The numerical imulation of the dynamic effect due to impellervolute interaction in a centrifugal pump wa tudied by Joe Gonzalez et al 1. The head and flow ditribution within the volute of a centrifugal pump in comparion with the characteritic of the impeller without caing wa given by P.Hergt et al 2. Alo Ahra A et al 3. dicued the flow rate influence on the interaction of a radial pump impeller and the diffuer. Jianjun Feng et al 4. decribed the numerical invetigation on preure fluctuation for different configuration of vane diffuer pump. The virtual performance experiment of a centrifugal pump wa given by Zhang Shujia et al 5.The CFD application and validation for a turbo machinery deign ytem wa decribed by Anderon M.R. et al 6.The numerical

2 MURUGESAN & RUDRAMOORTHY: EXPTAL AND NUMERICAL STUDY OF EFFICIENCY IMPROVEMENT 301 analyi of the unteady flow in the near tongue region in a volute-type centrifugal pump for different operation point wa preented by Raul Barrio, et al 7. Perez. J et.al 8. have done experiment in a two tage radial flow pump and compared it with numerical imulation. B. Jafarzadeh et al 9. have tudied the flow imulation of turbulent fluid flow in a low pecific peed centrifugal pump.paul Cooper et al 10. have analyed the complex internal flow in the centrifugal pump. Stefania Della Gatte et al 11 have done CFD for the aement of axial thrut balance in radial flow multitage pump. Milan Sedlar et al 12. have numerically analyed the mixed-flow pump with volute. The analyi of flow inide the multitage mixed flow centrifugal pump wa not thoroughly done in the pat. Few reearch article were available in the technical journal. So, the author have decided to tae up the tudy of flow inide the multitage mixed flow pump and analye the interaction between the impeller and diffuer in detail. Pump Parameter A 3 tage pump wa contructed with bronze impeller with urface finih of 2.5µm Ra and Cat iron diffuer tage with urface roughne of 2.5µm Ra. A et of 3 impeller and diffuer were coated with ceramic enamel coating with urface roughne of 0.8 µm Ra. Another et of 3 impeller and diffuer were coated with a polymeric coating of 0.2µm Ra. The author have teted the ame pump with three configuration for thi tudy. Performance teting wa conducted in the ame pump with coated impeller and diffuer and without coating.specification of the tet pump i given in Table 1. Experimental Performance Analyi Experimental Tet Setup The three pump configuration were teted in the experimental tet et-up a per the pump teting tandard ISO The preure meaurement and pump input (W) were taen for different ma flow rate of the pump. The output i calculated a the product of head (preure difference acro inlet and outlet) and ma flow rate. Fig. 1Submerible pump Mixed flow type Table 1Specification of Tet Pump Parameter Value Unit Nomenclature Head (Nominal) of 3 Stage at BEP 24 ( 8 x 3) m Hn Dicharge Rate (Nominal) at BEP m³/ Qn Speed of Rotation 2880 rpm N Specific Speed (metric) N = n Q n H n Impeller Diameter, Inlet 64 / 27 mm D 1 Shroud/ D 1 Hub Impeller Diameter, Outlet 94 /93 mm D 2 Shroud / D 2 Hub Impeller Width, Outlet 13 mm b 2 Impeller Width, Inlet 21.5 mm b 1 No. of Impeller Vane 7 - Z i Vane Thicne 3 mm t Diffuer Inlet Diameter, Mean 108 mm D 3 Diffuer Outlet Diameter,Mean 50 mm D 5 No. of Diffuer Vane 8 - Z d Power Rating of 3 tage (Pump Input) 3.35 (1.11 x 3) W P n Bet Efficiency Point - - BEP Meter of Water Column - - Mwc Surface Roughne Average - µm Ra Pump Efficiency - % η p

3 302 J SCI IND RES VOL 75 MAY 2016 Experimental Performance Comparion Pump performance characteritic for all the three pump configuration are compared a hown in Figure 2. The outcome of the experimental teting i dicued in the ection 5. Numerical Simulation Fundamental Equation for Numerical Simulation The Numerical analyi i baed on the governing equation of fluid dynamic. They are ma and momentum conervation equation. Turbulence Model The variou turbulence model viz, -Epilon tandard, -Omega tandard and -Omega SST were evaluated and the -Omega SST wa elected due to it cloe accuracy with experimental reult at off duty point. The two equation (1) and (2) for the - Omega SST model given in Fluent 13 are ( ) + t Y + S, ( ) + t ( u i ) = xi ( u j ) = x j x j x j x j + G - + G x j - Y + D + S... (1) Where - Turbulence inetic energy, - Specific diipation rate, & - effective diffuivity of & Y & Y -diipation of &, G & G generation of &, D - cro- diffuion term and S & S - ource term. In the equation (1), omega include the effect of wall roughne and wall function i pecified a = where ( u*) µ 2 = 2 50 when (2) < 25 and it i 100 when 25, where = max 1, u µ i the roughne height, u* i the friction velocity and i the vicoity. * Fig. 2Experimental Performance Curve

4 MURUGESAN & RUDRAMOORTHY: EXPTAL AND NUMERICAL STUDY OF EFFICIENCY IMPROVEMENT 303 Torque about Impeller Centre The total force component (F ) along the pecified vector on a wall zone i the ummation of preure force component. Fp and vicou force component on each face with the pecified force vector. Fv F = a a. F + p a. F v... (3) The moment along the impeller axi were computed and it i the total torque imparted by the impeller. M = A r AB x F p + rab x F v... (4) where, A = Impeller centre, B = Force origin, r AB =Moment Vector (radiu), F p = Preure force vector, F v =Vicou force vector, M A =Total Moment Surface Integral The ma flow rate, preure, velocity and torque were computed uing urface integration of the repective field variable on elected urface in the fluid domain. Thee urface are the et of data point created by Any Fluent for each of the zone in the fluid model. Numerical Setup and Senitivity Analyi The flow domain wa modelled and mehed with optimum grid ize for a 3 tage pump. Different turbulence model were tried and -Omega SST model wa elected for all the imulation. Preure difference acro inlet-outlet and rotation peed were given a initial boundary condition to the flow volume domain. After the convergence of the olution the urface integral for the preure difference acro inlet and outlet wa calculated and total head wa arrived. The urface integral of ma flow rate at outlet give the dicharge rate. The impeller wall urface and blade urface where the momentum wa imparted to the fluid were elected. The urface integral of the momentum in thee urface were calculated to arrive at the torque imparted by the impeller and the input power to the pump. For the given total head and reulting dicharge rate, the output wa calculated. The value of grid ize and election of turbulence model play vital role to achieve cloe matching with experimental data. Senitivity analyi i required before carrying out thee imulation. The flow volume wa plit into 4 domain a inlet duct, outlet duct, diffuer and impeller. The grid dependency tudy wa done in the three tage with the grid cell ranging from 2.5 lah to 10 lah for the entire ma flow region from 0.5 to 1.5 time the nominal flow. 7.5 lah grid cell were elected conidering accuracy and computation time. The influence of turbulence model on the prediction wa invetigated with the elected grid cell. The invetigation wa done with -Epilon Standard, -Omega Standard and -Omega SST. It wa oberved that the -Omega SST model give accurate prediction in higher flow rate condition alo. The -Omega SST model wa choen finally for further analyi. Numerical Performance Comparion Three imulation were done for the performance analyi of uncoated, enamel coated and polymeric coated impeller and diffuer. Figure 3 how the preure and velocity ditribution plot. Figure 4 how the performance comparion of numerical imulation and experimental curve. Reult and Dicuion Experimental Performance Comparion Analyi Figure 2 reveal that all the three dicharge v head performance curve are imilar and group within mall band. There i no improvement in head value due to urface finih improvement. Figure 2 alo compare the three dicharge rate v input performance curve. It how that ubtantial reduction in input power wa achieved by reducing the urface roughne value by coating method. Fig. 3Velocity (m/) & Preure (Pacal) Ditribution

5 304 J SCI IND RES VOL 75 MAY 2016 The 0.8 µm Ra urface roughne of ceramic enamel coated impeller and diffuer reduce the input power by 200 watt average from 0.5Qn to 1.75 Qn than that of the uncoated pump performance. From 0 to 0.5 Qn the difference in input power i minimal. The maximum reduction in input power wa achieved by the polymeric coating impeller and diffuer. Subtantial power reduction of 300 to 500 watt over the entire dicharge range wa oberved when compared with uncoated impeller and diffuer. Figure 2 reflect the efficiency improvement of ceramic enamel and polymeric coating. At nominal dicharge rate Qn, the efficiency achieved for uncoated impeller and diffuer wa 66.5%. The ceramic enamel coated impeller and diffuer give an efficiency of 69% at Qn. Thi value ha increaed to 71% in the cae of polymeric coating in impeller and diffuer paage. Numerical Performance Comparion Analyi Figure 4 how the performance value of 3 pump configuration by numerical analyi. Head V Dicharge rate value are matching with the experimental reult and group within a mall band. There i no improvement of head value due to lower urface roughne by ceramic enamel and polymeric coating. The input power value of enamel coated pump configuration wa lower than the uncoated pump configuration and how efficiency improvement of 3% higher than uncoated pump configuration. The input power value of polymeric coating reult in ubtantial reduction in power which account for 6% increae in efficiency. Firt tage impeller with polymeric coating conume 997 watt at Qn and econd & third tage impeller conume 1135 watt each. Firt tage uncoated impeller conume 1100 watt at Qn and econd and third tage conume 1324 watt each. Difference in total input power i around 481 watt which reult in increae of efficiency. Power conumed by firt tage impeller of both uncoated and polymeric coated wa coniderably le compared to econd & third tage impeller. Thi i due to unfavourable flow velocitie at inlet of econd and third tage hown in Fig 3. Reduction in power wa due to the low preure and vicou momentum imparted on the wall of the impeller by fluid. Leer in friction between the rotating impeller wall and fluid molecule reduce the momentum on the impeller wall. Thicne of laminar ub-layer on the wall urface ha a major impact on energy tranfer. On coated urface, thicne of laminar ub-layer i ufficient to cover the urface irregularitie and mae it hydraulically mooth. Experimental and Numerical Comparion Figure 4 how the comparion of reult obtained by experimantal and numerical analyi at 2.5µm. The Dicharge rate V Head and Dicharge rate V Efficiency characteritic by numerical analyi were found cloely matching with the experimental reult. Fig. 4Numerical Analyi Curve and Comparion with Experimental Curve

6 MURUGESAN & RUDRAMOORTHY: EXPTAL AND NUMERICAL STUDY OF EFFICIENCY IMPROVEMENT 305 Concluion The tudy reveal the effect of urface roughne of hydraulic component, impeller and diffuer on the pump performance. Dicharge rate V Head characteritic for all the three configuration are imilar and there i no influence due to urface roughne. Dicharge rate V Input power characteritic curve how a coniderable decreae in the input power taen by the pump configuration with coated impeller and diffuer. The ceramic enamel coated impeller and diffuer having urface roughne of 0.8µm Ra value how a marginal reduction of 200 watt average power in the operating region of 0.5 Qn to 1.75 Qn and an efficiency increae of 2.5% at Qn. The polymeric coated impeller and diffuer having urface roughne of 0.2µm Ra value give a ubtantial reduction of 300 to 500 watt average power in the entire operating region and an efficiency increae of 4.5% at Qn. The polymeric coating proce can be adopted for efficiency improvement in mixed flow ubmerible borewell pump. Acnowledgement The author than Dr. K.M. Srinivaan, Dr. P.R. Thiyagarajan, Dr. K. Mayilamy and Dr. T.Prabhu of PSG College of Technology for their valuable input during thi tudy. Author than the management of M/ Aquaub Engineering, P.Rameh and G.Praath for their upport in carrying out the experimental tudy. Reference 1 Joe G, Joaquin F, Eduardo B & Carlo S, Numerical Simulation of the Dynamic Effect Due to Impeller Volute Interaction in a Centrifugal Pump, J Fluid Eng, Tran ASME, 124 (2002) Peter H, Stephan M & Bernd S, The Flow and Head Ditribution with in the Volute of a Centrifugal Pump in Comparion with the Characteritic of the Impeller Without Caing, J Comput Appl Mech, Miolc Univerity Pre, Hungary, 5(2004), Ahra A, El Hajem E, Morel R & Champagne J Y, The Flow Rate Influence on the Interaction of a Radial Pump Impeller and the Diffuer, Int J Rotating Mach, Taylor & Franci, 10(2004) Jianjun F, Friedrich-Karl B & Han J D, Numerical Invetigation on Preure Fluctuation for Different Configuration of Vaned Diffuer Pump, IJRM, Hindawi, Zhang S, Zhu B,Hu Qo & Li X, Virtual Performance Experiment of a Centrifugal Pump, Proc 16 th Int Conf on Artificial Reality and Tele exitence (ICAT 06), IEEE, Anderon M R, Gu, Fahua, MacLeod P D, Application & Validation of CFD in a Turbo Machinery Deign Sytem, Int Mech Engg Congre and R & D Expo, ASME. 7 Barrio R, Fernandez J, Blanco E & Parrondo J,Etimation of radial load in centrifugal pump uing computational fluid dynamic, Eur J Mech B-Fluid, 30(2011) Perez J, Chiva S, Segala W, Morale R,Negrao C, Julia E & Hernandez L,Performance Analyi of Flow in a Impeller- Diffuer Centrifugal Pump uing CFD: Simulation and Experimental Data Comparion, EECMV,ECCOMAS CFD Jafarzadeh B,Hajari A,Alihahi M M & Abari M H, The flow imulation of a low - pecific- peed high-peed centrifugal pump, Appl Math Model, Elevier, 35(2011) Paul C, Edward G & Timothy L, Computational Fluid Dynamic Analyi of Complex Integral Flow in Centrifugal Pump, Proc Int Pump Uer Sym, (Turbomachinery Laboratory, Texa A & M Univerity Sytem), Stefania D G, Simone S, Paolo A & Laura B, CFD Study For Aement of Axial Thrut Balance in Centrifugal Multitage Pump, Proc Int Conf Fluid Flow Tech, CMFF Milan S, Numerical Invetigation of Flow in Mixed-Flow Pump with Volute, Ta u, 5 (2001) Any, Fluent theory Guide, 2012.