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Finite element analysis and experimental investigations on small size wind turbine blades
Finite element analysis and experimental investigations on small size wind turbine blades
Finite element analysis and experimental investigations on small size wind turbine blades
Finite element analysis and experimental investigations on small size wind turbine blades
Finite element analysis and experimental investigations on small size wind turbine blades
Finite element analysis and experimental investigations on small size wind turbine blades
Finite element analysis and experimental investigations on small size wind turbine blades
Finite element analysis and experimental investigations on small size wind turbine blades
Finite element analysis and experimental investigations on small size wind turbine blades
Finite element analysis and experimental investigations on small size wind turbine blades
Finite element analysis and experimental investigations on small size wind turbine blades
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Finite element analysis and experimental investigations on small size wind turbine blades

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  • 1. INTERNATIONALMechanical Engineering and Technology (IJMET), ISSN 0976 – International Journal of JOURNAL OF MECHANICAL ENGINEERING 6340(Print), ISSN 0976 – 6359(Online) Volume 3, Issue 3, Sep- Dec (2012) © IAEME AND TECHNOLOGY (IJMET)ISSN 0976 – 6340 (Print)ISSN 0976 – 6359 (Online) IJMETVolume 3, Issue 3, September - December (2012), pp. 493-503© IAEME: www.iaeme.com/ijmet.aspJournal Impact Factor (2012): 3.8071 (Calculated by GISI) ©IAEMEwww.jifactor.com FINITE ELEMENT ANALYSIS AND EXPERIMENTAL INVESTIGATIONS ON SMALL SIZE WIND TURBINE BLADES T.Vishnuvardhan, Associate Professor, Intell Engineering College, Anantapur.A.P Dr.B.Durga Prasad, Associate Professor, JNT University, Anantapur.A.P ABSTRACT The demand for Small / Micro Wind Turbines is increasing worldwide and the basic advantage of using small size wind turbines is the production of power at low wind speeds. The electricity produced by wind power is cost effective when compared with remaining green energy sources. Small wind turbine systems can be easily installed near the site where the power is required thus the investment on power transmission lines can be reduced. The paper presents the development of small wind turbine blade models in two different profiles R21 and R22. NACA 63-415 airfoil is used for the development of blades. The blades are developed and fabricated for one kW wind turbine generator system. Finite element analysis was conducted by varying the composition of materials used for blade fabrication. Experimental investigations through load deflection test and cyclic load bench test conducted on six blade varieties. The results show the degradation of material properties as the experiment is getting progressed. Finally a better performing blade was identified from the result obtained from FEA, load deflection test and cyclic load bench test. Key Words: Small Wind Turbine – Blade Profiles – Load Deflection Test - Cyclic Load Bench Test. 1. INTRODUCTION Most small / micro size wind turbines are developed to produce power at the locations where the availability of wind at low speeds. Most of the small wind turbines use permanent 493
  • 2. International Journal of Mechanical Engineering and Technology (IJMET), ISSN 0976 –6340(Print), ISSN 0976 – 6359(Online) Volume 3, Issue 3, Sep- Dec (2012) © IAEMEmagnet alternators which are simplest and robust generator configurations. As the windturbine size decreases the rotor speed increases and the power extraction will be more basedon the wind velocity parameter. The blades on the rotor experience a high number of flexingcycles which impacts their life. The aerodynamics, material properties are the key factors inidentifying a better performing blade model. The following sections deal with profiledevelopment, FEA and experimental investigations on small size wind turbine blades withdifferent profiles.2. BLADE PROFILE DEVELOPMENT The present paper focuses on the development of small wind turbine bladesdeveloped from R21 and R22 profiles using a specified design methodology for small sizehorizontal axis wind turbine systems. NACA 63-415 airfoil is used to develop the windturbine blades in R21 and R22 profiles. The investigations are carried out by varying thematerial compositions used for blade development. The following are the materials used forfabrication of wind turbine blades. i) Glass fiber reinforced with polyester resin ii) Glassfiber reinforced with polyester resin sandwiched with UV hard foam and iii) Glass fiberreinforced with Epoxy resin sandwiched with UV hard foam. UV hard foam is used as acentral beam, which increases the stiffness properties of the blade [1]. NACA 63-415 airfoilshape used for the development of blade profiles is shown in the Figure 1. Thecorresponding station and ordinate values for both upper and lower surfaces are shown inTable 1. Table 1 Stations Values along with Ordinates NACA 63-415 Upper Surface Values Lower Surface Values Station Ordinate Station Ordinate 0 0 0 0 0.3 1.2870 0.7 -1.0870 0.5249 1.5889 0.9755 -1.3075 0.9927 2.0677 1.5081 -1.6398 2.1990 2.9571 2.8019 -2.2126 4.6599 4.2652 5.3409 -3.0019 7.1476 5.2629 7.8580 -3.5669 9.6477 6.0757 10.3528 -4.0065 14.6689 7.3487 15.3318 -4.6579 19.7051 8.2802 20.2963 -5.0952 24.7506 8.9388 25.2582 -5.3595 29.8051 9.3651 30.2011 -5.4759 34.8529 9.5591 35.1484 -5.4373 39.9049 9.5279 40.0957 -5.2435 44.9547 9.2891 45.0453 -4.9083 50 8.8704 50 -4.4576 494
  • 3. International Journal of Mechanical Engineering and Technology (IJMET), ISSN 0976 –6340(Print), ISSN 0976 – 6359(Online) Volume 3, Issue 3, Sep- Dec (2012) © IAEME 55.0398 8.2975 54.9618 -3.9167 60.0704 7.5947 59.9296 -3.3102 65.0937 6.7793 64.9070 -2.6576 70.1060 5.8748 69.8949 -1.9859 75.1089 4.9056 74.8911 -1.3257 80.1017 3.8978 79.8983 -0.7122 85.0848 2.8821 84.9152 -0.1918 90.0595 1.8851 89.9405 0.1844 95.0289 0.9336 94.9721 0.3309 100 0 100 0 L.E. Radius = 1.473 percent c Slope of Mean Line at LE = 0.1685 U p p e r S u r f a c e V a lu e s L o w e r S u r f a c e V a lu e s 10 Airfoil Ordinates 8 6 4 2 0 -2 -4 -6 0 20 40 60 80 100 A ir fo il S t a tio n s Fig: 1 NACA 63-415 Airfoil Upper and Lower Surfaces developed from Ordinates and Stations3. FINITE ELEMENT ANALYSIS OF SMALL WIND TURBINE BLADES Finite element analysis is carried out for all blade varieties to extract the behavior ofthe blades when they are subjected to loading. The solid models of R21 and R22 bladevarieties are developed in pro/engineer software and they are shown in Figures 2 & 3. Using ANSYS static analysis was carried out and the Vonmises stresses andcorresponding blade deformations are calculated. Figure 4 and 5 shows the values ofdisplacement and Vonmises stresses corresponding to SWT blade from R22 profile, GFRPwith epoxy resin UV sandwiched material. The vibration characteristics of the blades are analyzed by performing modalanalysis. Further the excitation forces on the blades caused by the stochastic wind loads areimposed on the rotor model and the stable response of the system is calculated by harmonicanalysis. Mode shapes developed for R22 GFRP + Epoxy + SW are shown in Figures 6, 7,8, 9 and 10. Harmonic analysis results for the same blade are shown in Figures 11, 12, 13,14, 15 and 16. Tables 2, 3, 4, 5, 6 and 7 show the frequency values for different modes forall blade varieties. 495
  • 4. International Journal of Mechanical Engineering and Technology (IJMET), ISSN 0976 –6340(Print), ISSN 0976 – 6359(Online) Volume 3, Issue 3, Sep- Dec (2012) © IAEME Fig: 2 R21 SWT Blade Assembly Fig: 3 R22 SWT Blade Assembly Fig:4 Static Analysis of R-22- GFRP + Epoxy + SW Fig:5 Static Analysis of R-22- GFRP + Epoxy +Blade - at 0.02450 N/mm2 Wind Pressure - Displacement SW Blade - at 0.02450 N/mm2 Wind Pressure - Vonmises Stress Fig:6 Modal Analysis of R-22- GFRP + Epoxy + SW Fig:7 Modal Analysis of R-22- GFRP + Epoxy + Blade – I Mode SW Blade – II Mode Fig:8 Modal Analysis of R-22- GFRP + Epoxy + SW Fig:9 Modal Analysis of R-22- GFRP + Epoxy + Blade – III Mode SW Blade – IV Mode 496
  • 5. International Journal of Mechanical Engineering and Technology (IJMET), ISSN 0976 –6340(Print), ISSN 0976 – 6359(Online) Volume 3, Issue 3, Sep- Dec (2012) © IAEMEFig:10 Modal Analysis of R-22- GFRP + Epoxy + SW Blade – V Fig: 11 Harmonic Analysis of R-22- GFRP + Epoxy + Mode SW Blade – Root– at 0.02450 N/mm2 Wind Pressure - Displacement Fig: 13 Harmonic Analysis of R-22- GFRP + Epoxy +Fig: 12 Harmonic Analysis of R-22- GFRP + Epoxy + SW Blade SW Blade – Tip– at 0.02450 N/mm2 Wind Pressure - – Mid – at 0.02450 N/mm2 Wind Pressure - Displacement DisplacementFig: 14 Harmonic Analysis of R-22- GFRP + Epoxy + SW Blade Fig: 15 Harmonic Analysis of R-22- GFRP + Epoxy + – Root– at 0.02450 N/mm2 Wind Pressure - Vonmises Stress SW Blade – Mid – at 0.02450 N/mm2 Wind Pressure - Vonmises StressFig: 16 Harmonic Analysis of R-22- GFRP + Epoxy + SW Blade Fig: 17 Partial Deflection of the Blade – Tip– at 0.02450 N/mm2 Wind Pressure - Vonmises Stress 497
  • 6. International Journal of Mechanical Engineering and Technology (IJMET), ISSN 0976 –6340(Print), ISSN 0976 – 6359(Online) Volume 3, Issue 3, Sep- Dec (2012) © IAEME Fig: 18 Cyclic Load of 15 Kg. Applied on the Fig:19 Cyclic Load of 25 Kg. Applied on the Blade Blade 600 Lo ad D eflectio n T es t Lo ad A pp lied a t T IP B la de P ro file - R 22 500 M a te ria l - G F R P + E P O X Y+ S W 400 Deflection in mm 300 200 100 T ip M id 0 R o ot -10 0 10 20 30 40 50 60 70 Lo a d in K g s Fig: 20 Failure at the Root of Blade in Cyclic Fig:21 Load Deflection Test - R-22 - GFRP + Load Test Epoxy + SW Blade – Load Applied at Tip 180 50 Load D eflection Test Load D eflection Test Load Applied at MID Load Applied at RO O T 160 Blade Profile - R 22 Blade Profile - R 22 Material - G FR P+EPO XY+ SW 40 M aterial - G FR P+Polyester + SW 140 120 30 Deflection in mm Deflection in mm 100 80 20 60 40 10 20 Tip T ip Mid M id 0 0 Root R oot -10 0 10 20 30 40 50 60 70 80 0 20 40 60 80 Load in Kgs Load in K gs Fig:22 Load Deflection Test - R-22 - GFRP + Fig:23 Load Deflection Test - R-22 - GFRP + Epoxy + SW Blade – Load Applied at Mid Epoxy + SW Blade – Load Applied at Root4. LOAD DEFLECTION TEST The moments, thrust torque and power on the rotor can be produced from the variousforces that cause loads on the small wind turbine rotor system are aerodynamic forces,centrifugal forces and gravitational forces. For small wind turbine rotors aimed to producethe power approximately 1 kW, their blades which actually experience these forces are to betested for their ability in withstanding them. The turbine blades can be tested for theirultimate strength by conducting load deflection test. A fixture setup is constructed, to holdthe blade at its root section. 498
  • 7. International Journal of Mechanical Engineering and Technology (IJMET), ISSN 0976 –6340(Print), ISSN 0976 – 6359(Online) Volume 3, Issue 3, Sep- Dec (2012) © IAEME Table 2 R21 GFRP + Polyester Solid Blade - MODE Frequency Values Sno Mode Frequency (Hz) 1 I 23.607 2 II 100.775 3 III 110.642 4 IV 233.534 5 V 300.236 Table 3 R21 - GFRP + Polyester + SW - MODE Frequency Values Sno Mode Frequency (Hz) 1 I 24.801 2 II 105.709 3 III 115.140 4 IV 243.166 5 V 311.784 Table 4 R21 GFRP + Epoxy + SW - MODE Frequency Values Sno Mode Frequency (Hz) 1 I 25.134 2 II 107.128 3 III 116.686 4 IV 246.430 5 V 315.969 Table 5 R22 GFRP + Polyester Solid Blade - MODE Frequency Values Sno Mode Frequency (Hz) 1 I 17.471 2 II 72.585 3 III 83.156 4 IV 187.266 5 V 259.289 Table 6 R22 GFRP + Polyester + SW - MODE Frequency Values Sno Mode Frequency (Hz) 1 I 22.051 2 II 91.441 3 III 104.551 4 IV 235.532 5 V 323.911 Table 7 R22 GFRP + Epoxy + SW - MODE Frequency Values Sno Mode Frequency (Hz) 1 I 22.437 2 II 93.043 3 III 106.381 4 IV 239.661 5 V 329.595 The blade resembles a cantilever beam when it is fixed, critical sections areidentified on which the load is to be applied and corresponding deflections are measured. 499
  • 8. International Journal of Mechanical Engineering and Technology (IJMET), ISSN 0976 –6340(Print), ISSN 0976 – 6359(Online) Volume 3, Issue 3, Sep- Dec (2012) © IAEMEThe three critical sections are at tip, middle and root. The experiment is conducted for allblade varieties and it contains three phases initially the load is applied at tip of the blade,deflections are measured at tip, mid and root. In the second phase the load is applied at midsection and the deflection is measured at tip, mid and root. In the final phase the load isapplied at root and the deflection is measured at three locations. The load is increased with aunit value from 0 Kgs, and is continued till the blade fails. The experimental setup showingthe partial deflection of the blade when the load is applied at the tip is represented in Figure17. Table 8 show the measured distances for R21 and R22 profile blades at which the loadshould be applied and the deflections are to be measured. Table 8 Distance Measurement from Fixed End to Critical SectionsSno Blade Distance from the fixed Distance from the fixed Distance from the fixed Profile end to Root Section end to Mid Section end to Tip Section 1 R21 150 mm 610 mm 950 mm 2 R22 200 mm 660 mm 1030 mm The load deflection test results for R22 profile blade produced from GFRP + Epoxy +SW material are represented in Figures 21, 22 and 23.5. CYCLIC LOAD BENCH TEST A wind turbine blade is subjected during life time a large number of dynamic loadsproduced by the rotation and turbulent nature of wind on blades[3]. Fatigue comes in topicture for wind turbine blades as they are subjected to cyclic loading. These loading causefailures of blade like cracks and rupture and it is very much essential to identify the fatiguebehavior of the wind turbine blades [7,8] . As there is no standard procedure for determining the spectrum loads on small windturbines, cyclic load bench test was developed to understand the behavior of the blade basedon the failures by causing strain on the blades[6]. The cyclic load bench test setup is shownin the Figures 18 and 19.5.1 Cyclic Load Test Procedure The bench can be used for small wind turbine blades with a maximum length of 1.5meters. The test bench is having a load cell located at the top portion of the setup. A fixtureis also developed for holding the blade at its root section and the blade is instrumented withstrain gauges to measure the deformation. In the test a cyclic load will be applied on the 500
  • 9. International Journal of Mechanical Engineering and Technology (IJMET), ISSN 0976 –6340(Print), ISSN 0976 – 6359(Online) Volume 3, Issue 3, Sep- Dec (2012) © IAEMEblades with constant number of cycles (30000) and the load which is applied on the bladewill be further increased once the blade can withstand the cyclic loads. The test procedure is performed based on “constant cycles-incremental load-strainmeasurement”, will be continued till the crack or any other failure occurs. The strainmeasurement is carried out after the completion of prescribed number of cycles at eachmagnitude of load applied on the blade. The experimental results are shown in Figures 24,25, 26, 27, 28 and 29. 1 C y clic L o a d - D e fle ctio n T e sti - R 2 1 - 1 C y c lic L o a d - D e f le c t io n T e s t i - R 2 2 - G F R P + P o lys te r S o lid B la d e G F R P + P o ly s te r S o lid B la d e 0 0 -1 -1 Deflection in mm Deflection in mm -2 -2 -3 -3 -4 -4 3 Kg. 3 K g. 6 Kg. -5 6 K g. -5 9 Kg. 9 K g. 1 2 K g. 12 K g. -6 1 5 K g. 15 K g. -6 0 50 0 0 1 0 00 0 1 50 0 0 2 00 0 0 25 0 00 3 00 0 0 0 5000 10000 15000 20000 25000 30000 N u m b er of C yc le s N u m b e r o f C y c le s Fig.24 Cyclic Load Test Results of R-21 – Fig.25 Cyclic Load Test Results of R-22 – GFRP + Polyester Solid Blade GFRP + Polyester Solid Blade 1 .0 C y c lic L o a d - D e fle c tio n T e s ti - R 2 1 - 1 C y c li c L o a d - D e f l e c t i o n T e s t i - R 2 2 - G F R P + P o ly s te r + S W B la d e G F R P + P o ly s te r + S W B la d e 0 .5 0 0 .0 - 0 .5 -1 - 1 .0 Deflection in mm Deflection in mm -2 - 1 .5 - 2 .0 -3 - 2 .5 -4 - 3 .0 3 K g. 3 K g. 6 K g. - 3 .5 6 K g. -5 9 K g. 9 K g. 12 Kg. - 4 .0 12 K g. 15 Kg. 15 K g. -6 - 4 .5 18 Kg. 0 5000 10000 15000 20000 25000 30000 0 5000 10000 15000 20000 25000 30000 N u m b e r o f C y c le s N u m b e r o f C y c le s Fig.26 Cyclic Load Test Results of R-21 – Fig.27 Cyclic Load Test Results of R-22 – GFRP + Polyester + SW Blade GFRP + Polyester + SW Blade C y c lic L o a d - D e fle c tio n T e s ti - R 2 1 - C y c lic L o a d - D e fle c tio n T e s ti - R 2 2 - 2 G F R P + E p o x y + S W B la d e 1 G F R P + E p o x y + S W B la d e 0 0 -1 -2 -2 -3 -4 -4 -5 -6 -6 Deflection in mm Deflection in mm -7 -8 -8 -9 -1 0 -1 0 3 Kg. -1 2 3 K g. -1 1 6 Kg. 6 K g. -1 2 9 Kg. -1 4 9 K g. -1 3 12 K g. 12 Kg. -1 4 15 K g. -1 6 15 Kg. -1 5 18 K g. 18 Kg. -1 6 21 K g. -1 8 21 Kg. 25 K g. -1 7 0 5 00 0 10 00 0 1 50 00 200 00 2 50 00 3 00 00 0 5000 10000 15000 20000 25000 30000 N u m b e r o f C y c le s N u m b e r o f C y c le s Fig.28 Cyclic Load Test Results of R-21 – Fig.29 Cyclic Load Test Results of R-22 – GFRP + Epoxy + SW Blade GFRP + Epoxy + SW Blade 501
  • 10. International Journal of Mechanical Engineering and Technology (IJMET), ISSN 0976 –6340(Print), ISSN 0976 – 6359(Online) Volume 3, Issue 3, Sep- Dec (2012) © IAEMECONCLUSIONS The paper shows a specific methodology to determine the load deflectioncharacteristics and the cyclic load behavior of small wind turbine blades. The following aresome of the important conclusions drawn from the experiments All the blades are capable to bear maximum loading value when applied at the root section and the blades will fail at lower magnitude of loading, when the load is applied at tip of the blade. It is observed that all the blades when subjected to loading irrespective of the location at which the load is applied, the failure crack is observed near the root of the blade. The blade tends to fail by creating a crackling sound. When the load deflection test results are compared for all varieties, the R22 profile blade produced from GFRP + Epoxy + SW is showing more structural strength. Even in R21 profile also the produced from the same material is showing more structural strength. In cyclic load bench test, the GFRP + Epoxy + SW blades have shown a better performance in both R21 and R22 blade profiles. Out of all the six varieties of blades R22 profiled based blade fabricated from GFRP + Epoxy +| SW has shown the leading performance by with standing a cyclic load of 25 Kgs. with a deflection of 16mm below the reference point, at 30000 cycles. In R21 profile, the blade fabricated from GFRP + Epoxy +| SW has shown the leading performance by with standing a cyclic load of 21 Kgs with a deflection of 16.75 mm below the reference point, at 30000 cycles.REFERENCES 1) T.Y. Kam, J. H. Jiang, H. H. Yang, R. R. Chang, F. M. Lai, and Y. C. Tseng, “Fabrication and Testing of Composite Sandwich Blades for a Small Wind Power System”, PEA-AIT International Conference on Energy and Sustainable Development: Issues and Strategies (ESD 2010), June 2010. 2) Jorge Antonio Villar A1e, Gabriel da Silva Simioni, Joao Gilberto Astrada Chagas Filho, “Procedures Laboratory for Small Wind Turbines Testing”. 3) Jorge Antonio Villar A1e, Carlos Alexander dos, Santos, “Aerodynamic Loads of Fatigue of Small Wind Turbine Blades: Standards and Testing Procedure” EWEA 2011-Europe’s Premier Wind Energy Event 14-17-March 2011, Brussels, Belgium. 502
  • 11. International Journal of Mechanical Engineering and Technology (IJMET), ISSN 0976 –6340(Print), ISSN 0976 – 6359(Online) Volume 3, Issue 3, Sep- Dec (2012) © IAEME 4) Brian Hayman, Jakob Wedel-Heinen, Povl Brondsted, “Materials Challenges in Present and Future Wind Energy” Harnessing Materials for Energy, MRS Bulletin, Volume 33, April 2008. 5) Jayantha A Epaarachchi and Philip D Clausen “Accelerated full scale fatigue testing of a Small Composite Wind Turbine Blade using a Mechanically operated test rig” SIF-2004 Structural Integrity and Fracture. 6) DET Norske Veritas “Design and Manufacture of Wind Turbine Blades, Offshore and Onshore Wind Turbines”– October 2006. 7) Jayantha A. Epaarachchi, Philip D. Clausen “An empirical model for fatigue behavior prediction of glass fiber-reinforced plastic composites for various stress ratios and test frequencies” Journal of Applied Science and manufacturing – 2003. 8) P.Rajaram 1 A.Murugesan 2 and G.S.Thirugnanam “Experimental Study on behavior of Interior RC Beam Column Joints Subjected to Cyclic Loading” International Journal Of Applied Engineering Research, Dindigul Volume 1, No 3, 2010 Research Article Issn 09764259. 9) Nitin Tenguria 1 , Mittal.N.D 1 , Siraj Ahmed 2 “Design and Finite Element Analysis of Horizontal Axis Wind Turbine blade” Journal of Materials Processing Technology 167 (2005) 463–471 10) M. Grujicic, G. Arakere, E. Subramanian, V. Sellappan, A. Vallejo, and M. Ozen “Structural-Response Analysis, Fatigue-Life Prediction and Material Selection for 1 MW Horizontal-Axis Wind-Turbine Blades” – 2009. 503

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