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  • 1. International Journal of Advanced Research in Engineering and Technology RESEARCH IN– INTERNATIONAL JOURNAL OF ADVANCED (IJARET), ISSN 09766480(Print), ISSN 0976 – 6499(Online) Volume 3, Number 1, January - June (2012), © IAEME ENGINEERING AND TECHNOLOGY (IJARET)ISSN 0976 - 6480 (Print)ISSN 0976 - 6499 (Online) IJARETVolume 3, Issue 1, January- June (2012), pp. 97-106© IAEME: www.iaeme.com/ijaret.html ©IAEMEJournal Impact Factor (2011): 0.7315 (Calculated by GISI)www.jifactor.com MODELING AND SIMULATION OF DUCTED AXIAL FAN FOR ONE DIMENSIONAL FLOW Manikandapirapu P.K.1 Srinivasa G.R.2 Sudhakar K.G.3 Madhu D. 4 1 Ph.D Candidate, Mechanical Department, Dayananda Sagar College of Engineering, Bangalore. 2 Professor and Principal Investigator, Dayananda Sagar College of Engineering, Bangalore. 3 Dean (Research and Development), CDGI, Indore, Madhya Pradesh . 4 Professor and Head, Mechanical Department, Government Engg. College, KRPET-571426.ABSTRACT The paper presents to develop the analogy for modeling and simulation of ductedAxial Fan by using the one dimensional flow equation of axial turbo machines. Mainobjective of this paper is to derive the flow model from radial equilibrium concepts andcompute the pressure rise for varying the functional parameters of inlet velocity, whirlvelocity, rotor speed and diameter of blade from hub to tip in ducted axial fan by usingsimulink software for one dimensional flow. In this main phase of paper, the analogiesfor modeling and simulation has been investigated for optimize the parameter of pressurerise in ducted axial flow fan. Keywords: Pressure rise, Whirl velocity, Pressure Ratio, Flow ratio, Rotor speed,Simulink, Axial Fan.1.INTRODUCTION Mining fans and cooling tower fans normally employ axial blades and or required towork under adverse environmental conditions. They have to operate in a narrow band ofspeed and throttle positions in order to give best performance in terms of pressure rise,high efficiency and also stable condition. Since the range in which the fan has to operateunder stable condition is very narrow, clear knowledge has to be obtained about thewhole range of operating conditions if the fan has to be operated using active adaptivecontrol devices. The performance of axial fan can be graphically represented as shown infigure 1. 97
  • 2. International Journal of Advanced Research in Engineering and Technology (IJARET), ISSN 0976 –6480(Print), ISSN 0976 – 6499(Online) Volume 3, Number 1, January - June (2012), © IAEME Fig: 1 Graphical representation of Axial Fan performance curve2. TEST FACILITY AND INSTRUMENTATION Experimental setup, fabricated to create stall conditions and to introduce unstallconditions in an industrial ducted axial fan is as shown in figure 2. Fig: 2 Ducted Axial Fan Rig A 2 HP Variable frequency 3 phase induction electrical drive is coupled to 3-phasethe electrical motor to derive variable speed ranges. Schematic representation ofducted fan setup is shown in figure 3. 98
  • 3. International Journal of Advanced Research in Engineering and Technology (IJARET), ISSN 0976 –6480(Print), ISSN 0976 – 6499(Online) Volume 3, Number 1, January - June (2012), © IAEME Fig: 3 Ducted Axial Fan - SchematicThe flow enters the test duct through a bell mouth entry of cubic profile. The bell mouthperforms two functions: it provides a smooth undisturbed flow into the duct and alsoserves the purpose of metering the flow rate. The bell mouth is made of fiber reinforcedpolyester with a smooth internal finish. The motor is positioned inside a 381 mmdiameter x 457 mm length of fan casing. The aspect (L/D) ratio of the casing is 1.2. Thehub with blades, set at the required angle is mounted on the extended shaft of the electricmotor. The fan hub is made of two identical halves. The surface of the hub is madespherical so that the blade root portion with the same contour could be seated perfectly onthis, thus avoiding any gap between these two mating parts. An outlet duct identical inevery way with that at inlet is used at the downstream of the fan. A flow throttle is placedat the exit, having sufficient movement to present an exit area greater than that of theduct.3.0 GOVERNING EQUATION3.1 Continuity Equation A continuity equation in physics is a differential equation that describes the transportof some kind of conserved quantity. Since mass, energy, momentum, electric charge andother natural quantities are conserved. Continuity equation ߩଵ × ‫ܣ‬ଵ × ܸଵ ߩଶ × ‫ܣ‬ଶ × ܸଶ (3.1)3.2 Momentum Equation A body of mass m subject to a net force F undergoes an acceleration that has the samedirection as the force and a magnitude that is directly proportional to the force andinversely proportional to the mass. Alternatively, the total force applied on a body isequal to the time derivative of linear momentum of the body.Momentum equation 99
  • 4. International Journal of Advanced Research in Engineering and Technology (IJARET), ISSN 0976 –6480(Print), ISSN 0976 – 6499(Online) Volume 3, Number 1, January - June (2012), © IAEME డ ଶ ሺߩ௠ ߭௠ ) + ∇. ሺߩ௠ ߭௠ ) = డ௧ ∆p + ∇. [μ୫ (∆߭௠ + Δ߭௠ )]+ ߩ௠ ݃ + ‫ + ܨ‬Δ. ൫∑௡ ߙ௞ ߩ௞ ߭ௗ௥,௞ ߭ௗ௥.௞ ൯ (3.2) ் ௞ୀଵ3.3 Energy Equation Energy may be stored in systems without being present as matter, or as kinetic orelectromagnetic energy. The law of conservation of energy is a law of physics. It statesthat the total amount of energy in an system remains constant over time (is said to beconserved over time). A consequence of this law is that energy can neither be created nordestroyed: it can only be transformed from one state to another Energy equation డ ∑௡ ሺߙ௞ ߩ௞ ‫ܧ‬௞ ) + ∆. ሺ∑௡ ሺߙ௞ ߭௞ ሺߩ௞ ‫ܧ‬௞ + ܲ)) = ∆. ൫݇௘௙௙ ∇ܶ൯ + ܵா (3.3) ௞ୀଵ ௞ୀଵ డ௧4.0 FLOW MODELING FOR ONE DIMENSIONAL FLOW4.1 Radial Equilibrium Concepts and evaluationConsider a small element of fluid of mass dm as shown in fig.4 and fig.5 of unit depthand subtending an angle dθ at the axis and rotating about the axis with tangential velocityand ܿ௾ at radius r. C asing p+dp Mass/Unit depth Streamlines dr = ρrdθdr Velocity = c θ p+1/2 dp p+1/2 dp p r dθ Hub AxisFig: 4 Radial equilibrium flow through a rotor blade row Fig: 5 A fluid element in radial equilibrium ( Cr = 0) The general three dimensional momentum equation of inviscid fluid in a radialdirection expressed in a cylindrical coordinate system can be written as follows: ଵ ப୮ ப୚୰ ୚୳ ப୚౨ ப୚౨ ୴మ − ቀ ஡ ப୰ ቁ = Vr ቀ ப୰ ቁ + ቀ ப஘ ቁ + Va − ౭ (4.1) ୰ ப୸ ୰ 100
  • 5. International Journal of Advanced Research in Engineering and Technology (IJARET), ISSN 0976 –6480(Print), ISSN 0976 – 6499(Online) Volume 3, Number 1, January - June (2012), © IAEMEAssuming axisymmetric flow and imposing a zero radial flow velocity, it can besimplified to ଵ ப୮ ୴మ = ஡ ப୰ ౭ ୰ (4.2)The equation 4.2 is consider as the governing equation of axial flow fan for 1-Dimensional flow ୴మ dp = ࣋ ౭ ୰ dr (4.3) ந v୵ = v୧ × ౬౟ (4.4) ଶ ౫ ந ×୳ ந × ஠ୈ୒ v୵ = ଶ = ଺଴×ଶ (4.5) ந ×ଷ.ଵସ ×ଶ ×୒×୰ v୵ = (4.6) ଺଴ ×ଶ ࣒ ×ଷ.ଵସ ×ே ‫ݒ‬௪ = ቀ ଺଴ ቁ‫ݎ‬ (4.7) ࣒ ×૜.૚૝ ×ࡺ ૛Pressure Rise = ∆p =࣋ ቀ ቁ × ‫ݎ݀ ݎ ׬‬ ૟૙ ்௜௣ ట ×ଷ.ଵସ ×ே ଶ ௥మPressure Rise = ∆p = ࣋ ቀ ቁ × ቀ ଶ ቁ (4.8) ଺଴ ு௨௕ The aim of the flow modeling is to measure the pressure rise as a function ofwhirl velocity and rotor speed for different diameter of blade from hub to tip in ductedaxial flow fan. In this flow modeling equation helps to optimize the parameter of pressurerise for different whirl velocity in a ducted axial fan.5.0 SIMULINK Simulink is a software package for modeling, simulating and analyzing dynamicsystems. It supports linear and nonlinear systems, modeled in continuous time, sampledtime, or a hybrid of the two. For modeling simulink provides a graphical user interfacefor building models as block diagrams, using click and drag mouse operations. Simulinkincludes a comprehensive block library of source, sink of linear and nonlinearcomponents and connectors.5.1 SIMULINK MODEL FOR ONE DIMENSIONAL FLOW The one dimensional flow model is considered for simulation study. Thegoverning parameters of the fan considered are density of the fluid, diameter of bladefrom hub to tip, inlet velocity, pressure ratio, rotor speed and the effects of variation of 101
  • 6. International Journal of Advanced Research in Engineering and Technology (IJARET), ISSN 0976 –6480(Print), ISSN 0976 – 6499(Online) Volume 3, Number 1, January - June (2012), © IAEMEthese parameters are testified through simulink simulation model. Constant block, gainblock, Math function, Sum block, inverse block, and display block are the typical blocksused for simulink mathematical model in one dimensional flow is shown in fig.6. Fig: 6 Simulink Flow Simulation Model for One Dimensional Flow in Ducted Axial Fan6.0 RESULTS AND DISCUSSION The aim of the flow modeling and simulation is to compute the pressure rise as afunction of whirl velocity and rotor speed for different diameter of blade from hub to tipin ducted axial flow fan. Flow modeling and simulation of one dimensional flow helps tooptimize the parameter of pressure rise for different whirl velocity in a ducted axial fan. 35 Rotor Speed 3000 Rpm 30 Rotor Speed 3600 Rpm Pressure Raise in N/m2 25 Rotor Speed 3300 Rpm 20 Rotor Speed 2700 Rpm 15 10 5 0 0.0575 0.072 0.08625 0.115 0.23 Pressure Ratio Fig.7 Pressure Raise Variations for fixed diameter of Blade Rotor at 0.381 m 102
  • 7. International Journal of Advanced Research in Engineering and Technology (IJARET), ISSN 0976 –6480(Print), ISSN 0976 – 6499(Online) Volume 3, Number 1, January - June (2012), © IAEME Analysis of one dimensional flow modeling and their governing parameters weremade as a function of whirl velocity, diameter of hub from tip to hub and rotor speed forducted axial fan. The variations in pressure rise for different pressure ratio at a constantdiameter of blade of 0.381m is shown in fig.7. Maximum pressure magnitude is found tobe 32 N/ m2 for the pressure ratio of 0.23. Further, it varies from 1 to 10 N/ m2 when therotor speed is incremented by 300 rpm. 8 Pressure Ratio 0.115 7 Pressure Ratio 0.0575 Pressure Raise in N/m2 6 Pressure Ratio 0.08625 Pressure Ratio 0.072 5 4 3 2 1 0 2400 2600 2800 3000 3200 3400 3600 Rotor Speed ( Rpm )Fig.8 Pressure Raise Variations for fixed diameter of Blade Rotor at 0.381 m The variations in pressure rise for different rotor speed from 2400 rpm to 3600 rpmfor fixed diameter of blade of 0.381 m is shown in fig.8. Maximum pressure magnitude isfound to be 8 N/ m2 for the pressure ratio of 0.115. Further, it varies from 1 to 5 N/ m2when the rotor speed is incremented by 200 rpm. 250 Rotor Speed 3000 Rpm 200 Rotor Speed 3600 Rpm Pressure Raise in N/m2 Rotor Speed 2400 Rpm 150 Rotor Speed 2700 Rpm Rotor Speed 3300 Rpm 100 50 0 0.0131 0.0714 0.01651 0.381 0.881 2.04 Blade Diameter in mFig.9 Pressure Raise Variations for fixed Pressure Ratio of 0.115 103
  • 8. International Journal of Advanced Research in Engineering and Technology (IJARET), ISSN 0976 –6480(Print), ISSN 0976 – 6499(Online) Volume 3, Number 1, January - June (2012), © IAEME The variations in pressure rise for different diameter of blade from 0.0131m to 2.04m at a constant pressure ratio of 0.115 is shown in fig.9. Maximum pressure magnitude isfound to be 210 N/ m2 for the blade diameter of 2.04 m. Further, it varies from 0 to 45 N/m2 when the rotor speed is incremented by 300 rpm. 160 Pressure Ratio 0.115 140 Pressure Ratio 0.0575 Pressure Rise in N/m2 120 Pressure Ratio 0.08625 100 Pressure Ratio 0.072 80 60 40 20 0 0.0131 0.0714 0.01651 0.381 0.881 2.04 Blade Diameter in mFig.10 Pressure Raise Variations at constant Rotor Speed of 3000 Rpm The variations in pressure rise for different diameter of blade from 0.0131m to 2.04m at constant rotor speed of 3000 rpm is shown in fig.10. Maximum pressure magnitudeis found to be 160 N/ m2 for the pressure ratio of 0.115. Further, Pressure magnitude isfound to be varying from 0 to 160 N/ m2 for every double increment of rotor diameter.7.0 CONCLUSION In this paper, an attempt has been made to develop the flow modeling andsimulation for one dimensional flow in ducted axial fan by using theory of radialequilibrium equation. It is useful to design the operating condition of axial fan to measurethe parameters of pressure rise as a function of pressure ratio, rotor speed, and diameterof blade from hub to tip in ducted axial fan. Further, this work can be extended byworking on the modeling and simulation of characteristic study in stall control. Theresults so far discussed, indicate that flow modeling and simulation of one dimensionalflow in ducted axial fan is very promising.ACKNOWLEDGEMENT The authors gratefully thank AICTE (rps) Grant. for the financial support of presentwork. 104
  • 9. International Journal of Advanced Research in Engineering and Technology (IJARET), ISSN 0976 –6480(Print), ISSN 0976 – 6499(Online) Volume 3, Number 1, January - June (2012), © IAEMENOMENCLATURE cx = Axial velocity in m/s ܿఏ = Whirl velocity in m/s r2 = Radius of blade tip in m r1 = Radius of blade hub in m N = Tip speed of the blades in rpm va = Axial velocity in m/s dp= P2 - P1 = Pressure rise in N/m2 d = Diameter of the blade in m ρair = Density of air in kg/m3 vw = Whirl velocity in m/s η = Efficiency of fanREFERENCES[1] Day I J,”Active Suppression of Rotating Stall and Surge in Axial Compressors”, ASME Journal of Turbo machinery, vol 115, P 40-47, 1993[2] Patrick B Lawlees,”Active Control of Rotating Stall in a Low Speed Centrifugal Compressors”, Journal of Propulsion and Power, vol 15, No 1, P 38-44, 1999[3]C A Poensgen ,”Rotating Stall in a Single-Stage Axial Compressor”, Journal of Turbo machinery, vol.118, P 189-196, 1996[4] J D Paduano,” Modeling for Control of Rotating stall in High Speed Multistage Axial Compressor” ASME Journal of Turbo machinery, vol 118, P 1-10, 1996[5] Chang Sik Kang,”Unsteady Pressure Measurements around Rotor of an Axial Flow Fan Under Stable and Unstable Operating Conditions”, JSME International Journal, Series B, vol 48, No 1, P 56-64, 2005[6] A H Epstein,”Active Suppression of Aerodynamic instabilities in turbo machines”,Journal of Propulsion, vol 5, No 2, P 204-211, 1989[7] Bram de Jager,”Rotating stall and surge control: A survey”, IEEE Proceedings of 34thConference on Decision and control, 1993[8] S Ramamurthy,”Design, Testing and Analysis of Axial Flow Fan,” M E Thesis, Mechanical Engineering Dept, Indian Institute of Science, 1975[9] S L Dixon, Fluid Mechanics and Thermodynamics of Turbo machinery, 5th edition, Pergamon, Oxford, 1998[10] William W Peng, Fundamentals of Turbo machinery, John Wiley & sons.Inc, 2008AUTHORSManikandapirapu P.K. received his B.E degree from Mepco SchlenkEngineering college, M.Tech from P.S.G College of Technology,AnnaUniversity,and now is pursuing Ph.D degree in Dayananda Sagar College ofEngineering, Bangalore under VTU University. His Research interest include:Turbomachinery, fluid mechanics, Heat transfer and CFD. 105
  • 10. International Journal of Advanced Research in Engineering and Technology (IJARET), ISSN 0976 –6480(Print), ISSN 0976 – 6499(Online) Volume 3, Number 1, January - June (2012), © IAEMESrinivasa G.R. received his Ph.D degree from Indian Institute of Science,Bangalore. He is currently working as a professor in mechanical engineeringdepartment, Dayananda Sagar College of Engineering, Bangalore. His Researchinterest include: Turbomachinery, Aerodynamics, Fluid Mechanics, Gas turbinesand Heat transfer.Sudhakar K.G received his Ph.D degree from Indian Institute of Science,Bangalore. He is currently working as a Dean (Research and Development) inCDGI, Indore, Madhyapradesh. His Research interest include: SurfaceEngineering, Metallurgy, Composite Materials, MEMS and FoundryTechnology.Madhu D received his Ph.D degree from Indian Institute of Technology (NewDelhi). He is currently working as a Professor and Head in GovernmentEngineering college, KRPET-571426, Karnataka. His Research interest include:Refrigeration and Air Conditioning, Advanced Heat Transfer Studies, Multiphase flow and IC Engines. 106