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  • 1. C.Hariharan and M.Govardhan Chennai – 36 Indian Institute of Technology Madras Loss in Input Power due to Increase in Clearance between Inlet Duct and Impeller in an Industrial Centrifugal Blower Thermal Turbomachines Laboratory Department of Mechanical Engineering Indian Institute of Technology Madras 1
  • 2. Introduction • Lee [3] • C Hariharan et al [5] Chennai – 36 Indian Institute of Technology Madras • Aayder et al. [1] 2
  • 3. • In most of the time while design we omit the clearance gap in between suction duct and impeller. Chennai – 36 Indian Institute of Technology Madras Problem definition • The area of clearance is only 0.5 to 2% of inlet area. 3
  • 4. Design Chennai – 36 Indian Institute of Technology Madras Specification: specific work Design mass flow rate operating range Speed - 24000 m2/s2 - 28.5 kg/s - 20 kg/s to 31.5 kg/s - 3000rpm 4
  • 5. Dimension Blades Inlet Diameter Inlet Blade angle Exit Blade angle - 15 - 0.7 m - 32o - 48o Clearance gap Chennai – 36 Indian Institute of Technology Madras Impeller: - 1mm, 3mm and 5mm - 0.6 %, 1.8% and 3% clearance area 5
  • 6. - constant angular momentum - tongue clearance 5% of impeller exit diameter Chennai – 36 Indian Institute of Technology Madras Volute : - Ratio between volute width and impeller exit width 5. 6
  • 7. Chennai – 36 Indian Institute of Technology Madras Fan Assembly with Ratio 5 volute 7
  • 8. Numerical simulation simplification -Steady state -Compressible (air ideal gas) Chennai – 36 Indian Institute of Technology Madras - commercial CFD code CFX 14 - (3-D) Full fan 8
  • 9. Chennai – 36 Indian Institute of Technology Madras - (3-D) -Mass -Momentum -Energy - turbulence model (K-Ɛ) 9
  • 10. -Rotating domain - impeller Interface Chennai – 36 Indian Institute of Technology Madras - Stationary domain - suction duct - volute Frozen Rotor Technique 10
  • 11. -Suction duct 0.8 million -Impeller 4.5 million -Volute 5.5 million Chennai – 36 Indian Institute of Technology Madras Meshing Y+ < 50 volume expansion factor < 25 Number of nodes in interfaces maintained almost same 11
  • 12. Chennai – 36 Indian Institute of Technology Madras Suction duct mesh 12
  • 13. Chennai – 36 Indian Institute of Technology Madras Impeller mesh 13
  • 14. Chennai – 36 Indian Institute of Technology Madras Impeller pasage 14
  • 15. Chennai – 36 Indian Institute of Technology Madras Volute mesh 15
  • 16. Chennai – 36 Indian Institute of Technology Madras Impeller inlet duct mesh 16
  • 17. Chennai – 36 Indian Institute of Technology Madras Clearance between impeller and inlet duct 17
  • 18. circumferential radial 10 1100 Chennai – 36 Indian Institute of Technology Madras Number of nodes in clearance 18
  • 19. -Stage performance -Component performance Chennai – 36 Indian Institute of Technology Madras Results 19
  • 20. Chennai – 36 Indian Institute of Technology Madras Stage Pressure raise 20
  • 21. Chennai – 36 Indian Institute of Technology Madras Change in Stage Pressure raise 21
  • 22. Chennai – 36 Indian Institute of Technology Madras Stage Efficiency 22
  • 23. Chennai – 36 Indian Institute of Technology Madras Change in Stage Efficiency 23
  • 24. Chennai – 36 Indian Institute of Technology Madras Change in Total pressure at impeller exit 24
  • 25. Chennai – 36 Indian Institute of Technology Madras Change in static pressure at impeller exit 25
  • 26. Chennai – 36 Indian Institute of Technology Madras Increase in input power 26
  • 27. Chennai – 36 Indian Institute of Technology Madras Return mass flow rate 27
  • 28. Chennai – 36 Indian Institute of Technology Madras Flow angle at inlet to impeller for design mass flow rate 28
  • 29. Chennai – 36 Indian Institute of Technology Madras Flow angle at inlet to impeller for lowest mass flow rate 29
  • 30. Chennai – 36 Indian Institute of Technology Madras Static pressure at impeller exit for design mass flow rate 30
  • 31. Chennai – 36 Indian Institute of Technology Madras Static pressure at impeller exit for lowest mass flow rate 31
  • 32. Chennai – 36 Indian Institute of Technology Madras Total pressure at impeller exit for design mass flow rate 32
  • 33. Chennai – 36 Indian Institute of Technology Madras Total pressure at impeller exit for lowest mass flow rate 33
  • 34. Chennai – 36 Indian Institute of Technology Madras Flow angle at Exit of impeller for design mass flow rate 34
  • 35. Chennai – 36 Indian Institute of Technology Madras Flow angle at Exit of impeller for lowest mass flow rate 35
  • 36. Chennai – 36 Indian Institute of Technology Madras Stream lines in impeller for clearance of (a) 0mm 36
  • 37. Chennai – 36 Indian Institute of Technology Madras Stream lines in impeller for clearance of (a) 1mm 37
  • 38. Chennai – 36 Indian Institute of Technology Madras Stream lines in impeller for clearance of (a) 3mm 38
  • 39. Chennai – 36 Indian Institute of Technology Madras Stream lines in impeller for clearance of (a) 5mm 39
  • 40. Chennai – 36 Indian Institute of Technology Madras Volute Pressure recovery coefficient 40
  • 41. Chennai – 36 Indian Institute of Technology Madras Change in volute Pressure recovery coefficient 41
  • 42. Chennai – 36 Indian Institute of Technology Madras Volute loss coefficient 42
  • 43. Chennai – 36 Indian Institute of Technology Madras Volute loss coefficient 43
  • 44. Chennai – 36 Indian Institute of Technology Madras Change in Total pressure at volute exit 44
  • 45. Chennai – 36 Indian Institute of Technology Madras Change in static pressure at volute exit 45
  • 46. -The overall stage performance at design and off design conditions, especially at higher mass flow rate is not favorable Chennai – 36 Indian Institute of Technology Madras conclusion -Stage efficiency drops considerably as the mass flow is increased and also there is an increase in input power up to 32 kW -There is a noticeable drop in total and static pressure at exit of impeller 46
  • 47. As the clearance increases, the flow is found to be more uniform at the exit of the impeller and also the possibility of flow separation gets reduced at lower mass flow rates especially near the trailing edge of impeller. Chennai – 36 Indian Institute of Technology Madras conclusion The increased pressure recovery and reduced loss at higher clearance has positive effect on volute at all mass flow rates. 47
  • 48. Chennai – 36 Indian Institute of Technology Madras Thank you 48

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