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Analysis of Pumps & Fans

Analysis of Pumps & Fans. P M V Subbarao Professor Mechanical Engineering Department I I T Delhi. Machines to Convert Shaft Power to Micro Kinetic Power……. Selection of Appropriate Momentum Transfer Principle…. Classification of Inversions of Turbines. Incompressible Flows.

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Analysis of Pumps & Fans

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  1. Analysis of Pumps & Fans P M V Subbarao Professor Mechanical Engineering Department I I T Delhi Machines to Convert Shaft Power to Micro Kinetic Power……. Selection of Appropriate Momentum Transfer Principle….

  2. Classification of Inversions of Turbines Incompressible Flows Compressible Flows Centrifugal Pumps Mixed Pumps Axial Pumps Centrifugal Compressors Mixed Compressors Axial Compressors

  3. The Major Pump Categories

  4. Flow in Centrifugal Action for Pumping • Rotate a cylinder containing fluid at constant speed. • Supply continuously fluid from bottom. • See What happens? • Any More Ideas?

  5. Early Types of Centrifugal Pumps

  6. Rotodynamic Pumps/Fans: Basic Principles • The whole family of so-called rotodynamic pumps depends on propelling fluid using a spinning impeller or rotor. • Two possible mechanisms are used either alone or in combination: • Mechanism 1 : Demands low Specific speed: • Water is continuously expelled from the impeller by being whirled into a circular path. • The centrifugal force carries the fluid away. • The earliest practical rotodynamic pumps were developed in the 18th and early 19th century. • Mechanism 2 : Demands High Specific speed: • Water is continuously expelled from the impeller by being Deflected by the impeller blades (airfoils).

  7. Anatomy of A Centrifugal Pump/Fan : Low Ns Discharge Nozzle - K Impeller - J Shaft - C Eye of Impeller - G Casing - F

  8. Basic Structure of Centrifugal Pump/Fan

  9. Steamline Flow Through An Impeller

  10. Impeller Velocity Diagrams Vf2 Vr2 Va2 Va1 Vr1

  11. High Flow Rates : Pumps in Parallel

  12. Newton’s Third Law used by Natural Genius

  13. Motor control strategies : Multiple Skills of Natural Genius Larva of Chinook Salman Larval Lamprey Northern Pike

  14. Development of an Ultimate Fluid Machine An Invention thru Adventure in First Decade of 20th Century

  15. Development of an Ultimate Fluid machine

  16. Newton’s Third Law for a Lifting Device Any solid body that can force the air downward clearly implies that there will be an upward force on the airfoil as a Newton's 3rd law reaction force.

  17. Axial Flow Pumps Pump or Fan Blades The power, P of a fluid Machine

  18. Direction of Lift & drag in Axial Flow Pump/Fan F

  19. Axial Flow Pump Stage

  20. Vertical Axis Axial Flow Pumps

  21. Kinematics of Flow in Cascade Exit Velocity Triangle Inlet Velocity Triangle

  22. Geometrical Parameters of Axial Flow Pump Hub to tip Ratio Geometry of Aerofoil:

  23. Standard Aerofoils C For NACA 428, 682, 364 & 480 For NACA 408, 490, 436 & 387

  24. Popular Airfoils used as Axial Pump Blades C For NACA 622, 623, 624 & 384 For NACA 23012

  25. Layout of A General Pump

  26. Basic Erection of A Pump STATIC SUCTION HEAD

  27. Water Flow Path in A Pump

  28. Variation of Absolute Pressure inside A Pump pabsolute Flow Path

  29. Cavitation • As the liquid flows onto the impeller of the pump it is accelerated and initially its pressure falls (Bernoulli). • The pressure subsequently increases as the fluid leaves the impeller and as the kinetic energy is recovered in the volute chamber. • If the pressure of the liquid falls below the vapour pressure, pv, the liquid boils, generating vapour bubbles or cavities-cavitation. • The bubbles are swept into higher pressure regions by the liquid flow, where they collapse creating pressure waves and cause mechanical damage to solid surfaces. • Moreover, pump discharge head is reduced at flow rates above the cavitation point. • Operation under these conditions is not desirable and damages the equipment.

  30. NPSH NPSH

  31. Loss of NPSH

  32. Kinetic power mVs2/2 Frictional loss in suction piping Available NPSH At Site

  33. Specific Speed Vs Suction Velocity Suction Velocity:

  34. Power Losses in Pump • Head losses due to suction and delivery pipe fittings, entrance losses, impeller frictional losses and casing frictional losses. • Power loss due Leakages and recirculating fluid. • Disc Friction loss • Mechanical Losses

  35. Specific Speed Vs Pump Losses

  36. Specific Speed Vs Total Power Loss

  37. Performance Parameters Differential head of pump:

  38. Non-dimensional Performance Parameters , CH = head coefficient , CQ = flow coefficient , Re = Reynolds number

  39. A similar analysis may be carried out for the power consumption of the pump, P:

  40. Universal Design Chart for Power Consuming Turbo-machines

  41. Pump Curves & Selection of Speed Constant Head & Discharge Curve P  N3 Constant Discharge Curve H  N2 Constant Head Curve Q N

  42. Pump Curves @ constant Speed Head (H) Efficiency () Power Input (Pin) Fluid Power or Output Power (Phyd)

  43. In-Situ Demand

  44. High Head Applications: Pumps in Parallel

  45. Multi-stage Pumps and Fans

  46. High Capacity : Pumps in Parallel.

  47. Matching of A Pump with Site Pump Curve Efficiency Curve Power Curve System Curve

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