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TSM 363 Applied Fluid Power

TSM 363 Applied Fluid Power. Principle of Hydraulic Pumps. Goals of this Lecture. Basics of hydraulic pump Principle of Positive displacement pumping Key parameters Principles of typical hydraulic pumps Gear pumps Vane pumps Piston pumps. It’s Powerful, What Provides the Power?.

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TSM 363 Applied Fluid Power

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  1. TSM 363 Applied Fluid Power Principle of Hydraulic Pumps

  2. Goals of this Lecture • Basics of hydraulic pump • Principle of Positive displacement pumping • Key parameters • Principles of typical hydraulic pumps • Gear pumps • Vane pumps • Piston pumps

  3. It’s Powerful, What Provides the Power?

  4. vo, Fo • P1 Q1 • P4 Q4 • ni, Ti • M • no, To • EnergyLevel Energy Flow in a Fluid Power System

  5. Positive Displacement Pumping

  6. Key Hydraulic Pump Parameters • Rated discharge pressure –the maximum continuous operating pressure of a pump under normal operating condition • maximum discharge pressure • minimum discharge pressure (or margin pressure) • maximum inlet pressure • Rated speed –the speed at which the pump can continuously operate to discharge flow at the rated pressure • maximum speed • minimum speed

  7. M R P M H T Pressure Rating of the Pump Pressure rating is the maximum pressure that should be encountered at the pump discharge port. Pressure is determined by Load!

  8. Pump Power Output HPout = (Q·P)/1714 Q = flow rate, in gpm P = pressure, in psi Power Output from a Hydraulic Pump In a hydraulic displacement pump, the power output is determined by the setting pressure and the actual output flow rate, and the pump efficiency using the equation below:

  9. Pump Capacity (flow rate) Q =D·n/k Q =flow rate, in GPM or L/min D =Displacement, in in3 or cc n =Pump shift speed, in rev/min Delivery Capacity of a Pump In practice, the pump is rated in terms of how much fluid is supplied per unit of time, and expressed in terms of: Gallons per minutes (GPM) liters per minutes (L/min) k =Unit conversion constant

  10. Q = 0.641 (in3/rev) x1000(rev/min)/231(in3 /gal) Q = 2.77 (gal/min) K = unit conversion constant K = 231(gal/in3), because 1 gal = 231 in3 Example: Determination of Pump Capacity From the catalog of a hydraulic pump manufacturer, we can find the following information: Pump Delivery @ 1000 RPM & 0.641 in3/rev. Please try to determine the pump capacity: Q = D·n/K

  11. Commonly Used Hydraulic Pumps • Vane Pumps • Unbalanced vane pump • Balanced vane pump • Gear Pumps • External gear pump • Internal gear pump • Piston Pumps • Radial piston pump • Axial piston pump

  12. Vane Pumps • Construction with a round cam ring • Low cost • Limited pressure capability • Unbalanced hydraulic loading (side-loading) • Popular with fixed displacement pumps • Prevents side-loading • Limited pressure range • Relatively more expensive

  13. Gear Pumps • Fixed displacement only • High pressure capability • Unbalanced • Available as single, multiple or through drive version • One external gear and one internal gear • fixed displacement only • Unbalanced • More compacted in size

  14. Piston Pumps • Pistons arranged radially in a cylinder block • High efficient • medium-high pressure range • Rotating cylinder block (centrifugal force) • Pistons parallel to axis of the cylinder block • High efficient • medium-high pressure range • Compacted size

  15. Operation Principle of Piston Pumps

  16. M 1,000 psi P R H T M Needs for Variable-Displacement Pump Fixed displacement pumps discharge a set volume of fluid regardless of the system requirement. An amount of excess will generate heat to the system.

  17. Power Wasted in a Fixed-Displacement Pump Pump displacement “Corner” horsepower Pump output flow Metering point Wasted Power Relief setting Useable Power Operating pressure

  18. Operation of Variable Displacement

  19. Variable Displacement Pump • The volume of supplying fluids may be change based on demands Key Feature of a V-Displacement Pump • Fixed Displacement Pump • A fixed volume of fluids will be provided in each revolution

  20. Lecture Summary • Discussed a few basic theoretical equations, and their applications in hydraulic systems: • Principle of Positive displacement pumping • Key parameters of hydraulic pumps • Common types of hydraulic pumps • The need for variable displacement pumps

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