ABE 223 ABE Principles – Machine systems Pumps and Motors Tony Grift Dept. of Agricultural & Biological Engineering University of Illinois

Agenda Units, Pumps, Pressure Relief Valve Pressure, Flow, Torque and Power in pump/motors Volumetric and Torque efficiency of pump/motors Pump implementations

Hydraulic Units (SI) Pascal Newton Watt

Control can take place in various ways Control can take place in various ways. Power is pressure times flow rate Pressure control Pressure relief valve Pressure reducing valve (regulator) Pressure compensation: Only provide the pressure needed to move the load(s). In idle reduce energy loss by providing a open center condition Pressure compensated pump. Make the pressure independent of the flow required to move the load at a preset speed. Deal with multiple cylinders that need to move simultaneously Flow control Throttle (needle valve, very crude, Orifice equation applies) Pressure compensated Flow Control Valve: Assure a preset flow rate independent of the pressure drop across the valve Pressure and Flow control Load sensing systems: combine pressure and flow control to reduce energy losses

Choice of pump depends on these factors Application Max and working Pressure and Flow rate requirements Constant rate / Variable rate Pump efficiency Leakage Noise level Contamination sensitivity Price

Pump ‘family tree’

Video 8: Power units (3:26) Power supply unit Components Converts Mechanical energy into hydraulic energy Hydraulic Fluid is conditioned (cooled, cleaned) Components Drive motor Safety valve Oil reservoir Pump External Gear pump function (constant delivery) Where teeth unmesh, volume increases, oil enters Where teeth mesh, volume decreases, oil leaves Pressure only builds when there is a resistance (load) Safety valve needed to prevent failure when cylinder stalls Pressure Relief Valve diverts flow back to tank when cylinders are stalled Reservoir Cools oil Cleans oil from suspended particles, water and air which takes time (Capacity) Filters trap impurities 70% of all malfunctions are due to impurities

Mechanical Torque in a pump/motor In case of a motor shaft, the Work can be found by multiplying a force through a distance. Suppose we assume a force at a distance . The total work per radian of the shaft is now equal to

Mechanical Power in a pump/motor The power is now equal to this value divided by the time per radian. If the shaft is turning at it takes seconds per radian. Since for Power we have to divide the Work by time, this leads to:

Hydraulic Power in pump/motor ( )

Pump/Motor flow is proportional to the speed of rotation and the displacement per revolution Pump displacement is a volume per angular displacement (radian). Assuming the volumetric efficiency is 1.0 (no leakage) More realistic, with Volumetric Efficiency (why in numerator?)

Torque Required to drive a pump is proportional to Pressure (No losses here) More realistic, with Torque Efficiency (why in the denominator?)

Power Efficiency of Pumps From before: And Power Efficiency: Without loss Efficiencies

Data sheet Eaton MHT vane pump

Types of Pumps and Motors External Gear Internal Gear Vane Axial Piston Radial Piston

External Gear pump Poorly sealing Low flow rates Low pressures Fixed displacement Low cost

Internal Gear pump Poorly sealing Low flow rates Medium pressures Fixed displacement Medium cost

Vane pump Medium sealing Higher pressures Inexpensive Fixed or variable flow rate

Axial piston pump with swash plate Axial piston pump with swash plate. In this case the swash plate angle is variable, which results in a variable delivery pump Excellent sealing High pressures Relatively simple design Variable flow rate No need for valves Expensive

Axial piston pump with swash plate Axial piston pump with swash plate. In this case the swash plate angle is constant, which results in a constant delivery pump Here fixed flow rate

Radial piston pump with variable rate through changing eccentricity between shaft and ‘pintle’ Excellent sealing High pressures Relatively expensive Variable flow rate Valves are needed Complex design

Radial piston pump with variable rate through changing eccentricity between shaft and ‘pintle’ Excellent sealing High pressures Relatively expensive Variable flow rate

External Gear Fixed Displacement

Pump ‘family tree’

Dept. of Agricultural & Biological Engineering University of Illinois ABE 223 ABE Principles – Machine systems Pumps and Motors The End Tony Grift Dept. of Agricultural & Biological Engineering University of Illinois