A gear pump uses the meshing of gears to pump fluid by displacement.[1] They are one of the most common types of pumps for hydraulic fluid power applications. The gear pump was invented around 1600 by Johannes Kepler.[2]
An exploded view of an external gear pumpFluid flow in an external gear pumpFluid flows from left to right in this internal gear pump.Oil pump from a scooter engine
Gear pumps are also widely used in chemical installations to pump high-viscosity fluids. There are two main variations: external gear pumps which use two external spur gears, and internal gear pumps which use an external and an internal spur gear (internal spur gear teeth face inwards, see below). Gear pumps provide positive displacement (or fixed displacement), meaning they pump a constant amount of fluid for each revolution. Some gear pumps are designed to function as either a motor or a pump.
As the gears rotate they separate on the intake side of the pump, creating a void and suction which is filled by fluid. The fluid is carried by the gears to the discharge side of the pump, where the meshing of the gears displaces the fluid. The mechanical clearances are small— on the order of 10 μm. The tight clearances, along with the speed of rotation, effectively prevent the fluid from leaking backwards.
The rigid design of the gears and houses allow for very high pressures and the ability to pump highly viscous fluids.
Many variations exist, including helical and herringbone gear sets (instead of spur gears), lobe shaped rotors similar to Roots blowers (commonly used as superchargers), and mechanical designs that allow the stacking of pumps. The most common variations are shown below (the drive gear is shown blue and the idler is shown purple).
Internal gear (crescent internal gear) pump design for high-viscosity fluids
External precision gear pumps are usually limited to maximum working pressures of around 210 bars (21,000 kPa) and maximum rotation speeds around 3,000 RPM. Some manufacturers produce gear pumps with higher working pressures and speeds but these types of pumps tend to be noisy and special precautions may have to be made.[3]
Suction and pressure ports need to interface where the gears mesh (shown as dim gray lines in the internal pump images). Some internal gear pumps have an additional, crescent-shaped seal (shown above, right). This crescent functions to keep the gears separated and also reduces eddy currents.
Pump formulas:
Flow rate = pumped volume per rotation × rotational speed
Power = flow rate × pressure
Power in HP ≈ flow rate in US gal/min × (pressure in lbf/in2)/1714
Efficiencyedit
Gear pumps are generally very efficient, especially in high-pressure applications.
Factors affecting efficiency:
Clearances: Geometric clearances at the end and outer diameter of the gears allows leakage and back flow. However sometimes higher clearances help reduce hydrodynamic friction and improve efficiency.
Gear backlash: High backlash between gears also allows fluid leakage. However, this helps to reduce wasted energy from trapping the fluid between gear teeth (known as pressure trapping).
Applicationsedit
Petrochemicals: Pure or filled bitumen, pitch, diesel oil, crude oil, lube oil etc.
Chemicals: Sodium silicate, acids, plastics, mixed chemicals, isocyanates etc.
Paint and ink
Resins and adhesives
Pulp and paper: acid, soap, lye, black liquor, kaolin, lime, latex, sludge etc.
Food: Chocolate, cacao butter, fillers, sugar, vegetable fats and oils, molasses, animal food etc.
Aviation: Jet engine fuel pumps
Developmentedit
The invention of the gear pump is not uniformly solved. On the one hand, it goes back to Johannes Kepler in 1604; on the other hand, Gottfried Heinrich Graf zu Pappenheim is mentioned, who is said to have constructed the capsule blower with two rotating axes for pumping air and water. Pappenheim should have adopted Kepler’s design without mentioning his name.
^Pinches, M J (2000). Kempe's Engineers Year-Book, p. 2070. Miller Freeman, Kent. ISBN0863824420.
External linksedit
Wikimedia Commons has media related to Gear pump.
External gear pump description
Internal gear pump description
January 01, 1970
gear, pump, this, article, needs, additional, citations, verification, please, help, improve, this, article, adding, citations, reliable, sources, unsourced, material, challenged, removed, find, sources, news, newspapers, books, scholar, jstor, february, 2010,. This article needs additional citations for verification Please help improve this article by adding citations to reliable sources Unsourced material may be challenged and removed Find sources Gear pump news newspapers books scholar JSTOR February 2010 Learn how and when to remove this message A gear pump uses the meshing of gears to pump fluid by displacement 1 They are one of the most common types of pumps for hydraulic fluid power applications The gear pump was invented around 1600 by Johannes Kepler 2 An exploded view of an external gear pump Fluid flow in an external gear pump Fluid flows from left to right in this internal gear pump Oil pump from a scooter engine Gear pumps are also widely used in chemical installations to pump high viscosity fluids There are two main variations external gear pumps which use two external spur gears and internal gear pumps which use an external and an internal spur gear internal spur gear teeth face inwards see below Gear pumps provide positive displacement or fixed displacement meaning they pump a constant amount of fluid for each revolution Some gear pumps are designed to function as either a motor or a pump Contents 1 Theory of operation 2 Efficiency 3 Applications 4 Development 5 See also 6 References 7 External linksTheory of operation editAs the gears rotate they separate on the intake side of the pump creating a void and suction which is filled by fluid The fluid is carried by the gears to the discharge side of the pump where the meshing of the gears displaces the fluid The mechanical clearances are small on the order of 10 mm The tight clearances along with the speed of rotation effectively prevent the fluid from leaking backwards The rigid design of the gears and houses allow for very high pressures and the ability to pump highly viscous fluids Many variations exist including helical and herringbone gear sets instead of spur gears lobe shaped rotors similar to Roots blowers commonly used as superchargers and mechanical designs that allow the stacking of pumps The most common variations are shown below the drive gear is shown blue and the idler is shown purple nbsp External gear pump design for hydraulic power applications nbsp Internal gear Gerotor pump design for automotive oil pumps nbsp Internal gear crescent internal gear pump design for high viscosity fluids External precision gear pumps are usually limited to maximum working pressures of around 210 bars 21 000 kPa and maximum rotation speeds around 3 000 RPM Some manufacturers produce gear pumps with higher working pressures and speeds but these types of pumps tend to be noisy and special precautions may have to be made 3 Suction and pressure ports need to interface where the gears mesh shown as dim gray lines in the internal pump images Some internal gear pumps have an additional crescent shaped seal shown above right This crescent functions to keep the gears separated and also reduces eddy currents Pump formulas Flow rate pumped volume per rotation rotational speed Power flow rate pressure Power in HP flow rate in US gal min pressure in lbf in2 1714Efficiency editGear pumps are generally very efficient especially in high pressure applications Factors affecting efficiency Clearances Geometric clearances at the end and outer diameter of the gears allows leakage and back flow However sometimes higher clearances help reduce hydrodynamic friction and improve efficiency Gear backlash High backlash between gears also allows fluid leakage However this helps to reduce wasted energy from trapping the fluid between gear teeth known as pressure trapping Applications editPetrochemicals Pure or filled bitumen pitch diesel oil crude oil lube oil etc Chemicals Sodium silicate acids plastics mixed chemicals isocyanates etc Paint and ink Resins and adhesives Pulp and paper acid soap lye black liquor kaolin lime latex sludge etc Food Chocolate cacao butter fillers sugar vegetable fats and oils molasses animal food etc Aviation Jet engine fuel pumpsDevelopment editThe invention of the gear pump is not uniformly solved On the one hand it goes back to Johannes Kepler in 1604 on the other hand Gottfried Heinrich Graf zu Pappenheim is mentioned who is said to have constructed the capsule blower with two rotating axes for pumping air and water Pappenheim should have adopted Kepler s design without mentioning his name See also editGerotor Hydraulic pump Vane pumpReferences edit Welcome to the Hydraulic Institute Pumps org Archived from the original on 2013 06 26 Retrieved 2013 08 18 Frank Prager Kepler as inventor Vistas in Astronomy Volume 18 1975 Pages 887 889 https doi org 10 1016 0083 6656 75 90184 1 Pinches M J 2000 Kempe s Engineers Year Book p 2070 Miller Freeman Kent ISBN 0863824420 External links edit nbsp Wikimedia Commons has media related to Gear pump External gear pump description Internal gear pump description Retrieved from https en wikipedia org w index php title Gear pump amp oldid 1219856263, 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