Lekce 1: Axial Piston Pumps and Motors
Kapitola 1: Axial Piston Pumps and Motors
Axial piston pump is a type of a positive displacement pump with several pistons arranged in a circular array inside a rotor. It is usually used as an independent pump, a hydraulic motor or an air conditioning compressor.
Description
Axial piston pumps have reciprocating pistons. Their name is derived from the fact that the pistons move axially. The pistons are located at the opposite sides of the cylinder block and they bear against a cam. As the shaft rotates, the movement of the cam results in reciprocation of the pistons, and pumping. The displacement of the pump is determined by the so called cam angle, that is the angle between the cam plane and the axis of rotation. The cam angle is usually fixed, but in some types of the axial piston pumps the cam is moveable, which enables them to change the angle during their operation and thus vary their displacement.
Manufacture
Axial piston pumps are quite difficult to manufacture, because the rotary parts have to be able to turn very quickly (often at a speed of several thousand revolutions per minute) and at the same time the mating faces between the piston-cylinder arrangement and the body of the pump have to be almost perfectly watertight. This is very demanding for the precision of the production of this type of pumps.
Vocabulary
axial piston pump – axiální pístové čerpadlo
positive displacement pump – objemové čerpadlo
array – rozložení, rozmístění
air conditioning – klimatizace
reciprocating – s vratným pohybem; pístový
reciprocate – pohybovat se vpřed a vzad
piston – píst
be located – být umístěn
derived – odvozen
axially – podél osy
cylinder – válec
bear against – opírat se o
cam – vačka
shaft – hřídel
rotate – rotovat
movement – pohyb
pumping – čerpání
displacement – objem válce
determined – daný, určený
angle – úhel
plane – rovina
axis of rotation – osa rotace
fixed – pevný
moveable – pohyblivý
enable – umožnit
vary – měnit
manufacture – vyrobit
rotary – rotační
revolutions per minute – otáčky za minutu
mating faces – dotýkající se části
watertight – vodotěsný
precision – přesnost
Obrázky a fotografie použité v této kapitole pochází ze stránek {Wikimedia Commons XH http://commons.wikimedia.org}, kde byly zveřejněny pod licencí {GNU FDL XH http://commons.wikimedia.org/wiki/Commons:GNU_Free_Documentation_License}.
Kapitola 2: Cvičení
- Studenti zpracují na téma Axial Piston Pumps and Motors powerpointovou prezentaci.
Kapitola 3: Kontrolní otázky
- Can you briefly describe axial piston pumps?
- Why are they called "axial"?
- Why are they difficult to manufacture?
Kapitola 4: Autotest
- Axial piston pumps are a type of:
- Pistons of this type of pumps are located:
- How is the displacement of the pump determined?
- How fast do rotary parts of the axial piston pumps turn?
- The cam angle
Lekce 2: Radial Piston Pumps and Motors
Kapitola 1: Radial Piston Pumps and Motors
Construction
Radial piston pumps are a type of piston pumps, where pistons are, unlike with the axial piston pumps, arranged in a radial direction, symmetrically around the drive shaft. The shaft is usually hollow and eccentric.
The types, where the cylinders are filled from inside of the pump, are called inside impinged radial piston pumps. Those, which are filled from outside, are called outside impinged radial piston pumps.
Operation
The way of operation can be seen on the picture. The positions of the outer ring with pumping piston and the hollow shaft are eccentric, thanks to which the different strokes of the piston are enabled. The suction process begins at the inner dead centre (IDC). As the shaft rotates, the suction area is filled with liquid. After it gets to the outer dead centre, the liquid starts to be driven out again.
Advantages and disadvantages
Radial piston pumps are very efficient and highly reliable. They work very quietly. They can generate quite high pressure (up to 1,000 bars) and because of hydrostatically balanced parts very high load at lowest speed is possible. There are now axial internal forces at the drive shaft bearing.
The main disadvantage in comparison with the axial piston pump are bigger radial dimensions, which can be partly compensated with smaller size in axial direction.
Vocabulary
piston pump – pístové čerpadlo
radial piston pump – radiální pístové čerpadlo
piston – píst
axial piston pump – axiální pístové čerpadlo
shaft - hřídel
drive shaft – hnací hřídel
hollow shaft – dutý hřídel
eccentric – výstředný, nesoustředný
cylinder – válec
dead centre - úvrať
inner – vnitřní
outer – vnější
rotate – rotovat, otáčet se
suction – sání
liquid – tekutina
drive (drove, driven) – hnát
efficient – výkonný
reliable – spolehlivý
generace – vytvářet
pressure – tlak
up to – až
balanced – vyvážený
load – zatížení, zátěž
speed – rychlost
axial – axiální, ve směru osy
internal forces – vnitřní síly
bearing – ložisko
radial – radiální, kolmý k ose
Obrázky a fotografie použité v této kapitole pochází ze stránek {Wikimedia Commons XH http://commons.wikimedia.org}, kde byly zveřejněny pod licencí {GNU FDL XH http://commons.wikimedia.org/wiki/Commons:GNU_Free_Documentation_License}.
Kapitola 2: Cvičení
- Studenti zpracují na téma Radial Piston Pumps and Motors powerpointovou prezentaci.
Kapitola 3: Kontrolní otázky
- Can you briefly describe radial piston pumps?
- What is the main difference between radial and axial piston pumps?
- What is the main difference between outside and inside impinged radial piston pumps?
Kapitola 4: Autotest
- Pistons of radial piston pumps are
- The shaft is usually
- How high pressure can radial piston pumps generate?
- What is their main disadvantage in comparison with axial piston pumps?
- What can we say about their noise?
Lekce 3: Rotary Vane Pumps and Motors
Kapitola 1: Rotary vane pumps and motors
A rotary vane pump is a type of a positive-displacement pump, invented by a Canadian engineer Charles C. Barnes in 1874.
Basic description
Rotary vane pumps contain two or more vanes on a rotor, which rotates inside a cavity. The rotor is placed in the cavity eccentrically. The vanes can have various lengths. They are usually tensioned (using a spring) so that they can keep contact with the walls during the rotation. They divide the cavity into two chambers.
Way of operation
Because the rotor of rotary vane pumps is placed inside their cavity eccentrically, the vanes have to slide into and out of it to keep contact with the walls and seal the chambers. As the vanes rotate, the chamber on the intake side increases in volume and is filled with fluid, which is driven in by the inlet pressure (often the pressure from the atmosphere is sufficient). After the chamber gets to the discharge side of the pump, it starts decreasing in volume, and the fluid is forced to flow out of the pump. Each rotation of the vanes conveys the same volume of the fluid.
Some vane pumps can be also used as a vane motor. In this case the rotor is forced to spin by the unbalanced pressure of the fluid on the vanes.
Application
Rotary vane pumps are often used in some high pressure car equipment, such as superchargers, power steering and automatic transmission boxes. Midrange fluid pressure applications include fountain drink dispensers or espresso coffee machines. Sometimes also low pressure applications can be seen, such as secondary air injection used for automobile emissions control, or in some air conditioners, where it pumps a refrigerant.
Vocabulary
rotary vane pump – rotační lamelové čerpadlo
positive-displacement pump – objemové čerpadlo
vane – lamela
cavity – dutina
eccentric – výstřední, mimostředový
tensioned – napjatý
spring – pružina
chamber – komora
slide – klouzat
seal – těsnit
intake – sání
volume – objem
increase in volume – nabývat na objemu
decrease in volume – ztrácet objem
fluid – kapalina
drive – hnát, pohánět
inlet – vstup
inlet pressure – vstupní tlak
sufficient – dostatečný
discharge – výtlak
forced – nucen
convey – dopravit
vane motor – lamelový hydromotor
spin – otáčet se
unbalanced – nevyvážený, nerovnoměrný
application – využití
supercharger – turbodmychadlo
power steering – posilovač řízení
automatic transmission box – automatická převodovka
midrange – střední, středního rozsahu
fountain drink dispenser – výčepní zařízení, výčepní automat
coffee machine – kávovar
secondary air injection – vhánění přídavného vzduchu
automobile emissions control – kontrola emisí motorových vozidel
air conditioner – klimatizační zařízení
refrigerant – chladivo, chladicí kapalina, chladicí plyn
Obrázky a fotografie použité v této kapitole pochází ze stránek {Wikimedia Commons XH http://commons.wikimedia.org}, kde byly zveřejněny pod licencí {GNU FDL XH http://commons.wikimedia.org/wiki/Commons:GNU_Free_Documentation_License}.
Kapitola 2: Cvičení
- Studenti zpracují na téma Rotary Vane Pumps and Motors powerpointovou prezentaci.
Kapitola 3: Kontrolní otázky
- What are the main parts of this type of pumps?
- Can you describe their way of operation?
- Can you say some examples of their application?
Kapitola 4: Autotest
- How many vanes are there?
- Where are the vanes located?
- The rotor is placed
- When the vanes rotate, they convey
- Rotary vane motors
Lekce 4: Gear Pumps and Gear Motors
Kapitola 1: Gear Pumps and Gear Motors
Basic information
Gear pumps are a type of positive displacement pumps, which use gears to pump fluid. They are one of the most common types of hydraulic pumps. They are also often used for pumping various chemicals with certain viscosity. They belong among the pumps, which convey a fixed amount of fluid with every rotation.
Operation
Rotating gears develop underpressure on the intake side, making the fluid to flow in. Then it is conveyed to the discharge side, where the gears push it out. The meshing of the gears has to be very tight so that the fluid could not leak backwards.
Types
Two main types of gear pumps are designed.
Gear motor
Some gear pumps can also work as a motor. Such a motor has two gears, one is driven and the other is idler. High pressure fluid flows aroung the gears to the outlet port. The driven gear rotates, meshing with the idler gear, and does not allow the fluid to flow back.
gear pump – zubové čerpadlo
positive displacement pump – objemové čerpadlo
gear – ozubené kolo
pump – čerpat
fluid – kapalina
hydraulic pump – hydraulické čerpadlo
viscosity – viskozita
convey – dopravit
fixed – stálý
amount – množství
develop – vytvářet
underpressure – podtlak
intake – sání
discharge – výtlak
meshing – proplétání
mesh – proplétat se
leak – unikat, prosakovat
backwards – nazpět
external gear pump – klasické zubové čerpadlo
internal gear pump – excentrické zubové čerpadlo
spur gear – ozubené kolo s přímými zuby
gear motor – zubový hydromotor
driven gear – poháněné ozubené kolo
idler gear – vložené ozubené kolo
pressure – tlak
outlet port – výstup, vývod
Obrázky a fotografie použité v této kapitole pochází ze stránek {Wikimedia Commons XH http://commons.wikimedia.org}, kde byly zveřejněny pod licencí {GNU FDL XH http://commons.wikimedia.org/wiki/Commons:GNU_Free_Documentation_License}.
Kapitola 2: Cvičení
- Studenti zpracují na téma Gear Pumps and Motors powerpointovou prezentaci.
Kapitola 3: Kontrolní otázky
- Why are "gear pumps" called this way?
- Can you brifly describe their way of operation?
- What is the main difference between external and internal gear pumps?
Kapitola 4: Autotest
- Gear pumps
- When they rotate,
- On the intake side the rotating gears
- Why does the fluid not leak backwards?
- Internal gear pumps