11.11 Pressure Generation Flashcards
what are the two clasifications of pumps?
- positive displacement
- non-positive displacement ( variable displacent )
what is a constant delivery pump?
a constant amount of displacement is forced through the outlet per rotation
what are gear type power pumps?
positive displacement pump that consists of two meshed gears that rotate in opposite ways
what is a gerotor pum
another positive displacement displacement pump with a smaller star shaped placed in an eccentric position, which drives an exterior housing
what is the most common type of main system pump?
piston pumps
what sort of displacement does a piston pump provide?
constant or variable displacement
a pump drive shaft is usually paired with a pump drive coupling, what is the purpose of this?
a short shaft with a set of male splines on the other and engage with the female splines in the pump shaft
what other benifit does a drive coupling give?
if the pump becomes unusually hard to turn or jammed, the coupling will shear, as a safety mechanism, to prevent damage to surrounding systems and itself
what are the two types of piston pump ?
- bent axis pump
- inline piston pump
what is a bent axis piston pump?
a constant displacement type pump that has an angular housing causing cylinders to dispce fluid
in an inline piston pump, what determines the displacement?
determined by the size and number of pistons, aswell as their stroke length
how is a vane type pump comstructed?
rotor is positioned off-centre within the sleeve, the vanes are mounted in the slots of the rotor, dividing the chamber into sections, when the pump rotates, the spring loaded vanes compress decreasing volume and expand increasing volume , allowing fluid to travel through the pump
what is special about a variable displacement pump?
allows flow rate and outlet pressure to be changed during operation
what causes pressure in a hydraulic system ?
restriction of fluid flow
what is the most common type of pump used in modern aircraft?
variable delivery or compensator controlled type
what is the term used to describe the generation of primary hydraulic power?
main pressurisation
where are the pumps providing primary pressure generation mounted?
generally on the accessory gearbox and is rotated by a shaft
what sort of displacement does the EDP provide ?
variable displacement
what is different between the ACMP and the EDP?
generally the same pump, however the pump is driven by an electrical motor instead of the engine gearbox
why might an aircraft have an ACMP installed?
installed as primary pumps and for use in emergencies or during ground operation when engines are not running
when are air driven pumps usually used?
used as demand pumps to supplement the primary pumps
what sort of displacement does an ADP provide?
variable displacement
where are hand pumps used?
in older aircraft or in newer aircraft incase of an emergency
why might a hand pump be installed?
intalled for testing purposes, emergencies and to service the reservoirs from a single refilling station
