Pumps, Bearings, and Turbines_DOT2 Flashcards
How does pressure affect a pumps delivery rate within a non-positive displacement pump?
As a flow from the pump is blocked or resisted, the pressure increases. This pressure works against the centrifugal force produced by the pump an reduces the pump delivery rate (velocity)
Positive displacement pumps?
As each pumping chamber begins to increase in size, it expands, which causes pressure within the chamber to decrease to below atmospheric pressure. The slight vacuum causes fluid to flow into the tank, which is forced into the pump outlet due to the atmospheric pressure. Slots in the port plate or especially shaped so that fluid enters pumping chambers as they increase in size and this forced out of the chambers as a decrease in size creating a system of high pressure.
External gear pumps?
Are a type of pump where chambers are formed in spaces between gear teeth and the pump housing
The delivery rate of a pump depends on what two characteristics?
Displacement: which is amount of fluid delivered each time the drive shaft rotates.
Drive speed: the number of times the drive shaft rotates each minute. To change the delivery rate, when would vary either the pumps displacement or the speed of the drive shaft rotation period
Cavitation?
Cavitation occurs at any point in a hydraulic system where reduction of pressure reaches a point where water vapor is formed. A partial vacuum is maintained at the turbine discharge of reaction turbines to create to increase the power output of the unit. If this vacuum is increased sufficiently, the water will begin to boil. In the process bubbles of water vapor form and, as the pressure increases, they collapse with violent action occurring. This process is cavitation it should not be confused with pinning or erosion or exposed surfaces which is a direct result of corrosion.
