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Pump

A pump is a mechanical device used to move liquids or gases. Also the heart is an essential pump in humans and animals to move the blood around.

The earliest pump was described by Archimedes around 300 BC and is known as the Archimedes screw pump. Pumps work by using mechanical forces to push the material, either by physically lifting, or by the force of compression.

Table of contents

Types of pump Pumps fall into two categories: positive displacement pumps, which force fluid from one sealed chamber to another with little leakage, and dynamic pumps, which use the momentum of the fluid to move it across an unsealed chamber.

Positive displacement pump

This type of pump forces the fluid from one chamber to another by reducing the volume of the first chamber while increasing the volume of the second. Such a pump produces a constant flow regardless of intake pressure or outlet pressure, unless the intake pressure drops below a certain limit, causing cavitation, or the outlet pressure exceeds the capacity of the pump, causing pump failure. These pumps often have a relief valve to prevent the latter problem.

Reciprocating positive displacement pump

Rotary positive displacement pump

Dynamic pump

The dynamic pump causes the fluid to move from inlet to outlet under its own momentum. This type tends not to need a release valve, because as the outlet pressure rises the pump simply becomes less efficient. Fluid motion can be rotary, as in centrifugal pumps, or linear, as in reciprocating dynamic pumps.

Rotary dynamic (centrifugal) pump

This type of pump contains a rotating part called the impeller inside a stationary cavity called the volute. The impeller forces the fluid to rotate, and thereby to move from inlet to outlet under its own momentum.

Examples:

Linear or reciprocating dynamic pump

  • no examples yet
The Vortec Transvector is one example of a no-moving-parts air pump. A stream of high pressure air is discharged adjacent a surface, and drags ambient air along with it. I have tested this device and can report that the higher the pressure of the primary air supply, the worse the performance. In other words, there's no way to provide enough high pressure air to make it fly with the compressor or a tank onboard. The compressor or tank would simply be too heavy.

It is an example of an ejector pump. Steam ejectors are used to cool bleach water so it will retain the chlorine, which comes out at high temps. They simply discharge a boiler into a tube, sucking water vapor out from above a sealed tank. The water inside slowly cools. Not very efficient, but does something useful with waste steam, simply.

Ejectors are used to augment the flow in turbojets, near the aft end.

The Coanda effect[?] is the tendency of such a moving stream to cling to a surface, even when the surface deflects the stream away from its original direction. The surface seems to pull the stream.



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