Table of contents:
General Components of Centrifugal Pump
Definition of Important terms
Assumptions and Calculations
A centrifugal pump is a rotodynamic pump that uses a rotating impeller to increase the pressure of a fluid. Centrifugal pumps are commonly used to move liquids through a piping system. The fluid enters the pump impeller along or near to the rotating axis and is accelerated by the impeller, flowing radially outward into a diffuser or volute chamber, from where it exits into the downstream piping system. Centrifugal pumps are used for large discharge through smaller heads. In this context we are attempting to design a simple radial flow centrifugal pump which has a maximum efficiency of partial fulfillment of the course work on Turbo machinery. At first the necessary literature is reviewed to support our project work. The design is carried out by assuming the, mass flow rate and the Head, rotational speed. Standard consistent data are used in assumption for design. Finally the efficiency, blade angle and different velocities calculated.
A pump is a device used to move fluids, such as gases, liquids or slurries. A pump displaces a volume by physical or mechanical action. One common misconception about pumps is the thought that they create pressure. Pumps alone do not create pressure; they only displace fluid, causing a flow. Adding resistance to flow causes pressure.
TYPES OF PUMPS:
Pumps fall into two major categories as shown below: * Positive displacement pumps * Rotodynamic pums Their names describe the method for moving a fluid.
POSITIVE DISPLACEMENT PUMPS:
By definition, positive-displacement (PD) pumps displace a known quantity of liquid with each revolution of the pumping elements. This is done by trapping liquid between the pumping elements and a stationary casing. Pumping element designs include gears, lobes, rotary pistons, vanes, and screws.
A positive displacement pump can be further classified as: * a rotary-type, for example, the lobe, external gear, internal gear, screw, shuttle block, flexible vane or sliding vane pumps. * the wendelkolben pump or the helical twisted Roots pump. * the liquid ring vacuum pump.
A centrifugal pump uses a spinning "impeller" which has backward swept arms. |
These types of pumps have a number of characteristics: 1. Continuous energy 2. Conversion of added energy to increase in kinetic energy (increase in velocity) 3. Conversion of increased velocity to increase in pressure 4. Conversion of kinetic head to pressure head 5. Meet all heads like kinetic, potential, and pressure
This uses a jet, often of steam, to create a low pressure. This low pressure sucks in fluid and propels it into a higher pressure region.
Centrifugal Pump Design
A common type of kinetic or momentum-based pump is a centrifugal pump. A centrifugal pump consists of an impeller with blades rotating inside a casing. The impeller rotation reduces the pressure at the pump inlet causing fluid to flow into the pump. The fluid is then accelerated outward along the blades and exits the pump. Centrifugal pumps are suitable for use with low iscosity fluids that can withstand a moderate amount of shear.
The primary advantages of centrifugal pumps are simplicity, low purchase cost, and low maintenance. Since centrifugal pumps are momentum based, tolerances are not critical. They can also be used to pump low viscosity fluids. In addition, centrifugal umps provide a more steady fluid flow at the pump outlet.
However, a centrifugal pump has several limitations. It is inefficient at pumping fluids of high viscosity due to the large amount of work required to rotate the impellers in the presence of a viscous fluid. Because of the speed of the impeller, a fluid is