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Centrifugal pump by fdhjkl rfghjtkl
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Centrifugal pump |
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According to Reti, the Brazilian soldier and historian of science, the first machine that could be characterized as a centrifugal pump was a mud lifting machine which appeared as early as 1475 in a treatise by the Italian Renaissance engineer Francesco di Giorgio Martini. True centrifugal pumps were not developed until the late 1600's, when Denis Papin made one with straight vanes. The curved vane was introduced by British inventor John Appold in 1851.
Radial Flow Centrifugal Pump Principle
A centrifugal pump works by converting kinetic energy into potential energy measurable as static fluid pressure at the outlet of the pump. This action is described by Bernoulli's principle.
With the mechanical action of an electric motor or similar, the rotation of the pump impeller imparts kinetic energy to the fluid through centrifugal force. The fluid is drawn from the inlet piping into the impeller intake eye and is accelerated outwards through the impeller vanes to the volute and outlet piping.
As the fluid exits the impeller, if the outlet piping is too high to allow flow, the fluid kinetic energy is converted into static pressure. If the outlet piping is open at a lower level, the fluid will be released at greater speed.
A centrifugal pump containing two or more impellers is called a multistage centrifugal pump. The impellers may be mounted on the same shaft or on different shafts.
If we need higher pressure at the outlet we can connect impellers in series.
If we need a higher flow output we can connect impellers in parallel.
All energy added to the fluid comes from the power of the electric or other motor force driving the impeller.
Efficiency of large pumps
Unless carefully designed, installed and monitored, pumps will be, or will become inefficient, wasting a lot of energy. Pumps need to be regularly tested to determine efficiency.
The energy usage in a pumping installation is determined by the flow required, the height lifted and the length and friction characteristics of the pipeline. The power required to drive a pump (Pi), is defined simply using SI units by:
Single Stage Radial Flow Centrifugal Pump
Pi is the input power required (W)
is the fluid density (kg/m3)
g is the gravitational constant (9.81 m/s2)
H is the energy Head added to the flow (m)
Q is the flow rate (m3/s)
is the efficiency of the pump plant as a decimal
The head added by the pump (H) is a sum of the static lift, the head loss due to friction and any losses due to valves or pipe bends all expressed in metres of water. Power is more commonly expressed as kW (103 W) or horsepower (multiply kW by 0.746). The value for the pump efficiency may be stated for the pump itself or as a combined efficiency of the pump and motor system.
The energy usage is determined by multiplying the power requirement by the length of time the pump is operating.
Problems of Centrifugal Pumps
Cavitation - The NPSH of the system is too low for the selected pump
Wear of the Impeller - can be worsened by suspended solids
Corrosion inside the pump caused by the fluid properties
Overheating due to low flow
Leakage along rotating shaft
Lack of Prime - centrifugal pumps must be filled (with the fluid to be pumped) in order to operate
Centrifugal pumps for solids Control
An oilfield solids control system needs many centrifugal pumps to sit on or in mud tanks. The types of centrifugal pumps used are sand pumps, submersible slurry pumps, shear pumps, and charging pumps. They are defined for their different functions, but their working principle is the same.
Small centrifugal pumps (e.g. for garden fountains) may be magnetically coupled to avoid leakage of water into the motor. The motor drives a rotor carrying a pair of permanent magnets and these drag round a second pair of permanent magnets attached to the pump impeller. There is no direct connection between the motor shaft and the impeller so no gland is needed and, unless the casing is broken, there is no risk of leakage.
Net Positive Suction Head (NPSH)
Specific Speed ( Ns or Nss )
Ladislao Reti, rancesco di Giorgio (Armani) Martini's Treatise on Engineering and Its Plagiarists, Technology and Culture, Vol. 4, No. 3. (Summer, 1963), pp. 287-298 (290)
Categories: Fluid dynamics Pumps Oilfield terminologyHidden categories: Articles needing additional references from March 2009 All articles needing additional references I am an expert from China Agriculture Net, usually analyzes all kind of industries situation, such as motorized curtain tracks , decorative shower curtain rods.
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