Thursday, 11 March 2021

Construction and Working of Dynamic Pumps (#biochemistry)(#centrifugalpumps)(#physics)(#turbines)(#ipumusings)

Construction and Working of Dynamic Pumps

Construction and Working of Dynamic Pumps (#biochemistry)(#centrifugalpumps)(#physics)(#turbines)(#ipumusings)


Dynamic pumps are the pumps in which kinetic energy is increased by increasing the fluid velocity. The velocity decreases prior to exit, converting the kinetic energy into potential energy. There are three types of dynamic pump: 

  1. Centrifugal pumps, 
  2. Propeller and 
  3. Turbines.


Centrifugal Pump

Construction and Working of Dynamic Pumps (#biochemistry)(#centrifugalpumps)(#physics)(#turbines)(#ipumusings)

Typical centrifugal pump

In these specific types of pumps, generation of head or pumping of liquid is affected by rotary motion of impellers. Impellers are rotating wheels in pumps. It consists of a rotating element, stationery element, suction pipe, strainer and foot valve; and delivery pump and delivery valve. Rotating element has a shaft and vaned rotor or impeller. The impeller is mounted on top of the shaft coupled with a driving unit which can be an internal combustible engine or an electric motor. The interaction between vanes and liquid causes the mechanical energy into flow energy of liquid.Stationery element consists of casing, stuffing box and bearings. Casing is an airtight chamber that surrounds the impeller. The spiral casing where the liquid leaves the impeller is called volute. In the volute the velocity heard of liquid is converted into pressure head.Packings are for preventing any kind of leakage from the pump system. Suction pipe connects the impeller to the sump from which liquid is to be lifted. It is airtight so that no packets of air are formed. Below the suction pipe there is a strainer to filter out any solid particles if present. Presence of such particles can have adverse effects on the performance. Foot valve is above the strainer to let the liquid into the pump for filling and prevent any backflow. Delivery pump discharges the liquid to the point of its use.

In ideal conditions of a frictionless pump, the mechanical efficiency of the pump is 100%. An ideal pump for a given speed, pump delivers a specific discharge rate for a specific head. But in actual practice, because of friction and other departures from perfection fall short for idealisation. These pumps have, in common, different kinds of impellers like open spider, enclosed or shrouded. It may be double suction as well. .[1]


Turbines

Turbines are devices that harnesses kinetic energy of fluids in rotational motion and thereafter used for doing some work. The four basic turbines are the water turbine, wind turbine, gas turbine and steam turbine. Water turbines are further classified into impulse and reaction turbines. In an impulse turbine, fluid is fired through a nozzle and the blades of turbine spins because of the impulse force. Pelton and cross flow turbines are impulse turbines. Reaction turbine has the kinds Francis and Kaplan.


Pelton turbine consists of a nozzle and flow regulating arrangement, runner and buckets, casing and braking jet. The nozzle and flow regulating arrangement has a penstock, nozzle and a spear. Fluid enters from the penstock and is fired through the nozzle. The spear moves axially and is used to control the fluid discharge from the nozzle. A runner is a circular disc on the periphery of which buckets are arranged. These buckets are made up of stainless steel and can be ellipsoidal or hemispherical.A splitter dived the bucket in two halves. Buckets, runner, inlet and breaking jet all are covered by a casing. This casing prevents the hydraulic splashes from leaving while working.Breaking jets are used to stop the runner when the nozzle is closed. When a jet strikes the splitter, the runner rotates. The kinetic energy of a jet is reduced when it hits the bucket and the direction of the jet changes due to the spherical shape of the bucket. [2]

Construction and Working of Dynamic Pumps (#biochemistry)(#centrifugalpumps)(#physics)(#turbines)(#ipumusings)


Typical Pelton Turbine


Propellers

Propellers are provided in ships and aircrafts. Propellers create thrust from rotational motion that pushes the body in the opposite direction of fluid. Propellers are blade-like structures which rotate in the fluid. Marine propellers are found in ships. These are made of corrosion resistant material as they have to be operated in water.  A ship propels on the basis of Newton's third law and Bernoulli principle. A pressure difference is created on the front side and aft of the blade and water is accelerated behind the blades. The thrust through the impeller is transmitted through the transmission which consists of the most engine, intermediate shaft and bearings, stern tube shaft and it’s bearing and eventually by the propeller itself.

Various types of propeller are available classified on the basis of number of blades as 3 , 4, 5 and 6 blades and by pitch of the blade as fixed and controllable pitch. [3]


Citations:

1. Centrifugal Pumps, Hydraulic pumps, (Fluid Mechanics By D S Kumar)

2. Pelton Turbine Working, Main Parts, Application with Diagram - Mechanical Booster; Mechanical Booster; weblink

3. Propeller, Types of Propellers and Construction of Propellers; Marine Insight; weblink


About the Author


Maitri Kumari, pursuing Biochemical Engineering from University of Chemical Technology (GGSIPU). 






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