Positive Displacement & Axial Pumps

Created by: Evan Croft, Chandler Croneigh & Jon Cronin

CIVE 401—Spring 2015

Axial Pumps Type of Centrifugal Pump

Applies a centrifugal force to the fluid moving through the impeller

Centrifugal force becomes greater than gravity force holding water in place

Fluid rises and flows out of the pipe

Conversion of energy using principles of angular momentum

Momentum is conserved along axis of the pump

Configuration & Operation

Axial Pump Consists of:

Rotating element known as the “impeller”

Closed housing to seal pressurized water inside

Vanes within housing guide and direct flow through pump

Motor connected to shaft supplies power to impeller

Hydraulic Operations

Impeller draws water in through the eye to a region of low pressure

Water is directed toward the outside of the housing to a region of high pressure

Energy is converted from velocity head at the eye of the impeller to pressure head at the outlet

Positive Displacement Pumps

Two Types Reciprocating

Plunger/Piston

Single Acting: Fills pump cylinder with fluid on suction stroke and forces fluid out on discharge stroke.

Diaphragm

Uses reciprocating action of diaphragm and valves to trap fluid and force it into discharge pipe

Work by drawing in a fixed amount of fluid and forcing it out of the pump at a constant rate.

Diaphragm pump in use at the water quality lab at CSU. Pumps water through electro-coagulation device and discharges it into small reservoir.

Positive Displacement Pumps: Types

Rotary Rotating mechanism

draws fluid in from region of low pressure and discharges to a region of high pressure

Self Priming

Typically located above the fluid source

i.e. A drinking straw in a glass of water

Advantages/DisadvantagesPDPs Advantages PDPs DisadvantagesFixed volume of fluid ejected each time Oscillating PDPs less suitable with high speeds

Continuous flow despite differential pressure and/or high pressure differentials

Safety issues can arise due to ability of pump to produce extremely high pressures requiring use of pressure-release mechanism

Handle high-viscosity liquids efficiently Larger number of parts prone to wear

Create suction lift Cannot achieve high flow rates necessary for industrial applications

Axial Pump Advantages Axial Pump Disadvantages

Wide range of pressure, flow & capacities Not well-suited for high-pressure applications

Fewer moving parts Do not handle high-viscosity fluids well

No excess pressure build-up No suction lift capabilities

Produce high flow rates necessary for industrial applications

Common ApplicationsPositive Displacement Pumps Axial Pumps

Rotary Reciprocating Single Suction

Metering Suction Lifti.e. wells

Sewage handling—Domestic, Industrial, Commercial

Pulsed Deliveryi.e. fuel injection for engines

Agriculture—Lift water for irrigation and drainage

Wastewater treatment plants

Governing Equation #1 –Pump HeadBernoulli’s Equation:

Where: = Pressure Head, = Velocity Head, = Elevation Head,

= Friction and Minor Losses Through Pipe, = Pump Head

Conditions:

0 ( at surface)

0 ( 0 at surface)

Yields:

∆

Governing Equation #2 –Pump PowerDefinition:

∗

or∗

∗ ∗ ∗ ∗ ∗

∗ ∗

Conversions:∗ ∗

550 fromEnglishunitstoHorsepower

∗ ∗745 fromEnglishunitstokiloWatts

Example #1The pipe system shown must provide a discharge rate of 10 ft3/s. Determine the power in HP required by the pump.

Using Governing Equation #1:

∆

∆ 5

Find :

. ∗ 1.8 , 0.04, 1.0 , 0.9

/∗

12.73 /.

∗ . /2.52

Example #1 (continued)

∗ 2 1.8 0.04 1.0 0.9 ∗ 2.52ft 9.41ft

∆ 5 9.41 14.41

Using Governing Equation #2:

∗ ∗62.4

∗ 14.41 ∗10

8,994∗

Conversion:∗ ∗

5508,994550 16.4

Example #2If the pipe system shown must provide a flow

rate of 4ft3/s, would a displacement pump as shown be be adequate to provide the needed power?

Using Governing Equation #1:

∆

∆ 2

Find :

. ∗.

1.6 , 0.5, 1.0

/∗ .

20.37 /.

∗ . /6.44

Example #2 (continued)

∗ 2 1.6 0.5 1.0 ∗ 6.44ft 19.98ft

∆ 2 20 22

4 ∗ 450 1,800

According to the pump classification chart,

the pump type should be “axial flow”.

Therefore, a linear displacement pump

is adequate for these conditions.

Axial Flow Pump Applications

Pumps used for high flow and low head

Flood Control

Agricultural Irrigation

Raw Water Intake at Water Treatment Plant

Raw Water Intake at Coal-Fired Power Plant

Flood Control

Flood control system in New Orleans, Louisiana

Storm water temporarily stored in a canal

Storm water pumped from a canal to a lake

Protects lives and property during floods

Agricultural Irrigation

Simple pump system is relatively inexpensive, easy to operate, and transportable

Moves large flows of water from nearby waterway to crops

Improves agricultural production which drives subsistence and economy

Displacement Pump Applications

Pumps used for constant flow of various fluids (e.g. air, water, oil, etc.)

Pump for water filtration system (Rotary Pump)

Pump water from well (Reciprocating Pump)

Water Treatment Plant –Membrane Filtration

Water Treatment Plant in Beijing, China

14 rotary pumps achieve a total output of up to 10,000 m3/h

Direction of flow is easily reversed to backwash filters

Low maintenance pumps may be serviced on-site by plant operators

Hand Pump for Well Water

Reciprocating pumps system is relatively inexpensive to install and easy to operate

Provides access to groundwater

Improves quality of life

Conclusion

Axial Pumps

Type of Centrifugal pump

Good for high flow rate, low pressure applications

Do not handle highly viscous fluids well

Used in industrial applications

Positive Displacement Pumps Two Types:

Reciprocating & Rotary

Good for applications with high pressure differentials requiring suction lift and fixed volumes

Used in many types of engines and well-pumps

References “Axial Flow Pumps.” Pump Scout. Pump Scout, 2014. Web. 22 Oct. 2015.

"Axial Flow Pumps Information." IHS Engineering 360. IHS Engineering 360, 2015. Web. 23 Oct. 2015.

Eisler, Peter. “Probe: New Orleans flood control pumps not reliable.” USA Today. USA Today, 29 Aug 2009. Web. 22 Oct. 2015.

"Positive Displacement Pumps." Engineering Toolbox. Engineering Toolbox, n.d. Web. 23 Oct. 2015.

“Positive Displacement Pumps.” Positive Displacement Pumps. Pump Scout, 2014. Web. 22 Oct. 2015.

"Pump School's Rotary Pump Family Tree." Pump School's Rotary Pump Family Tree. Viking Pump, 2014. Web. 23 Oct. 2015.

“Rotary Lobe Pumps: Membrane Filtration.” Boerger. Boerger, 2015. Web. 22 Oct. 2015

"Rotary Pumps." Rotary Pumps. Freelance Software, n.d. Web. 23 Oct. 2015.

"Rotating Machinery Design Basis – Pump." Harmadipedia. Harmadipedia, 27 June 2013. Web. 21 Oct. 2015.

Stuck, Dietmar. “Hand Pumps for Water Wells: Comparison.” New Solar Pump. New Solar Pump, n.d. Web 22 Oct. 2015