University of Engineering and Technology (UET), Peshawar
Faculty of Mechanical, Chemical, Industrial, Mechatronics
&
Energy Engineering
Department of Mechanical Engineering
Fluid Mechanics (ME-223L)
Experiment 10 Title: To study the characteristics of centrifugal pump
Objectives
1. Determining the head/flow rate characteristics of a single centrifugal pump at a single
speed.
Theory Background
Pumps are machines which lifts liquid from lower level to higher level or convert
mechanical energy into hydraulic energy or which increase the pressure of water with the
help of external work done.
Types of pumps:
In Positive displacement pumps, a fixed volume is forced from one chamber to another i.e.
in flow is exactly equal to out flow. Examples of such pumps are reciprocating vane, gear
and screw pumps.
High pressure + High Head + Low flow rate + Unsteady flow
In rotodynamic/ negative displacement pumps, the suction amount and the delivery
amounts are not equal i.e. in and out flow is not exactly equal. Examples of such pumps are
centrifugal, submersible pumps, etc.
Low pressure + Low Head + High flow rate + Steady flow
Centrifugal Pump:
The centrifugal pump converts energy supplied from a motor or turbine, first into kinetic
energy and then into potential energy. The motor driving the impeller imparts angular
velocity to the impeller. The impeller vanes then transfer this kinetic energy to the fluid
passing into the center of the impeller by spinning the fluid, which travels outwards along the
vanes to the impeller casing at increasing flow rate. This kinetic energy is then converted into
potential energy (in the form of an increase in head) by the impeller casing (a volute or a
circular casing fitted with diffuser vanes) which provides a resistance to the flow created by
the impeller, and hence decelerates the fluid. The fluid decelerates again, in the outlet pipe.
As the mass flow rate remains constant, this decrease in velocity produces a corresponding
increase in pressure as described by Bernoulli’s equation. It consists of following four major
parts
•
Involute casing
•
Impeller
•
Suction pipe
• Delivery pipe
The performance of a centrifugal pump at a fixed speed can be represented by the following
relationships:
•
Total head H against Discharge Q
•
Power input P against Discharge Q
•
Efficiency η against Discharge Q
These relationships plotted in graph form are known as the “performance Characteristics”
of a pump.
Power Input = Volts x Amperes ( W )
Water Power = ρ g H Q
Efficiency = Water Power / Input Power
Where g = 9.8 m/s2 and ρ = 1000 kg / m3
Figure 1 Centrifugal Pump Apparatus
Figure 2 Centrifugal Pump Apparatus
Apparatus
Hydraulic Bench, auxiliary pump, hoses, Clamps, Tachometer, etc. The Experimental setup is
shown is Figure 2.
Procedure
1. Position the manifold block into the working channel of the bench, and the auxiliary pump
on the floor at the left hand side of the bench and connect the auxiliary pump to the bench
as shown in figure.
2. Connect the auxiliary pump to the bench using appropriate hoses.
3. Connect the apparatus to a single-phase electrical supply and open the drain and discharge
valve of the bench.
4. Switch on the pumps and choose a suitable RPM.
5. Tabulate readings on the gauges and meters and determine the flow rate as well.
6. Slowly close the discharge valve to give a convenient reading on the gauge i.e. 2 m and
tabulate new values.
7. Repeat in steady increments until the valve is fully closed.
8. Repeat the same experiments at other RPMs.
Observation and Calculations:
Record the data in Table 1.
Table 1. Results for Centrifugal pump apparatus
S.No
1
2
3
RP
M
Suctio
n Head
H1
Deliver
y Head
H2
Gauge
correcti
on
factor
H3
Head
H= H1
+ H2 –
H3
Volu
me
Time
Discar
ge Q
Water
Power
ρgQH
Amper
e
Volt
age
Power
input
Efficiency
4
Avg
Precautions
• Apparatus shouldn’t be moved / disturbed while flow is on.
• Volumetric Flow rate should be measured cautiously.
• All the tapings and connections should be properly secured before starting the pumps.
• The equipment should be allowed to rest and cool down after a continuous operation of 30
minutes.
• While operating the equipment, water and electric hazards should be kept in mind.
******************************* THE END******************************
University of Engineering and Technology (UET), Peshawar
Faculty of Mechanical, Chemical, Industrial, Mechatronics
&
Energy Engineering
Department of Mechanical Engineering
Fluid Mechanics (ME-223L)
Experiment 11 Title: Series and Parallel pumps configuration.
Objectives
1. Determining the head/flow rate characteristics of two similar pumps operating in a parallel
configuration at the same speed
Theory Background
The introduction of a second pump to the Hydraulic Bench system allows the study of two
pump performance, both in series and parallel operation. This accessory comprises a fixed
speed pump assembly and independent discharge manifold interconnected by flexible
tubing with quick release connectors. This auxiliary pump is intended to be used in
conjunction with the basic Hydraulics Bench. The auxiliary pump is mounted on a support
plinth which stands adjacent to the Hydraulics Bench primary pump.
If two or more similar pumps are connected in parallel, the head across each pump is the
same and the total flow rate is shared equally between the pumps. In the parallel operation,
the flow rate does not increase in proportion to the number of pumps switched in.
Figure 1 Block Diagram in Parallel Configuration and Centrifugal Pump Apparatus
If two or more pumps are connected in series, the discharge passes through each pump in turn
and undergo a head boost HD/n at each pump, Where n = number of pumps and HD is the
total head.
Figure 2. Block Diagram in Series Configuration and Centrifugal Pump Apparatus
Apparatus
Hydraulic Bench, Series / Parallel Pump test accessory. The Experimental setup is shown is
Figure 1 and figure 2.
Procedure
1. Position the manifold block into the working channel of the bench, and the auxiliary pump
on the floor at the left-hand side of the bench and connect the auxiliary pump to the bench
with appropriate hoses and Y connector as shown in figure.
2. Connect the auxiliary pump to the bench using appropriate hoses.
3. Connect the apparatus to a single-phase electrical supply.
4. Open the sump drain valve. And Close discharge control valve.
5. Switch on the main pump and now open the discharge control valve fully, then record
inlet pressure, outlet pressure, and flow rate using volumetric tank.
6. Slowly close discharge valve to obtain a convenient reading on the manifold pressure
gauge (e.g. mm of H20) and tabulate results at different discharge conditions.
7. By adjusting the sump drain valve, the complete experiment may be carried out under
different static system pressures and can also demonstrate the effects of net positive
suction head on the performance of the pump.
Observation and Calculations:
Record the data in Table 1.
Table 1. Results for head/flow rate characteristics of two similar pumps operating in a parallel
configuration at the same speed
S.no
Manifold pressure
(m of H2O)
Inlet
(m of H2O)
Datum head
correction m
Total head
((m of H2O))
Volume
(litre)
Time
(sec)
Flow rate
Precautions
• Apparatus shouldn’t be moved / disturbed while flow is on.
• Volumetric Flow rate should be measured cautiously.
• All the tapings and connections should be properly secured before starting the pumps.
• The equipment should be allowed to rest and cool down after a continuous operation of 30
minutes.
• While operating the equipment, water and electric hazards should be kept in mind.
******************************* THE END******************************