mechanical lab i.new11

MECHANICAL LAB I

(Group-B)GROUP MEMBERS:NAMES ROLL NUMBERS DISCIPLINE

Afraz Ahmed 2102 Electrical Akhter Hussain 2104

Chemical Amin Siddique 2118 MaterialsSalman Sarwar 2131 CivilZeeshan Sadiq 2151 Electrical

Lab Instructor:

MASOOD ALAM

Lab Coordinator:

DR. Rashid Ali KhosooKARACHI INSTITUTE OF POWER ENGINEERIGContents

3ABSTRACT

4Chapter # 01

4Introduction to Mechanical Equipment

41. Types of Pump

41.1Positive Displacement Gear Pump

51.2 Rotor Dynamic Pump

51.2.1 Axial flow Pump

51.2.2 Radial Flow Pump (Centrifugal)

61.2.3 Turbine Pump

61.3 Cavitation

61.4 Reynolds Number

71.5 Bernoulli's principle

9CHAPTER # 2

9EXPERIMENTS

92.1 Experiment no.1

92.1.1 Objective

92.1.2 Procedure

112.1.3 Observations & Calculations

162.2 Experiment no.2

162.2.1 Objective:

162.2.2 Procedure:

162.2.3 Observations & calculations:-

212.3 Experiment no. 3

212.3.1 Objective

212.3.2 Procedure: -



262.4.1 Objective

262.4.2 Procedure:-


332.5 Experiment No. 5

332.5.1 Objective

332.5.2 Description

332.5.3 Observation and Calculations

2.6 to 2.8 Experiments. (35-37)

ABSTRACT

Pumps are important mechanical equipments that are used in almost every industry. Besides its also a part of household equipments for water transportation/storage. Knowledge about their performance and characteristics is therefore, very important. This experiment is to study the characteristics of four most widely used pumps; axial flow pump, centrifugal pump, gear pump, and turbine pump; using arm field multi-pump test rig. Main objective of this experiment is to develop understanding of characteristics of pumps. Performance parameters are pump head, flow rate, power input, power output, and efficiency. Gear pumps provide highest head while axial flow pumps give highest flow.

Chapter # 01

Introduction to Mechanical Equipment

A pump is a device that moves fluids by mechanical action. Pumps can be classified into three major groups according to the method they use to move the fluid. Pumps operate by some mechanism (typically reciprocating or rotary), and consume energy to perform mechanical work by moving the fluid. Pumps operate via many energy sources, including manual operation, electricity, an engine of some type, or wind power.

1. Types of Pump

On the basis of transfer of mechanical energy the pumps can be broadly classified as follows:

Positive displacement pump

Rotor dynamic pumps

Axial flow pumps

Radial flow pumps (Centrifugal)

Mixed flow pumps

Positive Displacement Gear Pump

The positive displacement Gear Pump has a cast casing and two gear-shaped impellers, rotating with close clearance, enmeshing such that water entering the suction port is trapped in the spaces between adjacent teeth and carried round to be squeezed out and discharged through the outlet port. High pressures are achieved with Gear Pumps and a pressure relief valve is incorporated set to 75m head, to protect the pump and system.

An important advantage of this type of pump is that no valves are required in the suction or delivery: it is capable of pumping air, gas, or liquid without any detrimental effect and does not require priming. High pressures are possible, although the flow rates are limited.

The main disadvantage of this type of pump is that very close clearances are required between the ends of the rotors and the casing.

Advantages

1. The efficiency is high regardless of changes in required head. Efficiencies on the order of85% to 95% are common.

2. The efficiency remains high regardless of pump speed, although it tends to decrease slightly with increasing speed.

3. Reciprocating pumps run at much lower operating speeds than centrifugal pumps and thus are better suited for handling viscous fluids.

4. For a given speed the flow rate is constant regardless of head. The pump is limited only by the power of the prime mover and the strength of the pump parts.

Disadvantages1. They have higher maintenance cost and lower availability because pulsating flow and large number of moving parts.

2. There are poorer at handling liquids containing solids that tend to erode valves and seats.

3. Because of the pulsating flow and pressure drop through the valves they require larger suction pressures (net positive suction head) at the suction flange to avoid cavitation.

4. They are heavier in weight and require more space.

5. Pulsating flow requires special attention to suction and discharge piping design to avoid both acoustical and mechanical vibrations disadvantages.

6. Oscillating motion of the plungers creates disturbances (pulsations) that travel at the speed of sound form the pump cylinder piping system. There pulsations cause the pressure level of the system to fluctuate with respect to time.1.2 Rotor Dynamic Pump

Rotor dynamic pump is divided into following types

1.2.1 Axial flow Pump

Axial flow pump has a 50 mm pitch propeller running in a casing with fine clearances between propeller and asking. Water enters the propeller axially through a ring of fixed inlet guide vanes. In passing through the propeller, the blades impart a whirl component into the fluid which the outlet guide vanes remove prior to the fluid entering the discharge pipe.

The Axial Flow Pump is best suited to conditions where a large discharge flow is to be delivered against a low head. Land drainage, irrigation and sewage pumping are some typical applications. The pump efficiency is comparable with that of the centrifugal type. However, its higher relative speed permits smaller and cheaper pumping and driving units to be provided.

1.2.2 Radial Flow Pump (Centrifugal)The Pedestal type, Centrifugal Pump has a shrouded impeller running on an extension of the main spindle, supported on double ball bearings. This type of pump is not self-priming but operates with a flooded suction. As the fluid passes through the impeller, energy is imparted to it by the curved blade of the impeller resulting in fluid leaving the impeller with an increase of both pressure and velocity.

Centrifugal pumps are capable of transferring large volumes without any dependence on valves or fine clearance and can be run against a closed valve without developing a very high pressure. They can handle a wide range of slurries, or solids in suspension, in addition to liquids with high viscosities. Advantages & Disadvantages of Centrifugal Pump over Positive Displacement pump

The centrifugal pump claims the following advantages and disadvantages with respect to a positive displacement pump.

Advantages

1. They are relatively inexpensive.

2. They have few moving parts and therefore tend to have greater on stream availability and lower maintenance costs than positive displacement pump.

3. There have relatively small space and weight requirements relative to positive displacement pump.

4. There are no close clearances in the fluid stream and therefore they can handle liquids containing dirt, abrasives, large solids, etc.

5. Because there is very little pressure drop and no small clearances between the suction flange and the impeller, they can operate at low suction pressure.

6. Due to shape of the head capacity curve, centrifugal pumps automatically adjust to changes in head. Thus capacity can be controlled over a wide range at constant speed

Disadvantages

There are only practical for achieving high pressure when they are large flow rates.

They have low maximum efficiencies when compared to reciprocating pumps

1.2.3 Turbine Pump

The Turbine Pump (also known as a re-generative or peripheral pump) with a straight bladed impeller in an annular casing, and a drive shaft supported on two grease-packed ball races. The seal, which is of the rotary mechanical type, is self-lubricating. This pump is not self-priming and operates from flooded suction. The suction is connected directly to the sump tank. The turbine pump may therefore be classified as a viscosity pump.

1.3 CavitationCavitation means that cavities or bubbles are forming in the liquid that we're pumping. These cavities form at the low pressure or suction side of the pump, causing several things to happen all at once

The cavities or bubbles will collapse when they pass into the higher regions of pressure, causing noise, vibration, and damage to many of the components.

We experience a loss in capacity.

The pump can no longer build the same head (pressure)

The pump's efficiency drops.

The cavities form for five basic reasons and its common practice to lump all of them into the general classification of cavitation. This is an error because we'll learn that to correct each of these conditions; we must understand why they occur and how to fix them. Here they are in no particular order:

Vaporization

Air ingestion (Not really cavitation, but has similar symptoms)

Internal recirculation

Flow turbulence

The Vane Passing Syndrome

1.4 Reynolds Number

Influid mechanics, theReynolds number(Re) is adimensionless numberthat gives a measure of theratioof inertial forces toviscousforces and consequently quantifies the relative importance of these two types of forces for given flow conditions.

Reynolds numbers frequently arise when performingdimensional analysisof fluid dynamics problems, and as such can be used to determinedynamic similitudebetween different experimental cases.

They are also used to characterize different flow regimes, such aslaminarorturbulent flow: laminar flow occurs at low Reynolds numbers, where viscous forces are dominant, and is characterized by smooth, constant fluid motion; turbulent flow occurs at high Reynolds numbers and is dominated by inertial forces, which tend to produce chaoticeddies,vorticesand other flow instabilities.

Reynolds number can be defined for a number of different situations where a fluid is in relative motion to a surface.These definitions generally include the fluid properties of density and viscosity, plus a velocity and acharacteristic lengthor characteristic dimension. This dimension is a matter of convention for example a radius or diameter is equally valid for spheres or circles, but one is chosen by convention. For aircraft or ships, the length or width can be used. For flow in a pipe or a sphere moving in a fluid the internal diameter is generally used today

Where:

is the mean velocity of the object relative to the fluid (SI units: m/s)

is a characteristic linear dimension, (travelled length of the fluid;hydraulic diameterwhen dealing with river systems) (m)

is thedynamic viscosityof thefluid(Pas or Ns/m or kg/(ms))

is thekinematic viscosity() (m/s)

is thedensityof the fluid (kg/m).

1.5 Bernoulli's principleInfluid dynamics,Bernoulli's principlestates that for anin viscid, an increase in the speed of the fluid occurs simultaneously with a decrease in pressureor a decrease in thefluid'spotential energy.

Bernoulli's principle can be applied to various types of fluid flow, resulting in what is loosely denoted asBernoulli's equation. In fact, there are different forms of the Bernoulli equation for different types of flow. The simple form of Bernoulli's principle is valid forincompressible flows(e.g. mostliquidflows) and also forcompressible flows(e.g.gases) moving at lowMach numbers. More advanced forms may in some cases be applied to compressible flows at higherMach numbers.

Bernoulli's principle can be derived from the principle ofconservation of energy. This states that, in a steady flow, the sum of all forms of mechanical energy in a fluid along astreamlineis the same at all points on that streamline. This requires that the sum of kinetic energy and potential energy remain constant. Thus an increase in the speed of the fluid occurs proportionately with an increase in both itsdynamic pressureandkinetic energy, and a decrease in itsstatic pressureandpotential energy. If the fluid is flowing out of a reservoir, the sum of all forms of energy is the same on all streamlines because in a reservoir the energy per unit volume (the sum of pressure and gravitational potentialgh) is the same everywhere.Bernoulli's principle can also be derived directly from Newton's 2nd law. If a small volume of fluid is flowing horizontally from a region of high pressure to a region of low pressure, then there is more pressure behind than in front. This gives a net force on the volume, accelerating it along the streamline.

In most flows of liquids, and of gases at lowMach number, thedensityof a fluid parcel can be considered to be constant, regardless of pressure variations in the flow. Therefore, the fluid can be considered to be incompressible and these flows are called incompressible flow. Bernoulli performed his experiments on liquids, so his equation in its original form is valid only for incompressible flow. A common form of Bernoulli's equation, valid at anyarbitrarypoint along astreamline, is:

CHAPTER # 2

EXPERIMENTS

2.1 Experiment no.12.1.1 Objective To investigate the characteristics of Turbine Pump.2.1.2 Procedure

a) Calibration of torque balance:-

Open access door at the front of the test rig to remove the toothed drive belt. Release the dynamometer clamping knob and swing the dynamometer assembly to the right or left in order to release the toothed belt from its pulleys.

With the belt freed from the dynamometer, close the front access door.

Set the motor speed control to zero, and switch on the motor.

Using the motor speed control set the motor speed the 1000 rev/min. to allow the bearings etc. to attain running conditions.

Unscrew the lower sliding weight on the torque measurement beam and set the captive weight to the zero datum on the upper scale.

Adjust the position of the counterbalance weight to set the beam horizontal, so that the engraved line on the beam is coincident with the notch in the end plate.

Switch off Motor.

Open access door and re-fit the toothed drive belt between the dynamometer pulley and the pulley of the pump to be tested.

Close the access door.

b)Measurement of Flow:-

Volumetric Tank Method

This technique is usually used when testing the gear pump, centrifugal pump and turbine pump.

Open the dump valve (item 19). Pull the knob upwards and rotate it to retain the valve open.

Having followed the pump operating Instructions selected the appropriate running speed or operating pressure setting; run passing through the channel and into the volumetric tank.

The volume of water in the tank is measured directly on the sight glass scale. It will be noted that there are two scales. The lower scale, which is calibrated from 0 to 6 liters, is used when measuring low rates of flow, scale, which is calibrated from 0 to 40 liters, is used when the rates of flow are high.

Prepare the stopwatch set to zero.

Twist and lower the dump valve knob.

The water will now start to fill the volumetric tank. When it reaches the zero mark appropriate sight glass scale, start the stopwatch.

Observe the sight glass scale and when a measured volume of water has entered the volumetric tank, stop the stopwatch and note the elapsed time.

Volume in liters

Flow Rate in liters per second =____________________

Time

If required, the dump valve may now be opened and the measurement repeated. Averaging of a number of readings will improve the accuracy of determination of rate of flow.

c) Test Rig Operating Instructions:-

Connect the toothed drive belt between the DC motor pulley and the turbine pump.

Open dump valve in volumetric tank.

Ensure that rubber plug to axial flow pump inlet at bottom of volumetric tank is in position.

Close flow control valve.

Set motor speed to zero.

Switch ON motor and rotate the motor speed controller clockwise to give required revolutions per minute.

Open turbine pump isolating and selection valve no. 4.

Open flow control valve and set it, and suction regulating valve to give the required rate of flow.

Pressures reading for turbine pump are taken from pressure gauge no. 1.

Shutting down procedure for turbine pump is carried out by simply reversing the above sequence of operations.

2.1.3 Observations & CalculationsPump is a fluid motive device i.e. it is used to transport the fluid from one point to the other.For centrifugal and turbine pump, the following relationship relates to Flow rate, Input power, Hydraulic power, Efficiency etc.

Flow rate =

Input Power =

Hydraulic Power = gQH x 10-3

Efficiency = x 100

=

=

=

Pump Speed (N) = Where,

N = Pump speed in rpm

T = Torque in N-m

H = Pressure head in meter of H2O

( = Density of water in Kg/m3g = 9.8m/s2

Q = Flow rateFlow calculations for axial flow pump:

Q = Cd B H

Following is the table which gives us observations obtained from the operation of the turbine pump which operated at 1400 and 1500 rpm.a) Case 1:-

Motor Speed=1400rpmPressureVacuumPump HeadVolumeTimeFlowTorqueInput PowerHydraulic PowerEfficiency

m.H2Om.H2Om.H2Oliterssecliters/secNmWattWatts%

16016553.080.0942.13312.114.794.74

14014538.30.1311.96287.217.936.24

12012520.140.2481.85271.129.2310.78

100105170.2941.75256.428.8511.25

8085140.3571.67244.728.0311.45

606512.70.3941.57230.123.1710.07

Graphs:

Following are the plots that describe the pump characteristics at 1400 rpm:

(b) Case 2:-



18018547.640.1052.25353.318.535.25

16016530.470.1642.13334.425.767.70

14014522.960.2182.03318.729.919.38

12012518.280.2741.9298.332.2010.79

10010515.260.3281.81284.232.1411.31

808513.50.3701.75274.829.0710.58

Graphs:


2.2 Experiment no.2

2.2.1 Objective: To investigate the characteristics of Centrifugal Pump .

2.2.2 Procedure: a) Test Rig Operating Instructions:-

Connect the toothed drive belt between the DC motor pulley and the centrifugal pump.



Close flow control valve.

Open suction regulating valve.

Set motor speed to zero.


Open centrifugal pump isolating and selection valve no. 1.


Following is the table which gives us observations obtained from the operation of the centrifugal pump which operated at 1400 and 1500 rpm:

b) Case 1:-



3.503.5543.750.1140.3754.23.927.24

3.2503.25524.70.2020.3957.16.4511.29

303513.10.3820.45566.711.2316.85

2.7502.7559.90.5050.573.313.6318.60

2.502.558.630.5790.5479.114.2117.96

2.2502.2557.520.6650.5783.514.6817.57

Graphs:


c) Case 2:-



404549.890.1000.4265.93.935.96

3.7503.75522.780.2190.4367.58.0711.96

3.503.5513.970.3580.49577.712.2915.81

3.2503.25510.680.4680.5281.614.9318.28

30358.680.5760.5789.516.9518.94

2.7502.7558.210.6090.694.216.4317.44

Graphs:



2.3.1 Objective

To investigate the characteristics of Gear Pump .

2.3.2 Procedure: -

a) Test Rig Operating Instructions:-

Connect the toothed drive belt between the DC motor pulley and the gear pump.



Open gear pump isolating selection valve.

Open flow control valve. Set motor speed to zero.


Pressures reading for gear pump are taken from pressure gauge no 3.

Vacuum readings for the gear pump are obtained by opening vacuum selector valve no. 3


Following is the table which gives us observations obtained from the operation of the gear pump which operated at 700 and 800 rpm:

a) Case 1:- Motor Speed=700

PressureVacuumPump HeadVolumeTimeFlowTorqueInput PowerHydraulic PowerEfficiency


80822700.0071.3598.90.580.59

7072910.0221.395.21.511.58

6062430.0471.2591.62.742.99

5052300.0671.2289.43.273.66

4042220.0911.1785.73.574.16

3032180.1111.1282.13.273.98

Graphs:


b) Case 2:-



1001021380.0141.54128.91.421.10

8082520.0381.44120.63.022.50

6062290.0691.35113.04.063.59

4042190.1051.26105.54.133.92

3032150.1331.1798.03.924.01

2022120.1671.1192.93.273.52

Graphs:



2.4.1 ObjectiveTo investigate the characteristics of Axial flow Pump.

2.4.2 Procedure:-

a) Test Rig Operating Instructions Close dump valve in volumetric tank.

Fill the tank with water by using gear pump.

Connect the toothed drive belt between the DC motor pulley and the axial flow pump.


Open flow control valve. Set motor speed to zero.


Pressures reading for axial flow pump are taken from pressure gauge no 4.

Vacuum readings for the axial flow pump are obtained by opening vacuum selector valve no. 4

b) Measurement of Flow:-

The Hook and Point Gauge Method

This technique is usually used when testing the axial flow pump.

Gauge meter is placed over the delivery tank side.

Set the meter reading to zero.

Now switch ON the motor and adjust it to required speed.

Adjust the pressure head by adjusting the axial flow control valve.

Adjust the meter knob so that it just touches the upper level of the water.

Read the height from the gauge meter.


Following is the table which gives us observations obtained from the operation of the axial flow pump which operated at 1400 and 1500 rpm:

a) Case 1:-

Motor Speed=1400rpmPressureVacuumPump HeadWidth (B)Height (H)FlowTorqueInput PowerHydraulic PowerEfficiency

m.H2Om.H2Om.H2Ommmmm3/secNmWattWatts%

1.101.150130.0001311.54225.71.420.63

10150220.0002891.44211.02.841.34

0.900.950310.0004841.35197.84.272.16

0.800.850380.0006561.26184.65.152.79

0.700.750430.0007901.17171.45.423.16

0.600.650500.0009901.11162.75.833.58

Graphs:


b) Case 2:-

Motor Speed=1500rpmPressureVacuumPump HeadWidth (B)Height (H)FlowTorqueInput PowerHydraulic PowerEfficiency

m.H2Om.H2Om.H2Ommmmm3/secNmWattWatts%

1.201.250140.0001470.4976.91.732.25

1.101.150220.0002890.4469.13.124.52

10150280.0004150.4164.44.076.33

0.900.950350.0005800.4164.45.127.96

0.800.850420.0007630.462.85.989.53

0.700.750470.0009030.3758.16.2010.67

Graphs:


2.5 Experiment No. 52.5.1 Objective

To demonstrate the appearance and sound of cavitations in a hydraulic system.

To demonstrate the conditions for cavitations to occur (liquid at its vapor pressure)

To show how cavitations can be prevented by raising the static pressure of a liquid above its vapor pressure.

2.5.2 Description

The apparatus consists of a rectangular venturi section with a window allowing full visualization. The venture section is contained between two end fittings, the one on the upstream side incorporating a flow regulating valve. The complete assembly is mounted on a backboard arranged for wall mounting and requires the services of an Armfield Hydraulics Bench (F1-10) or laboratory water supply, flow measurement and drainage system. Pressure tappings are provided at the throat and inlet of the venturi and each is connected to a gauge mounted on the backboard.

2.5.3 Observation and CalculationsSrP1P1(abs)P2P2 (Abs.)P3VolumeTimeFlow Rate

barbarbarbarbarliterSm3/s

11.82.8-0.5050.4950517.670.0002820

21.52.5-0.4990.5010517.470.0002862

31.22.2-0.480.520518.720.0002670

40.91.9-0.450.550521.000.0002380

50.61.6-0.3990.6010525.430.0001960

60.31.3-0.220.780535.820.0001390

Fig 2.34: Cavitations: Flow Rate vs. Throat Pressure

2.6 Experiment # 06

Objective: To calculate the Reynoldss number of the fluid in case of Laminar,

Transition and Turbulent flow

Equipments: Hydraulic Bench, Reynoldss Apparatus, Volumetric cylinder, Stop watch

Procedure

a. First of all we set the Reynoldss apparatus and switched on the motor.b. The Head tank in Reynoldss apparatus was filled to the required level.

c. The ink drop from the upper cylinder was allowed to fall into the water tank and the tank valve was opened.

d. The flow behavior (laminar, transition and turbulent) of ink water was visualized by increasing the flow rate slowly and corresponding flow rate was determined by dividing the volume observed in the cylinder by the time noted. Q = Ave. The Reynolds Number is calculated for each case as shown in the observations and calculations.

Re= Observations and Calculations

Diameter of test pipe, d= 0.01mDensity of water, = 1000 kg / m3 Dynamic viscosity, = 1.002 10-3 Ns/m2Area of test pipe, A = 7.85 10-5 m2For Laminar Flow

1)

2)

3)

For Turbulent Flow

1)

2)

3)

For Transition Flow

..

2.7. Experiment # 072.7 Objective:To determine the head/ flow-rate characteristics of a centrifugal pump for a number of different configuration.2.7.1. Method:

By measurement of pressure at pump inlet and outlet and discharge flow-rate .

2.7.2 Equipment:

In order to complete the demonstration, we need a number of pieces of equipment

The Hydraulic Benches, which provides one of the two pumps used during this experiment and allows the volume flow rate to be measured by time volume collection.

The F1-26 Test Accessory

A stopwatch to allow us to determine the flow-rate of water (not supplied).

2.7.3. Technical Data

The following dimensions from the equipment are used in the appropriate calculations. If required these values may be checked as part of the experimental procedure and replaced with your measurement.

Head Correction Values:

Datum to manifold gauge: hd = 0.96m

Datum to F1-26 outlet gauge: hd = 0.170m

Datum to F1-26 inlet gauge: hd = 0.020m

Datum to Bench pump inlet: hd = 0.240m

2.7.1. Observation for Single Pump Operation:

Vacuum(m)Discharge head(m)Volume(liter)Time(sec)flow(liter/sec)

020118.650.05361930

01818.260.121065375

01616.730.148588414

-11513.380.261096191

-21413.550.281690141

-21212.550.24

2.7.1.1. Characteristic Curve:

2.7.2. Observation for Parallel Pump Operation:

Vacuum(m)

Discharge head(m)Volume(ltr)Time(sec)Flow rate(ltr/sec)

02014.850.206185567

01835.530542495479

01645.520.724637661

014551

01254.51.111111111

2.7.2.1. Characteristic Curves:

.2.7.3.1. Observation for Series Pump Operation:Discharge(m)Volume(ltr)Time(sec)Flow rate(liter/sec)

3054.941.01214574

2553.951.265822785

2053.711.347708895

1553.031.650165017

1052.711.84501845

2.7.3.2. Characteristic Curves:

2.8. Experiment # 088.1. Objective:

To investigate the validity of Bernoulli Equation when applied to steady flow of water in tapered duct.

8.1.1. Method:

To measure flow-rates and both static and total pressure heads in a rigid convergent/divergent tube of known geometry for a range of steady flow-rates.

8.1.2. Equipment:

In order to complete the demonstration of the Bernoulli Equation, we need a number of pieces of equipment.

The F1-10 Hydraulic Bench which allows us to measure flow by timed volume collection.

The F1-15 Bernoulli Apparatus Test Equipment

A stopwatch for timing the flow measurement

8.1.3. Technical Data:

The following dimensions from the equipment are used in the appropriate calculations. If required these values may be checked as part of the experimental procedure and replaced with your own measurement

The dimensions of tube are detailed below:

Tapping Position Manometer Legend Diameter

A h1 25.0

B h2 13.9

C h3 11.8

D h 4 10.7

E h5 10.0

F h6 25.0

8.2. Observation Column:

P1P2P3P4P5P6P7P8Volume(ltr)TimeFlow (ltr/sec)

180163145125105135135180113.060.0765675

170160145125125135140140116.040.0623456

160155150140135140145170122.250.0449456

150149147145144144135140170.440.0141967

190170145120100130130170110.80.0925967

20017014511080125130200111.430.0874834

2101801401056512013025018.90.112359

2201851401005512012522018.40.119047

Bernoullis proofFlow Rate (m^3/s)Diameter (mm)Area (m^2)Velocity (m/s)Dynamic Head (m)Static Head (m)Total Head (m)Percentage Error Exp(head=0.21)

0.000112250.0004910.2288970.002670430.180.1826704313.01408098

0.00011213.90.0001520.7404410.0279435790.140.1679435820.02686733

0.00011211.80.0001091.0274390.053803830.1050.1588038324.37912838

0.00011210.78.99E-051.2495470.0795803990.0650.144580431.15219

0.000112107.85E-051.4306060.104313670.120.2243136-6.81603323

0.000112250.0004910.2288970.002670430.130.1326704336.82360479

Results and DiscussionExperiment # 1 ~ 4 The conversion of mechanical energy into fluid energy by machines is of major concern in many applications. The types of hydraulic machines available for this conversion vary considerably in principle and design. The selection of correct pump for a particular application is essential for efficient, satisfactory operation.

In this experiment the multi-pump rig is used to measure the characteristics of the following pumps.

1. turbine pump

2. centrifugal pump

3. gear pump

4. axial flow pump

Graphs were plotted for pump head, input power, and efficiency (ordinate) versus flow rate (abscissa) and compared with typical curves. It has been found that graphs of all pumps (plotted for pump head, input power and efficiency) showed the trends typical of pump performance curves.

Centrifugal and Turbine pumps:- Pumps action and performance of a pump are defined in terms of their characteristics curves. These curves correlate the capacity of pump in unit time versus discharge or differential pressures. These curves usually supplied by pump manufacturers are for water only. These curves usually shows the following relationships ( for centrifugal pump). A plot of capacity versus differential head. The differential head is the difference in pressure between the suction and discharge.

The pump efficiency as a percentage versus capacity.

The net positive head required by pump versus capacity. The required NPSH for pump is a characteristic determined by manufacturer. Centrifugal pumps are usually rated on the basis of head and capacity at the point of maximum efficiency.

Gear pump:- The typical characteristics curves of gear pump are drawn for three different speeds of 700, 800 and 900 rpm. As obvious from the curves the pump has the efficiency increases with increasing head to a certain point then start decreasing with increasing the rpm.

It is observed that by increasing the rpm, torque increases due to which input power and efficiency increases.

In gear pump, the time for measurement of flow is much higher than centrifugal and turbine pump, which shows the lesser flow rate.

Higher heads characterized by gear pumps allow comparison with centrifugal and turbine pumps even though the rpm of gear pump are nearly the half of both described pumps. The flow of gear pumps is lower than the turbine and centrifugal pumps. Thus lower hydraulic power and hence lower efficiencies but at higher head the efficiencies are comparable to that turbine pumps. Efficiencies of gear pumps are increasing with increasing rpm, but still over all lesser than turbine and centrifugal pumps.

Axial flow pump:- Axial flow pumps are best suited for application requiring high flow rate but the head they develop is low. This makes them unsuitable for applications requiring both high and relatively higher head.

Sources of Error:-

The mechanical equipments have some limitations due to which the error in the observations may arise. In the current system the following are the major source of error

Voltage fluctuation may change the RPM of the motor due to which the torque changes.

More power loss if the motor become hot.

If the density of the fluid changes during the experiments also affect the efficiency and observations of the system.

Experiment # 5

Cavitation occurs when the suction pressure is below the saturation pressure at a given temperature. From the above mentioned results, it is evident that the suction pressure is well above the saturation pressure at room temperature except at the last pressure value (0.3 bar) so cavitation has occurred at 0.3 bar.

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mechanical lab i.new11

Documents

centrifugal pump

pump head

turbine pump

type of pump

types of pump

gear pumps

characteristics of pumps

radial flow pump centrifugal