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Remote Laboratory Exercise

Determination of the Pump Operation Characteristics

Remote Pump Lab Notes 2 2011-10-04

KTH/EKV/AC-LM

Content

1. Introduction ................................................................................................................................................ 4

2. Objectives of the Laboratory ...................................................................................................................... 4

3. Theory ........................................................................................................................................................ 5

3.1. Pump Operating Characteristics ........................................................................................................ 5

3.2. Serial Operation of Pumps ................................................................................................................. 6

3.3. Parallel Operation of Pumps .............................................................................................................. 6

4. Experimental Equipment............................................................................................................................ 8

4.1. Overall description ............................................................................................................................. 8

4.2. Parallel connection rig ....................................................................................................................... 8

4.3. Serial connection rig .......................................................................................................................... 9

4.4. Flow rate measurement, orifice plate .............................................................................................. 10

4.5. Pump efficiency ............................................................................................................................... 12

5. Graphical interface, control panel ............................................................................................................ 13

5.1. General information ......................................................................................................................... 13

5.2. Parallel Rig Interface ....................................................................................................................... 13

5.2.1. A and B– Pump control panel and Indicators panel ................................................................ 14

5.2.2. C – Pressures and Temperature panel ................................................................................... 15

5.2.3. D – Multitask control tab .......................................................................................................... 15

5.3. Serial Rig Interface .......................................................................................................................... 19

5.3.1. A and B – Pump control panel and indicators panel ............................................................... 19

5.3.2. C – Pressures and Temperature panel ................................................................................... 20

5.3.3. D - Multitask control tab ........................................................................................................... 20

6. Audio and Video Resources .................................................................................................................... 21

6.1. Preset Views .................................................................................................................................... 21

6.2. Settings Control Panel ..................................................................................................................... 22

6.3. Tools ................................................................................................................................................ 22

6.4. Audio Panel ..................................................................................................................................... 22

7. Laboratory Instructions ............................................................................................................................ 23

7.1. Preparation ...................................................................................................................................... 23

7.2. Performing the experiments ............................................................................................................. 23

7.2.1. Parallel connected pumps ....................................................................................................... 23

7.2.2. Serial connected pumps .......................................................................................................... 25

7.1. Reporting ......................................................................................................................................... 25

7.1. Self evaluation ................................................................................................................................. 25


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Nomenclature

Symbols

A Surface area m3 c Absolute velocity m/s d Diameter m H Head m p Pressure Pa Q Volume flow rate m3/s u Tangential velovcity m/s v Flow velocity m/s w Relative velocity m/s α Discharge coefficient deg β Relative flow angle deg

p∆ Differential pressure Pa γ Ratio of specific heats η efficiency - ρ density kg/m3 φ Flow coefficient - ψ Head coefficient -

Subscripts

0 Total

1 Impeller inlet

2 Impeller outlet

3 Stator outlet

tot Total d Delivery g Global i Intermediate el Electric orif Orifice plate out Output s Suction x Axial component ϑ Tangential component


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1. Introduction

Pumps are widely used in many engineering applications. In the present course the focus is put on rotodynamic pumps. One of the specific aspects of rotordynamic pumps is the variation of head with volume flow rate when running at constant speed while volumetric pumps feature an almost constant volume flow rate at constant speed.

Matching a pump to a system requires the exact knowledge of the pump operating characteristics (i.e. the dependency of head vs volume flow rate at constant speed). The shape of the characteristics depends thereby largely on the relative flow angle at impeller outlet. Furthermore, by combining two identical pumps, the overall operating characteristics can be modified in a controlled manner.

In the present laboratory exercise we focus on experimentally determining the operating characteristics of a single pump as well as on the effect of running identical pumps in serial and parallel mode.

2. Objectives of the Laboratory

The aim of the present laboratory exercise is to give a practical demonstration of the theory of parallel and serial connection of centrifugal pumps as well as study the influence of the parameters influencing the operation of the pumps. The high degree of automation of the facility and of the data acquisition system allows for a fast collection of data which can be used also to analyze the repeteability of the experiment.

At the end of laboratory exercise the student is expected to have:

− studied the theory of operating characteristics of pumps; − understood the principle of measuring pump operating characteristics; − acquired the necessary knowledge on the applied measurement techniques; − performed measurements of pump operating characteristics for single, parallel and serial

connection; − post-treated the measurement data; − determined the relative blade outlet angle and made a sketch of the pump impeller (front view); − analyzed the results; − written a brief laboratory report.

All measurements will be done in group (around 6 on-campus students). A number of distance students will be assigned to each on-campus group such as to share test data and write a common laboratory report.


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3. Theory

3.1.

In the present laboratory exercise the focus is put on centrifugal pumps.

Pump Operating Characteristics

Figure 3-1 depicts the velocity triangles of such pumps.

Radial direction 3 u2 2 c2 w2 1 ω u1 Centrifugal pump w1 c1 Axial direction

Figure 3-1: Impeller velocity triangles.

Pump operating characteristics tell us how the pump head changes as the flow through the pump, which can also be referred to as “off-design performance”.

For the sake of simplicity let us consider a pump with absolute axial inflow. Applying the Euler equation the head coefficient is then given by

2

2

2

22

2

2 uc

ugcu

ugH ϑϑψ ==

⋅= Eq. 3-1

The absolute circumferential velocity component shall be expressed by the relative flow angle 2β

and the radial outflow velocity as follows

222222 tan βϑϑϑ rcwuwc =→+= Eq. 3-2

With 22 ucr ⋅= φ the head coefficient can now be expressed by

( ) 2

2

222 tan11tan βφβφψ +=+⋅⋅=u

uu Eq. 3-3

In dependence of the blade metal angle at impeller exit various simplified pump characteristics are included in Figure 3-2.

In reality flow separation as well as incidence effects at low and high flow rates lead to the real characteristics being rather curved than straight (see dashed line in figure below).


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Ψ theoretical β2> 0 forward sweep

β2= 0 radial blades

β2< 0 backwards swee real

Φ

Figure 3-2: Dependence of the pump characteristics from blade metal angle

3.2.

The focus is now put on the serial operation of two identical pumps running at the same speed as included in

Serial Operation of Pumps

Figure 3-3. It shall be assumed that both pumps have the same operating characteristics.

1 2

Figure 3-3: Serial operation of pumps.

Following the conservation of mass, the mass flow rate (and consequently the volume flow rate) will be identical in both pumps (note: pump 2 has to “digest” what pump 1 delivers). At this given volume flow rate both pumps will add a certain head to the flow. As a consequence the total head of the two pumps running in series is as follows

21)21( HHH tot +=+ Eq. 3-4

The volume flow rate is given by

21)21( QQQ ==+ Eq. 3-5

3.3.

The focus is now put on the parallel operation of two identical pumps running at the same speed as included in

Parallel Operation of Pumps

Figure 3-4. It shall be assumed that both pumps have the same operating characteristics.

1

2

Figure 3-4: Parallel operation of pumps


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In this arrangement both pumps are forced to run at the same head. As we assume that both pumps have the same operating characteristics it follows that both pumps deliver the same volume flow rate. As a consequence the total volume flow rate of the two pumps running in parallel is as follows

21)21( QQQ +=+ Eq. 3-6

The total head is given by

21)21( HHHtot ==+ Eq. 3-7


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4. Experimental Equipment

4.1.

The laboratory exercise will be performed by executing experimental measurements with dedicated test facilities. The facilities are placed in the laboratory of Heat and Power Technology at KTH and they can be controlled remotely through a web page (one for each rig), which contains a complete control panel with measurement displays and diagrams.

Overall description

The rigs are respectively the parallel connection rig and the serial connection rig. Description follows.

4.2.

The parallel connection rig consists of two circulating pumps, A and B, placed in a closed circuit filled with water and a control and data acquisition system which allow to perform different measurements on the same facility, i.e.:

Parallel connection rig

− Automatic/manual measurement of the characteristic curves for pump A, pump B and the parallel connection of pump A and B when these are operated at the on design rotational speed;

− Automatic/manual measurement of the characteristic curve for pump A at off design rotational speed (keeping the rotational speed constant on a certain value between 0 and 100% of the design speed) ;

− Automatic/manual measurement of the curve Pump Head vs. Volume Flow Rate maintaining a constant opening of the variable valve and varying the rotational speed of pump A.

In addition it is also possible to get the overall efficiency for the different operations of the circuit.

The main components of the circuit and their connections are highlighted in Figure 4-1.

Figure 4-1: Parallel rig, 3D CAD model (left) and hydraulic scheme (right).

Pumps A and B can be run separately by an automatic positioning of the ON/OFF valves – valve A and B for pumps A and B respectively - in order to avoid a incorrect operation of one of the two pumps while just the other one is running. When pump A is selected, valve A is open while valve B is closed; the opposite when pump B is selected. For the operation of the parallel connection, both valves A and B are opened.


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The operating point instead, is set by means of a variable valve located at the delivery side of the pump. The valve acts directly on the volume flow rate and induces a pressure drop equal to the total head (closed circuit). Furthermore, pump A is controlled with an electrical drive (frequency inverter) which allows to vary the rotational speed by changing the supplied current frequency of the tri-phase asynchronous motor which drives the pump.

The circuit is equipped with three high accuracy pressure sensors (GE sensing), used to measure the pressure increase over the pumps and the pressure drop over the orifice plate. A resume of the main characteristics of the pressure sensors is included in Table 4-1.

Beside the pressure sensors, the equipment includes a PT100 probe which is used to measure the water temperature in the circuit. In order to prevent a damaging operation of the pumps without water in the circuit, a water level switch is placed in the reservoir: the pumps cannot be run if the water is below a certain level.

The volume flow rate is measured by means of a standard orifice plate. Further description is included in Section 4.4.

To obtain information about the pumps efficiency, the control circuit includes a power meter which allows measuring the electrical power absorbed by the motors driving the pumps.

Measurement Type Pressure Range [kPa] Output [V] Accuracy (*)

pd gauge 0 ÷ 200 0 ÷ 10 ± 0.2 % FS BSL

ps gauge -30 ÷ 40 0 ÷ 10 ± 0.2 % FS BSL

Δporif differential 0 ÷ 100 0 ÷ 10 ± 0.2 % FS BSL

Table 4-1: Pressure sensors characteristics, parallel rig.

(*) Full Scale, Best Straight Line

4.3.

The two pumps in this case are connected in series (the pressure side of pump A is connected to the suction side of pump B) and it is not possible to run them separately. The operating point is still varied by means of a variable valve with the same principle of the parallel rig.

Serial connection rig

The main components of the circuit and the hydraulic scheme for the serial rig are shown in

.

Four pressure sensors are included, whose main characteristics are resumed in Table 4-2.

The four pressure sensor allow to measure the head of both pumps – as difference between corresponding suction and delivery pressures - plus the drop in pressure given by the orifice; with this measurements, it is possible to draw three characteristic curves, one for each pump plus one for their serial connection.

Regarding the temperature probe and the water level switch, the same applies here. No power meter is included in the serial rig.

Measurement Type Pressure Range [kPa] Output [V] Accuracy (*)

pd gauge 0 ÷ 400 0 ÷ 10 ± 0.2 % FS BSL

pi gauge 0 ÷ 200 0 ÷ 10 ± 0.2 % FS BSL

ps gauge -30 ÷ 40 0 ÷ 10 ± 0.2 % FS BSL

Δporif differential 0 ÷ 100 0 ÷ 10 ± 0.2 % FS BSL

Table 4-2: Pressure sensors characteristics, serial rig.

(*) Full Scale, Best Straight Line


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Figure 4-2: Serial rig, 3D CAD model (left) and hydraulic scheme (rigth).

4.4.

The volume flow rate is calculated by measuring the pressure drop over an orifice plate. The orifices used in the lab facilities are made in accordance to the standard DIN 1952, which includes also regulations for a correct placement of the orifice inside the circuit.

Flow rate measurement, orifice plate

The orifice plates are placed on the upper part of the rigs on the pressure side pipe, as shown in Figure 4-3. The main dimensions of the orifice plate are also included.

Figure 4-3: Orifice plate, axial plane view (left) and placement inside the circuit for the parallel rig (center) and serial rig

(right).

The principle of orifice measuring technique is that the pressure difference up- and downstream of the orifice is measured and correlated to the velocity in the orifice throat. The Bernoulli equation applied between a point in the pipe and a point in the orifice throat gives:


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22

22SSRR vpvp

+=+ρρ

Eq. 4-1

with

ppp SR ∆=− Eq. 4-2

The following is obtained:

−=

−

=−=

∆22

222

22 112

RSRSRs AA

QAQ

AQvvp

ρ Eq. 4-3

or:

ρρp

AAAQ

AA

AQp

R

s

S

R

S

S

∆

−=⇒

−=

∆ 2

112

2

22

2

2

2

Eq. 4-4

Finally is simplified to:

ρp

mAQ S ∆−

=2

1 2

Eq. 4-5

This formulation does not account for effects of losses as well as contraction of streamlines in the orifice. To account for these effects a so-called discharge coefficient (α) is introduced leading to:

ρα pAQ S

∆⋅=

2

Eq. 4-6

The discharge coefficient is dependent on the Reynolds number as well as on the area ratio. In the present application it is to be determined graphically from Figure 4-4 assuming a high Reynolds number (1e6).

Figure 4-4: Coefficient of discharge, α.

Knowing the orifice data, it is essential to calculate the area AS and determine the discharge coefficient α that together with the parameter ρ, have to be inserted in the rig control panel in order to obtain a correct measurement of volume flow rate Q.


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4.5.

The pump efficiency is here defined as the ratio between the hydraulic power provided by the pump(s) and the electrical power absorbed by the motor(s) driving the pump(s).

Pump efficiency

( )el

sdg W

Qpp ⋅−=η

Eq. 4-7


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5. Graphical interface, control panel

As previously mentioned, the lab experience can be performed in remote without any on-campus assistance. For this reason it is important that the user knows exactly how to use the control panel interface. In the following sections the commands and the functions of both control panels are explained.

5.1.

Before to start with the control of the facilities, it is important to know some basics about the control platform used.

General information

The control of the rigs is programmed with LabVIEW which allows to publish a web-page with embedded controls.

In order to be able to see and control the web-page, it is necessary to download the LabVIEW plug-in LV Run Time Engine from the link:

http://ftp.ni.com/support/softlib/labview/labview_runtime/2010/LVRTE2010min.exe

After the setup on the local WINDOWS machine (MAC-OSX is not supported), by entering the address received from the lab assistants in the address bar of the browser INTERNET EXPLORER (release 6.0 SV3 or greater), the interface will be prompted on the screen.

By opening the web-page the rights to control the system are automatically requested and if there is no one else controlling the rig, the top-left corner of the window will show an active white arrow as in Figure 5-1, if instead someone is already controlling the system, the arrow will be disabled and in the

centre of the screen will appear the text .

Figure 5-1: Control of the rig enabled (left) or disabled (right).

The control management is governed by a timed queue where every connected user has 15 minutes to control the system. After the control time limit, the control is switched to the next user in the queue.

By right-clicking on the screen a list of commands is visualized: request or release the control and show the control time remaining or the last message from the server.

When the control is granted to the user, to run the software is then necessary to press the white arrow, after this action it is possible to interact directly with the facility.

After use of the control panel or before closing the browser, it is EXTREMELY important that the user presses the stop/reset program button as shown in Figure 5-2.

Figure 5-2: Procedure to stop the application before closing the browser.

5.2.

The interface is divided in four different functional areas, those are indicated in

Parallel Rig Interface

Figure 5-3.

http://ftp.ni.com/support/softlib/labview/labview_runtime/2010/LVRTE2010min.exe�


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Figure 5-3:Functional areas of the control interface, parallel rig.

5.2.1. A and B– Pump control panel and Indicators panel

The pump control panel (A) is used first to select which pump to run through the ring selector.

The possible alternatives are four:

Pump A; Pump B; Parallel connection (A+B); Pump A, variable Speed.

After the run-mode selection, if the button START is pushed, the circuit will automatically select the position of the ON/OFF valves depending on the run-mode, indicating the position of those in the indicator panel (B).

When the system recognizes that the valves A and B are in the correct position and the variable valve is completely opened (in order to avoid high initial pressure in the circuit due to the rapid start of the pumps), the pump(s) is/are switched on. It is possible to see if the pumps are running looking at the squared led indicators on the right side of panel B.

If option 4 is selected (A-Variable) a knob control will be activated in the pump control panel (A). The knob allows to set the rotational speed (as percentage of the on design value) of pump A. The value can be selected by means of the knob itself but can also be set writing a percentage value in the digital display uderneath it.

Going back to the indicators panel B, it is possible to notice that in addition to the led indicators for valves and motors, there are also:

− 1 progress bar, it indicates the opening position of the variable valve1

− 2 led indicators, the first is giving a information about the water level in the circuit; the second indicates when the water temperature value is out of the safety limits;

;

− 1 meter indicator, it gives the instantaneous speed of pump A (feedback).

It is important to know that if one or both water properties led are red, it is not possible to run the control

1 Percentage refers to the ratio between the actual angle of inclination of the sphere inside the valve with respect to the angle at fully opened valve: [0 π/2] -> [0 100%].

A

B

C

D


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program for safety reasons.

As additional information, it is possible to have the speed feedback just from pump A, because it is the only one driven by a frequency inverter which allows to have this measurement.

To stop the pumps it is important to press the stop button placed on the right side of the start button on panel A.

5.2.2. C – Pressures and Temperature panel

This panel is giving the instantaneous measurement of the three pressures and the water temperature value.

It is important to notice that the first display on the left is giving the reading of the pressure drop over the orifice, hence is giving a differential pressure measurement

The values of delivery and suction pressure are used to calculate the head of the pump operation for each measurement point by subtracting the suction value from the delivery.

, the second and the third displays are instead giving a relative pressure measurement with respect to the ambient pressure. All values in the displays are in indicated in kPa.

The temperature sensor gives a continuous measurement in Celsius degrees, shown in the red column on the right side of the suction pressure display.

5.2.3. D – Multitask control tab

The multitask control tab D includes four pages with several functions and ways of interaction with the rig. The pages are:

− Circuit scheme; − Measurement control panel; − Characteristic curve; − Curves overview.

The first page is dedicated to the circuit scheme, previously explained in Chapter 4.2.

The second page – measurement control panel - is divided in three main parts as shown in Figure 5-4 and here analyzed into detail.

Part A allows to enter an email address where the file of the desired set of measurements will be sent. In order to receive the email, it is necessary to press the button “Send email” before starting the measurement.

Part B requires the user to insert the parameters explained in Chapter 4.4 which are important for a correct calculation of the volume flow rate. Until the value of the parameter is not inserted correctly, a warning message is shown.

Part C of the page is fully dedicated to the data measurement procedure. First of all there is a ring selector named “DAQ Mode” which allows to choose the data acquisition method.

In case of measurement on pump A full speed, pump B and parallel connection A+B, the user can choose between two methods, “Auto (Constant Speed – Var Valve Opening)” and “Manual”.

If the rig is operating in modality “A - Variable”, a third DAQ method can be selected, “Auto (Variable Speed – Const Valve Opening)”, as shown in Figure 5-5.


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Figure 5-4: Measurement control panel, parallel rig.

Figure 5-5: DAQ mode selector for the “A-Variable” operation, parallel rig.

Right to the “DAQ Mode”, a selector allows defining the number of points which are the measurement points used in an automatic acquisition. In the case of “Auto (Constant Speed – Var Valve Opening)” the variable valve will change its position a number of times equal to the “# points” selected; the same applies in case of “Auto (Variable Speed – Const Valve Opening)” but in this case the points are indicating the number of rotational speeds that pump A will assume.

5.2.3.1. Performing the measurements

This type of measurement can be performed with every pump’s running mode.

Auto (Constant Speed – Var Valve Opening)

It is necessary to set a number of points between 2 and 33 (upper edge given by the accuracy of variable valve position reading, ±2%) and then press the “START MEASUREMENT” button. The variable valve will automatically reach the completely closed position and then it will be opened by an opening signal which depends on the number of points. It is possible to check both opening signal and actual position of the valve on the displays below the DAQ selector.

When the variable valve reaches the positions given by the opening signal, data are acquired over a sampling time of 2 seconds. Mean values, standard deviations and other calculated quantities are then automatically stored in a file and the characteristic curve is drawn instantaneously on the tab “CHARACTERISTIC CURVE”. An example of characteristic curve for a measurement with 10 points is given

A

B

C


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in Figure 5-6.

Figure 5-6: Characteristic curve for single pump, 10 measurement points, parallel rig.

When the valve reaches the last position, the measurement procedure is automatically stopped.

If for any reason the user wants to stop the measurement before the end of the procedure, the button “STOP MEASUREMENT” should be pressed.

It is not possible to start a measurement without starting the pump/s in advance (“START” button on pump control panel pressed).

This type of measurement can be performed with “A – VARIABLE” running mode only.

Auto (Variable Speed – Const Valve Opening)

It is necessary to set a number of points and decide the position of the variable valve for which the measurement will be performed. The position of the variable valve is set by means of the “CONTROL VALVE POSITION” handle situated on the right side of the panel. After having set the parameters, press the “START MEASUREMENT” button and the variable valve will move the set position. Starting from 0% speed, pump A will reach different speeds (expressed as percentage with respect to the maximum speed), given by a speed signal, depending on the number of points.

It is possible to check both speed signal and actual speed of the pump on the lower display of the panel and on the meter located on the indicators panel.

As previously described, data is automatically stored in a file and the characteristic curve is drawn instantaneously on the tab “CHARACTERISTIC CURVE”.

An example of a measurement with 10 speed points and variable valve opening equal to 60%, is given in Figure 5-7.


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Figure 5-7: Curve for A variable speed, 60% valve opening, 10 measurement points, parallel rig.

When the last speed is reached, the measurement procedure is automatically stopped.

If for any reason the user wants to stop the measurement before the end of the procedure, the button “STOP MEASUREMENT” should be pressed.

It is not possible to start a measurement without starting the pump/s in advance (“START” button on pump control panel pressed).

For both automatic measurements, the curves produced in the same “run program” session, are resumed in the tab “CURVES OVERVIEW”. An example of curves resume resulting from a series of measurements is given in Figure 5-8.

Figure 5-8: Curves overview, parallel rig.


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The same measurements performed in auto-mode can be done manually for different operating points, varying the position of the variable valve and/or the speed of pump A.

Manual

The main change with respect to an auto-measurement is that the data are stored and plotted by manually clicking on the button “Save data” under the handle “CONTROL VALVE POSITION” for each measurement point.

In order to receive the email with the attached measurement file, it is necessary to press the buttons in the following sequence:

Send email; START MEASUREMENT; Save data (for the current operating point); STOP MEASUREMENT (after the last measurement point desired)

The experimental curve is plotted in the same way on the tab “CURVES OVERVIEW” but the curves plotted in manual mode are not resumed in the “CURVES OVERVIEW” tab.

5.3.

The interface is divided in four different functional areas, those are indicated.

Serial Rig Interface

Figure 5-9: Functional areas of the control interface, serial rig.

5.3.1. A and B – Pump control panel and indicators panel

The pump control panel is used to start and stop the pumps. The pumps in serial connection can be run only simultaneously. When the system recognizes that the variable valve is completely opened (in order to avoid high initial pressure in the circuit due to the rapid start of the pumps), the pumps are switched on. It is possible to check if the pumps are running by looking at the squared led indicators on the left side of panel B. Panel B includes also a progress bar indicating the opening of the variable valve and two led for water level and water temperature limit, as for the parallel rig (refer to Section 5.2.1 ).

C

A D B


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5.3.2. C – Pressures and Temperature panel

This panel is giving the instantaneous measurement of the four pressures and the water temperature value.

The display on the top left is giving the reading of the pressure drop over the orifice, hence is giving a differential pressure measurement

5.3.3. D - Multitask control tab

. The other three displays are giving a relative pressure measurement with respect to the ambient pressure. All values in the displays are in indicated in kPa.

The multitask control tab for the serial rig is organized exactly as for the parallel rig. Refer to Section 5.2.3 for description and instructions. The differences in the multitask control tab between the two rigs are here listed:

− in the Measurement control panel, the Auto (Variable Speed – Const Valve Opening) is missing as on the serial rig the operation of the pumps at off design rotational speed is not available;

− in the Curves Overview, three graphs are present, as shown in . Moving from the top to the botton: Serial Pumps Characteristics, High Pressure Pump Characteristics, Low Pressure Pump Characteristics.

Figure 5-10: Curves overview, serial rig.


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6. Audio and Video Resources

The room in which the two rigs are placed is equipped with a video server and a microphone. The camera is controllable in pan, tilt and zoom. The resources are currently available at the address provided by the lab assistants. Once the link is open, a login window will be prompted on the screen.The username and password provided by the lab assistants have to be entered.

Figure 6-1 shows the appearance of the web page for the audio and video resources.

Figure 6-1: Audio and Video Panel

6.1.

The ring selector named ‘Sources’ allows selecting one of the preset views on the rigs. The camera will focus automatically on the target and all the settings will be automatically adjusted. The user can select among the following preset views:

Preset Views

− Overview Parallel − Pressure Sensors Parallel − Variable Valve Parallel − Circuit Parallel − … − …

A

B

C D


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6.2.

This panel allows adjusting the settings of the camera such as focus, iris and zoom. The camera can be moved in the horizontal direction with the pan bar and in the vertical with the tilt bar.

Settings Control Panel

6.3.

From left to right:

Tools

− Stop: to stop the live transmission from the camera − Snapshot: to take a snapshot of what the camera is currently focusing on − View full screen: to start the full screen mode − Set center mode: to select a zooming window with the mouse

6.4.

Allows adjusting the volume of the audio recorded from a microphone placed inside the room. Alll other audio settings have already been optimized.

Audio Panel


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7. Laboratory Instructions

7.1.

In advance to the remote laboratory exercise it is required that each student reads the laboratory notes (i.e. the present document) and performs the respective self-assessment test available on Bilda.

Preparation

Please note that only those students who have successfully passed the self-assessment test will be given the credentials to access the laboratory exercise.

7.2.

This section gives step-by-step the instructions to perform the present remote laboratory exercise.

Performing the experiments

First of all, it is recommended to connect to the audio and video resources and maintain a tab or window of the browser always open on it so to have a feedback on the system while controlling it. To access the audio and video resources refer to Chapter 6.

7.2.1. Parallel connected pumps

As mentioned before, the parallel rig allows testing the operation of two centrifugal pumps connected in parallel as well as test the operation of a single pump, either A or B.

7.2.1.1.

As a first task, complete the following steps which allow you to draw the characteristic curve for Pump A with an auto measurement:

Pump A Operation

1. decide a number of measurement points between 2 and 33; 2. run the parallel rig interface following the instructions in Chapter 5.1; 3. from the pump control panel, select ‘Pump A’; 4. run the pump by pressing the ‘START’ button on the pump control panel; 5. select the measurement control panel; 6. type your name and email address. If the laboratory exercise is performed in group, type

name and email address of the person in the group which has been selected as team leader;

7. type the name of the file you want the data to be stored in. Note that if you use the same name for different measurements, the file will be overwritten;

8. press ‘send email’ if you want to receive the measurement data file to the specified email address. The distant users are always required to press the mentioned button;

9. type the values of ρ,α,AS in part B of the measurement control panel; 10. enter the number of measurement point you have decided in step 1; 11. in the selection ring ‘DAQ mode’ select “Auto (Constant Speed – Var Valve Opening)” ; 12. press the button ‘START MEASUREMENT’. If the button becomes green, the measurement

has started correctly; 13. select the ‘CHARACTERISTIC CURVE’ tab to follow the live drawing of the curve; 14. when the measurement is finished (you can check this by either looking that the opening of

the valve has reached 100% on the relative bar or that the ‘START MEASUREMENT’ button in the ‘MEASUREMENT CONTROL PANEL’ has returned to the initial status) check that the curve has been drawn on the ‘CURVES OVERVIEW’ tab;

15. check that you have received the measurement data file at the specified email address; 16. stop the pumps by pressing the ‘STOP’ button on the pumps control panel.

Does the characteristic curve resemble the curve of a centrifugal pump?

From the shape of the curve, what would you say about the shape of the impeller? Does it have backward swept or forward swept blades?

From the led on the indicators panel you can notice that when running pump A valve A is open while pump B


KTH/EKV/AC-LM

is closed. What would it happen if both valves were open?

7.2.1.2.

As a second task, complete the following steps which allow you to draw the characteristic curve for the parallel connection of pumps A and B with an auto measurement:

Parallel Connected A and B Pumps Operation

17. from the pump control panel, select ‘PARALLEL’; 18. repeat steps 4 to 16. Use the same number of points specified in step 1 and remember to

change the filename if you want the data not to be overwritten.

Does the curves in the ‘CURVES OVERVIEW’ reflect the theory about parallel connection of pumps?

Why for fully opened valve it is not possible to reach the same value of minimum delivery pressure when running the parallel connection? How is this related to the circuit?

7.2.1.3.

As a third task, test the operation of pump B performing an auto measurement:

Pump B Operation

19. from the pump control panel, select ‘Pump B’; 20. repeat steps 4 to 16. Use the same number of points specified in step 1 and remember to

change the filename if you want the data not to be overwritten.

As pumps A and B are equal, you would expect that the two characteristic curves are the same. Are the two curves exactly similar in shape and in punctual values? If not, which are the main reasons for that?

If you imagine doing the sum in flow rate of the two pumps, would you overlap exactly the curve for the parallel connection?

7.2.1.4.

As a furhter task, you have to examine the operation of a centrifugal pump when running at an off design rotational speed. To do so, complete the following steps:

Pump A, Variable Speed

21. from the pump control panel, select ‘A – Variable Speed’; 22. set a value for the rotational speed of pump A by using either the control knob or typing a

value in the window underneath it. Both controls are placed on the pump control panel; 23. repeat steps 4 to 16;

Does the relative position between the characteristic curve for pump A and the one for A at an off design condition reflect your expectations?

Do you think it exists a linear relation between the speed – expressed as percentage of the on design rotational speed – and the position of the curve? Or between the speed and the head or between the speed and the mass flow?

You have tested a pump running at at constant but off design rotational speed. To vary the operational point you have varyed the resistance of the circuit by means of a variable opening valve. The following step would be to keep the opening of the valve constant and vary sistematically the rotational speed of the pump. Here the procedure to do so:

24. repeat steps 4 to 10; 25. in the selection ring ‘DAQ mode’ select “Auto (VariableSpeed – Const Valve Opening)” ; 26. set an opening valve position by either the dedicated control bar or the window underneath

it. Both controls are in part C of the ‘MEASUREMENT CONTROL PANEL’; 27. repeat steps12 to 16.

What does the curve you have now generated represent? Does it exist a relation between the rotational speed and the flow rate? Which kind of relation is this?

If you draw the same curve but for 100% opening of the valve, what would you obtain? Why?

7.2.1.5.

As a final task, you are now required to repeat one or more of the previous measurements. This has the objective to study the repeteability of the experiment.

Repeteability of Measurements


KTH/EKV/AC-LM

If you compare to equivalent measurements what do you notice? Are the differences small enough to conclude that they are regarded as errors from the measurement equipment? If not, would you associate them to instabilities in the flow or other phenomena?

7.2.2. Serial connected pumps

Complete the following steps which allow you to draw the characteristic curve for the serial operation of the pumps with an auto measurement:

1. decide a number of measurement points between 2 and 33; 2. run the serial rig interface following the instructions in Chapter 5.1; 3. run the pump by pressing the ‘START’ button on the pump control panel; 4. select the measurement control panel; 5. type your name and email address. If the laboratory exercise is performed in group, type

name and email address of the person in the group which has been selected as team leader;

6. type the name of the file you want the data to be stored in. Note that if you use the same name for different measurements, the file will be overwritten;

7. press ‘send email’ if you want to receive the measurement data file to the specified email address. The distant users are always required to press the mentioned button;

8. type the values of ρ,α,AS in part B of the measurement control panel; 9. enter the number of measurement point you have decided in step 1; 10. in the selection ring ‘DAQ mode’ select “Auto” ; 11. press the button ‘START MEASUREMENT’. If the button becomes green, the measurement

has started correctly; 12. select the ‘CHARACTERISTIC CURVE’ tab to follow the live drawing of the curve; 13. when the measurement is finished (you can check this by either looking that the opening of

the valve has reached 100% on the relative bar or that the ‘START MEASUREMENT’ button in the ‘MEASUREMENT CONTROL PANEL’ has returned to the initial status) check that the curve has been drawn on the ‘CURVES OVERVIEW’ tab;

14. check that you have received the measurement data file at the specified email address; 15. stop the pumps by pressing the ‘STOP’ button on the pumps control panel.

How do the curves look like? Do they reflect the theory for the serial connected pumps?

If you compare the curves for the two separate pumps, is there any difference? Are the differences small enough to conclude that they are regarded as errors from the measurement equipment? If not, which would be the reason of such differences?

You have now to repeat one or more measurements to be able to conclude about the repeatability of the results.

7.1.

Write a brief (4-5 A4 pages, pdf format) lab report. The lab report shall contain the following:

Reporting

- Measured data - Observations - Discussion

The lab report can be written and uploaded in group (lab groups organized by the lab instructor). All students in the group shall equally contribute to the lab report. Only reports uploaded to Bilda before a specific deadline will be taken into account.

7.1.

All students are asked to do an evaluation of their own performance during this lab exercise. Justification shall be given for the work contributed in group. Furthermore, a brief statement on “lessons learnt” shall be included. The self evaluation will only be available if the preparative self-assessment test has been passed.

Self evaluation


KTH/EKV/AC-LM

APPENDIX I Data File Format

Fig. App I-1 shows the format of the file in which the measurement data are stored for the cases ‘Pump A’, ‘Pump B’ and ‘PARALLEL’ when using the parallel rig control interface.

The data files contain a header row followed by N data rows (one for each measurement point). The columns included are (in order of their appearance):

− Date; − Time; − Valve open [%]: valve opening. It expresses the angular position of the valve as percentage of the

angle corresponding to fully open valve. It should be reminded that because of the geometry and operation of the ball valve, the opening percentage does not correspond to the equivalent ratio between actual cross section and maximum cross section for completely opened valve;

− p_orif [kPa]: differential pressure at the orifice plate. Values expressed in kPa; − p_deliv [kPa]: delivery pressure. Values expressed in kPa; − p_suct [kPa]: pressure at the suction side. Values expressed in kPa; − T [C]: water temperature. Values expressed in °C; − sddev orif: standard deviation for the measurement on the differential pressure at the orifice plate; − sddev deliv: standard deviation for the measurement on the delivery pressure at the orifice plate; − sddev suct: standard deviation for the measurement on the suction pressure at the orifice plate; − sddev T: standard deviation for the measurement on the water temperature; − dp_pump [kPa]: pump head. It is calculated using the formulaes in Chapter 4.2. Values of pump

head expressed in kPa; − Q [l/s]: flow rate. It is calculated using the formulaes in Chapter 4.2 and the values of ρ, A and α

tiped by the user on the measurement control panel. Values of flow rate expressed in l/s;

Date Time Valve Open [%] p_orif [kPa] p_deliv [kPa] p_suct [kPa] T [C]

17/03/2011 14:23:13 0 0,154 149,988 -1,727 39,472

17/03/2011 14:23:21 36,811 1,573 137,372 -1,274 39,542

17/03/2011 14:23:27 46,346 4,145 117,503 -0,866 39,56

17/03/2011 14:23:31 46,346 3,942 118,066 -0,57 39,587

17/03/2011 14:23:38 59,215 8,449 76,145 -0,365 39,621

17/03/2011 14:23:45 100 14,753 11,733 -2,381 39,689

17/03/2011 14:23:45 100 14,753 11,733 -2,381 39,689

sddev

orif

sddev

deliv

sddev

suct

sddev

T dp_pump [kPa] Q [l/s]

0,129 0,128 0,025 0,008 151,715 0,853

0,398 0,171 0,212 0,008 138,646 2,725

0,89 0,31 0,224 0,005 118,368 4,423

0,642 0,486 0,466 0,009 118,636 4,313

0,425 0,326 0,199 0,006 76,51 6,314

0,098 0,092 0,152 0,007 14,114 8,344

Fig. App I-1: Data file format for the cases Pump A, Pump B and PARALLEL, parallel rig.

Fig. App I-2 shows the format of the file in which the measurement data are stored for the case ‘A – variable’ when using the parallel rig control interface. With respect to the previous file, some additional quantities are included:

− Pump A Speed [%]: rotational speed of the pump. It is expressed as percentage of the pump design speed.

− W_el [kW]: electrical power consumption. Values expressed in kW. − sddev W_el: standard deviation for the power consumption; − W_out [kW]: hydraulic power generated by the pump.


KTH/EKV/AC-LM

− Eta_A [-]: overall pump efficiency. It is calculated from Eq. 4-7.

Date Time Pump A Speed [%]

Valve Open [%]

p_orif [kPa]

p_deliv [kPa]

p_suct [kPa] T [C] W_el [kW]

17/03/2011 14:24:17 0 56 0,148 -4,282 -1,678 39,84 0,01

17/03/2011 14:24:22 20 57 0,512 -1,17 -1,619 39,834 0,056

17/03/2011 14:24:27 40 57 1,502 6,954 -1,524 39,832 0,144

17/03/2011 14:24:32 60 57 3,609 22,616 -1,137 39,824 0,401

17/03/2011 14:24:37 80 56 6,569 44,318 -0,879 39,832 1,119

17/03/2011 14:24:41 100 57 9,18 66,382 -0,426 39,859 1,54

17/03/2011 14:24:41 100 57 9,18 66,382 -0,426 39,859 1,54

Sddev

orif

Sddev

deliv

Sddev

suct

Sddev

T

Sddev

W_el dp_pump [kPa] Q [l/s]

W_out [kW] eta_A [-]

0,018 0,027 0,008 0,004 0,001 -2,604 0,836 -0,002 -0,215

0,026 0,046 0,032 0,008 0,004 0,449 1,554 0,001 0,012

0,065 0,087 0,047 0,005 0,006 8,478 2,662 0,023 0,157

0,16 0,151 0,165 0,006 0,003 23,753 4,127 0,098 0,244

0,244 0,343 0,293 0,004 0,01 45,197 5,567 0,252 0,225

0,432 0,393 0,259 0,011 0,011 66,808 6,582 0,44 0,286

Fig. App I-2: Data file format for the case Pump A - Variable, parallel rig.

Fig. App I-3 shows the format of the file in which the measurement data are stored when using the control interface for the serial rig.

The data files contain a header row followed by N data rows (one for each measurement point). The columns included are (in order of their appearance):

− Date; − Time; − Valve open [%]: valve opening; − p_orif [kPa]: differential pressure at the orifice plate. Values expressed in kPa; − p_suct [kPa]: pressure at the suction side. Values expressed in kPa − p_interm [kPa]: intermediate pressure. Values expressed in kPa; − p_deliv [kPa]: delivery pressure. Values expressed in kPa; − T [C]: water temperature. Values expressed in °C; − sddev orif: standard deviation for the measurement on the differential pressure at the orifice

plate; − sddev suct: standard deviation for the measurement on the suction pressure at the orifice

plate; − sddev interm: standard deviation for the measurement on the intermediate pressure; − sddev deliv: standard deviation for the measurement on the delivery pressure; − sddev T: standard deviation for the measurement on the water temperature; − dp_pump tot [kPa]: serial connection pump head. Values of pump head expressed in kPa; − dp_pump lp [kPa]: low pressure pump head. Values of pump head expressed in kPa; − dp_pump hp [kPa]: high pressure pump head. Values of pump head expressed in kPa; − Q [l/s]: flow rate. It is calculated using the formulaes in Section 4.4 and the values of ρ, A

and α tiped by the user on the measurement control panel. Values of flow rate expressed in l/s.

Date Time Valve Open [%]

p_orif [kPa]

p_suct [kPa]

p_interm [kPa]

p_deliv [kPa] T [C]

Sddev

orif

17/03/2011 18:09:57 0 -0,219 -2,267 153,248 294,387 29,584 0,335


KTH/EKV/AC-LM

17/03/2011 18:10:04 35,989 1,676 1,298 131,753 252,946 29,732 0,532

17/03/2011 18:10:09 46,883 4,508 2,995 96,811 203,323 29,765 0,862

17/03/2011 18:10:15 67,159 11,617 4,666 19,379 87,149 29,904 0,97

17/03/2011 18:10:21 84,522 14,037 2,11 -17,069 36,125 30,065 0,85

17/03/2011 18:10:26 100 14,886 0,304 -21,358 16,122 30,233 0,689

17/03/2011 18:10:26 100 14,886 0,304 -21,358 16,122 30,233 0,689

Sddev

suct

Sddev

interm

Sddev

deliv

Sddev

T

dp_pump

tot [kPa]

dp_pump

lp [kPa]

dp_pump

hp [kPa] Q [l/s]

0,022 0,411 0,38 0,009 296,654 155,516 141,139 1,016

0,539 0,894 0,707 0,015 251,647 130,455 121,193 2,812

0,904 1,095 0,895 0,005 200,328 93,815 106,512 4,612

0,638 1,668 1,207 0,012 82,483 14,714 67,769 7,404

0,719 2,705 0,988 0,019 34,015 -19,179 53,194 8,138

0,346 0,048 0,331 0,017 15,818 -21,662 37,48 8,381

Fig. App I-3: Data file format for the serial rig

remote laboratory exercise determination of the … pump lab notes 2 2011-10-04 kth/ekv/ac-lm...

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