Laboratory Notes Determination of Losses in a Linear Cascade (approx. hours laboratory exercise) Blades Stepper motor for moving the probes By Navarathna N. and Wei N. Division of Heat and Power Technology Laboratory Notes Heat and Power Division Royal Institute of Technology 100 44 Stockholm, Sweden
CONTENTS NOMENCLATURE... 3 SUMMARY... 5 1. INTRODUCTION AND OBJECTIVES... 6. EXPERIMENTAL FACILITY... 7.1. INTRODUCTION... 7.. AIR SUPPLY... 7.3. CASCADE FACILITY... 8.4. LAB USER INTERFACE... 10 3. MEASURING EQUIPMENT... 1 3.1. INTRODUCTION... 1 3.. AERODYNAMIC PROBES... 1 3.4. TEMPERATURE... 15 3.6. MEASUREMENT ACCURACY... 15 4. HOW TO DETERMINE LOSSES... 17 4.1. EQUATIONS FOR DETERMINING THE LOSS COEFFICIENT... 17 4.. TO OBTAIN AVERAGE VALUES... 19 5. LABORATORY PROCEDURE... 1 5.1. START THE TEST SYSTEM... 1 5.. MEASUREMENTS... 1 5.3. EVALUATION... 4 6. REFERENCES... 6 Appendix 1: Coordinates of a Blade Appendix : Correction Method for Pressure Gradient Appendix 3: The General Requirements for Writing a Laboratory Exercise Report at the Chair of Heat and Power Technology Appendix 4: Selected Images of the Linear Cascade Lab Appendix 5: Linear Cascade virtual lab exercise
NOMENCLATURE c absolute velocity m/s c p specific heat capacity at constant pressure kj/(kg o C) C blade chord m H span of blade m h specific enthalpy kj/kg Δh specific enthalpy change kj/kg p pressure Pa s distance on pitch wise direction of cascade m T temperature K t blade pitch m u tangential velocity m/s α flow angle between absolute velocity and axial direction of cascade α 1,R reading of probe angle downstream o blades reference to vertical direction γ ratio of heat exchange, c p /c v - γ stagger angle o ρ density kg/m 3 η efficiency Δη efficiency change - ζ loss coefficient - index 0 upstream of the cascade 1 downstream of the cascade c stagnation values in absolute frame of reference c i stagnation value at the cross section i, i=0, 1 in inlet out outlet p process at the condition of the constant pressure s isentropic v process at the condition of the constant specific volume o 3
LIST OF ABBREVIATIONS 4
SUMMARY The laboratory exercise Flow Losses in a Linear Cascade aims at providing practical training to the students in measuring pressure losses in a linear turbine cascade. Great effort has been put to simulate the real state where a gas turbine is supplied with a flow of high velocity gas passing through it. Here, an air stream (around.6 kg/s air mass flow rate) passes through a row of blades representing the linear turbine cascade. The measurement of the pressure of the airflow upstream and downstream of the cascade at various traverse locations gives the pressure losses over the blades. Students use the experimental data with relations given for determination of pressure losses in a linear turbine cascade. The pressure loss coefficient is calculated for the different positions and illustrated in a diagram with the measuring positions in the horizontal axis 5
1. INTRODUCTION AND OBJECTIVES The participants are expected to acquire an understanding of losses in turbomachines and be able to determine losses in a linear cascade measurement. The exercise will be performed in the cold flow linear test cascade which is fixed at the open subsonic wind tunnel system at the laboratory of the Heat and Power Technology, KTH and from a remote location through the internet. The main equipment used to take measurements for this exercise are two aerodynamic probes and pressure transducers/manometers. The flow through the cascade is air. With the aerodynamic probes, total pressures at upstream and downstream locations of the cascade will be measured to determine the aerodynamic losses. The downstream flow angle of the cascade is also determined with the aerodynamic probe. As it is an open test facility, the static pressure of the downstream flow of the cascade is the same as the atmospheric pressure. Details of the test facility, the lab exercise procedure and the principle of determining the losses will be described in the following chapters. 6
. EXPERIMENTAL FACILITY.1. Introduction The exercise can be performed in the laboratory of Heat and Power Technology or from a remote location through the internet. The experimental facility for the laboratory consists of an air supply system and a test cascade... Air Supply A high-speed fan delivers a maximum of.5 kg/s of air to the cascade. The flow scheme of the experimental facility is shown in figure.1. The technical data of the compressor is shown in table.1. Type Two stages compressor Max. power 90 kw Max. revolution 3600 rpm Max. pressure 16 kpa Max. mass flow.5 kg/s Max. volume flow.1 m 3 /s Table.1: Technical data of the compressor Inlet air from outside the building Valve for Inlet air from within the building Inlet air from within the building Valves Wall Valve for Inlet air from outside Compressor Control switches Linear cascade facility Motor Fig..1: Flow scheme of the experimental facility. 7
Laboratory on cascade losses.3. Cascade Facility Fig.. shows the scheme of the test section and cascade facility. 1. Stepper motor controlled micrometer for moving the probes. Grid holder 3. Side walls 4. Aerodynamic probes Stepper motor for moving the probes Fig..: The scheme of the test section and the cascade facility with close-up of the blades The side walls of the cascade facility, 3 in Fig.., are vertically moveable, and the grid holder, in Fig.., can be adjusted, thereby the inlet flow angle can be varied by changing the position of the side walls and the lean angle of the grid holder, i.e. turn the entire cascade. 8
All blades in the cascade are identical (within manufacturing tolerances) and of impulse design. The geometrical coordinates can be found in appendix 1. The cascade blades are shown in Fig..4 _ α0 + γ 0.7 mm α1 _ + Fig..4: The cascade blades Geometry of the cascade is shown in Table.. Chord, C 0.030 m Axial Chord 0.007 m Span, H 0.100 m Pitch, t 0.0 m Stagger angle, γ 19.3 0 Number of blades 14 Table.: geometry of test cascade 9
.4. Lab user interface The users perform the lab exercise with the graphic user interface shown in fig..5. This user interface contains two live video streaming windows. The users have full control of Pan, Tilt and Zoom of the two cameras. The location of the cameras and the layout of the room where the linear cascade lab is located are shown in fig..6. Users are advice to visit virtual tour of the Linear Cascade remote lab website to watch the video of the room where Linear cascade lab located. The user interface also contains an audio control button so that the users can regulate or mute the sound. Below the streaming windows there are several sub control panels as described in fig.5. Two live video streaming windows with full control of Pan, Tilt and Zoom of the cameras Probe rotation sub control panel The gauge shows the actual probe angle. Probe rotation can be done by clicking on the arrow. The probe should be rotated until the differential pressure is close to zero (check blue bars represent the manometer) Quit button Help button Sound control indicator lamps indicate current activities Message from Remote Lab & CET Clock Chat window Probe position control The movement can be done in incremental steps by pushing the direction arrow or type a value in the blue box and hit enter Pressure readings Blue bars represent manometers Data log button Fig..5 Linear cascade lab computer interface (control panel) 10
Air exhaust Liquid manometers Camera (right side live video window in lab interface) Air out Lab server computer Camera (left side live video window in lab interface) Fig..6 Layout of the room where Linear cascade lab located The probe sub-control panel consists of two parts: probe rotation and probe positioning. Here, the user can control the probes using incremental and absolute values as well as get information about the position of the probes. Blue bars represent manometers used to align the probes with the airflow. A chat window permits the users to communicate within the user group and share the experience. The users can also employ the chat window to communicate with the lab instructor. The message window displays important information during the lab. The data logging consists of one altering window that can switch between graph and indicator mode. Indicator mode shows current activity and the graph shows the values of the logged data points. The data points are logged manually by pressing the Log data button. The users are able to select the last data point or eliminate and repeat the measurement. 11
3. MEASURING EQUIPMENT 3.1. Introduction Following measurements are taken during the laboratory exercise. Upstream: Downstream: p c0, stagnation pressure p c1, stagnation pressure Δp, difference of pressure measured by the probe p 1, static pressure, same value as atmospheric pressure p atm T 1, static temperature, same as ambient temperature All the pressure data are measured using pressure-transducers 1. The users can read the pressure measurements on the computer screen. Users also have the possibility to view the U-tube manometers filled with water which are hanging on the wall of the testing room. 3.. Aerodynamic Probes Two aerodynamic probes are utilized for measuring total pressure and flow angles at downstream and upstream. Probe DA 10, a 3-hole probe, is mounted at downstream location of the cascade, and probe DA 15, a 3-hole probe is mounted at upstream location of the cascade. Fig. 3.1: The head of the downstream probe DA 10 1 The model number of the pressure transducers are SENSYM HCXM100D6V (downstream) and SENSYM HCXM100D6V (upstream) 1
SH 01 SH 0 MH 01 Fig. 3.: A close up photo and the drawing of the head of the downstream probe DA 10 The length of the probe DA 10 shown in Fig. 3.4. is 0.5 m. The pitch-wise angle and total pressure of the flow can be measured using this probe. Fig. 3.3.: Photo of the entire probe DA 10 Fig. 3.1 shows the head of the probe DA 10. In Fig. 3., the middle hole (MH 01 ) measures the total pressure of flow, and the side holes (SH 01 & SH 0 ) are used to measure differential pressures to determine the pitch-wise angles of the flow. Fig. 3.3 shows the snapshot of the entire probe DA 10. Fig. 3.4 shows the drawing of the entire probe DA 15 together with a snap shot of the probe. Such a probe can also be used to, after detailed calibration, determine the local static pressure of the flow. This is however not done in the present lab exercise 13
Fig. 3.4.: A photo and the drawing of the probe DA 15 Fig. 3.5 shows the principle of measuring the pitch-wise flow angle with 3 holes on a probe. φ p SH p SH 1 1 p MH 1 Fig. 3.5: Principle of measuring the pitch-wise flow angle with a 3- hole probe In Fig. 3.5, the relationship between the angle φ and the difference of pressure (pressure of SH 1 - pressure of SH ), can be expressed as: φ=f(δp) (.1) For each probe, the exact expression of the formula could be obtained after calibration of the probe. 14
For a well manufactured probe, φ=0, when Δp=0. In this lab exercise it is assumed that the stagnation pressure (p 0 ) is measured at the center pressure tap (MH 1 ) when the pressure difference (Δp) for the side pressure taps (SH 1 and SH ) is equal to zero. Measurements with aerodynamic probes concern a wide field of aerodynamic knowledge and is not discussed in this document 3. During the lab exercise, downstream flow angles will be measured with the probe DA 10. The upstream flow angle will not be measured as the flow direction is assumed to be vertical and does not change with the probe location. The probes are installed on the frame of the test cascade which can move along the pitch direction. A stepper motor controlled micrometer moves that frame (i.e. moves both probes together) along the pitch direction as shown in Fig..4. The total pressure at the upstream and downstream locations of the cascade can be measured by probe DA 15 and probe DA 10 respectively. The pressure readings measured using the pressure transducers, connected to the probes, are displayed on the computer screen (Fig.5). The angle between the downstream flow and the probe DA 10 can be changed by turning the downstream probe using the stepper motor connected to it. When this angle is changed, the pressure difference Δp, which is measured by the two side holes (SH 1 and SH in figure 3.5) on the probe, also varies. When Δp is equal to zero, the angle between the probe and the flow (φ in Fig, 3.5) is zero. The turned angle of the probe can be read on the computer screen, thereby the flow angle at the outlet of the cascade can be obtained. 3.4. Temperature The downstream static temperature is considered to be the same as the environment temperature which is measured with a normal thermometer kept in the room. 3.6. Measurement Accuracy In the experimental studies, there are always measurement errors. In general, accuracy of the measurements could be affected by: construction of measuring equipment calibration of measuring equipment installation of measuring equipment conditions of measurement human error 3 An interesting introduction about the probes can be found in papers by Fransson & Sari [1981] and Dominy & Hodson [199]. 15
In this laboratory exercise, the aerodynamic probes are the main measuring instruments. The construction and conditions of the probes will very much influence the accuracy of the measurement. For example, the diameter of the probes will influence the flow angle measurements. Smaller the diameter of probes, better the accuracy will be. It is difficult to estimate the accuracy of the probes. One possible way of compensating for the non-uniform flow conditions downstream of a blade row is to perform a gradient correction Wallen, [1981]. The pressure taps SH 1 and SH are not in exactly the same location on the probe head as the pressure tap MH 1 (as seen from the flow (Fig. 3.5). This can add a considerable error to the results in a flow with large pressure gradients (for example in a wake of a blade). A geometrical correction of the position of the pressure taps on the probe head should preferable be performed before the data collection. It is obvious that such a correction is only of value if a very detailed, closely spaced set of data points has been taken. If the distance between two measuring points, Δx, is much larger than the distance between the pressure taps, δ, the correction would be of no importance 4. Leakage from the tubes which connect the probes and manometers and pressure transducers is another factor which influences the measurement accuracy. This error could be difficult to estimate. According to the manufacturer of the pressure-transducers, the resolution of the pressure-transducers can be estimated as ±5 Pa. The user should thus be aware of the fact that the accuracy of the manometers is more than.5 times higher than the transducers. 4 More information about the measurement accuracy of aerodynamic probes can be found in the reports by Fransson & Sari, [1981] and Dominy & Hodson, [199]. 16
4. HOW TO DETERMINE LOSSES The loss coefficients are used for the calculation of stage efficiencies. It is thus very important to have as high accuracy as possible. 4.1. Equations for Determining the Loss Coefficient The efficiency of flow through a stator of turbine was defined by Söderberg [1989, p. 7..1] as: c1 η = 0 h c (4.1) Δ s+ and the coefficient of losses is as: ζ = 1 η (4.) Fig. 4.1 shows enthalpy-entropy diagram for the flow in a turbine stage. The quantities in the equation 4.1 are shown in Fig. 4.1. h P C0 h c C 0 / h o P 0 C 1 / Δh S Δh a a h 1 P 1 Δh a h 1S h C Δh S Δh f C / P C Δh Δh S h P Δh f h S S 0 S 1 S Fig. 4.1 Enthalpy-entropy diagram for flow through a turbine stage, [Söderberg, 1989, Fig..5.1] S 17
Let 1s c 0 s c = Δ h + (4.3) By substituting equation 4.3 into equation 4.1, we get: η = c c 1 1s (4.4) from Fig. 4.1, we get: h+ c 0 0 s h + c 1 = 1s (4.5) h + c 0 0 h+ c 1 1 = = h h 00 01 (4.6) (4.7) For perfect and polytropic gas, the basic thermodynamic relations apply as: Δh=c ΔT, T T p p p s = 1 0 1 0 γ -1 γ -1 γ, T0 TC0 = p0 pc0 γ, γ 1 c1 = p 1 p - 1 C1 γ T T Substitute these thermodynamic relations and equation 4.6 into equation 4.5, we get: c 1 γ s -1 = p c0 p c0 1 C0 γ c T - c T p p (4.8) In the same way, we can get: c γ - 1 = cptc1 - cpt 1 C1 (4.9) [ p1 pc1] γ Substitute equation (4.8) and (4.9) into equation (4.4), and consider T 00 =T 01, we get: η = 1 - p p 1 - p p 1 C1 1 C0 γ - 1 γ γ - 1 γ (4.10) Then substitute equation (4.10) into equation (4.), we finally get: ζ = γ -1 [ p1 pc1] γ [ p1 pc0] 1- [ p1 p ] C0 γ -1 γ γ -1 γ (4.11) In the equation 4.11, the loss coefficient ζ is determined by the upstream stagnation pressure p c0, the downstream stagnation pressure p c1 and the downstream static pressure p 1. 18
During the test, p c0 and p c1 are measured with the aerodynamic probes and p 1 is equal to the atmospheric pressure. Thereby the loss coefficient ζ can be calculated with equation (4.11). 4.. To Obtain Average Values With the equation 4.11, only the local loss coefficient at the measuring position will be determined. The average loss coefficient of the cascade must also be calculated. The averaged energy loss coefficient can be calculated on a mass-averaged basis Mobarak et al [1988]. On the mass-averaged basis, the general loss coefficient of a cascade with 3-D calculation is Moore & Ransmayr [1983]: ζ = ρ 1 ρ c c 1 1n ζdydz 1n dydz (4.1) Here, c 1n is the velocity component normal to the measuring plane downstream of the cascade, y and z are coordinates in pitch and span direction respectively. In our two-dimensional exercise, the variation of the loss coefficient along the blade span direction is not considered, so the above equation can be simplified as: ζ = i i ρ 1i 1ni i ρ c c 1i 1ni ζ Δs Δs (4.13) Here, Δs is the distance between two neighboring measuring positions in pitch direction, and the subscript i represents different measuring positions. From state equation, ρ 1i =p 1 /RT 1 (4.14) Since pressure p 1 and temperature T 1 are constant over the pitch-wise direction and the interval Δs is also constant, we get: ζ = c1 i c i ni ζ 1ni i (4.15) In equation (4.15), the local loss coefficient ζ i can be calculated by equation (4.11), the normal velocity component c 1ni can be calculated by: c 1n =c 1 cos(α 1 ) (4.16) 19
and from Fig. 3.1: c 1 =(h c0 -h 1 ) (4.17) From (h c0 -h 1 ) =c p T 1 (T c0 /T 1-1), and Tc T = pc p 0 1 0 1 γ -1 γ and from 4.16 and 4.17 we get: and γ -1 γ c1= ct p 1(( pc 0/ p1) 1) γ -1 γ c1n = cos( α1) ct p 1(( pc 0/ p1) 1) (4.18) (4.19) In this equation, p c0, p 1 and α 1 are measured by the aerodynamic probes. T 1. is the environment temperature and is measured by the thermometer. The c 1n is calculated at every measuring position with the above measured values. After the local loss coefficient is calculated with equation 4.11, the average loss coefficient of the cascade can be calculated from equations 4.19 and 4.15. 0
5. LABORATORY PROCEDURE 5.1. Start the Test System The start of the test system is taken care of by a lab technician. The computer interface shown in figure.5 is used to control the equipments and acquire the data. 1. Ensure that the equipment in the test section is fixed (taken care by a lab assistant).. Start the wind tunnel motor and wait until the motor has reached the right speed (taken care by a lab assistant). Then an indicator will turn to green on the computer interface. 5.. Measurements During the lab exercise, the pressures p c0 and p c1 are measured using aerodynamic probes. The value for the pressure p c1 and p c0 can be read from the computer screen. After the air-flow has started, wait until the pressure is stabilized. Keep watching the blue bars which represent the manometers at probe rotation sub control panel to see if the pressure readings on it become stabilized (refer to figure.5). Move the probes to the mm position in the linear motion sub control panel. Fig 5.1 shows the positions of the blades together with the approximate positions of the wakes. Fig. 5.1 Positions of the blades together with the approximate positions of the wakes Then take measurements as follows: 1. Write down the flow inlet angle α 0 in table 5.1 ( α 0 is pre-defined and has value of 19. 3 ). Write down atmospheric pressure value in table 5.1 as p 1. 3. Write down environment temperature value in table 5.1 as T 1. 1
4. Write down the span-wise probe position in table 5.1. (In this case it is 50% of span) 5. Check whether the downstream probe position is zero degree in the downstream probe rotation sub control panel. In this position the probe in the test rig is turned by -84.5 degree from the vertical axis i.e. α 1p, initial = 84. 5. Remember that this angle is the reference angle of the probe direction 6. Write the initial measurement position s in table 5.1. 7. Turn the downstream probe slowly and watch the manometer of the differential pressure of the probe until this differential pressure is equal to zero (or keep watching on the blue bars representing the manometers in the lab user interface in the computer until they reach the same level). Then you will see the green indicator showing selected probes are aligned. Read the angle difference, α 1,R, between the existing probe direction and the reference direction. Write the reading in table 5.1. Press log data button on the Data logging sub control panel in order to log pressures and flow angle values. 8. Read the upstream pressure value from computer screen and write it down in table 5.1. 9. Read the downstream pressure value from computer screen and write it down also in table 5.1. 10. Set the increment of linear motion of the probe to an appropriate distance (for example mm). Use your engineering skills to determine an appropriate distance. Then click on the direction arrow to move the probes mm along the pitch direction, and write down the new measurement position (-0mm), s, in table 5.1. 11. Wait for a few seconds for pressure field to get stabilized, repeat the steps 7, 8, 9 and 10, and continue until measurements are made for all positions. The first part measurement of the experiment is completed after the readings have been taken over pitches, (covering a 44 mm distance) i.e. as an example, the probes will be moved 3 times along the pitch direction in mm steps. Then go back and redo measurements with smaller steps (for example down to 0. mm) in the regions of large pressure gradients (refer the auto generated graph in the Data Logging sub control panel in Fig..5).
Name: Group: α 0 ( 0 ) p 1= p atm (p a ) T1 ( 0 c) Span-wise position of downstream probe Meas. positions 1 3 4 5 6 7 8 9 10 11 1 13 14 15 16 17 18 19 0 1 3 s (mm) α 1,R ( 0 ) p c1 (p a ) p c0 -p c1 (p a ) α 1 ( 0 ) p c0 (p a ) (p c0 - p c1 )/p c0 c 1n (m/s) ζ ζ η Table 5.1: Measured and calculated values 3
5.3. Evaluation After taking the measurements, following evaluations are to be performed and reported: 1. Calculate the downstream flow angle, α 1, by subtracting inflow angle α 0 from downstream probe angle α 1p, as described in equation (5.1) : α = α p (5.1) 1 1 α 0 The inlet flow angle, α 0, is defined by geometry of the setup and is α 0 = 19. 3 (following the notation defined in Figure.4.). α 1p, initial Downstream probe angle is equal to the initial probe angle,, minus angle difference that you can read after each time you align the downstream probe i.e. α = + (5.) 1p α1p, initial α1, R Initial probe angle is pre-settled to α = 84. 5 and corresponds to zero 1p, initial degree reading in downstream probe rotation sub control panel.. Calculate the upstream total pressure p c0 and the ratio (p c0 -p c1 )/p c0. 3. Calculate c 1n, the normal component of downstream flow velocity, with equation (4.19), γ=1.4, and c p is chosen according to T 1. 4. Calculate the local loss coefficient ζ with equation (4.11b). 5. Calculate the total average loss coefficient ζ with equation (4.15). 6. Calculate the cascade efficiency η with equation (4.). 7. Construct the diagram with "(p c0 -p c1 )/p c0 " as function f(s) 4
8. Discuss the results and write a report for this laboratory exercise including the measured data, evaluated results and discussions (Please refer to appendix 3). Hints Look at the exact shape of the curves? How do the flow angles and pressure change in the regions between blades? How do these change in the regions of the blade wakes? How large are the losses in the different regions? How periodic is the flow? If periodic, why? If not periodic, why not? Etc. 5
6. REFERENCES Söderberg, O.; 1989 "Termiska Strömningsmaskiner" HPT, KTH Dominy, R. G.; Hodson, H. P.; 199 "An Investigation of Factors Influencing the Calibration of 5-holes probes for 3-D Flow Measurements" ASME, 9-GT-16 Fransson, T.; Sari, I.; 1981 "Characteristics of Aerodynamic 5-Holes probes in Transonic and Supersonic Flow Regimes" Proc. of 6th Symp. on measuring techniques in transonic and supersonic flow in cascade and tubomachines, Lyon. Mobarak, A. Khalafallah, M. G.; Osman, A. M.; Heikal, H. A.; 1988 "Experimental Investigation of Secondary Flow and Mixing Downstream of Straight Turbine Cascade" ASME, Journal of Turbomachinery, Vol. 110, October 1988. Moore, J.; Ransmayr, A.; 1983 "Flow in a Turbine Cascade, Part1: Losses and Leading-Edge Effects" ASME, 83-GT-68 Navarathna, N., Fedulov, F., Martin, A., Fransson, T.; 004: Web-Based, Interactive Laboratory Experiments in Turbomachine Aerodynamics, ASME Turbo Expo 004,Power for Land, Sea and Air, 14-17 June, 004, Vienna, Austria. Wallen, G.; 1981: The influence of Reynolds Number and gradient correction method for five-hole pressure probes, Proceedings of the 5 th Symposium on Measuring Techniques in Transonic and Supersonic Flows in Cascades and Turbomachines, Lyon, France, October 15-16, 1981, pp.1-.19. 6
APPENDIX 1: Nominal Coordinates of a Blade with Cord Leangth100mm APPENDIX : Correction for pressure gradient Fig. 6.1 Correction for pressure gradient [Wallen, 1981, Fig 1] 7
8
APPENDIX : Correction method for pressure gradient Fig. 6.1 Correction for pressure gradients [Wallen, 1981, Fig. 1] Correction method for pressure gradient will be described here APPENDIX 3: 9
Guidelines for Writing the Laboratory Exercise Report This is a short description of how the lab exercise report should be structured. Front page Title of the lab exercise, Name and of the student, Email of the student, Name of the instructor, Course name, number and year, Date of the exercise was performed, Date of report submission Abstract A short summary of the report. Not more than one page. Introduction and background Explanation of why the lab exercise is performed. Objectives Objectives of the lab exercise Method of attack Describes how the lab exercise was performed. Observations Original lab observation sheet that use to record the data during the lab exercise Calculations Show an example calculation and fill the table 5.1. Show plots. Results Try to analyze the findings and explain them. Discussion (At least one A4 size page) Please discuss about the results, possible errors, possible mistakes, possible confusions, about computer interface, remote lab and virtual lab Do you find this as a interesting lab? explain As you feel what is missing in this lab exercise? What was the most difficult part and what was the most easiest part to understand in this lab exercise? Improvements and suggestions Other than the points mention here, please discuss your own ideas related to this lab exercise. Conclusions Describes in short the findings of the lab exercise. 30
References List of the literature used. The report should be submitted to the local lab instructor within two weeks of time after the lab exercise was performed. 31
APPENDIX 4: Selected images of the linear cascade lab Air exhaust from room Air Air Blades Air Fig. 6. Linear cascade facility and air exhaust from room 3
Upstream Probe rotation Indicator Downstream probe rotation Indicator Stepper motor for downstream probe rotation Liner actuator to locate the linear position Stepper motor for Upstream probe rotation Stepper motor to control linear motion Fig. 6.3 Equipment for control the probes in linear cascade facility Lab server computer Fig. 6.4 Lab server computer including audio and video server 33
Pressure Transducers Fig. 6.5 Pressure transducers 34
APPENDIX 5: Linear Cascade virtual lab exercise The Linear Cascade Virtual Lab exercise has developed based on collected real measurements. It resembles the remote lab interface in many ways although video images and audio effects are not included. Fig 6.6 shows a screen snapshot of the virtual lab. All necessary guidelines to perform the lab exercise appear on the top of the window; just above the linear cascade blades. At the top left hand corner the students can find the atmospheric conditions that they have to find at the beginning of the experiment. The small window below that is used to find the inclination of the row of blades. Students can virtually move the two probes using thumb in pitch wised position sub window which is at the lower middle window. Students can virtually rotate and align the probes towards the virtual air flow at the top left window. All virtual pressure readings appear on the window in the bottom right corner. In this virtual lab students are supposed to take three readings. After three readings the complete graphical representation will be plotted in the screen. Fig. 6.6: Virtual lab user interface 35