FOUR CHANNELS BLADE TIP CLEARANCE MEASUREMENT SOFTWARE
Release 0807a CAPAAB 22/32 sentier des Torques BAT 8 92290 Chatenay Malabry France + 33 1 71 22 73 72 www.capaab.fr
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BLADE TIP CLEARANCE MEASUREMENT SOFTWARE
FOUR CHANNELS BLADE TIP CLEARANCE MEASUREMENT SOFTWARE Contents 1 2 3
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INTRODUCTION .......................................................................................................................................... 3 THE ACQUISITION SOFTWARE MENU ................................................................................................... 4 FILE MENU ................................................................................................................................................... 5 3.1 NEW CONFIGURATION...................................................................................................................... 5 3.2 OPEN CONFIGURATION..................................................................................................................... 7 3.3 SAVE CONFIGURATION..................................................................................................................... 9 3.4 PRINT FRONT PANEL ......................................................................................................................... 9 3.5 QUIT ....................................................................................................................................................... 9 CONFIGURATION...................................................................................................................................... 10 4.1 MAIN ACQUISITION PARAMETERS .............................................................................................. 10 4.2 CHANGE SENSORS CONFIGURATION .......................................................................................... 12 4.3 ADD COMMENTS .............................................................................................................................. 13 BLADE TIP CLEARANCE (DISTANCE) MEASUREMENT ................................................................... 15 5.1 MEASUREMENT INITIALISATION................................................................................................. 16 5.2 DISPLAY TIME FUNCTION MEASUREMENT............................................................................... 17 5.3 FAST ACQUISITION WITHOUT VISUALISATION ....................................................................... 22 5.4 END MEASUREMENT ....................................................................................................................... 23 REPLAY ....................................................................................................................................................... 24 6.1 TIME FUNCTION MEASUREMENT REREADING......................................................................... 24 6.2 STOP REREADING ............................................................................................................................. 25 BACKUP ...................................................................................................................................................... 26 7.1 SAVE MEASUREMENT AS ............................................................................................................... 26 7.2 CONVERT VOLTAGE TO DISTANCE ............................................................................................. 27 HELP............................................................................................................................................................. 27
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BLADE TIP CLEARANCE MEASUREMENT SOFTWARE
1 INTRODUCTION Blade tip clearance measurement system includes a National Instruments PCI 6115 PCI local bus acquisition card with up to four 10 MS/s simultaneous sampling channels available, a PC computer with installed programs (LabView runtime engine, Ni-DAQmx driver) and the specific BTC application program developed by CAPAAB. Under the control of this program, the processor of the PC drives acquisition card, which reads the 4 incoming voltage from the 4 capacitive conditioning units. These capacitive measurement modules provide voltage proportional to the capacitance between the capacitive sensor and the tip of each passing blade. In this application, the target consists in the successive blades of a fan, a compressor or a turbine. Thanks to the calibration curve of each channel (get in a static mode), the actual voltages are automatically converted into distances and displayed on the PC screen (curves and actual values). So, it is possible to get a real time 4 channels monitoring of the engine blade tip clearance evolution. This document explains how acquisition programs run and how to use it.
The sketch below shows the CAPAAB typical set up for blade tip clearance measurements: Interconnection box
4 channels PCI acquisition card
Probes Conditioning unit
Acquisition card cable 4 Coaxial cables
DC power supply
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PC with AOIP BTC soft
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BLADE TIP CLEARANCE MEASUREMENT SOFTWARE
2 THE ACQUISITION SOFTWARE MENU The toolbar menu contains six main command : - FILE - CONFIGURATION - DISTANCE MESUREMENT - REPLAY MESUREMENTS - BACKUP - HELP
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BLADE TIP CLEARANCE MEASUREMENT SOFTWARE
3 FILE MENU This menu contains 5 sub menus : New configuration, Open configuration, Save configuration, Print front panel and Quit
3.1
NEW CONFIGURATION
As the “Password” is validated, the following “windows” appears: No Password is required for the first install.
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BLADE TIP CLEARANCE MEASUREMENT SOFTWARE
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All configuration parameters are set to zero or to the previous input values. Configuration numeric commands and measurement channels array appears on screen while graphic indicators are erased. The user has to input the selected names and / or values. The labels named a0offset, a1gain, a2, a3, a4 correspond to the probe calibration curve coefficients as described in the “CAP 1000 USER MANUAL” or “CAP 1800 USER MANUAL”.
When it’s completed, the “save configuration” command must be activated:
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BLADE TIP CLEARANCE MEASUREMENT SOFTWARE
The screen shown below appears and a name of the file name to be saved “****.cfg” must be typed.
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3.2
OPEN CONFIGURATION
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BLADE TIP CLEARANCE MEASUREMENT SOFTWARE
As the “Password” is validated, the following “windows” appears:
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In fact, the user has to open a configuration file with a double click on this file name, when dialogs box « Choose a configuration file to open » display on screen. All controls of acquisition are displayed (see Configuration menu). This command reloads the configuration parameters to values which have been saved on hard drive in the named configuration file. The copy of the screen below shows an example for a 2 channels configuration.
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BLADE TIP CLEARANCE MEASUREMENT SOFTWARE
Remark: the first channel number must start at 0 and not at 1 (it’s the acquisition card manufacturer choice!) 3.3
SAVE CONFIGURATION
This command allows saving all configuration parameters in a text format file. All parameters are saved in same order than for option “Open and Save”.
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3.4
PRINT FRONT PANEL Display actual measurement window, then print front panel which is displayed.
3.5
QUIT The “dialog box” asks for a confirmation if user wants to quit the program. If user selects “Yes”, front panel of virtual instrument is closed, then program returns back to the “WINDOWS” environment.
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BLADE TIP CLEARANCE MEASUREMENT SOFTWARE
4 CONFIGURATION In order to edit a configuration, as a first step, the user has to choose “yes” and then type the “password” and then validate: CAPAAB
4.1
MAIN ACQUISITION PARAMETERS
As the actual configuration is opened, the windows look like the next figure (2 channels example): CAPAAB
The meaning of each field is given below. The input values for the acquisition must be set to selected values:
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BLADE TIP CLEARANCE MEASUREMENT SOFTWARE
- « Sample rate » determines sample acquisition frequency for all measurement channels. It is recommended to chose 10 000 0000 Hz for rotor tested at high rotation speed. - « Measurement duration» set the duration for acquisition sequence. Value must be typed in minutes. At the end of this duration, acquisition will be stopped. The number of samples that will be recorded is dependent on the measurement duration, the sample rate and the number of active channels. - « Number of blades » value must be set to the number of fan, compressor or turbine blades (Nb > 2). - « Constant 1 (AB) » used when combination between measurements is wanted, settle constant 1 for operation: constant 1 – (distance A + distance B). - « Constant 2 (CD) » used when combination between measurements is wanted, settle constant 2 for operation: constant 2 – (distance C + distance D). -
« Delay between two measurements »: is equal to the time between the last buffer of samples of a given acquisition and the first sample of the next consecutive acquisition buffer of a channel or a group of channels (in seconds). If 0 is selected, all acquisitions are done one after the other, without pause.
When modifications are ended, user must “VALIDATE” and he has the possibility to add comments:
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BLADE TIP CLEARANCE MEASUREMENT SOFTWARE
If the answer is “YES”, the following “windows” appears at the screen: CAPAAB
Inside the white area, the user can type its own comments, and they will be saved in the associated configuration file. 4.2
CHANGE SENSORS CONFIGURATION
Allow to set configuration of the 4 available acquisition channels. Before, user must enter a password to have the right to modify any field. Array where channel parameters are saved: -
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Configuration parameters on distance sensors this array contains : sensor number sensor name (Label) physical unit of measurement (the same unit as used for calibration) channel number connected on the acquisition card terminal connector low limit of input signal on selected channel (in volts) High limit of input signal on selected channel (in volts). Allow you to adjust gain of the selected channel. Low threshold: is the voltage value from which the indicator becomes blue (if measurement value is between low threshold and high threshold, indicator is green). High threshold: : is the voltage value from which the indicator becomes red. It notifies to the user when sensor is out of prefixed range. a4, a3, a2, a1 gain, a0 offset: polynomial coefficients of selected sensor’s calibration curve (measurement in physical unit = (a4×Vs^4 + a3×Vs^3 + a2×Vs^2 + a1×Vs + a0) where Vs is in volt. Distance measurement = 1/(a4×Vs^4 + a3×Vs^3 + a2×Vs^2 + a1×Vs + a0)
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BLADE TIP CLEARANCE MEASUREMENT SOFTWARE
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4.3
ADD COMMENTS
Allow adding comments in configuration file (for instance: to explain measurement goal or test conditions). Like the upper option, a dialog box appears on screen, which asks if the user wants to modify the content of the comments. N.B : After having modified the configuration file, this one is automatically saved and replaces the actual configuration file.
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BLADE TIP CLEARANCE MEASUREMENT SOFTWARE
Save configuration file format: The following table gives the format of the recorded data (the *.cfg file can be loaded with a spreadsheet software like Excel): Configuration file Measurement Duration value(min) duration Sample rate Frequency value (Hz)
Number of Number blades Cste value Constant 1 Cste value Constant 2 Sensors Sensor number Label 1 … I
Unit
Sensor name
1 Unit
Channel number number
Sensor name
i Unit
number
High limit V
low limit V
Low High coef coef coef coef coef thresh thresh a4 a3 a2 a1 a0 mm mm x x x x x
V
V
mm
mm
x
x
x
x
Comments … Optional comments are included in the opened configuration file. WARNING : Channel numbers for each DAQ card must be scan in consecutive ascending order (0 to 3). NB : measurements are not possible if : - Sample rate is less than 1kS/s or greater than 10 MS/s. - Channel number is greater than 3. - There is no active channel selected - Measurement duration is equal to zero.
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BLADE TIP CLEARANCE MEASUREMENT SOFTWARE
5 BLADE TIP CLEARANCE (DISTANCE) MEASUREMENT Two graphic indicators are displayed on screen « distance measurement (mm) », « 2 channels combination ». Two selectors that contain sensors labels allow the user to choose the channel which he wants a graphic display. Also, there are eight numeric indicators, which display: - minimum clearance - mean clearance - Constant 1 – A – B (used to control the mean external diameter of the rotor if A & B are opposite probe referenced to the casing diameter) - (A-B)/2 (used to measure radial shaft movement if A & B are opposite probe) - A+B (used to detect unsymmetrical clearance evolution if A & B are opposite probe) - Constant 2 – C – D (used to control the mean external diameter of the rotor if C & D are opposite probe referenced to the casing diameter at a π /2 position compared to A & B probes) - (C-D)/2 (used to measure radial shaft movement if C & D are opposite probe) - C+D (used to detect unsymmetrical clearance evolution if C & D are opposite probe) There is also a tachometer (the frequency input of the acquisition card must be connected to one of the four input channel), which indicates engine rotation speed (in RPM). The displayed scale can be modified by the user. On / Off button allows user to control the measurement loop.
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BLADE TIP CLEARANCE MEASUREMENT SOFTWARE
5.1
MEASUREMENT INITIALISATION
As a first step, the user has to select “Distance measurement” and then “Measurement Initialisation” and “Click” the left mouse button. CAPAA
The new MMI (Man Machine Interface) appears: CAPAAB
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BLADE TIP CLEARANCE MEASUREMENT SOFTWARE
This step initialise and clear all graphs, light indicator « Acquisition » is active. All measurement indicators are displayed on the PC screen: - graphs - numeric indicators - selectors - On/Off button The user has 2 possibilities: “Display time function” or Perform fast acquisition”. If the “Display time function” is selected the following M.M.I appears: CAPAAB
5.2
DISPLAY TIME FUNCTION MEASUREMENT
This option runs acquisition loop on channels selected in the configuration array. This measurement display time function curves. First, the user must choose one of these display modes for acquisition: -
Time function strip chart Oscilloscope (mainly for check purpose or preview rough signals)
As a preliminary control, it is recommended to check if the incoming signal is correct, so the “Oscilloscope” mode has to be selected.
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BLADE TIP CLEARANCE MEASUREMENT SOFTWARE
After, user has to enter a filename where data will be saved. A dialog box appears on screen and asks the user to type the result file name. CAPAAB
Then, the “ON” “OFF” right down must be activated with a “left click” of the mouse. The acquisition start and it can take a few second to get the data on the screen. The all buffer is displayed, so the user has to use the graphic tools of M.M.I to zoom the time (or X) axis as shown.
The above copy of a typical M.M.I get in the oscilloscope X axis zoom mode. The Y axis unit is set in “Volts”.
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BLADE TIP CLEARANCE MEASUREMENT SOFTWARE
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To end the acquisition the user must click on the “OFF” / “ON” button with a “left click” of the mouse. To get out of the “Oscilloscope” mode, the user has to select the “End Measurement” command.
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BLADE TIP CLEARANCE MEASUREMENT SOFTWARE
When this preliminary control is finished and that the measured voltages suit the right value according to the expected clearance, it is now possible to go to the next step, so the “Time function strip chart” mode has to be selected. Before, it is recommended to select the command “Measurement initialisation” to get the M.M.I where this command appears. The following MMI is then available and the user has to type the name of its result file (****. dta).
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Four numeric indicators display mean clearance and 4 others show minimum clearance of the 4 capacitive distance probes. Theses values are displayed after converting digitised voltages into distance (in millimeters if it’s the selected unit) with the help of sensor’s polynomial calibration curves whose the user has loaded the coefficients during the configuration step in the array (in blue). Six other numeric indicators display 2 channels combination values. Minimum clearance indicators are monitored by “LED diodes” located on screen front panel. The acquisition card channels not used are indicated by a “black LED”. LED diodes become green if measured distances are greater than « low threshold » and lower than « high threshold ». It turns blue if clearance is greater than « high threshold ». Beyond « low threshold » LED diodes light in red. An example of blade tip clearance evolution versus time is given below.
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BLADE TIP CLEARANCE MEASUREMENT SOFTWARE
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Remark: in order to select curves, please, “left click” curves to be displayed in the selector while pressing on the keyboard “Capital” letter or “Shift”. Measurement principle: The measurement loop is executed sequentially in 4 phases addressing to PCI acquisition card: - Send channels configuration data : address, gain - Analog - digital conversion of measured signal - Signal analysis and conversion of voltage data into distance data - data are saved on PC hard drive and results are displayed on screen The measurement duration corresponds to the value displayed under « Measurement duration » which must be set in minutes (Set in the “Configuration” Menu). Nevertheless, if the user wants to stop the acquisition “left clicks” the button "On/Off" or selects the option "End measurement" in the measurement menu. NB: Please, take care to avoid exceeding a huge number of measurements otherwise these is a risk of overflow the system has there: (Number of measurements = sample rate × measurement duration in minutes × 60 × number of activated channels).
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BLADE TIP CLEARANCE MEASUREMENT SOFTWARE
5.3
FAST ACQUISITION WITHOUT VISUALISATION
This function is very useful if users want to see fast phenomena on the signals applied to the acquisition card. To select this mode, just “left click” to the “Perform fast acquisition” box. CAPAAB
In the case of the temporal scanning, the cadence of scanning of channels is not respected because the system is slow down by the management of the indicators and graphs. On the other hand, in the case of fast acquisition, the cadence of the acquisition is respected and no data are loosed because there is no time wasted for the management of the displayed results and indicators. The available resources allow sending data directly into memory (DMA). It is only at the end of the measurement buffer that the data are transferred to a file on hard disk. This acquisition mode uses a buffered acquisition and process the measurement of the same parameters as this described above but by digitizing the whole expected stream of data. The data are recorded directly on the PC hard drive. The display is not refreshed and as soon as the measure is launched, user can stop it by press “On/Off” button. At the end of the acquisition, the data are transferred in a same file format as that of the scanning vs time. So, this file can be read again with the option "replay measurements".
In “Fast acquisition” mode, the “measurement duration” must be set to a maximum of a few seconds (depends on the size of the onboard PC memory), due to the risk of overflow of the PC. As a first step, it is strongly recommended to use a configuration where only a single channel is active because, due to the very wide amount of data, if more of 1 channel is active, the PC may not be able (depending of its clock speed, memory size, data transfer maximum flow) to record all the data, and consequently it stop.
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BLADE TIP CLEARANCE MEASUREMENT SOFTWARE
At the end of the acquisition, it is possible (and recommended) to convert the rough voltage into mm for the selected channels in the configuration file.
5.4
END MEASUREMENT Stop the actual acquisition vs time.
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BLADE TIP CLEARANCE MEASUREMENT SOFTWARE
6 REPLAY
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6.1
TIME FUNCTION MEASUREMENT REREADING
Display on screen measurements made accordingly to time already saved in a file on the hard disk. When the user selects this menu, it displays a dialog box asking which is the name of the file to load. As soon as this file is loaded, the program simulates the scanning of the measurement channels according to the elapsed time.
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BLADE TIP CLEARANCE MEASUREMENT SOFTWARE
The same indicators and graphs than these found in menu « measurement » are displayed on screen: Two graphs: 1 for clearance measurement and 1 for 2 channels combination. Eight numeric indicators for minimum and mean clearance Six indicators for 2 channels combination On/Off button permits the user to stop replay before end of file. The saved results file contains the name of the associated configuration file; so, this last one is loaded in memory: - Measurement duration is initialised to duration saved in result file. - Configuration parameters on distance sensors are initialised to already saved values. The strip chart displays minimum and mean clearance of chosen channels with the selector. As soon as one arrives at the end of the array of data, the loop stops.
6.2
STOP REREADING Like On/Off button, this option allows to stop the replay before the end of file.
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BLADE TIP CLEARANCE MEASUREMENT SOFTWARE
7 BACKUP 7.1
SAVE MEASUREMENT AS
Allow measurement record to hard drive which operator made according to time. This provides an extra means to save and secure the measurements into a file. So, when the user selects this option, a dialog box appears, allowing choosing a new results file. User can enter a file name to save measurement (file name with 64 characters maximum). The values of voltage or distance of the selected channels and the instant of recorded measurements are saved into this file. The following table gives the format of the recorded data: Measurement file Created /date Time
Actual C:\….\….cfg configuration’s file path Sensor 1 label Sensor 2 label
Instant t1 of Clearance 1 at t1 measurement1 instant t2 of Clearance 1 at t2 measurement 2 … … instant ti of Clearance 1 at ti measurement i
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Sensor j label
Clearance 2 at t1
Clearance j at t1
shaft Speed ω at t1
Clearance 2 at t2
Clearance j at t2
ω at t2
Clearance 2 at ti
Clearance j at ti
ω at ti
Clearance in millimetres (if calibration curve is set in mm) ω : Shaft rotation speed value in RPM NB: if the acquisition file is very long and \ or if the sampling frequency is high, the file will certainly include many lines, which could be long or difficult to process with a simple spreadsheet. For files whose number of lines is less than 65000, an example is given below:
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BLADE TIP CLEARANCE MEASUREMENT SOFTWARE
Example of result “*.dta” file loaded into “Excel” spreadsheet.
7.2
CONVERT VOLTAGE TO DISTANCE
This command makes the conversion of the input voltage into distance and record measurement data into the PC hard drive. From a measurement file to be opened containing the voltage data (dialog box of distance with the loaded opening file), the program makes the conversion voltage coefficients of the polynomial calibration curve of the selected sensors, contents in the configuration file. The user has to rename the file in which will be recorded these data after conversion (writing to a file dialog box).
8 HELP Allows online help. It gives a resume of the explanations given in the user manual available with the acquisition system.
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