CA2204980A1 - Method and apparatus for surface pressure mapping of rotating objects by synchronized optical imaging of luminescent coating - Google Patents
Method and apparatus for surface pressure mapping of rotating objects by synchronized optical imaging of luminescent coatingInfo
- Publication number
- CA2204980A1 CA2204980A1 CA 2204980 CA2204980A CA2204980A1 CA 2204980 A1 CA2204980 A1 CA 2204980A1 CA 2204980 CA2204980 CA 2204980 CA 2204980 A CA2204980 A CA 2204980A CA 2204980 A1 CA2204980 A1 CA 2204980A1
- Authority
- CA
- Canada
- Prior art keywords
- light
- photoluminescent
- pressure
- rotating
- light source
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Abandoned
Links
- 238000000034 method Methods 0.000 title claims abstract description 29
- 238000000576 coating method Methods 0.000 title claims abstract description 16
- 239000011248 coating agent Substances 0.000 title claims abstract description 15
- 230000001360 synchronised effect Effects 0.000 title claims abstract description 11
- 238000013507 mapping Methods 0.000 title claims description 15
- 238000012634 optical imaging Methods 0.000 title abstract description 6
- 238000009826 distribution Methods 0.000 claims abstract description 31
- 238000005259 measurement Methods 0.000 claims description 10
- 238000012545 processing Methods 0.000 claims description 7
- 238000001914 filtration Methods 0.000 claims description 3
- 239000000463 material Substances 0.000 claims 2
- 238000001514 detection method Methods 0.000 claims 1
- 230000003287 optical effect Effects 0.000 abstract description 17
- 238000004020 luminiscence type Methods 0.000 abstract description 13
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 abstract description 12
- 229910052760 oxygen Inorganic materials 0.000 abstract description 12
- 239000001301 oxygen Substances 0.000 abstract description 12
- 239000003973 paint Substances 0.000 abstract description 9
- 238000010791 quenching Methods 0.000 abstract description 5
- 230000000171 quenching effect Effects 0.000 abstract description 5
- 229920000642 polymer Polymers 0.000 abstract description 4
- 230000007423 decrease Effects 0.000 abstract description 3
- 238000002156 mixing Methods 0.000 abstract description 3
- 238000005424 photoluminescence Methods 0.000 abstract description 3
- 238000009530 blood pressure measurement Methods 0.000 description 7
- 238000012360 testing method Methods 0.000 description 3
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 2
- 101150085390 RPM1 gene Proteins 0.000 description 2
- 238000004364 calculation method Methods 0.000 description 2
- 238000011088 calibration curve Methods 0.000 description 2
- 238000010586 diagram Methods 0.000 description 2
- 239000005101 luminescent paint Substances 0.000 description 2
- BFZUFHPKKNHSAG-UHFFFAOYSA-N [N].[P].[S] Chemical compound [N].[P].[S] BFZUFHPKKNHSAG-UHFFFAOYSA-N 0.000 description 1
- 238000004458 analytical method Methods 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- 238000005286 illumination Methods 0.000 description 1
- 238000010191 image analysis Methods 0.000 description 1
- 238000000050 ionisation spectroscopy Methods 0.000 description 1
- 239000007788 liquid Substances 0.000 description 1
- 229910052757 nitrogen Inorganic materials 0.000 description 1
- 238000005457 optimization Methods 0.000 description 1
- 230000003094 perturbing effect Effects 0.000 description 1
- 238000011160 research Methods 0.000 description 1
- 238000012552 review Methods 0.000 description 1
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 1
- 229910052724 xenon Inorganic materials 0.000 description 1
- FHNFHKCVQCLJFQ-UHFFFAOYSA-N xenon atom Chemical compound [Xe] FHNFHKCVQCLJFQ-UHFFFAOYSA-N 0.000 description 1
Classifications
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01M—TESTING STATIC OR DYNAMIC BALANCE OF MACHINES OR STRUCTURES; TESTING OF STRUCTURES OR APPARATUS, NOT OTHERWISE PROVIDED FOR
- G01M9/00—Aerodynamic testing; Arrangements in or on wind tunnels
- G01M9/06—Measuring arrangements specially adapted for aerodynamic testing
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01L—MEASURING FORCE, STRESS, TORQUE, WORK, MECHANICAL POWER, MECHANICAL EFFICIENCY, OR FLUID PRESSURE
- G01L1/00—Measuring force or stress, in general
- G01L1/24—Measuring force or stress, in general by measuring variations of optical properties of material when it is stressed, e.g. by photoelastic stress analysis using infrared, visible light, ultraviolet
Landscapes
- Physics & Mathematics (AREA)
- General Physics & Mathematics (AREA)
- Fluid Mechanics (AREA)
- Force Measurement Appropriate To Specific Purposes (AREA)
Abstract
The present invention provides a new synchronized optical method for measuring surface pressure on rotating objects such as propellers or other rotating objects. The technique is based on the phenomenon of oxygen quenching of luminescence coatings and synchronized optical imaging. A
surface coating, referred to as a pressure sensitive paint (PSP), is formed by mixing photo-luminescence molecules in an oxygen permeable polymer. The luminescence excited by an appropriate light source decreases as the oxygen concentration rises due to quenching. As a result, the luminescence intensity of light emitted from the coating varies as a function of the partial pressure of oxygen. A digital camera measures the luminescence intensity distribution over the object and the pressure distribution can be computed.
surface coating, referred to as a pressure sensitive paint (PSP), is formed by mixing photo-luminescence molecules in an oxygen permeable polymer. The luminescence excited by an appropriate light source decreases as the oxygen concentration rises due to quenching. As a result, the luminescence intensity of light emitted from the coating varies as a function of the partial pressure of oxygen. A digital camera measures the luminescence intensity distribution over the object and the pressure distribution can be computed.
Description
CA 02204980 1997-0~-09 METHOD AND APPARATUS FOR SURFACE PRESSURE MAPPING OF
ROTATING OBJECTS BY SYNCHRONIZED OPTICAL IMAGING OF
LUMINESCENT COATING
FIELD OF THE INVENTION
The present invention relates to a method and device for pressure mapping of rotating objects by synchronized optical imaging of luminescent paint.
BACKGROUND OF THE INVENTION
Aerodynamic data of aircraft propellers and other rotating objects are important for optimization of blade and spinner geometries for maximum aerodynamic efficiency and for providing aerodynamic loading information. To generate aerodynamic data, several methods have been used. The one was strip analysis technique which involves the calculation of the aerodynamic angleof attack at each radius along a lifting line from a solution of the equations describing the distribution of circulation in the wake, see for example Wong P.C.W., Maina M. Forsey C.R., Bocci A.J. "SINGLE AND CONTRA-ROTATION
HIGH SPEED PROPELLERS: FLOW CALCULATION AND PERFORMANCE
PREDICTION:, ICAS 88-2.4.2.1988; and Bocci, A.J. and Morrison J.l., "A
REVIEW OF ARA RESEARCH INTO PROPELLER AERODYNAMIC
PREDICTION METHODS", AGARD-CP-366, 1984. The other was the scaled-model test employing pressure tapped blades and spinner to obtain a database for high speed propellers as disclosed in N. Scrase and M. Maina, International Council of Aeronautical Science, ICAS-94-6. 1 .2.
- - -CA 02204980 1997-0~-09 Luminescent barometry on stationary airfoils in wind tunnels has been previously reported, see for example Janet Kavandi, James Callis, Martin Gouterman, Gamal Khalil, Daniel Wright, Edmond Green, David Burns and Blair McLachlan, LUMINESCENT BAROMETRY IN WIND TUNNELS, Rev. Sci.
Instrum., Vol. 61, No. 11, November 1990 and X.J. Gu, J. Coll, D. Lye, F.A. Ellis, V.D. Nguyen and J. Bureau, AN OPTICAL PRESSURE MEASUREMENT
SYSTEM FOR WIND TUNNEL TESTING, in Applications of Photonic Technology, Ed. G.A. Lampropouleos et al., Plenum Press, New York, 1995, which is incorporated herein by reference.
It is very difficult to obtain pressure distribution information on rotating objects such as propellers or water turbines. It would be very advantageous to be able to obtain this type of data in real time use of a rotating object. The use of pressure taps is problematic since it involves perturbing thesurface of the propeller. Placing pressure taps on rotating objects is problematic due to attachments added to the pressure taps which make rotation of the object inconsistent. Therefore, it would be very advantageous to provide a remote sensing method for detecting the surface pressure on the surface of a rotating object.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a method and apparatus for measuring surface pressure on a rotating object.
A new optical method is disclosed for measuring surface pressure on rotating objects. The technique is based on the phenomenon of oxygen CA 02204980 1997-0~-09 quenching of luminescence and synchronized optical imaging. A surface coating, referred to as a pressure sensitive paint (PSP), is formed by mixing photo-luminescence molecules in an oxygen permeable polymer. The luminescence excited by an appropriate light source decreases as the oxygen 5 concentration rises due to quenching. As a result, the luminescence intensity of light emitted from the coating varies as a function of the partial pressure of oxygen. A digital camera measures the luminescence intensity distribution over the model and the pressure distribution can be computed. This method, referred to as an optical pressure measurement system (OPMS) has been tested in small 10 high speed wind tunnels.
The present invention provides a method of surface pressure mapping rotating objects comprising providing an object having an outer surface and applying to the outer surface a pressure sensitive photoluminescent paint coating. The method includes rotating the object at a preselected rotational 15 velocity and directing a train of light pulses from a light source at the rotating object. The light pulses are synchronized to the rotational velocity of the rotating object and the light pulses are of a first wavelength. The method includes detecting and storing photoluminescent light intensity due to emission from the photoluminescent pressure sensitive paint on the rotating object of the light 20 pulses impinging on the coated rotating object. The method includes processing the photoluminescent light intensity to convert the photoluminescent light intensity into a pressure distribution over the surface of the rotating object.
In another aspect, the present invention provides a method of surface pressure mapping rotating objects. The method comprises providing an CA 02204980 1997-0~-09 object having an outer surface and applying to the outer surface a pressure sensitive photoluminescent paint coating. The object is then rotated at a preselected rotational velocity and directing a train of light pulses from a light source at the rotating object with the light pulses being synchronized to the 5 rotational velocity of the rotating object with the light pulses being of a first wavelength. The method includes filtering photoluminescent light emitted from the photoluminescent pressure sensitive paint on the rotating object to filter out light of the first wavelength, and detecting and storing the filtered photoluminescent light and converting the filtered photoluminescent light into a 10 first image. The method includes providing a second photoluminescent image of the object measured when the object is stationary and ratioing the second image of the stationary object to the image of the rotating object, and converting the ratio into a pressure distribution over the surface of the rotating object.
The present invention provides a system for measurement of 15 surface pressure on an object being rotated. The system comprises a photoluminescent pressure sensitive paint which can be coated onto a surface of the object to be rotated. Included is a light source for emitting a train of light pulses directed at the object, the light source including means for synchronizing the light source to the rotational velocity of the object, the light source emitting 20 light at a first wavelength. The system includes a photodetection means for detecting photoluminescent light intensity emitted from the photoluminescent pressure sensitive paint and processing means for storing and processing the emitted photoluminescent light intensity to convert such intensity into a pressure distribution over the surface of the rotating object.
CA 02204980 1997-0~-09 BRIEF DESCRIPTION OF THE DRAWINGS
The following is a description, by way of example only, of a method and device for optical surface pressure mapping of rotating objects in accordance with the present invention, reference being had to the 5accompanying drawings, in which:
Figure 1 is a schematic diagram of a system and apparatus for the optical surface pressure mapping of a propeller surface by synchronized optical imaging of luminescent paint according to the present invention;
Figure 2 illustrates the intensity ratioed image of a propeller blade 10rotating at 4150 RPM with a wind speed of 300 feeVsecond in a 6 x 8 feet wind tunnel;
Figure 3a shows optical surface pressure mapping measurements of pressure distributions at 50% of full radius at 6600 RPM, blade angle of 32~
and a wind speed of 200 feeVsecond in a 6x8 feet wind tunnel;
15Figure 3b shows optical surface pressure mapping measurements of pressure distributions at 75% full radius at 6600 RPM, blade angle of 32~ anda wind speed of 200 feeVsecond in a 6x8 feet wind tunnel;
Figure 3c shows optical surface pressure mapping measurements of pressure distributions at 90% full radius at 6600 RPM, blade angle of 32~ and20a wind speed of 200 feeVsecond in a 6x8 feet wind tunnel;
Figure 4a shows the optical surface pressure mapping measurements of pressure distributions at 50% full radius at 4150 RPM, blade angle of 52~ and a wind speed of 300 feeVsecond in a 6x8 feet wind tunnel;
Figure 4b shows the optical surface pressure mapping CA 02204980 1997-0~-09 measurements of pressure distributions at 75% full radius at 4150 RPM, blade angle of 52~ and a wind speed of 300 feeVsecond in a 6x8 feet wind tunnel;
Figure 4c shows the optical surface pressure mapping measurements of pressure distributions at 90% full radius at 4150 RPM, blade angle of 52~ and a wind speed of 300 feeVsecond in a 6x8 feet wind tunnel;
Figure 5a shows the optical surface pressure measurements of pressure distributions at 50% full radius at 3300 RPM, blade angle of 60~ and a wind speed of 355 feeVsecond in a 6 x 8 feet wind tunnel.
Figure 5b shows the optical surface pressure measurements of pressure distributions at 75% full radius at 3300 RPM, blade angle of 60~ and a wind speed of 355 feeVsecond in a 6 x 8 feet wind tunnel; and Figure 5c shows the optical surface pressure measurements of pressure distributions at 90% full radius at 3300 RPM1 blade angle of 60~ and a wind speed of 355 feeVsecond in a 6 x 8 feet wind tunnel.
DETAILED DESCRIPTION OF THE INVENTION
With reference to Figure 1, a schematic diagram of the system and apparatus for making optical surface pressure measurements, or optical pressure measurement system (OPMS) is shown generally at 10. A propeller 12 is mounted on the end of a propeller shaft 14 connected to a motor 16 for rotation about the longitudinal axis of shaft 14. The propeller 12 and motor 16 are located in a 6x8 feet wind tunnel 18. The surface of propeller 12 is coated with a thin surface coating 20 of a pressure sensitive paint (PSP), which is formed by mixing photo-luminescence molecules in an oxygen permeable CA 02204980 1997-0~-09 polymer. The luminescence excited by an appropriate light source decreases as the oxygen concentration rises due to quenching. As a result, the luminescence intensity of light emitted from the coating varies as a function of the partial pressure of oxygen, see for example Zhen Pang, Xijia Gu, Ahmad Yekta, Zahra 5 Masoumi, John B. Coll, Mitchell A. Winnik and lan Manners, PHOSPHORESCENT OXYGEN SENSORS UTILIZING SULFUR-NITROGEN-PHOSPHORUS POLYMER MATRICES; Adv. Mater. 1996, 8, No.9, which is incorporated herein by reference.
A strobe light source 24 emits a train of light pulses 26 which are 10 synchronized to the rotation of propeller 12 by a sensor 28 coupled to propeller shaft 14. A detector such as a charge coupled device (CCD) digital camera 30 records the luminescence image over the model and the pressure distribution can be computed. A band pass filter 32 is positioned in front of the camera aperture so that CCD camera 30 only detects the luminescence from the 15 propeller surface which is inversely proportional to the pressure. The output of CCD camera 30 is input into processor 34.
The pulse width of the flash lamp 24 is set to between about 1 to about 2 microseconds so that the CCD camera only sees the propeller 12 in a fixed or frozen position. At a propeller speed of 4000 RPM and with a blade 20 length of 1 foot (scaled model), the blade image on the CCD camera would be blurred to be less than one pixel.
Image analysis was used to convert the luminescent light distribution into the pressure distribution. To correctly calculate the pressure distribution over the propeller blade, two images are acquired. One image was CA 02204980 1997-0~-09 taken when the propeller was rotating and tunnel wind on (called "on-image") where the pressure distribution on the blade surface was unknown. The other image was taken when the propeller 12 and tunnel wind were stopped (called "off-image"), in that case, the pressure distribution was a constant over the 5 blade surface. The off-image was divided by the on-image and the resulting image has the darker color corresponding to lower pressure and the lighter color corresponds to higher pressure, as shown in Figure 2.
The strobe light source 24 used was a Xenon lamp (Model MVS-220, EG & G Electro-Optics) with a mean flash power of 40 Watts. The detector 10 30 used was a liquid nitrogen cooled CCD camera (Model LN/CCD, Princeton Instruments Inc.) with 578x384 pixels in a cell size of 13.25x8.83 mm2. The camera 30 has a low dark noise of 0.05 counts/(pixel@second)05 and high dynamic range of 14 bits which are necessary for this test. The luminescent light from the outer surface of propeller 12 was collected with a zoom lens (Nikon, 28-85 mm, 1 :3.5-4.5) and imaged onto the CCD camera 30.
A calibration curve was measured by taking the luminescence intensity readings over a pressure range of 0.05 to 2.5 atm. The resulting intensity reading at ambient pressure, 1.0 atm was taken as lo A nearly linear relationship between IJI versus p/pO was obtained, as predicted by the Stern-20 Volmer relation. The intercept and the slope were determined by least-squares fitting as 0.52 + 0.02 and 0.44 + 0.04 respectively. The sum of these two numbers is unity within experimental error.
Figure 2 shows a processed image for the suction side of the propeller blade 12 rotating at 4150 RPM1 at a blade angle of 52~ and with a wind CA 02204980 1997-0~-09 speed of 300 feeVsec. The direction of rotation of the propeller is count-clock-wise. The pixel intensity in this image is proportional to pressure. It can be seen that there is a high pressure build up at the leading edge, followed by a lower pressure region, the pressure increases towards the trailing edge.
Figures 3a-c show the pressure data for propeller 12 rotating at 6600 RPM and wind speed of 200 ft/sec which simulates take-off conditions. The intensity ratio IJI was measured at the cross sections taken at various radial positions on the blade, such as at 50%, 75% and 90% of full radius respectively.The pressure distributions across these sections were calculated using the calibration curve and were plotted in Figures 3a, 3b, and 3c. The intensity ratio lo/l was scaled down by a factor of 1.03 (to correct the different illumination intensities for the on and off-images) so the pressure at the tail edge at 50% of radius can match the atmospheric pressure. These results clearly show that pressure distributions can be measured over the coated surface of a rotating 1 5 object.
The pressure distributions in Figures 3a to 3c show two key features: 1 ) there is a sharp pressure increase at the leading edge followed bya pressure "well"; the pressure then increases towards the trailing edge; and 2)the pressure "well" becomes deeper at large radial distance (~11.7 psi at 50%R, ~10.5 psi at 75%R and ~9.0 psi at 90%R respectively).
The plots shown in Figures 3b and 3c are down shifted by 2.8 and 5.6 psi respectively so the pressures at their tail edges match the atmospheric pressure.
Similar measurements were carried out at a speed of 4150 RPM
CA 02204980 1997-0~-09 and wind speed of 300 fVsec that simulates climb-up conditions. The pressure data is shown in Figures 4a, 4b and 4c. The pressure distributions show a similar trend as that seen in Figures 3a to 3c, except that the pressure "wells"are not as deep due to the lower propeller speed.
In addition to propeller blades, any rotating object may surface mapped using the present method including turbine cascades, compressor components to mention just a few.
The pressure data for measurements at 3300 RPM and wind speed of 355 ft/sec that simulates cruise conditions are shown in Figure 5a, 5b and 5c.
The foregoing description of the preferred embodiment of the invention has been presented to illustrate the principles of the invention and not to limit the invention to the particular embodiment illustrated. It is intended that the scope of the invention be defined by all of the embodiments encompassed within the following claims and their equivalents.
ROTATING OBJECTS BY SYNCHRONIZED OPTICAL IMAGING OF
LUMINESCENT COATING
FIELD OF THE INVENTION
The present invention relates to a method and device for pressure mapping of rotating objects by synchronized optical imaging of luminescent paint.
BACKGROUND OF THE INVENTION
Aerodynamic data of aircraft propellers and other rotating objects are important for optimization of blade and spinner geometries for maximum aerodynamic efficiency and for providing aerodynamic loading information. To generate aerodynamic data, several methods have been used. The one was strip analysis technique which involves the calculation of the aerodynamic angleof attack at each radius along a lifting line from a solution of the equations describing the distribution of circulation in the wake, see for example Wong P.C.W., Maina M. Forsey C.R., Bocci A.J. "SINGLE AND CONTRA-ROTATION
HIGH SPEED PROPELLERS: FLOW CALCULATION AND PERFORMANCE
PREDICTION:, ICAS 88-2.4.2.1988; and Bocci, A.J. and Morrison J.l., "A
REVIEW OF ARA RESEARCH INTO PROPELLER AERODYNAMIC
PREDICTION METHODS", AGARD-CP-366, 1984. The other was the scaled-model test employing pressure tapped blades and spinner to obtain a database for high speed propellers as disclosed in N. Scrase and M. Maina, International Council of Aeronautical Science, ICAS-94-6. 1 .2.
- - -CA 02204980 1997-0~-09 Luminescent barometry on stationary airfoils in wind tunnels has been previously reported, see for example Janet Kavandi, James Callis, Martin Gouterman, Gamal Khalil, Daniel Wright, Edmond Green, David Burns and Blair McLachlan, LUMINESCENT BAROMETRY IN WIND TUNNELS, Rev. Sci.
Instrum., Vol. 61, No. 11, November 1990 and X.J. Gu, J. Coll, D. Lye, F.A. Ellis, V.D. Nguyen and J. Bureau, AN OPTICAL PRESSURE MEASUREMENT
SYSTEM FOR WIND TUNNEL TESTING, in Applications of Photonic Technology, Ed. G.A. Lampropouleos et al., Plenum Press, New York, 1995, which is incorporated herein by reference.
It is very difficult to obtain pressure distribution information on rotating objects such as propellers or water turbines. It would be very advantageous to be able to obtain this type of data in real time use of a rotating object. The use of pressure taps is problematic since it involves perturbing thesurface of the propeller. Placing pressure taps on rotating objects is problematic due to attachments added to the pressure taps which make rotation of the object inconsistent. Therefore, it would be very advantageous to provide a remote sensing method for detecting the surface pressure on the surface of a rotating object.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a method and apparatus for measuring surface pressure on a rotating object.
A new optical method is disclosed for measuring surface pressure on rotating objects. The technique is based on the phenomenon of oxygen CA 02204980 1997-0~-09 quenching of luminescence and synchronized optical imaging. A surface coating, referred to as a pressure sensitive paint (PSP), is formed by mixing photo-luminescence molecules in an oxygen permeable polymer. The luminescence excited by an appropriate light source decreases as the oxygen 5 concentration rises due to quenching. As a result, the luminescence intensity of light emitted from the coating varies as a function of the partial pressure of oxygen. A digital camera measures the luminescence intensity distribution over the model and the pressure distribution can be computed. This method, referred to as an optical pressure measurement system (OPMS) has been tested in small 10 high speed wind tunnels.
The present invention provides a method of surface pressure mapping rotating objects comprising providing an object having an outer surface and applying to the outer surface a pressure sensitive photoluminescent paint coating. The method includes rotating the object at a preselected rotational 15 velocity and directing a train of light pulses from a light source at the rotating object. The light pulses are synchronized to the rotational velocity of the rotating object and the light pulses are of a first wavelength. The method includes detecting and storing photoluminescent light intensity due to emission from the photoluminescent pressure sensitive paint on the rotating object of the light 20 pulses impinging on the coated rotating object. The method includes processing the photoluminescent light intensity to convert the photoluminescent light intensity into a pressure distribution over the surface of the rotating object.
In another aspect, the present invention provides a method of surface pressure mapping rotating objects. The method comprises providing an CA 02204980 1997-0~-09 object having an outer surface and applying to the outer surface a pressure sensitive photoluminescent paint coating. The object is then rotated at a preselected rotational velocity and directing a train of light pulses from a light source at the rotating object with the light pulses being synchronized to the 5 rotational velocity of the rotating object with the light pulses being of a first wavelength. The method includes filtering photoluminescent light emitted from the photoluminescent pressure sensitive paint on the rotating object to filter out light of the first wavelength, and detecting and storing the filtered photoluminescent light and converting the filtered photoluminescent light into a 10 first image. The method includes providing a second photoluminescent image of the object measured when the object is stationary and ratioing the second image of the stationary object to the image of the rotating object, and converting the ratio into a pressure distribution over the surface of the rotating object.
The present invention provides a system for measurement of 15 surface pressure on an object being rotated. The system comprises a photoluminescent pressure sensitive paint which can be coated onto a surface of the object to be rotated. Included is a light source for emitting a train of light pulses directed at the object, the light source including means for synchronizing the light source to the rotational velocity of the object, the light source emitting 20 light at a first wavelength. The system includes a photodetection means for detecting photoluminescent light intensity emitted from the photoluminescent pressure sensitive paint and processing means for storing and processing the emitted photoluminescent light intensity to convert such intensity into a pressure distribution over the surface of the rotating object.
CA 02204980 1997-0~-09 BRIEF DESCRIPTION OF THE DRAWINGS
The following is a description, by way of example only, of a method and device for optical surface pressure mapping of rotating objects in accordance with the present invention, reference being had to the 5accompanying drawings, in which:
Figure 1 is a schematic diagram of a system and apparatus for the optical surface pressure mapping of a propeller surface by synchronized optical imaging of luminescent paint according to the present invention;
Figure 2 illustrates the intensity ratioed image of a propeller blade 10rotating at 4150 RPM with a wind speed of 300 feeVsecond in a 6 x 8 feet wind tunnel;
Figure 3a shows optical surface pressure mapping measurements of pressure distributions at 50% of full radius at 6600 RPM, blade angle of 32~
and a wind speed of 200 feeVsecond in a 6x8 feet wind tunnel;
15Figure 3b shows optical surface pressure mapping measurements of pressure distributions at 75% full radius at 6600 RPM, blade angle of 32~ anda wind speed of 200 feeVsecond in a 6x8 feet wind tunnel;
Figure 3c shows optical surface pressure mapping measurements of pressure distributions at 90% full radius at 6600 RPM, blade angle of 32~ and20a wind speed of 200 feeVsecond in a 6x8 feet wind tunnel;
Figure 4a shows the optical surface pressure mapping measurements of pressure distributions at 50% full radius at 4150 RPM, blade angle of 52~ and a wind speed of 300 feeVsecond in a 6x8 feet wind tunnel;
Figure 4b shows the optical surface pressure mapping CA 02204980 1997-0~-09 measurements of pressure distributions at 75% full radius at 4150 RPM, blade angle of 52~ and a wind speed of 300 feeVsecond in a 6x8 feet wind tunnel;
Figure 4c shows the optical surface pressure mapping measurements of pressure distributions at 90% full radius at 4150 RPM, blade angle of 52~ and a wind speed of 300 feeVsecond in a 6x8 feet wind tunnel;
Figure 5a shows the optical surface pressure measurements of pressure distributions at 50% full radius at 3300 RPM, blade angle of 60~ and a wind speed of 355 feeVsecond in a 6 x 8 feet wind tunnel.
Figure 5b shows the optical surface pressure measurements of pressure distributions at 75% full radius at 3300 RPM, blade angle of 60~ and a wind speed of 355 feeVsecond in a 6 x 8 feet wind tunnel; and Figure 5c shows the optical surface pressure measurements of pressure distributions at 90% full radius at 3300 RPM1 blade angle of 60~ and a wind speed of 355 feeVsecond in a 6 x 8 feet wind tunnel.
DETAILED DESCRIPTION OF THE INVENTION
With reference to Figure 1, a schematic diagram of the system and apparatus for making optical surface pressure measurements, or optical pressure measurement system (OPMS) is shown generally at 10. A propeller 12 is mounted on the end of a propeller shaft 14 connected to a motor 16 for rotation about the longitudinal axis of shaft 14. The propeller 12 and motor 16 are located in a 6x8 feet wind tunnel 18. The surface of propeller 12 is coated with a thin surface coating 20 of a pressure sensitive paint (PSP), which is formed by mixing photo-luminescence molecules in an oxygen permeable CA 02204980 1997-0~-09 polymer. The luminescence excited by an appropriate light source decreases as the oxygen concentration rises due to quenching. As a result, the luminescence intensity of light emitted from the coating varies as a function of the partial pressure of oxygen, see for example Zhen Pang, Xijia Gu, Ahmad Yekta, Zahra 5 Masoumi, John B. Coll, Mitchell A. Winnik and lan Manners, PHOSPHORESCENT OXYGEN SENSORS UTILIZING SULFUR-NITROGEN-PHOSPHORUS POLYMER MATRICES; Adv. Mater. 1996, 8, No.9, which is incorporated herein by reference.
A strobe light source 24 emits a train of light pulses 26 which are 10 synchronized to the rotation of propeller 12 by a sensor 28 coupled to propeller shaft 14. A detector such as a charge coupled device (CCD) digital camera 30 records the luminescence image over the model and the pressure distribution can be computed. A band pass filter 32 is positioned in front of the camera aperture so that CCD camera 30 only detects the luminescence from the 15 propeller surface which is inversely proportional to the pressure. The output of CCD camera 30 is input into processor 34.
The pulse width of the flash lamp 24 is set to between about 1 to about 2 microseconds so that the CCD camera only sees the propeller 12 in a fixed or frozen position. At a propeller speed of 4000 RPM and with a blade 20 length of 1 foot (scaled model), the blade image on the CCD camera would be blurred to be less than one pixel.
Image analysis was used to convert the luminescent light distribution into the pressure distribution. To correctly calculate the pressure distribution over the propeller blade, two images are acquired. One image was CA 02204980 1997-0~-09 taken when the propeller was rotating and tunnel wind on (called "on-image") where the pressure distribution on the blade surface was unknown. The other image was taken when the propeller 12 and tunnel wind were stopped (called "off-image"), in that case, the pressure distribution was a constant over the 5 blade surface. The off-image was divided by the on-image and the resulting image has the darker color corresponding to lower pressure and the lighter color corresponds to higher pressure, as shown in Figure 2.
The strobe light source 24 used was a Xenon lamp (Model MVS-220, EG & G Electro-Optics) with a mean flash power of 40 Watts. The detector 10 30 used was a liquid nitrogen cooled CCD camera (Model LN/CCD, Princeton Instruments Inc.) with 578x384 pixels in a cell size of 13.25x8.83 mm2. The camera 30 has a low dark noise of 0.05 counts/(pixel@second)05 and high dynamic range of 14 bits which are necessary for this test. The luminescent light from the outer surface of propeller 12 was collected with a zoom lens (Nikon, 28-85 mm, 1 :3.5-4.5) and imaged onto the CCD camera 30.
A calibration curve was measured by taking the luminescence intensity readings over a pressure range of 0.05 to 2.5 atm. The resulting intensity reading at ambient pressure, 1.0 atm was taken as lo A nearly linear relationship between IJI versus p/pO was obtained, as predicted by the Stern-20 Volmer relation. The intercept and the slope were determined by least-squares fitting as 0.52 + 0.02 and 0.44 + 0.04 respectively. The sum of these two numbers is unity within experimental error.
Figure 2 shows a processed image for the suction side of the propeller blade 12 rotating at 4150 RPM1 at a blade angle of 52~ and with a wind CA 02204980 1997-0~-09 speed of 300 feeVsec. The direction of rotation of the propeller is count-clock-wise. The pixel intensity in this image is proportional to pressure. It can be seen that there is a high pressure build up at the leading edge, followed by a lower pressure region, the pressure increases towards the trailing edge.
Figures 3a-c show the pressure data for propeller 12 rotating at 6600 RPM and wind speed of 200 ft/sec which simulates take-off conditions. The intensity ratio IJI was measured at the cross sections taken at various radial positions on the blade, such as at 50%, 75% and 90% of full radius respectively.The pressure distributions across these sections were calculated using the calibration curve and were plotted in Figures 3a, 3b, and 3c. The intensity ratio lo/l was scaled down by a factor of 1.03 (to correct the different illumination intensities for the on and off-images) so the pressure at the tail edge at 50% of radius can match the atmospheric pressure. These results clearly show that pressure distributions can be measured over the coated surface of a rotating 1 5 object.
The pressure distributions in Figures 3a to 3c show two key features: 1 ) there is a sharp pressure increase at the leading edge followed bya pressure "well"; the pressure then increases towards the trailing edge; and 2)the pressure "well" becomes deeper at large radial distance (~11.7 psi at 50%R, ~10.5 psi at 75%R and ~9.0 psi at 90%R respectively).
The plots shown in Figures 3b and 3c are down shifted by 2.8 and 5.6 psi respectively so the pressures at their tail edges match the atmospheric pressure.
Similar measurements were carried out at a speed of 4150 RPM
CA 02204980 1997-0~-09 and wind speed of 300 fVsec that simulates climb-up conditions. The pressure data is shown in Figures 4a, 4b and 4c. The pressure distributions show a similar trend as that seen in Figures 3a to 3c, except that the pressure "wells"are not as deep due to the lower propeller speed.
In addition to propeller blades, any rotating object may surface mapped using the present method including turbine cascades, compressor components to mention just a few.
The pressure data for measurements at 3300 RPM and wind speed of 355 ft/sec that simulates cruise conditions are shown in Figure 5a, 5b and 5c.
The foregoing description of the preferred embodiment of the invention has been presented to illustrate the principles of the invention and not to limit the invention to the particular embodiment illustrated. It is intended that the scope of the invention be defined by all of the embodiments encompassed within the following claims and their equivalents.
Claims (10)
1. A method of surface pressure mapping rotating objects, comprising;
a) providing an object having an outer surface and applying to said outer surface a pressure sensitive photoluminescent coating;
b) rotating said object at a preselected rotational velocity and directing a train of light pulses from a light source at said rotating object, synchronizing said light pulses to said rotational velocity of said object, with said light pulses being of a first wavelength;
c) detecting and storing a photoluminescent light intensity due to emission from said pressure sensitive photoluminescent coating on said rotating object due to said light pulses impinging on the coated outer surface of the rotating object; and d) processing said photoluminescent light intensity to convert said photoluminescent light intensity into an image of a pressure distribution over the surface of the rotating object.
a) providing an object having an outer surface and applying to said outer surface a pressure sensitive photoluminescent coating;
b) rotating said object at a preselected rotational velocity and directing a train of light pulses from a light source at said rotating object, synchronizing said light pulses to said rotational velocity of said object, with said light pulses being of a first wavelength;
c) detecting and storing a photoluminescent light intensity due to emission from said pressure sensitive photoluminescent coating on said rotating object due to said light pulses impinging on the coated outer surface of the rotating object; and d) processing said photoluminescent light intensity to convert said photoluminescent light intensity into an image of a pressure distribution over the surface of the rotating object.
2. The method according to claim 1 wherein the step of detecting said photoluminescent light intensity includes filtering light emitted from said object prior to detection to filter out light of said first wavelength.
3. The method according to claims 1 or 2 wherein said light source is a strobe light source and said light pulses have a pulse width in the range of no more than microseconds.
4. The method according to claims 1, 2 or 3 including providing a photoluminescent image of said object measured when said object is stationary, and wherein the step of processing said photoluminescent light intensity includes ratioing the image of the object when stationary to said image of the rotating object.
5. A method of surface pressure mapping rotating objects, comprising;
a) providing an object having an outer surface and applying to said outer surface a pressure sensitive photoluminescent coating;
b) rotating said object at a preselected rotational velocity and directing a train of light pulses from a light source at the rotating object, said light pulses being synchronized to said rotational velocity of said object, said light pulses being of a first wavelength;
c) filtering photoluminescent light emitted from said pressure sensitive photoluminescent coating on said rotating object to filter out light of said first wavelength, detecting and storing the filtered photoluminescent light and converting said filtered photoluminescent light into a first image; and d) providing a second photoluminescent image of said object measured when said object is stationary and ratioing the second image of the object when stationary to said first image of the rotating object, and converting said ratio into a pressure distribution over the surface of said rotating object.
a) providing an object having an outer surface and applying to said outer surface a pressure sensitive photoluminescent coating;
b) rotating said object at a preselected rotational velocity and directing a train of light pulses from a light source at the rotating object, said light pulses being synchronized to said rotational velocity of said object, said light pulses being of a first wavelength;
c) filtering photoluminescent light emitted from said pressure sensitive photoluminescent coating on said rotating object to filter out light of said first wavelength, detecting and storing the filtered photoluminescent light and converting said filtered photoluminescent light into a first image; and d) providing a second photoluminescent image of said object measured when said object is stationary and ratioing the second image of the object when stationary to said first image of the rotating object, and converting said ratio into a pressure distribution over the surface of said rotating object.
6. The method according to claim 5 wherein said light source is a strobe light source and said light pulses have a pulse width in no more than microseconds in order to freeze motion of said rotating object.
7. An system for measurement of surface pressure of an object being rotated, comprising;
a) a photoluminescent pressure sensitive coating material adapted to be coated onto a surface of said object to be rotated;
b) light source adapted to emitting a train of light pulses directed at said object, said light source including means for synchronizing said light source to rotation of said object, said light source adapted to emitting light at a first wavelength;
c) photodetection means adapted to detect photoluminescent light intensity emitted from a photoluminescent pressure sensitive material; and d) processing means for storing and processing photoluminescent light intensity to convert photoluminescent light intensity into a pressure distribution over a surface of a rotating object.
a) a photoluminescent pressure sensitive coating material adapted to be coated onto a surface of said object to be rotated;
b) light source adapted to emitting a train of light pulses directed at said object, said light source including means for synchronizing said light source to rotation of said object, said light source adapted to emitting light at a first wavelength;
c) photodetection means adapted to detect photoluminescent light intensity emitted from a photoluminescent pressure sensitive material; and d) processing means for storing and processing photoluminescent light intensity to convert photoluminescent light intensity into a pressure distribution over a surface of a rotating object.
8. The system according to claim 7 wherein said light source means is a strobe lamp producing light pulses having a pulse width not greater than microseconds.
9. The system according to claim 7 wherein said photodetection means includes a charged coupled device camera.
10. The system according to claims 7, 8 or 9 wherein said photodetection means includes a band pass filter located in front of said charged coupled device camera to filter out light at said first wavelength.
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CA 2204980 CA2204980A1 (en) | 1997-05-09 | 1997-05-09 | Method and apparatus for surface pressure mapping of rotating objects by synchronized optical imaging of luminescent coating |
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CA 2204980 CA2204980A1 (en) | 1997-05-09 | 1997-05-09 | Method and apparatus for surface pressure mapping of rotating objects by synchronized optical imaging of luminescent coating |
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Cited By (1)
Publication number | Priority date | Publication date | Assignee | Title |
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CN114739626A (en) * | 2022-06-13 | 2022-07-12 | 中国空气动力研究与发展中心高速空气动力研究所 | Rotating blade grid pressure measurement test method based on quick response pressure-sensitive paint |
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1997
- 1997-05-09 CA CA 2204980 patent/CA2204980A1/en not_active Abandoned
Cited By (1)
Publication number | Priority date | Publication date | Assignee | Title |
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CN114739626A (en) * | 2022-06-13 | 2022-07-12 | 中国空气动力研究与发展中心高速空气动力研究所 | Rotating blade grid pressure measurement test method based on quick response pressure-sensitive paint |
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