| CPC H04N 25/773 (2023.01) [G01L 27/002 (2013.01); H04N 25/40 (2023.01); H04N 25/53 (2023.01); H04N 25/711 (2023.01)] | 9 Claims |
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1. A periodic pressure field measurement method based on a superposed lifetime of pressure sensitive paint, comprising the following steps:
step 1, providing respective components of a periodic pressure field measurement system of the pressure sensitive paint, wherein the periodic pressure field measurement system comprises: a test piece, a pulse light source, a camera, a synchronizer and a computer, wherein a test surface of the test piece is uniformly sprayed with the pressure sensitive paint (PSP); the pulse light source directly faces the test surface of the test piece and is centered relative to the test surface; the pulse light source is connected to the synchronizer; the camera is fixed above the pulse light source; a lens of the camera is aligned with the test surface of the test piece, and the test surface of the test piece is completely in the range of the lens of the camera; and the camera is connected to the synchronizer and the computer respectively;
step 2, uniformly spraying the pressure sensitive paint onto the test surface of the test piece;
step 3, enabling the pulse light source to directly face the test surface of the test piece, mounting the camera above the pulse light source, and aligning the lens of the camera with the test surface of the test piece;
step 4, enabling a modulation mode of the camera, and uniformly dividing a pressure field with a period of T into n parts in time, wherein a phase corresponding to a pressure field within an ith time period is φi, and phases corresponding to pressure fields within respective time periods are respectively φ1, φ2 . . . φn;
step 5, placing the periodic pressure field measurement system of the pressure sensitive paint in a lightless environment for experiment, and starting to measure a pressure field of the PSP after an experimental pressure field satisfies periodic changes;
step 6, adjusting the pulse light source by using the synchronizer to enable a pulse emitted by the pulse light source to have a width of tp and to enable the number of light emissions under phase φ1 to be M;
step 7, controlling, by the computer, the camera via the synchronizer to enable the camera to shoot images after the pulse light source emits light for tp; selecting the modulation mode of the camera, setting the frequency of the modulation mode to be M, setting the single exposure time of the camera to be t1, accommodating M light emitting lifetimes of the PSP within t1 in the modulation mode, recording the lifetimes by the computer, and outputting an image I1;
step 8, performing delay setting on the camera to enable the camera to start exposure after the pulse light source emits light for tp+t1; selecting the modulation mode of the camera, setting the frequency of the modulation mode to be M, and setting the exposure time to be t2; accumulating M light emitting lifetimes of the PSP within t2 in the modulation mode, recording the lifetimes by the computer, and outputting an image I2;
step 9, dividing, by the computer, gray values of the same pixels of the image I1 and the image I2 to obtain an image I1/I2, and then restoring pressure information of the phase φ1 according to an image light intensity and pressure calibration formula of the PSP; and
step 10, adjusting the pulse light source to emit light in other phases by using the synchronizer according to a time-space relationship between the periodicity of a pressure field and the phase, and repeating steps 6 to 9 to obtain pressure change processes at n moments within one period, thus realizing dynamic pressure measurement.
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