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A simultaneous three-dimensional (3D) surface profile and pressure measurement method that integrates phase-shift profilometry and pressure-sensitive paint (PSP2) is proposed. The advantages of this novel technique over previous 3D pressure-sensitive paint (3D-PSP) techniques include a simplified system with low cost, no interference with PSP coatings, high spatial resolution, and high accuracy. A modified digital light-processing (DLP) projector-structured light generator is used to encode ultraviolet light and generate fringe projection to excite the pressure-sensitive paint. The 3D profile is reconstructed using four phase-shifting emission images. Meanwhile, the surface intensity ratio distribution is obtained. The PSP2 method is applied to a nitrogen jet impingement experiment onto a spherical model. The intensity ratio results obtained using the PSP2 method differ little from the conventional PSP results obtained using uniform excitation. The phase distortion due to the emission intensity fluctuation leads to errors in surface profile measurement, and the fringe projection with high contrast improves surface profile measurement accuracy. In most of the final results, the average total errors between the reconstructed 3D surface and the CAD geometry are less than 0.1 mm.

This paper proposes a dual-camera single-shot lifetime method for pressure-sensitive paint (PSP) measurements on fast-rotating surfaces. Two cameras with fully controllable exposure gates are used for image acquisition to reduce the motion blur due to the open-ended exposure of the interline transfer charge-coupled device camera which was typically used for the single-shot lifetime method. The images can thus be processed without deblurring for a wider rotating speed range than is possible with existing techniques. More importantly, both frames have equal exposure times and therefore equal blur lengths. This enables precise pixel-to-pixel image matching and minimizes image registration errors. In addition, the signal strengths of the frames can be balanced, enabling shot-noise-induced errors to be reduced by independent adjustment of the aperture ratio. A pressure uncertainty estimation model is established to evaluate the measurement errors, which helps determine the system parameters. The dual-camera PSP system is calibrated and then validated through the surface pressure measurement of a fast-rotating disk. It is found that the exposure time te has little effect on the PSP sensitivity, whereas the delay time td affects both the pressure sensitivity and the measurement error. Both te and td are set to 5 μs in the rotating disk experiment. Images with a blur length of 1.4 pixels are captured and processed without deblurring to yield reasonable surface pressure results. The pressure error is decreased from 1.05 to 0.65 kPa by increasing the aperture ratio F from 2 to 4.

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