Effect of Quenching Kinetics on Unsteady Response of Pressure-Sensitive Paint

Abstract

Pressure-sensitive paints (PSP) have recently been extended to high-frequency flowfields. Paint formulations have been used effectively to characterize pressure fluctuations on the order of 100 kHz. As the limits of PSP are extended, various experimental results indicate that the unsteady response characteristics are nonlinear. A thorough understanding of the photophysical mechanisms in paint response is needed. Gas transport properties, coupled with the nonlinear nature of the Stern-Volmer relationship have an effect on the paint response. This work discusses the full implications of a diffusion-based model for the unsteady response of pressure-sensitive paint. Based on this model, it is shown that the indicated pressure response of PSP is faster for a decrease in pressure, and slower for a pressure increase. Effects of other factors, such as pressure-jump magnitude, pressure-jump range, and Stern-Volmer nonlinearity, are evaluated. Furthermore, a fluidic oscillator is used to demonstrate experimentally the quenching kinetics of two types of PSP-polymer/ceramic and fast FIB. Results from the oscillator operated with argon, nitrogen, and oxygen gases at 1.59 kHz demonstrate behavior that agrees with the diffusion model. The polymer/ceramic PSP exhibited no delay between different test gases, indicating a flat frequency response of at least 1.59 kHz. Fast FIB, on the other hand, demonstrated a significant delay in rise time between the nitrogen and oxygen cases. Both the diffusion model and the experimental results demonstrate that the different responses to nitrogen and oxygen only become critical when the period of the flowfield oscillations is shorter than the response time of the paint formulation.

A review of pressure-sensitive paint for high-speed and unsteady aerodynamics

“…The PSP characteristic response time was 3 -6 ms. To reduce the temperature effect of PSP, they applied PSP directly on the metal model surface rather than a white basecoat. For a very thin layer of PSP without a white basecoat, however, the luminescent intensity of PSP was so low that the The PSP response to both nitrogen and oxygen is significantly attenuated from the input waveform, and the nitrogen response is faster that the oxygen response [63] accuracy of the acquired pressure image was limited. Overall pressure uncertainty estimated from shock tube measurements ranged up to 5 per cent over one atmosphere.…”

“…Gregory and Sullivan [63] also employed diffusion-based models to investigate the nonlinear quenching kinetics of PSP formulations. Their work Fig.…”

“…Fluidic oscillators have been used by Gregory et al [31,62,63] as a dynamic calibration device. The fluidic oscillator, commonly found in automotive applications as a windshield washer fluid nozzle, produces an oscillating jet when supplied with a pressurized fluid.…”

Measurement Techniques for Shock Movement Capture on a NACA 0012 in Unsteady Compressible Flow

“…A fast-response, two-color porous polymer paint was selected for this experiment, which was recently developed by Peng et al 15 This paint is a polymer/ceramic based PSP, which was designed specifically to improve the diffusivity of the binder material, thus allowing faster response times. Its kinetic characteristics were studied in detail by Gregory et al 22 ; its frequency response can be well beyond 5 kHz, which is sufficient to study the flow field on airfoils with oscillating freestream frequencies less than 21 Hz. PtTFPP, a typical platinum porphyrin based luminophore, was used as the pressure sensor in this experiment while a combination of perylene and laser dye were added as the reference or temperature sensor.…”

Unsteady surface signature of a pulsed vortex generator jet

“…The application of porous PSP to unsteady flows, such as the study of transient phenomena in shock tubes and Hartmann oscillators, has been well documented (Gregory et al 2008, Gregory and Sullivan 2006, Gregory et al 2007). However, much of the previous work with PSP on turbomachinery components in particular has dealt with steady-state measurement in a rotating frame of reference, such as axial compressors and rotors (Lepicovsky and Bencic 2002, Liu et al 1997, Bencic 1998, Navarra et al 2001.…”