Spatially Nonuniform Self-Quenching of the Pressure-Sensitive Paint PtTFPP/FIB*

It has long been the experience at the Arnold Engineering Development Center (AEDC) that when performing lifetime-based pressure-sensitive paint (PSP) measurements in a wind tunnel, the lifetime response of the painted test article may vary significantly, both in magnitude and in spatial uniformity, from the response of coupons that are painted at the same time, and under the same conditions, as the test article. This paper documents an extreme example of such behavior and deduces, by analysis of the lifetime response, that the likely culprit is nonuniformly distributed self-quenching of the PtTFPP probe molecules in the FIB binder. This work indicates that lower probe concentrations may be required to avoid the resulting calibration difficulties and that the parameters of the paint application process may have to be specified more tightly.