Accuracy limitations of lifetime-based pressure-sensitive paint (PSP) measurements

PSP systems determine air pressure by measuring the luminescence lifetime of an oxygen-quenched luminophor in a porous matrix. While traditionally lifetime was inferred from measurements at different pressures, it is becoming increasingly common to make direct lifetime measurements by taking images at different points on the luminescence decay curve using a gated camera. Here, the accuracy of the lifetime method is evaluated through theoretical analysis, bench top studies, and small scale wind tunnel tests, with the primary aim of determining whether the lifetime method is suitable for measurements in very low speed flows (Mach/spl sim/0.1). It is found that the luminescence lifetime of a PSP-coated surface can vary from point to point even at constant pressure and temperature. This variation is a significant source of error in low speed measurements, and can be reduced significantly by careful paint application procedures.