Development of Fast and Highly Accurate Surface Pressure Measurement System with Pressure Sensitive Paints

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Pressure sensitive paints (PSPs) are a kind of a functional paint. Recently, pressure measurement technique based on these paints is being developed and used for aerodynamic applications. This approach uses the luminescent molecules that emit light whose intensity increases with the decrease in partial pressure of oxygen. This coating can give the surface pressure data with high spacial resolution in the windtunnel testing. In this work, the time-response and the effect of temperature of the PSPs, which were important characteristics in measuring pressure, were obtained experimentally. The PSPs studied in the present works were PtOEP , PtTFPP, H_2TFPP, and H_2TCPP; they were painted on a porous silica thin-layer chromatography (TLC) plate. The following results were obtained.(1) The emission spectrum of each PSP was measured. The luminescence intensity data in various range of temperature and pressure were accumulated experimentally for each PSP.(2) The luminescence intensity of a PSP decreases during irradiation due to photodegradation. This phenomenon was measured for each PSP, and the time constant representing the degree of degradation was estimated.(3) The time-response of the paints was investigated by using a shock tube. Results indicated that the response time was on the order of 20-40 microseconds.(4) The effect of the sudden change in gas temperature on the luminescence intensity was investigated by using the contact surface of the shock tube flow, and it was found that the luminescence intensity depended only on the wall temperature and was affected little by the gas temperature.