Simultaneous measurement method of pressure and temperature using dual-layer PSP/TSP with lifetime-based method

Recently, the application field of the pressure measurement technique using pressure sensitive paint (PSP) has been expanding. However, the temperature dependence of PSP is a serious obstacle to accurate pressure measurement in low gauge pressure conditions because PSP is an absolute pressure sensor. Therefore, the temperature information of PSP is indispensably required for accurate pressure measurement, especially in low gauge pressure conditions. As a result, both temperature information and pressure information with a function of temperature are required simultaneously to use the PSP in low gauge pressure conditions. Dual-layer PSP/temperature sensitive paint (TSP) (DL-PTSP) is one solution, but simultaneous measurement of pressure and temperature requires two optical filters to separate the luminescence of PSP and TSP, resulting in complex equipment and additional error caused by parallax. To solve the problem, we introduce a lifetime-based method for DL-PTSP that allows simultaneous measurement of pressure and temperature. It is a method which separates each component of luminescence with different lifetimes. Firstly, the DL-PTSP developed in this study was optimized by reducing the luminescence intensity of the PSP with a longer lifetime while maintaining the luminescence intensity of the TSP with a shorter lifetime, considering the lifetime measurement method. Secondly, we have clarified the optimum time conditions of the monolayer TSP and the monolayer PSP by analysing their luminescence decay process, by controlling the irradiation delay of the light source relative to the camera shutter. Thirdly, the sensitivity of the DL-PTSP was examined using conditions optimized for mono-layer TSP and PSP. The luminescence decay of the TSP component shows sufficient temperature dependence, while the pressure dependence is very small. On the other hand, the dependence of the luminescence decay of the PSP component on the temperature and pressure is almost equal to that of the mono-layer PSP. The results confirm the feasibility of the simultaneous measurement of pressure and temperature using DL-PTSP.