Newsletter  2023.11  Index

Theme : "Mechanical Engineering Congress, 2023 Japan (MECJ-23)" Preface Hideo MORI, Tetsuya KANAGAWA Why do mistakes communicate and spread? (Diffusion and prevention of misperceptions regarding fluid mechanics) Ryozo ISHIWATA (Kanagawa Institute of Technology) Toward Digital Twin Numerical Turbine Satoru YAMAMOTO (Tohoku University) Measurements of turbulent wall pressure fluctuation field in a turbulent boundary layer and the wing-flat plate juncture flow using the many-channel microphone array Yoshitsugu NAKA (Meiji University) PSP and TSP for measuring pressure and temperature fields on wall surfaces and their applications Yasuhiro EGAMI (Aichi Institute of Technology) Flow measurement using MEMS differential pressure sensor Hidetoshi TAKAHASHI (Keio University), Takuto Kishimoto (Keio University), Kei Ohara (Keio University), Kyota Shimada (Keio University) Flexible Sheet Sensor for Advanced Flow Monitoring Masahiro MOTOSUKE (Tokyo University of Science)

 

PSP and TSP for measuring pressure and temperature fields on wall surfaces and their applications

Abstract

Yasuhiro EGAMI Aichi Institute of Technology

Pressure-Sensitive Paint (PSP) and Temperature-Sensitive Paint (TSP) have been widely used in recent years to measure pressure and temperature distribution on walls using cameras optically. PSP measures pressure using a photochemical reaction called oxygen quenching, in which the emission intensity of a dye changes with the oxygen partial pressure (~pressure). On the other hand, TSP measures temperature by utilizing the change in luminescence intensity of dyes (thermal quenching) caused by changes in temperature. While conventional pressure taps and thermocouples are discrete point sensors, PSP and TSP can measure with high spatial resolution because each luminescent dye in the paint acts as a sensor. The PSP and TSP can measure a wide range of objects, from tiny microchannels where it is difficult to install sensors, such as pressure taps, to actual aircraft and automobile surface flows. When research began in the 1980s, PSP measurements were mainly performed on steady flows in the transonic and supersonic ranges, where significant pressure changes could be obtained. Subsequently, applying low-speed flows with minor pressure changes and unsteady measurements using PSP with improved time response by making the binder more porous was conducted. When nano-particles are mixed with polymers at a ratio higher than the critical pigment volume concentration, the thin film becomes porous, as in Fig.1. This can significantly improve the time response of PSP. In recent years, fast-response PSPs with response times of 1 to 20 µs have been developed, and unsteady measurements at low speeds with small pressure fluctuations have also been performed (Fig.2).　

In addition to measuring temperature distribution, TSP is also used to visualize boundary layer transitions. In particular, TSP has been reported to be useful for measurements in Cryogenic Wind Tunnel and underwater, where it is difficult to use infrared cameras. Since TSP measures visible light, it is also advantageous to use ordinary high-speed cameras, lenses, and optical windows. TSP is also used for heat flux measurement because the time response of TSP is equivalent to that of a thermocouple by reducing the thickness of the TSP film.

Your feedback on new applications of PSP and TSP, as well as on required technical elements, is essential for further developing PSP/TSP technology. We will continue to develop more user-friendly sensors and more accurate measurement methods.

Key words

Pressure-Sensitive Paint (PSP), Temperature-Sensitive Paint (TSP), Optical measurement method, Luminescence, Unsteady global measurement.

Figures

Fig.1 Fast-responding PSP: (a) schematic and (b) SEM image.

Fig.2 Kármán vortex street measured by fast-responding PSP at =20 m/s.

Fig. 3 Detection of boundary layer transition by TSP in a cryogenic wind tunnel.