Hirotaka Sakaue

Open-system pressure sensitive paint for surface pressure measurements in a cryogenic wind tunnel

Pyrene-, ruthenium-, and porphyrin-based, anodized aluminum pressure sensitive paint (AA-PSP) is developed for surface pressure measurements in a cryogenic wind tunnel. These AA-PSPs were calibrated to determine the pressure sensitivity by injecting a small amount of oxygen in the test gas. The mole fraction of oxygen was varied from 4 ppm up to 2000 ppm. The calibration tests were conducted in the 0.1 m Transonic Cryogenic Wind Tunnel (TCWT) at National Aerospace Laboratory, Japan. Luminophore choice affected the pressure sensitivity with a pyrene-based AA-PSP having the best sensitivity. These AA-PSPs were applied for surface pressure measurements on a 14% thick circular arc-bump model in the TCWT. The results of pyrene- and ruthenium-based AA-PSPs showed good agreement with pressure taps. Pressure sensitivity, signal level, and uniformity of luminescent coating affected the pressure measurements.

Global Pressure and Temperature Measurements of Ballistic-Range Testing by PSP and TSP Techniques

A ballistic-range testing gives great insights into a free-flight aerodynamics. It can be seen in a wide flow regime such as from a high-speed flow (ex. a capsule re-entry test and a debris test) to a low-speed flow (ex. a baseball trajectory test and a soccer-ball trajectory test). The surface pressure and temperature are two important factors to determine the motion of the free-flight object. However, there are limited experimental tools available to capture the surface information. We are developing the pressureand temperature-sensitive paint techniques to capture the surface pressure and temperature of a free-flight object. Two approaches are described in this paper. One is a motion-capturing PSP/TSP system that extracts global pressure or temperature information of a free-flight object. The other is an electro-luminescence PSP/TSP system that combines the illumination source on a free-flight object.

Unsteady Pressure Distribution on a Fluttering Airfoil using Motion-Capturing PSP System

A motion-capturing pressure-sensitive paint (PSP) system is applied to a fluttering motion of an airfoil. It consists of a two-color PSP combined with a high-speed color camera. By simply rationing the green and red images, we can cancel the illumination non-uniformity and the change in the camera-PSP distance that causes substantial error for a time-resolved PSP measurement. The system is applied to an YXX wing with 30% span. The time-resolved pressure measurement is obtained at the camera frame rate of 100 Hz. The wing oscillates at the primary frequency of 13.7 Hz. The unsteady pressure distribution including the shock oscillation over the wing is captured.

Development of Temperature-Cancelled Motion-Capturing PSP System and Its Application to a Hypersonic Wind Tunnel

A motion-capturing pressure-sensitive paint (PSP) system is applied to a hypersonic wind tunnel application. The 8 system consists of a two-color PSP and a fast-frame color camera. The supporting matrix of the PSP is anodized 9 aluminum, giving a fast time response as well as providing a temperature tolerance in the hypersonic flow. Our 10 developed PSP has a reference luminescence in green and a pressure-sensitive luminescence in red regions. 11 Generally, the temperature effect of a PSP measurement is a great issue. The developed system can reduce the 12 temperature effect of the PSP measurement by simply rationing the green and red images acquired from a high13 speed color camera. The system description and characterizations in terms of the pressure and temperature is 14 included in this paper. A hypersonic wind tunnel test is done at The Hypersonic and High Enthalpy Wind Tunnel at 15 The University of Tokyo, Kashiwa Campus. It provides Mach 7 flow for the test duration of 12 s. Our developed 16 system can capture the pressure distributions during the model insertion to the flow as well as the steady flow 17 conditions. 18

Pressure/Temperature Measurement of a Free-Flight Object by PSP/TSP

A motion-capturing pressure-sensitive paint (PSP)/temperature-sensitive paint (TSP) system is applied to capture a free-flight object for the ballistic measurement. It consists of a two-color PSP/TSP combined with a high-speed color camera. By simply rationing the green and the red images, we can capture the pressure/temperature distribution of a moving object. The PSP/TSP-coated object travels around the speed of sound, which can be captured by our system. We adopted the image processing method, which combined with deconvolution with Wiener filter, multiplication by binary image and application of median filter, to reduce motion blur and random noise and the method was effective.

Quantum Dots as Global Temperature Measurements

ZnS-capped CdSe semiconductor nanocrystals (quantum-dots, QDs) provide size-tunable optical properties. QDs show shifted luminescent peaks due to crystal size. They exhibit strong and stable luminescence with a 50 % quantum yield at room temperature [1]. Walker et al. used QDs as a global temperature probe [2]. They used a polymer support of poly(lauryl methacrylate) to create a global temperature sensor. This type of sensor, called a temperature-sensitive paint (TSP), has been widely used in aerospace measurements [3]. Conventional TSP uses a phosphorescent molecule as a temperature probe. This type of molecule has a relatively wide FWHM (full width at half maximum), which is roughly 100 nm. When applying a QD as a temperature probe, the FWHM is narrower than that of phosphorescent probes and is roughly 40 nm [1]. A low FWHM will widen the selection of probe molecules to prepare multi-color sensors in the visible wavelength range. In addition, a high quantum yield of QDs can be beneficial as an optical temperature sensing probe to increase the signal-to-noise ratio.

Temperature Cancellation Method of Motion-Capturing PSP System

We introduce a temperature-cancellation method of motion-capturing PSP (pressure-sensitive paint) 8 system. This uses two-luminescent outputs from a two-color PSP. These are simultaneously acquired as 9 images by the motion-capturing PSP system. The advantages of this combined system are that it reduces and 10 has a potential to cancel the temperature influence of a PSP system, and captures surface pressure 11 information of a moving object. The temperature-cancellation method is described in this paper. A validation 12 test is performed, which is also included in this paper. 13