Temperature Sensitive Paint Research Articles

IR sensor array using photo-patternable temperature sensitive paint for thermal imaging

This paper reports an infrared-to-visible transducer array made of temperature sensitive paint (TSP) for a low-cost thermal imaging application. A novel fabrication process using a photo-patternable temperature sensitive paint (PTSP) combined with an SU-8 transfer method was developed. A PTSP microstructure as small as 2 μm was successfully patterned by the normal photolithography process, and sensitivity as high as −0.5%/°C was obtained. The proposed method simplifies the fabrication process, and prevents the TSP from plasma-induced damage. A self-suspended structure as small as 70 μm was successfully fabricated with a large-gap of 40 μm from the substrate. The heated object at 250 °C was detectable with a spatial resolution of about 380 μm.

A detailed characterization of BaMgAl10O17:Eu phosphor as a thermal history sensor for harsh environments

Knowledge of component temperatures in gas turbines is essential for the design of thermal management systems and to maintain the lifetime of highly loaded parts as the firing temperature increases in pursuit of improved thermal efficiency. When on-line methods such as pyrometers and thermocouples are not suitable, a thermal history sensor can be used to record the maximum temperatures and read them out after operation. Currently, temperature sensitive paints are applied to obtain temperature profiles in gas turbine components but they present some limitations. A new method based on irreversible changes in the optical properties of thermographic phosphors can potentially overcome some of these difficulties. In particular, a sensor based on the oxidation of europium based phosphors has shown great potential. In this work the temperature sensing capabilities of the phosphor BaMgAl10O17:Eu are investigated in the temperature range from 700°C to 1200°C, and suitable measurands defined. The influence of practical factors comprising excitation fluence, exposure time, dopant concentration, cooling down time and atmosphere composition, on measurement accuracy and sensitivity are also reported.

Effects of wall temperature on skin-friction measurements by oil-film interferometry

Wind-tunnel skin-friction measurements with thin-oil-film interferometry have been taken on an aluminum sample to investigate the effects of wall temperature on the accuracy of the technique. The sample has been flush-mounted onto a flat plate with an electric heater at its bottom and mirror-smooth temperature-sensitive paint sprayed on its top. The heater has varied the sample temperature from ambient to 328 K, and the paint has permitted wall temperature measurements on the same area of the skin-friction measurements and during the same test. The measured wall temperatures have been used to calculate the correct oil viscosities, and these viscosities and the constant nominal viscosity at 298 K have been used to calculate two different sets of skin-friction coefficients. These sets have been compared to each other and with theoretical values. This comparison shows that the effects of wall temperature on the accuracy of skin-friction measurements are sensible, and more so as wall temperature differs from 298 K. Nonetheless, they are effectively neutralized by the use of wall temperature measurements in combination with the correct oil viscosity–temperature law. In this regard, the special temperature-sensitive paint developed for this study shows advantages with respect to more traditional wall temperature measurement techniques.

Effect of polymer matrix on temperature sensitivity of temperature sensitive paints

The thermal quenching behaviors of the temperature sensitivity paints (TSP) composed of europium(III) thenoyltrifluoroacetonate (EuTTA) and Eu-phenanthrene complex (Eu-2) in polystyrene (PS), polymethylmethacrylate (PMMA) and epoxy resin (EP) were investigated. It is found that both the emission intensity and temperature sensitivity were not only affected by the luminescence probes, but also by the polymer matrix. The interaction between probes and matrix results in the alteration of both the non-radiation decay rate and the activation energy of the non-radiative process for the thermal quenching process, i.e. larger activation energy of the non-radiative process shows higher temperature sensitivity and less emission intensity. Therefore, it was confirmed that the temperature sensitivity and luminescent intensity of TSP depended not only on the luminescence probes but also on the polymer matrix.

A grid-pattern PSP/TSP system for simultaneous pressure and temperature measurements

A novel combined pressure- and temperature-sensitive paint system has been developed for simultaneous pressure and temperature measurements using a monochrome camera. This grid-pattern PSP/TSP system consists of an array of PSP dots (PtTFPP in polymer-ceramic binder) on top of a TSP layer (Ru(dpp) in clearcoat). The physical separation of PSP and TSP eliminates problems involving chemical interactions and spectral interference which are commonly seen in dual-luminophore PSPs. Both PSP and TSP are excited by a 400nm LED and the signals are captured simultaneously by a monochrome charged-couple device (CCD) camera. The key challenge is to precisely identify PSP and TSP regions from the grid pattern in each image. This has been realized by first creating a sharp environmental change in temperature or oxygen concentration, and then separating PSP region from TSP region based on the difference in intensity-ratio caused by paint properties. Full pressure and temperature fields are recovered by performing 2-D interpolation on PSP and TSP data, and the temperature field is then used to remove the temperature-induced errors in PSP results. This PSP/TSP system has been demonstrated in oblique jet impingement experiments.

Europium 1,3-di(thienyl)propane-1,3-diones with outstanding properties for temperature sensing

The synthesis of novel Eu complexes with 1,3-di(thienyl)propane-1,3-diones as ligands as well as their luminescence properties in different polymers are reported. The new temperature sensitive paints (TSPs) exhibit not only exceptional high temperature sensitivity over a wide range of temperatures but are also characterized by negligible pressure sensitivity and marked photostability. This is why they are outstandingly suitable for applications, e.g. in aerodynamics and hydrodynamics.

A Study of Wildfire Ignition by Rifle Bullets

Experiments were conducted to examine the potential for rifle bullets to ignite organic matter after impacting a hard surface. The tests were performed using a variety of common cartridges (7.62 × 51 [.308 Winchester (The use of tradenames is provided for informational purposes only and does not constitute an endorsement by the U.S. Department of Agriculture.)], 7.62 × 39, 7.62 × 54R, and 5.56 × 45 [.223 Remington]) and bullet materials (steel core, lead core, solid copper, steel jacket, and copper jacket). Bullets were fired at a steel plate that deflected fragments downward into a collection box containing oven-dried peat moss. We found that bullets could reliably cause ignitions, specifically those containing steel components (core or jacket) and those made of solid copper. Lead core-copper jacketed bullets caused one ignition in these tests. Thermal infra-red video and temperature sensitive paints suggested that the temperature of bullet fragments could exceed 800°C. Bullet fragments collected from a water tank were larger for solid copper and steel core/jacketed bullets than for lead core bullets, which also facilitate ignition. Physical processes are reviewed with the conclusion that kinetic energy of bullets is transformed to thermal energy by plastic deformation and fracturing of bullets because of the high-strain rates during impact. Fragments cool rapidly but can ignite organic matter, particularly fine material, if very dry and close to the impact site.

Boundary-layer transition on a rotor blade measured by temperature-sensitive paint, thermal imaging and image derotation

Transition measurements using temperature-sensitive paint (TSP) and infrared (IR) imaging are shown for a model-scale rotor blade using derotation by an axial rotating mirror. Measurements were performed on a modified NACA0015 blade model by different angles of attacks at low-speed conditions. The effective angle of attack was computed from the geometric angle of attack and the downwash measured using particle image velocimetry (PIV) and from numerical computations by an actuator disc method based on blade element theory. The transition over a laminar separation bubble was detected in TSP and IR results for all investigated angles of attack. Additional two-dimensional high-resolution PIV measurements were performed near the surface of the modified NACA0015 model. The mean point of laminar separation (LS) and mean point of turbulent reattachment (TR) were extracted from TSP results. The single transition point was set at the 50 % between LS and TR and compared with predictions from Euler-boundary-layer code with an envelope-eN transition prediction.

Development of fast response bi-luminophore pressure-sensitive paint by means of an inkjet printing technique

A novel fast response bi-luminophore pressure-sensitive paint (PSP) by inkjet printing of sensor-dot arrays on an anodized aluminum (AA) substrate has been developed for unsteady flow measurements. A bi-luminophore AA-PSP, which is a combination of PSP and temperature-sensitive paint (TSP), is essential for precise pressure measurements, because the PSP result needs the temperature correction. However, a conventional bi-luminophore AA-PSP prepared by a dipping method does not work well due to the interference between the PSP and TSP luminophores. To overcome this problem, we have developed isolated dot arrays of PSP and TSP formed on an anodized aluminum substrate by an inkjet printing method. In this study, platinum tetrakis (pentafluorophenyl) porphyrin (PtTFPP) and ZnS-AgInS2 (ZAIS) were employed as pressure- and temperature-sensitive dyes, respectively. A suitable solvent was chosen for each dye to form the dots with uniform, high luminescence intensity, and high sensitivity. The developed bi-luminophore AA-PSP could simultaneously measure pressure and temperature and could reduce the temperature effect of the PSP from −0.97%/K (without temperature correction) to −0.01%/K (with temperature correction). It showed a pressure response time of 17.8 ± 0.8 μs at 90% pressure rise to a step change of pressure, which is in the same range as a conventional AA-PSP.

Multi-scale Responses of Eastern Massasauga Rattlesnakes (Sistrurus catenatus) to Prescribed Fire

The eastern massasauga rattlesnake (Sistrurus catenatus) is a threatened species that occurs in habitats frequently targeted by prescribed burns. There have been reports of massasauga mortality as a result of prescribed fires, but little is known regarding the indirect effects of fire on this species. The objective of this study was to monitor massasaugas during a prescribed fire to assess direct and indirect effects. We initially implanted radio transmitters in 13 massasaugas inhabiting an area targeted for periodic prescribed fires and tracked them following a prescribed fire to determine burn-related mortality and behavioral influences. Data loggers, temperature sensitive paint, and measuring posts were used to record detailed fire data. Of the five snakes on the burn unit at the time, two died as a result of the fire. No differences were observed in daily movements and home range sizes between burn categories (in the burn, same site not in the burn and at a nearby unburned site). Snakes on and off the burn unit at the same site exhibited the same habitat preference for wetland habitats, whereas snakes at the control site preferred herbaceous areas. Slight differences were observed in microhabitat selection related to litter depth, surface light intensity, distance to water, and surface temperature. The snakes did not appear to alter their seasonal activities as a result of the prescribed fire. The results of this study suggest ways to minimize impacts from prescribed fires on massasauga populations.

Nonadiabatic Surface Effects on Transition Measurements Using Temperature-Sensitive Paints

Tests were conducted at the Cryogenic Ludwieg-Tube Göttingen to investigate the influence on onset of boundary-layer transition of thermal gradients on the model surface, whereby the temperature-sensitive paint technique has been used to detect transition. The laminar airfoil under investigation was tested at high Reynolds and at both low and high subsonic Mach numbers. The influence on boundary-layer transition of the temperature difference between the flow and the model surface due to the temperature drop occurring during a test run at the Cryogenic Ludwieg-Tube Göttingen was examined. Various combinations of flow conditions and angles of attack were employed to investigate different stability situations. Linear-stability computations, based on the experimental data, were also carried out. The unfavorable impact of surface temperatures larger than the adiabatic-wall temperature was identified to be dependent on the considered boundary-layer-stability situation. For certain stability situations, it was shown that a nonadiabatic model surface can strongly influence the boundary-layer transition location.

Infrared thermal detector array using Eu(TTA)3-based temperature sensitive paint for optical readable thermal imaging device

This paper presents the design and fabrication of an infrared (IR) thermal detector array made of Eu(TTA)3-based temperature sensitive paint (TSP). The TSP emits 610 nm visible luminescence depending on temperature, and works as an IR-to-visible converter. An optical readout system was designed to excite and observe the detector array using a 355 nm light-emitting diode (LED) and a charge-coupled-device (CCD) camera, respectively. The temperature coefficient of the TSP was measured to be −1.58% K−1, and thermal images of a 400 °C object were successfully obtained. The noise analysis showed that the noise-equivalent temperature difference (NETD) of the imaging system was about 4.5 K.

Quiet Tunnel Measurements of HIFiRE-5 Boundary-Layer Transition

The Hypersonic International Flight Research Experimentation (HIFiRE) program is a hypersonic flight test program executed by the Air Force Research Laboratory and Australian Defence Science and Technology Organisation. The principal goal of HIFiRE flight five is to measure hypersonic boundary-layer transition on a three-dimensional body. The HIFiRE flight tests are supported by a ground test campaign; this paper presents measurements of heat flux and boundary-layer transition in the Boeing/AFOSR Mach-6 Quiet Tunnel. This facility has been developed to provide quiet flow at high Reynolds number, with low noise levels comparable to flight. This tunnel’s good optical access enabled global measurement of the heat flux by means of temperature-sensitive paint. Two modes of transition were observed: transition along the centerline, suspected to arise from the amplification of second-mode waves in the boundary layer, and transition roughly halfway between the centerline and leading edges, probably due to the breakdown of crossflow vortices. Reducing the noise level from conventional to quiet substantially delayed both transition modes. Increasing the angle of attack from 0 to 4 deg delayed the crossflow transition mode on the windward side. Transition moved forward as freestream unit Reynolds number increased from to .

S1910301 感温塗料を用いた高温衝撃風洞におけるHIFiRE模型の境界層遷移可視化

A visualization experiment of hypersonic boundary layer transition by Temperature-Sensitive Paint (TSP) was performed. The test facility was High-Enthalpy Shock Tunnel (HIEST) at Japan Aerospace Exploration Agency (JAXA) Kakuda Space Center. An elliptic cone model with a 2:1 aspect ratio, which is a full-scale model of HIFiRE-5, was used as the test model. This study visualized the hypersonic boundary layer transition on the side of the test model. TSP was excited by a Blue-LED and the luminescence from TSP was detected by a high-speed camera. Temperature distribution on the side of the test model was obtained by TSP. Moreover, boundary layer transition along the centerline of the model and in approximately halfway between the centerline and leading edge were visualized. The trend of temperature rise along the centerline is same in TSP and thermocouples, which is inserted on the centerline of the test model.

1031 感圧・感温塗料に何ができるのか? : 分子イメージング計測の現状

The current status of pressure sensitive paint (PSP) and temperature-sensitive paint (TSP) has been presented in this paper. PSP and TSP are molecular imaging techniques and enable to measure global pressure and temperature distribution on a model surface. PSP has been achieving a remarkable improvement in responsiveness and detecting resolution of pressure. TSP is used to measure not only temperature distribution but also heat flux and to detect boundary-layer transition.

1003 超高速応答型TSPによる衝撃波管内壁の非定常流体現象の可視化

This paper describes the visualization for unsteady fluid phenomena occurring on shock-tube wall by means of Temperature-Sensitive-Paints (TSP). TSP measurement used in this research has been developed for heat-flux estimation in hypersonic shock tunnels which have a few milliseconds test duration, thus TSP has to measure temperature in a few hundred kHz of sampling frequency for highly-accurate heat-flux estimation. Results measured by TSP show a detailed flow structure on the wall, where temperature/heat-flux variations by the incident/reflected shocks, the laminar to turbulent boundary-layer transition, the streak in turbulent boundary-layer, the shock/boundary-layer interaction and the interference between the reflected shock and the contact surface, are clearly visualized and accurately quantified.

S1910203 感温塗料法を応用した柔軟構造大気圏突入機が受ける空力加熱の評価

Temperature measurements on flexible test model in hypersonic flow were performed. Temperature Sensitive Paint (TSP) that includes two kinds of dye was employed as a temperature sensor which is able to measure temperature distribution on flexible and deforming surface during wind tunnel operation. To detect the emission which is emitted from those respective dyes, an optical system which can distinguish two deferent wave length zones was installed. As results, temperature distribution on flexible surface that is deformed due to wind tunnel operation was obtained by using new TSP measurement system

J0550402 感温塗料(TSP)を用いた時間変動温度場測定システムの開発

J0550402 感温塗料(TSP)を用いた時間変動温度場測定システムの開発

Experimental Investigation of the Effect of Forward-facing Steps on Boundary Layer Transition

The effect of geometric forward-facing steps on boundary layer transition was experimentally investigated at a high subsonic Mach number in a blow-down wind tunnel facility in Göttingen, Germany. Boundary layer transition was detected non- intrusively by means of the Temperature-Sensitive Paint (TSP) technique. Forward-facing steps of different height were installed on a spanwise invariant wind tunnel model. Streamwise pressure gradient and high chord Reynolds number were systematically varied and their effect on boundary layer transition was studied in the presence of forward-facing steps on the model surface. At all tested stability situations, the surface imperfections were shown to reduce the extent of the laminar region. Transition was observed to move gradually towards the step location with increasing step Reynolds numbers and increasing relative step height. For a given combination of step height and chord Reynolds number, more pronounced negative pressure gradients led to an increase in transition Reynolds number. The reduction in transition Reynolds number due to the effect of the surface imperfection was more marked at larger flow acceleration. The plots of the relative change in transition location as a function of the step Reynolds number and of the relative step height gave good correlation of the results. The correlations were found to be practically independent of the streamwise pressure gradient in the examined range. Criteria for the allowable tolerances on low- sweep Natural Laminar Flow surfaces can now be derived from the functional relations determined in this work.

Fast-response temperature-sensitive-paint measurements on a hypersonic transition cone

Experiments are performed using a fast-response temperature-sensitive-paint (TSP) technique to measure the heat-flux distribution on a slender cone in a hypersonic shock tunnel under both laminar and transitional conditions. The millisecond-order test duration together with the self-luminosity of shock layers place stringent conditions on the choice of TSP luminophore and the TSP-layer thickness that can be employed. The luminosity and dimming from particulates in the free-stream cause additional problems in interpreting the obtained intensity profiles. Nevertheless, favorable agreement with thermocouple-based measurements show that it is possible to derive quantitatively accurate heat-flux distributions with the TSP technique for temperature rises of up to approximately 40 K above room temperature. The technique accuracy is adversely affected at higher temperatures, which is thought to result from non-constant thermal properties of the insulating base layer. At high unit Reynolds number conditions, time-resolved heat-flux distributions show large-scale unsteadiness in the boundary-layer transition location and reveal transient streamwise streaks developing in the transitional region.