Transition detection by temperature sensitive paint at cryogenic temperatures in the European Transonic Wind tunnel (ETW)

Fey, Uwe; Engler, Rolf; Egami, Yasuhiro; Iijima, Yoshimi; Asai, Keisuke; Jansen, Uwe; Quest, Jürgen

doi:10.1109/iciasf.2003.1274855

Cited by 49 publications

(34 citation statements)

References 6 publications

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“…Heat generation in superconductors has been measured at temperatures down to 50 K [8][9][10]. Thermal imaging was also demonstrated in wind tunnel experiments at 110 K [11].…”

Section: Introductionmentioning

confidence: 98%

Temperature dependent photoluminescence down to 4.2K in EuTFC

Haugen¹,

Johansen²

2008

Journal of Luminescence

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“…Heat generation in superconductors has been measured at temperatures down to 50 K [8][9][10]. Thermal imaging was also demonstrated in wind tunnel experiments at 110 K [11].…”

Section: Introductionmentioning

confidence: 98%

Temperature dependent photoluminescence down to 4.2K in EuTFC

Haugen¹,

Johansen²

2008

Journal of Luminescence

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“…Transition detection by means of cryoTSP is done by acquiring a series of images of the luminophore's emission light (which is excited by the light at the shorter wavelength) and dividing the grey levels of images taken during the temperature change in the flow by grey levels of images taken at stationary conditions. Thus, the temperature difference in the boundary layer is highlighted and laminar and turbulent regions can be distinguished [1] [4] [5] [7].…”

Section: B Two Component Cryotspmentioning

confidence: 99%

Temperature-Sensitive Paint Application in Cryogenic Wind Tunnels: Transition Detection at High Reynolds Numbers and Influence of the Technique on Measured Aerodynamic Coefficients

Fey

Egami

Klein

2007

2007 22nd International Congress on Instrumentation in Aerospace Simulation Facilities

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The method of temperature-sensitive paint (TSP) adapted to industry-scale, cryogenic wind tunnels (i.e. cryoTSP) is used to detect the natural, laminar-to-turbulent transition of the boundary layer in high speed flows. Because of the small boundary layer thickness given in cryogenic testing at high Reynolds numbers, the influence of roughness of a TSP layer on the natural boundary-layer transition is analyzed for Tollmien-Schlichting and for crossflow instability. Using a special technique when spraying the paint, it is possible to operate pressure tappings on a model in parallel to transition detection by cryoTSP. Since the pressure orifices have to penetrate the paint layer, their shape and curvature are changed by the painting and polishing, which may lead to a deviation in the measured Cp distributions compared to the model without TSP. Furthermore, the thickness of the cryoTSP on the model can influence the pressure distribution and drag coefficient. The effect of the TSP paint layer on pressure tappings and drag measurement of a laminar type airfoil is experimentally investigated for Reynolds numbers of 6 Mio and 15 Mio and for Mach numbers of M = 0.30 and 0.62 in the Ludwieg-tube cryogenic wind tunnel DNW-KRG. I INTRODUCTIONTo highlight the laminar-turbulent transition on a model surface by use of thermographic methods, a sufficiently large temperature difference between laminar and turbulent part of the boundary layer has to be created. This can be done, besides other methods, by changing the temperature of the flow during testing: due to the larger convective heat transfer coefficient, the temperature change in the oncoming flow is transferred faster to the surface in the turbulent part of the boundary layer. For example, a (moderate) heating of the flow causes a warmer turbulent boundary layer for a certain amount of time. Cooling of the flow on the other hand leads to increased heat transport from the model surface to the flow in the turbulent region, making it cooler than the laminar part during application of the temperature change [1].This well known "method of temperature steps" [2] can easily be performed in a continuously driven cryogenic wind tunnel by increased injection of nitrogen (negative step, flow becomes cooler) or by stopping nitrogen injection completely (positive step, flow becomes warmer by heat input of the wind tunnel compressor). In a blow down type, cryogenic wind tunnel the negative step is established automatically during testing, since a high pressure storage volume of nitrogen is expanded quickly after opening the valve for the (short duration) test run. Thus, flow temperature drops immediately and the model is cooled by the flow during testing. Hence, a thermographic method is applicable for transition detection.A. Method ofcryogenic temperature-sensitive paint Since commercially available infrared (IR) cameras lose their sensitivity for temperatures T < 200 K, the technique of cryogenic temperature-sensitive paint (cryoTSP) has been established in recent years as a reliable...

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“…An alternative to these techniques for detecting transition at cryogenic temperatures is based on Temperature Sensitive Paint (TSP) [13,14,15]. TSP is typically composed of a gas impermeable binder in which a luminescent molecule is immobilized [16].…”

Section: Introductionmentioning

confidence: 99%

Boundary-Layer Detection at Cryogenic Conditions Using Temperature Sensitive Paint Coupled with a Carbon Nanotube Heating Layer

Goodman

Lipford

Watkins

2016

Sensors

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Detection of flow transition on aircraft surfaces and models can be vital to the development of future vehicles and computational methods for evaluating vehicle concepts. In testing at ambient conditions, IR thermography is ideal for this measurement. However, for higher Reynolds number testing, cryogenic facilities are often used, in which IR thermography is difficult to employ. In these facilities, temperature sensitive paint is an alternative with a temperature step introduced to enhance the natural temperature change from transition. Traditional methods for inducing the temperature step by changing the liquid nitrogen injection rate often change the tunnel conditions. Recent work has shown that adding a layer consisting of carbon nanotubes to the surface can be used to impart a temperature step on the model surface with little change in the operating conditions. Unfortunately, this system physically degraded at 130 K and lost heating capability. This paper describes a modification of this technique enabling operation down to at least 77 K, well below the temperature reached in cryogenic facilities. This is possible because the CNT layer is in a polyurethane binder. This was tested on a Natural Laminar Flow model in a cryogenic facility and transition detection was successfully visualized at conditions from 200 K to 110 K. Results were also compared with the traditional temperature step method.

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Transition detection by temperature sensitive paint at cryogenic temperatures in the European Transonic Wind tunnel (ETW)

Cited by 49 publications

References 6 publications

Temperature dependent photoluminescence down to 4.2K in EuTFC

Temperature dependent photoluminescence down to 4.2K in EuTFC

Temperature-Sensitive Paint Application in Cryogenic Wind Tunnels: Transition Detection at High Reynolds Numbers and Influence of the Technique on Measured Aerodynamic Coefficients

Boundary-Layer Detection at Cryogenic Conditions Using Temperature Sensitive Paint Coupled with a Carbon Nanotube Heating Layer

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