Application of Carbon Nanotubes and Temperature Sensitive Paint for the Detection of Boundary Layer Transition under Cryogenic Conditions (Invited)

Klein, Christian; Henne, Ulrich; Yorita, Daisuke; Beifuß, Uwe; Ondrus, Vladimir; Hensch, Ann-Katrin; Longo, Roberto C.; Hauser, Michael; Guntermann, Peter; Quest, Jürgen

doi:10.2514/6.2017-0336

Cited by 18 publications

(22 citation statements)

References 2 publications

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“…Examples include measurements for transition detection from the areas of aeronautics [38], railroad vehicles [39], wind energy [40] and aerospace [41]. However, application is not limited to aerodynamics but also includes hydrodynamics [42].…”

Section: Intensity Methodsmentioning

confidence: 99%

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

Ondrus

Meier

Klein

et al. 2015

Sensors and Actuators A: Physical

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Section: Intensity Methodsmentioning

confidence: 99%

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

Ondrus

Meier

Klein

et al. 2015

Sensors and Actuators A: Physical

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“…The cylindrical carbon structures have properties such as a very high electrical conductivity (>1,000 times greater than copper) that can be used for example as electrical resistance heater even in very thin layers. Previously, [4,5] we have embedded multiwalled CNT into an aqueous dispersion of an acrylate-based binder. Since polyacrylates can easily crack at cryogenic temperatures the corresponding CNT layer could not be operated safely below 150 K. It was observed that the complete coating cracked and finally peeled off the model surface [5].…”

Section: Carbon Nanotubes For Electrical Heatingmentioning

confidence: 99%

“…Since polyacrylates can easily crack at cryogenic temperatures the corresponding CNT layer could not be operated safely below 150 K. It was observed that the complete coating cracked and finally peeled off the model surface [5]. To overcome this difficulty we embedded CNT into the same PU binder material, which is known to be well suited for cryogenic temperatures [6]. For the combination of single-walled CNT (OCSiAL, TUBALL 201), which can be embedded easily into the PU polymer with high-speed mixing or/and by using a three-roll milling system (EXAKT, 80E PLUS), the resulting resistance values of the PU-based CNT layer reached values in kilo Ohm.…”

Section: Carbon Nanotubes For Electrical Heatingmentioning

confidence: 99%

“…CNT has several desirable properties: for example a very high electric conductivity and its ease of applicability as a coating with a thickness of some micrometers. This enables an effective combination of CNT with TSP to become a cntTSP for transition detection measurements in a wind tunnel environment [4,5,6,7]. One big advantage of cntTSP is that the boundary-layer transition can be detected without changing the flow parameters.…”

Section: Introductionmentioning

confidence: 99%

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Boundary layer transition detection on wind tunnel models in PETW during continuous pitch traverse

Klein

Yorita²,

Henne³

et al. 2019

AIAA Scitech 2019 Forum

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For aerodynamic profile tests on aircraft models, boundary-layer transition detection is of great interest. Under ambient flow conditions the infrared technique (IR) is a wellestablished image-based method for this purpose. In high Reynolds number tests that are conducted at cryogenic temperatures the IR technique is of only limited suitability. In contrast, the image-based Temperature-Sensitive Paint (TSP) technique is well suited for these conditions. Boundary layer transition detection by means of TSP generally requires an artificial temperature difference between model surface and flow. For wind tunnels operated under cryogenic conditions changing the liquid nitrogen injection rate of the working fluid causing a rapid change of the flow temperature can generate this temperature difference ("temperature-step method"). The drawback of this temperature-step method is that during the change of the flow temperature neither the Reynolds nor the Mach number can be kept constant. To overcome this problem, we have recently published an alternative approach where Carbon Nanotubes (CNT) are used to electrically heat the model surface and thus generate a well-defined temperature difference to visualize laminar-turbulent transition. The combination of CNT and TSP, which we call cntTSP, delivered excellent results in different wind tunnel tests from ambient temperatures down to 100 K. The cntTSP sensor visualizes the surface boundary-layer conditions as temperature distribution based on different heat transfer coefficients in the laminar and turbulent flow. Compared to the temperature-step method the cntTSP approach has the advantage and potential to measure boundary-layer transition in a time-resolved manner, e.g. on wind tunnel models when the wind tunnel is operated in continuous pitch traverse mode, which is desired in order to improve the data productivity of the wind tunnel tests. In this paper, the applicability of cntTSP to a continuous moving model (pitch-traverse or pitch-sweep test) is investigated in the pilot facility of the European Transonic Windtunnel (PETW). The laminar to turbulent boundary-layer transition appearing on a 2D model is visualized and compared between the pitch-traverse and pitch-pause tests.

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“…Recently, however, work has been presented combining TSP with a carbon nanotube (CNT) based heating layer [19,20]. The CNT heating layer acts as a resistive heater that can locally increase the temperature on the model surface when current is flowed through it.…”

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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Application of Carbon Nanotubes and Temperature Sensitive Paint for the Detection of Boundary Layer Transition under Cryogenic Conditions (Invited)

Cited by 18 publications

References 2 publications

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

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

Boundary layer transition detection on wind tunnel models in PETW during continuous pitch traverse

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

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