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Sensors 2016, 16(12), 2062; doi:10.3390/s16122062

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

1
Analytical Mechanics Associates, Inc., 18 Langley Blvd., MS 493, Hampton, VA 23669, USA
2
NASA Langley Research Center, 18 Langley Blvd., MS 493, Hampton, VA 23669, USA
*
Author to whom correspondence should be addressed.
Academic Editor: Vittorio M. N. Passaro
Received: 28 October 2016 / Revised: 21 November 2016 / Accepted: 29 November 2016 / Published: 3 December 2016
(This article belongs to the Section Physical Sensors)
View Full-Text   |   Download PDF [6307 KB, uploaded 12 April 2017]   |  

Abstract

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. View Full-Text
Keywords: temperature sensitive paint (TSP); carbon nanotubes (CNT); transition detection; cryogenic testing; natural laminar flow temperature sensitive paint (TSP); carbon nanotubes (CNT); transition detection; cryogenic testing; natural laminar flow
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This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. (CC BY 4.0).

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MDPI and ACS Style

Goodman, K.Z.; Lipford, W.E.; Watkins, A.N. Boundary-Layer Detection at Cryogenic Conditions Using Temperature Sensitive Paint Coupled with a Carbon Nanotube Heating Layer. Sensors 2016, 16, 2062.

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