An Ultra-Fast TSP on a CNT Heating Layer for Unsteady Temperature and Heat Flux Measurements in Subsonic Flows

Abstract

In this paper, the authors demonstrate the application of a modified Ru(phen)-based temperature-sensitive paint which was originally developed for the evaluation of unsteady aero-thermodynamic phenomena in high Mach number but short duration experiments. In the present work, the modified TSP with a temperature sensitivity of up to −5.6%/K was applied in a low Mach number long-duration test case in a low-pressure environment. For the demonstration of the paint’s performance, a flat plate with a mounted cylinder was set up in the High-Speed Cascade Wind Tunnel (HGK). The test case was designed to generate vortex shedding frequencies up to 4300 Hz which were sampled using a high-speed camera at 40 kHz frame rate to resolve unsteady surface temperature fields for potential heat-transfer estimations. The experiments were carried out at reduced ambient pressure of p∞ = 13.8 kPa for three inflow Mach numbers being Ma∞=[0.3;0.5;0.7]. In order to enable the resolution of very low temperature fluctuations down to the noise floor of 10−5 K with high spatial and temporal resolution, the flat plate model was equipped with a sprayable carbon nanotube (CNT) heating layer. This constellation, together with the thermal sensors incorporated in the model, allowed for the calculation of a quasi-heat-transfer coefficient from the surface temperature fields. Besides the results of the experiments, the paper highlights the properties of the modified TSP as well as the methodology.

The Art of Fluorescence Imaging with Chemical Sensors: The Next Decade 2012–2022

“…Ozawa et al developed a fast-response TSP for studying unsteady aerothermodynamic phenomena on a shock-tube wall, based on (Ru(phen) 3 , which has a short luminescence lifetime of less than 1 µs [219][220][221]. Bitter et al demonstrated the application of a modified Ru(phen)-based ultra-fast TSP on a CNT heating layer for unsteady temperature and heat flux measurements in subsonic flows [222]. Ruthenium terpyridine chloride (Ru(trpy)Cl 2 ) is used very often for measurements under cryogenic conditions [223].…”

Evaluation of the frequency characteristics of cntTSP measurement for unsteady low-speed flow

“…cntTSP was proposed by Klein et al and was initially used to measure the boundary layer transitions in a transonic flow in a cryogenic wind tunnel test [10][11][12]. In a recent study, Bitter et al applied the cntTSP technique to measure the wake of a cylinder on a flat plate in transonic flow [13]. This study successfully captured the temperature change caused by Kármán vortex shedding at approximately 4300 Hz.…”

Temperature Dependency Model in Pressure Measurement for the Motion-Capturing Pressure-Sensitive Paint Method

“…However, such sensors acquire pressure information at a single point, which is insufficient for comprehensive study of a flow field. Pressure-sensitive paint (PSP) has received significant attention as a nonintrusive method for surface pressure measurements [ 1 , 2 , 3 , 4 , 5 , 6 , 7 , 8 , 9 , 10 , 11 , 12 , 13 , 14 ]. The luminescent intensity of PSP is sensitive to the partial pressure of oxygen in a test gas due to a photophysical process called oxygen quenching [ 15 ].…”