Catalytic Effects on Heat Transfer Measurements for Aerothermal Studies with CO2

Abstract

An investigation has been performed at CUBRC using the LENS facilities to study the behavior of surface heating augmentation due to catalytic surface recombination for carbon dioxide and air test gases. Three types of heat transfer instrumentation have been employed on a model that shows definitive heating enhancement which can only be caused by the effect of surface catalysis. The measured heat transfer data from all types of instrumentation correlate well with CFD predictions in baseline non-catalytic flows, but show consistently higher heating levels than can be predicted with a non-catalytic wall in a catalytic environment. A similar effect has been documented in air with atomic oxygen and nitric oxide recombination. The successful demonstration and understanding of this behavior is critical to optimum heat shield/TPS systems design for future Martian entry applications.

Numerical Assessment of Data in Catalytic and Transitional Flows for Martian Entry

“…Here, the comparison is more interesting. As we have shown in previous results for both CO 2 and air 1,31 , the surface heat transfer measurements compare very well with fully catalytic recombination at the wall for this enthalpy level. This trend is observed for this run also.…”

Comparative Surface Heat Transfer Measurements in Hypervelocity Flow

“…Tests were run at test gas enthalpies of 2, 6, and 8 MJ=kg. This study found good agreement between the gages, but found that all gage types measured heating levels higher than predicted assuming a noncatalytic wall, but less than that predicted assuming a fully-catalytic wall [3]. A recent study at the CUBRC facility found good agreement between both gages at enthalpies 5 and 10 MJ=kg [23].…”

“…Two types of sensors that can be used to measure surface heat flux are coaxial thermocouple gages and thin film resistance thermometers. Individually, both types of gages have been used successfully in a number of studies [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19]. Both thermocouple and thin film gages measure surface temperature from which heat transfer can be calculated.…”

Analysis and Ground Test of Aerothermal Effects on Spherical Capsule Geometries

“…The results have been shown to correlate well between the two techniques for all kinds of shapes and flows. The response of the different gage types in the presence of catalytic heating is a subject of active debate, but evidence has so far indicated that the response of each device is about the same despite the fact that different surface materials are exposed to the gas/surface interface 31 . In general, the trade-off between the two technologies is that the thin-film gages are significantly more sensitive and exhibit less noise in the signal while the thermocouple gages are significantly more robust in harsh environments.…”