A Method for Evaluation of Thermal Characteristics of Complex Heat-Shield Assembles at Extremely High Energy Fluxes
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A Method for Evaluation of Thermal Characteristics of Complex Heat-shield Assembles at Extremely High Energy Fluxes V. P. Petrovskya, E. P. Pakhomova, M. A. Sheindlina, *, T. M. Falyakhova, A. A. Vasina, and P. S. Vervikishkoa a
Joint Institute for High Temperatures, Russian Academy of Sciences, Moscow, 125412 Russia *e-mail: [email protected] Received September 13, 2019; revised September 13, 2019; accepted December 24, 2019
Abstract—A suitable laboratory test procedure is developed where a small fragment of the relatively thick multilayer heat shield is exposed to the extreme heat flux of up to several kW/cm2 in order to evaluate its performance. A nearly one-dimensional test condition has been achieved, where thermal behavior of a small fragment of a large shield became representative for the large heat-shield panel. A cylindrical test sample made of carbon-carbon composite has been surrounded by high-temperature thermal isolation made of zirconia concrete. The high heat flux has been provided by a power CW-laser. The conditions of one-dimensional axial heat flux through the cylindrical fragment of the heat shield are confirmed by the mathematical modeling of the experiment using experimentally measured temperature excursions along the sample axis. DOI: 10.1134/S0018151X20030153
INTRODUCTION
faces of the various high-temperature heat shield materials are utilizing panels with high power xenon arc lamps or tungsten halogen lamps [1]. In spite of extremely high power required for the operation of these kinds of facilities they are unable to deliver heat fluxes of several kW/cm2. Also, due to the continuum spectrum of the arc lamps any optical and temperature measurements using pyrometric methods are not acceptable. The other drawback of the lamp testing facilities is a difficulty of achieving the flat temperature distribution over the front face of the test sample [2]. Therefore, the very aim of the present study is to develop a suitable experimental procedure, where a small fragment of the relatively thick heat shield panel is exposed to the extreme heat flux during several tens of seconds while keeping almost one-dimensional conditions.
One of the possible ways to constructing advanced thermal protection shields, subjected to extreme heat fluxes, is most often based on the use of various kinds of the carbon-carbon (СС) composite materials. These composites can be assembled as multilayer packages to gain the advantage of various orientations of carbon fibers for better heat protection. The thickness of this kind of the heat shield can be up to several centimeters, whereas temperatures at the front face can reach a few thousand kelvins. The effectiveness of the thermal protection could provide keeping the rear face almost at room temperature. One can easily see that correct experimental evaluation of the capabilities of this kind of the thermal protection turns out to be a difficult deal, when the heat fluxes at the front face could rise up to several kW/(cm2). Here, the main problem is that at given thickne
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