Авіаційно-космічна техніка та технологія (Aug 2021)
Thermal characteristics of the heat protection package of the engine body at programmed heating
Abstract
An experimental determination of the temperature dependences of the thermophysical characteristics of the MFP-92 multifunctional coating in the operating temperature range under thermal loading, simulating standard flight conditions, has been carried out. Heating was carried out with a jet of an industrial oxygen-propane burner mounted on a tripod with the possibility of varying the distance to the surface of the sample. The programs of the material operating modes include two peaks of heating to a temperature of ~1400 ° C with a heating and cooling rate of 20 - 40 deg / s. Under such conditions, thermal degradation of the MFP-92 material occurs, which changes its phase composition, structure, and, accordingly, thermophysical characteristics (TPС). The main transformations in the MFP-92 material occur in the temperature range up to 1000 °C, therefore, the heat transfer in it for given heating programs can be described using a simplified TРС model. This model assumes the existence of material in two states - initial (phase A) and annealed with completely completed transformation processes (phase B), each of which is assigned its own set of TPC. To determine the TPC of the MFP-92 material in its samples during thermal testing, temperature fields were recorded, which were then processed using the method of solving the inverse (coefficient) problem of thermal conductivity on a computer model. As a result, the temperature dependences of the specific heat and the coefficient of thermal conductivity of phases A and B were obtained, as well as the value of the most powerful thermal effect of the phase transition at 110 °C in phase A. The remaining phase transitions were taken into account by the corresponding changes in the specific heat. During material testing, the emissive of the material is also determined. Verification of the two-phase model of the MFP-92 material and the obtained values of its TPC was carried out based on the temperature fields obtained during the thermal tests of the samples of the three-layer thermal protection package "MFP-92 material-thermal insulation-steel substrate" under heating conditions according to the operating mode program confirmed their adequacy.
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