One of the features of high-velocity atmospheric aircraft is the presence of thin aerofoils with edges characterised by a small blunt radius, subjected to high-temperature aerodynamic heating at temperatures of up to 2000 -- 2500 °C. In order to ensure correct operation of both the power plant producing thrust in such vehicles, assumed to be a supersonic combustion ramjet, and respective aerodynamic controls, the components subjected to high-velocity air flows must retain their geometric stability. A way to ensure their performance is to use methods and means of thermal protection, as well as materials that are resistant to high temperatures in an oxidising atmosphere, while one of the promising trends is employing refractory oxide materials such as oxides of aluminium, zirconium and hafnium. Since this class of materials has low thermal conductivity, large temperature gradients develop in the vicinity of the surface being heated, resulting in temperature stresses, all of which designers should take into account. We analysed the temperature state in a model of an acute zirconium oxide wedge featuring a small blunt radius, subjected to a high-velocity air flow. To reduce the edge temperature and temperature gradients, we propose a design solution implemented as a thermally conductive core lined with a thin layer of zirconium oxide. We consider using aluminium oxide and hafnium boride as core materials
Developing high-velocity atmospheric aircraft equipped with ramjet engines, which use atmospheric air as the oxidizer, is an important component of aerospace technology prospects. These craft may be employed to quickly deliver payloads over intercontinental distances and as boosters for spacecraft injection into orbit. A characteristic feature of high-velocity atmospheric aircraft is a presence of sharp aerofoil edges subjected to highly oxidative airflow. This means that actual implementation of numerous hypersonic atmospheric aircraft projects largely depends on whether it is possible to develop materials that could remain stable in an oxidative atmosphere at temperatures of 2000--2500 °C. We estimated the thermal state of a structural component in the shape of a blunted wedge made out of promising refractory ceramics under flight conditions at an altitude of 22 km and a velocity of Mach 7
One of the most important problems in the development of advanced products of aerospace engineering and highly efficient power plants is to make high-temperature structural, heat-shielding and heat-insulating materials with extremely high operating temperatures of 2000--2500 °C. Even for prototype models, it is necessary to make a qualitative breakthrough in the field of materials science and the production of new high-temperature composite and heat-insulating materials which provide thermal protection and the permissible temperature conditions of structural elements at high temperatures. The practical application of the developed materials requires an evaluation of the whole body of their physicomechanical, optical, and thermophysical characteristics, which can only be done in experimental studies. We developed the design of the experimental setup and the methodology for the approximate evaluation of the thermophysical characteristics of highly porous heat-insulating materials at temperatures up to 2000 °C. A propane / oxygen or acetylene / oxygen multi-nozzle torch serves as a heating source for samples with a characteristic size of up to 50 × 50 mm. The paper substantiates the methodology for processing the measurement results in order to determine the thermophysical characteristics, and gives the results of a study of the thermal conductivity of highly porous zirconium oxide-based material
Material selection for aerospace structural and power plant units subjected to thermal stresses is based on thorough investigation of their physical, mechanical and optical properties in a wide range of temperatures up to 2500--3000 K, which are in practice the highest possible. However, it is exceptionally difficult and expensive to obtain the whole extent of data on the properties of structural and refractive materials currently in development that is required to analytically estimate the thermal state and performance of the structures designed to be subjected to thermal stresses. Moreover, the theoretical thermal state models in use are most often based on a number of assumptions, which means that they will need to be validated against experimental investigation data. As a result, integral methods of estimating material performance under intended real-world thermal and force loads become highly important. Ground-based development testing using simulation installations will solve this problem. While testing, it is important to ensure that the simulated thermal modes of the object being tested match its real-world thermal modes. The paper considers these issues regarding estimating refractory ceramics performance subjected to a high-temperature gas flow
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