The hypersonic flow around bodies of different geometries, made of composite materials, was investigated and different methods of decreasing the maximum temperatures of their surface were estimated.

In development of earlier works on estimating the maximum temperatures of a shell immersed in a flow, a conjugate problem of nonstationary heat transfer in a supersonic flow around a spherically blunted hollow cylindrical model is considered for the conditions of some previous experimental studies [1–4]. The calculated and experimental data are compared, and the possible ways of reducing the maximum body temperatures are evaluated both by choosing the geometric characteristics of the model and of the thermophysical characteristics of materials, including the possible presence of a two-layered cylindrical holder. It is shown that the obtained dimensionless relations allow one to carry out quick estimation of the decrease in maximum temperatures.

The conjugate problem of nonstationary heat transfer in supersonic flow around a spherically blunted cone at a high Mach number (M∞ = 9.9) is considered. Under these conditions, the maximum temperatures of the streamlined shell can be as high as the material fracture temperature. Hence, it is essential to assess the potential methods of their reduction. The generalized criterion dependences derived from the numerical solution of the nonstationary conjugate problem make it possible to estimate the necessary decrease in the maximum temperature of the body surface via the selection of the proper geometry and thermophysical characteristics of the materials of the spherical and conical regions of the body.

The flow at different angles of attack past a spherically blunted cone, the spherical and conical parts of which are made of different materials is considered. It is shown theoretically that the manufacture of the side surface of such a body from a highly thermally conductive material provides heat removal from its spherical part, which experiences maximum thermal loads and, accordingly, a decrease in the maximum body temperatures in this area. Dimensionless expressions are obtained for estimating the decrease in the maximum temperatures of a conical body in the area of its spherical bluntness, when the body is immersed in a flow at different angles of attack, by choosing the geometry of the body and materials that have the necessary thermophysical characteristics to cover it.

The flow of a gas over a conic body, having a nose blunted over a sphere, with a supersonic velocity at different angles of attack was considered. The possibility of control of the temperature regime of such a body in the case of three-dimensional gas flow over it was investigated. The dependence of the temperature of the surface of the indicated body on the material of which it is made, the angle of attack of the body, and other constitutive parameters of the problem on conjugate nonstationary heat exchange between the body and the gas fl ow over it was determined for standard conditions of an aerodynamic experiment. Results of numerical solution of this problem for different angles of attack of the body were processed in the criteria form. The dependences obtained allow one to estimate the degree of decrease in the maximum temperature at the surface of a blunt-nosed conic body depending on the thermophysical parameters of the material of which this surface is made, including in the case of nonstationary gas fl ow over it. It is shown that a uniform heating of the peripheral part of such a body and a marked decrease in the temperature of its windward part at large angles of attack can be provided with the use of highly heat-conducting materials for these parts of the body.

In one of our earlier papers, we considered supersonic, laminar boundary-layer flows past bodies made of different materials and examined the possibility of controlling the temperature regime of a body immersed in flow. In the present work, for the conditions corresponding to aerodynamic experiments and to long flight times, we analyzed such values of deceleration parameters when regions of laminar, transitional, and turbulent regimes of flow are realized simultaneously in a boundary layer. The possibility of decreasing the level of maximal temperatures depending on the determining criteria of the problem has been evaluated for bodies made of different materials. The expediency of using simplified approaches is shown, including those for nonstationary conditions based on stationary solutions and on well-studied limiting cases of isothermal and adiabatic surface temperatures and allowing the determination of the temperature regimes in the entire range of thermophysical characteristics.

The problem of unsteady coupled heat and mass transfer in the course of motion of a spherically blunted conical body fabricated with the use of thermal protection materials is considered. Numerical integration is applied to study the characteristics of heat and mass transfer at constant stagnation parameters (Mach number 6, altitude 15 km, and flight time 600 s), which impose severe constraints on the choice of materials for thermal protection. It is demonstrated that the use of advanced ceramic materials ensures an admissible temperature regime and maintaining the initial geometry of the body, including its motion at an angle of attack.

The three-dimensional problem of conjugate heat and mass transfer upon the motion of a spherically blunted cone at various angles of attack along a set trajectory is theoretically explored. Thermal protection materials, including carbon materials with high heat-conducting properties, conventional carbon fiber-reinforced plastic coatings, and promising nondestructible ceramic materials, are analyzed. It is shown that the application of the latter makes it possible to preserve the initial geometry of the body and to attain a considerable temperature decrease in the coating surface upon the development of new materials with high thermal conductivity.

The problem of spatial flow around a hypersonic flying vehicle is considered for trajectories with different attack angles for flight through air with chemical equilibrium. The conjugate problem statement gives solutions for gas state in the boundary layer, thermal regime of streamlined body (made of different composites), and the rate of mass loss for heat protecting material. Physical processes in the condensed phase of carbon-containing coatings have complex nature: processes of heating, pyrolysis, heterogeneous oxidation, and sublimation. These processes result in protective material destruction. It was shown that using different materials for passive protection can be beneficial in reduction of the surface temperature, characteristics of thermochemical degradation, and this allows a control over heat and mass transfer for a flying body.

The new engineering technique for the experimental investigation of physical and mechanical characteristics of thermal protective intumescent coatings is offered. A mathematical model is proposed for predicting the thermal behavior of structures protected by coatings; the model is closed by the studied material characteristics. The heating of a metal plate under standard thermal loading conditions is modeled mathematically. The modeling results are in good agreement with bench test results for metal temperature under the coating. The proposed technique of studying physical and mechanical characteristics can be applied to identify and monitor the state of thermal protective intumescent coatings in the long-term operation.

A three-dimensional problem of conjugate heat-mass exchange (HME) under a high-enthalpy flow of a spherically blunted cone is analyzed theoretically with regard to the gas injection from the surface of a hemisphere, nonequilibrium chemical reactions in the boundary layer (BL), and thermochemical destruction in the screened zone. Controlled intense injection of a cooling gas during the flight of a body along a ballistic trajectory guarantees that the permeable blunting fabricated with the use of porous metals is not destroyed.

Aerodynamics and heat and mass exchange features of three-dimensional supersonic flows around sphere-cone are investigated, taking into account different complicating factors including homogeneous and heterogeneous reactions, various processes of material failure, rotation around a longitudinal axis.

Теоретически исследуется трехмерная задача сопряженного тепломассообмена при высокоэнтальпийном обтекании затупленного по сфере конуса с учетом вдува газа с поверхности полусферы, неравновесных химических реакций в пограничном слое и термохимического разрушения в завесной зоне. Управляемый интенсивный вдув охлаждающего газа при полете на баллистической траектории позволяет обеспечить неразрушение проницаемого затупления, для изготовления которого использованы пористые металлические материалы.

РоссияВ статье представлен подход метода граничных элементов (МГЭ) с явным учетом переменной времени по решению трехмерных динамических задач теории упругости для составных тел.Использована гранично-элементная техника построения дискретного аналога в

According to [1] equally with passive thermal heat protection systems (PTHPS) the active heat protection systems (ATHPS) take place. A combined usage’s characteristics of ATHPS and PTHPS for three dimensional hypersonic flows around spherically blunted cone at atmosphere entry by using into account conjugate heat and mass transfer were studied. This body consists of a spherical blunted porous part from Fe or Cu materials and conical part from graphite material. The hypersonic entry of blunting body with velocity less than first cosmic one are considered. For heights below 30 km within shock layer the model of chemically equilibrium air [2] consisting from 6 components are used. A chemically no equilibrium boundary layer equations system are known from [3]. It takes into account next system of no equilibrium homogeneous chemical reactions: Ar NO N N O O , , , , , 2 2

Some means of controlling thermal regimes in the case of a high-enthalpy flow past a blunt body at an angle of attack with a simultaneous influence of the gas blown-in from the permeable bluntness surface and overflowing of heat in the shell of the material are considered. The effectiveness of applying highly conducting materials in order to lower maximum temperatures in a zone of a screen is shown.

The paper deals with the solution of three-dimensional problem of heating and thermochemical destruction under conditions of hypersonic high-enthalpy flow of air past a spherically blunted cone made of materials of different thermophysical properties, with different flow rates of cooling gas injected through a porous blunting.

The initiation of free radicals and oxidizability of soap chips were studied by the methods of inhibited and initiated oxidation. A scheme accounting for the effect of phenolic inhibitors (with Ionol and 2-ethylhexyl gallate as examples) was suggested. The kinetic parameters of the main reactions determining the inhibiting activity of these additives were found.