Hydrodynamic of the Vacuum Valve | Chapter 6 | Current Research Progress in Physical Science Vol. 2

 

The problem of weak discontinuity in operation of vacuum valve is considered from an experimental and theoretical point of view. A model of gas flow as a function of two variable gas mass n and time t is created. The model allows you to define a point on the time axis where the continuity of the gas mass flow function breaks and define the discontinuity parameters. A model of operation of the vacuum valve as a gas flow control device was built based on the experimental data. It is shown that an inlet area inside the valve through which gas flow passes has the property of a weak discontinuity, provided that the area is considered as a time function. It is shown how this property is transmitted to a gas discharge function. The described actions result in the statement that the gas discharge function has the properties of weak discontinuity over mass and time variables. The theoretical conclusions were verified on a simple vacuum set with air overflow between two vessels, provided that the gas flow is controlled by the valve. It found a single point on the time axis where the gas discharge function has two weak discontinuities over mass and time variables simultaneously. The phenomenon of weak discontinuity in gas flow was recorded for the first time under such experimental conditions.

 

Author(s) Details

V.K. Konyukhov

A. M. Prokhorov General Physics Institute, Russian Academy of Sciences, Vavilov Street 38, 119991 Moscow, Russia.

 

Please see the link:- https://doi.org/10.9734/bpi/crpps/v2/1162

Thermal Deformation and Strength of Materials for Heat-shielding Coatings of a Spacecraft on the Trajectory of Descent from Orbit| Chapter 8 | Techniques and Innovation in Engineering Research Vol. 2

 The basis for a fundamental understanding of the process of material interaction with a medium is the agreement between experimental research and the actual operating conditions of a specific model or structure. Thermal Shield Materials (TSMs) are designed based on certain requirements, such as the characteristics of heating and material destruction under the least amount of shield weight. The more useful space load it can give, the lighter it must be. Since the thermal shield serves as a missile's ballast weight, it is only natural to want to lower the weight of TSMs without sacrificing their capacity to reliably perform their thermal shield role. Utilizing calculations based on the physical characteristics of materials discovered during conditions replicating a spacecraft's re-entry into the atmosphere, the performance of thermal shield structures was examined. The dependence of the temperature T of a thermal shield side surface on the period of descent in dense air layers serves as the basis for physical modelling of the natural conditions of thermal shield use (temperature, heating/cooling rate, composition, and pressure of gas medium). A thermal barrier was made composed of a laminated fibreglass shell with a phenol-phormaldehyde matrix. Investigations were done on temperature-dependent mechanical and thermophysical characteristics. By using numerical analysis, elasticity theory, and thermal conductivity equations to solve a 3D problem, it is possible to characterise the thermally stressed state of a cylindrical shield that is being impacted by a high-temperature gas flow. According to the results, the maximum compression stresses in a fibreglass thermal shield shell are located close to the heated surface and are not higher than the material's strength limit at that temperature. A new, 30% lighter thermal protection system for the re-entry vehicle was proposed and put into practise as a result of the experimental and theoretical investigations that were conducted.

Author(s) Details:

Lyudmila I. Gracheva,
G. S. Pisarenko Institute for Problems of Strength, National Academy of Sciences of Ukraine, Kiev - 01014, Ukraine.

Please see the link here: https://stm.bookpi.org/TAIER-V2/article/view/8276