Papers by Author: Alexei M. Essiptchouk

Abstract: The process of carbon dioxide reforming of hydrocarbon feedstock (like natural gas, coal, petroleum coke, residual oil, glycerine, etc) for hydrogen production has attracted great attention from both environmental and industrial perspectives. The plasma chemical reactor for study the CO₂ reforming of hydrocarbon gaseous feedstock is presented. The reactor consists of a DC plasma torch coupled to a compact quenching chamber. The linear plasma torch operates with a reverse vortex flow and hollow blind-end cathode for enhancing the thermal efficiency and enthalpy of the plasma jet. The quenching chamber consists of a set of refrigerated discs equipped with flow turbulent flow generator. Estimated quenching rates are up to 10⁷-10⁸ K/s. Electrical and thermal characteristics of the plasma-chemical reactor torch as well as the energy efficiency of the process are presented.

Abstract: Comparisons of heating tests at atmospheric pressure and low pressure by using a thermal plasma torch were performed. A constant heat flux on the sample surface was applied in the study of the oxidation mechanism of C/C-SiC composite, used in thermal protection systems. The SEM and EDS analysis show an intensive glassification at the surface, which are strongly depend on the oxygen partial pressure and the sample surface temperature. For vacuum conditions, at maximum surface temperature of 1450 °C and the oxygen partial pressure of about 66 Pa, a uniform passivation layer of SiO₂ is formed. At atmospheric pressure, under an oxygen partial pressure of 2.1×10⁴ Pa, the maximum surface temperature is 400 °C higher than obtained in vacuum, reaching levels of 1850°C. Under these conditions, the protective oxide layer is partially volatilized with time, increasing the specific mass loss rate by a sublimation of the composite, directly exposed to the plasma jet. This effect is alike to what occurs in the process of transition from passive to active oxidation of SiC.

Abstract: A formula for quick calculation of thermal characteristics of materials used for thermal protection is proposed. The mode of heating of the sample external surface (subjected to thermal exposure) is approximated by two regions, which differ by corresponding boundary conditions on the heating surface: T_f=cτ (linear growing with time) and T_f=const (with permanent temperature of destruction). That approximation permits to obtain an analytical solution in integral form. In order to simplify and accelerate data treatment, a simple empirical formula is proposed. A contribution of each thermal region is proportional to the regime duration. A good agreement with an analytical solution is shown.