The impact of catalytic active surface on intensity of convective heat transfer

Аuthors

Nikitin P. V.^*, Shkuratenko A. A.^**

Moscow Aviation Institute (National Research University), 4, Volokolamskoe shosse, Moscow, А-80, GSP-3, 125993, Russia

*e-mail: petrunecha@gmail.com
**e-mail: Shkuratenko.anna@mail.ru

Abstract

This work presents the carried out analysis of catalytic active surface impact on heat transfer intensity while the body of axisymmetric shape is flown around by dissociated airflow. One has to tackle problems of such kind in the course of aircraft duration flight with supersonic speed in the atmosphere. The main feature of heat transfer on the surface of flying vehicles of such type consists in heat- and mass exchange between the surface of the lying vehicle and chemically active layer along the whole flight trajectory. The heat transfer intensity in this boundary layer depends entirely either on gas state parameters or chemical state of high-temperature air components mixture. Overall, these two features, in the end, determine the boundary layer type: equilibrium, non-equilibrium, «frozen». The above said is an important issue, since the boundary layer type determines the selection of the certain class of heat-protective material.

The studies of heat transfer in non-equilibrium flow of dissociated gas [1] conducted by various authors revealed that with flying vehicle flight at the altitudes above 40 km, high-temperature air parameters are such, that the molecules passing through the shock wave and compressed layer dissociate into atoms. The atomic gas in its turn enters the boundary layer zone, diffuses to the flying vehicle surface and recombines on it. As a result of this physico-chemical processes complex, heat currents into GLA structure drastically increase. The heat exchange intensity in this case strongly depends on catalytic activity of thermal protection materials.

American researcher R. Gulard analyzed for the first time the problem of catalytic activity of materials on heat transfer in dissociated currents. However, while deriving the equation for heat current density R. Gulard was incorrect while setting up the problem. This work modifies thereupon Gulard’s equation, and obtains new equation. The authors compared the calculated and experimental data on heat currents densities into catalytic active surface. The calculations were made both using Gulard’s equation and the newly obtained equation. The paper shows the mismatch of the calculation data obtained according to Gulard’s equation, experimental data and the results obtained using the newly obtained equation.

Keywords:

reactive boundary layer, surface catalytic activity, heat and mass transfer, thermal protection, hypersonic aircraft, mathematical model, processes of thermo-gas dynamics and heat-mass transfer

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