Mathematical modeling of complex technical objects with nonlinear properties illustrated by the investigation of porous media reactor reliability

The paper considers the approach to solving coupled thermomechanical problems for investigation of stresses, strains and crack resistance of high-temperature porous media combustion reactors and others energy setups. A coupled physical-mathematical model for definition of strains, stresses and temperatures in porous media reactors is formulated. In this paper, the three-dimensional simulation of technological process and reliability of a methane conversion reactor in filtrating mode is carried out. Thermal contours of the reaction region and structural elements of the reactor unit are obtained for different thicknesses of combustion zone lining. Structural elements of the reactor have a complex strain-stress state under normal operation conditions. Stress concentrators are detected near geometrical and thermal gradients. Results of numerical solution of coupled thermomechanical problems and calculation of structural elements strength where thermal contours were determined on the basis of analytical thermal calculations were analyzed. The comparison of the calculated strain-stress states shows that the maximum equivalent stress may differ to 30 % for considered methods. In the numerical solution of coupled problems, predicted stresses are distributed according to local changes of the heat transfer coefficient due to the effects of turbulence and non-uniformity of the hot gas velocity field.
The considered approach to solving coupled thermomechanical problems can be used for analyzing strain-stress states and crack resistance of energy setups. The influence of the parameters of high-temperature gas flow and modes of device operation on the stress level can be taken into account.