Thermodynamic consistent modeling of flame–solid interaction and thermo-mechanical response of high-temperature materials

A fully coupled flame–solid interaction problem is investigated using a laminar strained premixed ammonia/hydrogen/air flame stabilized at a plane wall. Heat transfer from the flame to the wall is explicitly considered, and the resulting transient temperature evolution within the solid leads to combustion-induced deformation and stress development. Inconel 718 is selected as a representative wall material, and its temperature-dependent thermo-physical properties are described using thermodynamically consistent formulations derived from the Helmholtz energy. It can be shown, that a linear temperature dependency for the bulk and shear modulus, as well as for the thermal expansion coefficient directly implies a strain dependency of the heat capacity at constant strain. This contribution to the heat capacity turns out to be negligible for the here investigated Inconel 718. Both steady-state and transient configurations are examined. In the steady-state configuration, the influence of thermal radiation on the temperature distribution inside the plane wall is assessed. In the transient configuration, a cold plane wall is suddenly introduced into the flame system and subsequently heated, and the entire heating process is investigated under varying imposed flame strain rates. The results show that increasing flame strain rate accelerates wall heating and shortens the time required for thermo-mechanical stress to reach the material yield strength, despite reduced flame temperatures. The quasi-static assumption for the balance equation of linear momentum is validated, while the Gough–Joule effect is shown to be negligible for the conditions considered. These findings provide fundamental insight into transient flame-induced heating and thermo-mechanical response of solid structures.