Modelling thermal barrier coatings and their influence on the lifetime of rocket engine nozzle structures

Abstract

The walls of rocket engine nozzle structures undergo extreme thermomechanical loadings during the engine cycle. These loads cause an accumulation of plastic strains due to creep and relaxation which finally lead to the failure of the hot gas wall. One approach to increase the lifetime of the hot gas wall is the reduction of the temperatures in the hot gas wall since the temperature is the main driver of this failure phenomenon. Special thermal barrier coating (TBC) systems are under development in order to protect the copper alloy of the hot gas wall from high temperatures. The present paper studies the influence of such thermal barrier coatings regarding the damage behaviour of the hot gas wall made of a copper alloy. In the first step, thermal analyses are performed to define an appropriate TBC thickness and the needed coolant power such that the maximum service temperature of the TBC is not exceeded. Furthermore the temperature distributions of the hot gas wall with and without TBC are compared, which show a reduction in temperature of approximately 200 K. In the second step static analyses with a recently developed viscoplastic damage model are presented. Here damage distributions as well as the deformation behaviour of the hot gas wall with and without TBC are compared. It is shown that the application of TBCs has an positive effect on the damage behaviour as well as the deformation of the hot gas wall.