Design and Lifetime Calculation of MHD Generator Walls Based on Subcritical CrackGrowth in Ceramics

摘要

The design and investigation of the material properties of a wall segment for aclosed cycle Magnetohydrodynamic (MHD) generator are described. Because of the maximum size of the available ceramics, the wall of a large generator has to be segmented. Considering the electrical processes in the generator, ceramics should be used as inner materials. Considering the heat flux through the wall a thermal insulating material should be applied. All these considerations are combined in the design. It was found that the bolt in the designed wall segment was loaded with both bending and tensile stresses. Two kinds of diagnostics to measure the load on the bolt are presented. The diagnostics are a laser interferometer in combination with a dynamical model of the construction and a strain gauge measuring system. Models which describe certain aspects of the wall segment are described. These are concerned with: thermal and dynamical modeling of the wall segment; modeling of crack growth; and probabilistic lifetime calculation. An experimental test rig was built to perform the lifetime tests and it proved to be a reliable device to load the wall segment with both thermal and mechanical loads.