Effects of coolant passage layout on low cycle fatigue life of milled channel nozzle

To investigate the effects of different coolant passage layouts on the thermal-structural response and low cycle fatigue life of 3D regeneratively cooled channel wall nozzle with high area ratio under cyclic working loads, the finite volume fluid-thermal coupling calculation method, nonlinear finite element thermal-structural coupling analysis method and local strain method were adopted to analyze the coolant backward flow layout, coolant forward flow layout and coolant forward to backward flow layout. Numerical simulation results show that the most serious strain on milled liner of channel wall nozzle mainly occurs at the intersectant regions of liner gas side wall and symmetric planes of rib and channel in the front of nozzle extension, where the minimum node low cycle fatigue life takes place. The node strain history of milled channel nozzle is primarily dominated by the plastic deformation, and the thermal-structural responses between liner nodes, respectively, locating on the symmetric planes of rib and channel exist significant difference. The largest strain amplitude and residual strain during cyclic operation of milled channel nozzle employing coolant backward flow layout result in the shortest fatigue service life. On the contrary, the milled channel nozzle employing coolant forward flow layout with the smallest strain amplitude and residual strain has the longest low cycle fatigue life. Both the thermal-structural response and fatigue life of milled channel nozzle employing coolant forward to backward flow layout fall in between above two nozzles, but it has eliminated the easily damaged aft manifold and coolant feed line.