Nondestructive Inspection Using Neutron for Regenerative Cooling Combustion Chamber

The regenerative cooling combustion chamber of a liquid rocket engine is exposed to large temperature difference between the combustion gas and the coolant such as liquid hydrogen. It induces thermal stress, and strain is accumulated over cyclic firing tests in the chamber wall. To evaluate the strain and the deformation of chamber walls is important since the chamber life usually relates to such strain and deformation. The primary objective of the present study is to establish a method to obtain experimental data on strains and deformations for correlation with the numerical data. In this study, residual strains and radiographs of a combustion chamber were obtained by applying a neutron diffraction method and a neutron radiography. Furthermore, two-dimensional nonlinear finite element method (FEM) analyses were conducted to calculate the residual strain in the chamber wall. From data of strain measurements, the feasibility of a neutron diffraction method for a combustion chamber was shown because the data from a X-ray diffraction method and FEM analyses qualitatively corresponded with those from a neutron diffraction method. Concerning neutron radiography, a higher resolution was necessary to observe chamber wall deformation.