Structural development of ultra-lean-burn preburners for small liquid engines

An ultra-lean-burn preburner has been developed by KARI. This paper describes the general structural design, the results of the finite element analyses (FEA) and the experimental results related to structural issues during the development. Before the fabrication, two burst experiments with the specimens simulating the brazing joints were performed and compared with the FEA results, which increases the reliability of the analyses and the design. Also, 2D FEA of the combustion chamber cooling channel were performed for the first combustion region upstream of the liquid oxygen (LOX) hole and the second region downstream of the hole, where the hottest spot locates downstream of the region between the adjacent LOX holes. Various structural modifications were analyzed by 3D FEA and a screen structure was introduced to reduce the stress over highly stressed regions. During the development, some proof and leakage tests were performed for the head, the chamber with and without flange, and the preburner assembly, of which the burst test was performed. Several firing tests of the assembly were performed to show the operation without any structural failure.