Carbon Deposition from Methane/Propane Mixtures in Surrogate Rocket Engine Cooling Channels

摘要

An experimental study was conducted at The Aerospace Corporation to investigate the dependence of carbon deposition on propane concentration for supercritical methane/propane mixtures flowed through an asymmetrically heated stainless-steel tubular test section at about 22.7 MPa. One side of the test section was in contact with a copper block heated to roughly 1010 K; the other side rested on a passive ceramic support. After each test run, the test section was cut into segments, split open, and analyzed with SEM/EDS to examine for carbon deposits. Various levels of carbon deposition were seen, even for cases with no propane (i.e., pure methane). Several forms of carbon deposition were observed, examples of which are presented herein. The extent of the surface that was covered with carbon and the form of the carbon deposits did not correlate significantly with propane concentration over the range tested. The roughness of the interior surfaces of the test sections varied from tube to tube; although this appeared to have a minor effect on the extent of carbon coverage, it was not examined in a controlled manner for this study. Under conditions favorable to deposit formation, the amount of carbon deposition was significant. If representative of rocket engine cooling channel conditions, then these are important implications for systems intended for long/repeated duty cycles or multi-mission reuse.