Synthetic Laser Diagnostics of Simulated RDRE Exhaust

In recent years, laser diagnostics for rotating detonation rocket engines (RDRE) have improved to the level at which they can be used in experimental design. However, the extreme newness of RDREs and their associated diagnostics incen- tivizes a close look at the data being produced, and numerical work provides a way to contextualize measurements in regard to the full reactive flow field. The present work compares the results of MHz-resolution laser measurements taken at the Air Force Research Lab of CO amount, temperature, and pressure in the exhaust produced by a 3 inch RDRE with high fidelity large eddy simulations done of the same gaseous methane/oxygen engine. It is found that exhaust plume of co-rotating RDRE has a characteristic “double peak” signal structure in CO molar fraction, where the dip corresponds to the RDRE shear layer. The simulations also indicate that a backward step at the exhaust of an RDRE has the potential to create a circulation zone that contains engine product – an important thing to consider when designing exhaust diagnostic setups.