Characterization of nozzle erosion phenomena in a solid-propellant rocket motor simulator

Understanding of the nozzle throat erosion processes and developing methods for mitigation of erosion rate can allow higher operating pressures for advanced rocket motors. To evaluate the individual effects of oxidizing species on the thermochemical erosion rate of rocket nozzles, a solid-propellant rocket motor simulator (RMS) was designed and tested. The RMS is equipped with a windowed nozzle section for real-time X-ray radiography diagnostics of the instantaneous throat variations for deducing the instantaneous erosion rates. To study the effectiveness of a nozzle boundary-layer control system (NBLCS), the RMS incorporates the feature of utilizing this control system. Several reactant mixtures were utilized in the study to determine the relative importance of different oxidizing species (such as H₂O, OH, and CO₂). RMS tests of G-90 graphite erosion process were performed under different operating pressures, reactant flow rates, and oxidizing species concentrations. A useful erosion rate correlation written in non-dimensional parameters was developed in terms of the pressure, Reynolds number at the throat, and the mole fraction of an effective oxidizer, which is a linear combination of X _{OH, th} and X_{H2O, th}. Agreement between correlated and measured erosion rates are within ± 15% or an absolute error 0.06 mm/s. Test results show that when the NBLCS was utilized, it can effectively mitigate nozzle erosion rates to zero.