A comprehensive analysis is performed to study the mitigation of graphite nozzle erosion in solid rocket motors loaded with nonmetallized ammonium perchlorate/hydroxyl-terminated polybutadiene composite propellants. The work extends our earlier model for predicting the chemical erosion of nozzle materials to include a nozzle boundarylayer control system. The strategy involves injection of relatively low-temperature species, obtained from reactions of an ablative material (succinic acid/polyvinyl acetate) and a small amount of propellant combustion gases, to a location slightly upstream of the nozzle throat. The formulation takes into account the detailed thermofluid dynamics of a multicomponent reacting flow, heterogeneous reactions at the nozzle surface, and condensed-phase energy transport. The effect of nozzle boundary-layer control system injection on the near-surface physiochemistry is investigated. Various fundamental mechanisms dictating the effectiveness of the nozzle boundary-layer control system are identified and quantified. The calculated erosion rates with the nozzle boundary-layer control system are negligible for the vertical injection, even at ultrahigh pressures. The mitigation of nozzle erosion is attributed primarily to the low temperature of the injected fluid, and secondarily to the reduced concentrations of oxidizing species, H2O, CO2, and OH, near the nozzle surface. A parametric study is also conducted to determine the influence of such nozzle boundary-layer control system operating parameters as temperature, velocity, and injection angle.
All Science Journal Classification (ASJC) codes
- Aerospace Engineering
- Fuel Technology
- Mechanical Engineering
- Space and Planetary Science