Pyrolysis/evaporation study of succinic acid/polyvinyl acetate for reducing nozzle erosion

A nozzle boundary-layer control systemis under consideration for application in high-pressure rockets tomitigate the erosion rates of a graphite nozzle. The current design contains multiple center-perforated solid grains of fuel-rich materials consisting of succinic acid and polyvinyl acetate. This combination of the fuel-rich grains was selected due to high carbon and hydrogen contents along with relatively low evaporation temperature for generating fuel-rich gases. The characterization of the pyrolysis behavior of fuel-rich grains is a requirement for any subsequent quantitative analysis pertaining to the effect of the nozzle boundary-layer control system on graphite rocket nozzle erosion rates. Two separate experiments were conducted: 1) to determine the regression rate of solid fuel-rich grains under controlled heat flux or temperature conditions, and 2) to characterize its chemical decomposition and/or evaporation behavior. An empirical correlation between heat flux and surface regression rate of fuel-rich grains was developed. From Fourier transform infrared spectroscopy measurements, the fuel-rich grains were found to melt and evaporate at temperatures up to 773 K. These results have been used in parallel study nozzle throat erosion processes using computational simulation.