Investigation of Graphite Nozzle Erosion in Hybrid Rockets Using Oxygen/High-Density Polyethylene

摘要

A recently developed reconstruction technique is used to investigate graphite nozzle erosion in two scales of hybridrocket motors, 30-N-thrust class and 2000-N-thrust class, using oxygen as the oxidizer and high-density polyethyleneas the fuel. Thermocouple measurements taken from within the nozzles are used to estimate nozzle throat walltemperature. Forty-four static firing tests were conducted under varying experimental conditions to confirm thevalidity of the reconstruction technique results, to investigate the conditions at the onset of erosion, and to formulatean empirical predictive model of nozzle erosion rate. Results show that a single formula that treats the combustion gasas a single oxidizing agent for which heterogenous rate constants are functions of equivalence ratio can satisfactorilyreplicate the erosion rate of graphite by a combustion gas containing multiple oxidizing species. Furthermore, thechemical-kinetic-limited conditions of the onset of nozzle erosion are specified by a novel empirical correlation, whichshows that erosion begins at lower temperature and pressure in oxidizer-rich combustion gas than in fuel-richcombustion gas.