Firing tests of hybrid engine with varying oxidiser nature and operating conditions

Abstract

Hybrid combustors are of increasing interest for space and civilian propulsion. A test facility has been settled to investigate high-density polyethylene combustion (propellant of length 0.15 m). A parametric study has been conducted on the oxidiser nature (gaseous oxygen diluted in nitrogen, from 31.4 vol.% to 69.2 vol.% of O2), on the oxidiser flow rate (from 28.6 g/s to 53.1 g/s), on the combustor pressure (from 11.4 bar to 25 bar) and on the nozzle diameter (from 6.4 mm to 12.9 mm). The regression rate has been estimated by weight loss (mean value of 0.207 mg/s) and by thermocouples (0.198 mg/s). Its values are compared to existing data through the Marxman law; this enlarges the range of validity of this law. The conduction heat flux in the solid reducer is estimated around 6000–8000 W; which is related to the low regression rate of the solid fuel. The axial thrust has been measured in addition to other parameters (pressures, temperatures and mass flow rates). Solid particles have been gathered at the combustor outlet to conduct additional chemical analyses. These particles were formed at the surface of the reducer and extracted by the oxidiser from the solid surface.