Experimental investigation of self-excited combustion instabilities in a small Earth storable bipropellant rocket combustor

摘要

A 1000 N scale liquid rocket combustion experiment was designed and conducted to investigate high-frequency combustion instabilities in small Earth storable bipropellant engines. The propellants were injected through unlike impingement injectors. Based on the Hewitt stability correlation, the first tangential combustion instabilities could be spontaneously initialized. As combustion instabilities grew, standing tangential modes gradually shifted to spinning modes. This eventually yielded limit-cycle instabilities with peak-to-peak amplitudes of 40 bar, about four times the static combustor pressure. One single pressure wave characterized by steep rising and falling edges rotated around the chamber at supersonic velocity during spinning mode, which could be defined as a detonation-like wave. However, the pressure oscillated in-phase in the axial direction of the combustor. The frequency of the spinning mode was about 10.9 kHz and was minimally influenced by operation conditions. In a series of test campaigns, the instabilities boundary was identified by the parameters of the Hewitt correlation coefficient (HCC) and the oxidizer/fuel mixing ratio (ROF). When the HCC of oxidizer was less than 0.101 and the HCC of fuel was less than 0.075, self-excited tangential combustion instabilities could be developed easily. The combustion instability with moderate amplitude was not observed. (C) 2020 Elsevier Masson SAS. All rights reserved.