Autoignition of Kerosene by Decomposed Hydrogen Peroxide in a Dump-Combustor Configuration

Abstract

In staged-bipropellant rocket combustors that use decomposed hydrogen peroxide as the oxidizer, a liquid fuel is injected into the hot decomposition products comprising oxygen and water vapor. For a well-designed combustor, the oxidizer is at a sufficiently high temperature to vaporize and to autoignite the liquid fuel; however, experimental autoignition data in key chamber contraction ratio and propellant equivalence ratio ranges are missing. In this study a transverse injector was used in a dump-combustor configuration to investigate the autoignition characteristics of JP-8 in decomposed hydrogen peroxide, specifically fuel-rich autoignition limits at contraction ratios less than 6 and with high hydrogen peroxide concentrations. The chamber contraction ratio was varied between 3 and 5 to evaluate the effects of chamber gas Mach number (0.45 and 0.27), and the hydrogen peroxide concentration was varied from 85 to 98% by weight to evaluate the effects of oxidizer temperature. Three regimes were noted: strong, weak, and no autoignition. Chamber pressure oscillations with a dominant frequency between 27 and 47 Hz occurred in the weak-autoignition regime. Results showed that as hydrogen peroxide concentration and/or contraction ratio was increased the equivalence ratio that defined the autoignition boundary increased as well. At a contraction ratio of 3.0, no autoignition was achieved at equivalence ratios of 1.37 and above using 85% hydrogen peroxide, but with 98% hydrogen peroxide autoignition occurred at an equivalence ratio as high as 2.06. When the contraction ratio was increased to 5.0, autoignition was achieved at an equivalence ratio of 1.38 using 85% hydrogen peroxide. These data provide a starting point for the development of an accurate autoignition model and an empirical basis for the design of efficient combustors.