Operating Characteristics of a 10-mm Rotating Detonation Rocket Engine
C. Knowlen, Tyler Mundt, Quentin Roberts, Ali Hamza, David Menn, M. Kurosaka
Abstract
The conventional approach for scaling of rotating detonation rocket engines relates the detonation wave cell width to the combustor outer wall radius of curvature and annular gap width to estimate the minimum size scale of feasible combustors. For methane-oxygen and hydrogen-oxygen propellants, it is predicted that an annulus with 10-mm-outer diameter and 2-mm-gap width is about the minimum scale at which RDRE operation can be sustained while operating with combustor pressures less than 0.5 MPa. The operating characteristics of such a combustor are currently being explored. Experiments without a core in a 10-mm-diameter cylindrical combustor using methane-oxygen propellant have demonstrated single wave operation at frequencies up to 65 kHz, corresponding to about 81% Chapman-Jouguet detonation speed. The operational envelope with respect to equivalence ratio was found to be smaller than that observed in larger diameter coreless combustors. With hydrogen-oxygen propellant, one, two, and three wave operation at frequencies of 94 kHz, 135 kHz and 167 kHz, respectively, have been observed. The operational envelope of hydrogen-oxygen propellant is much broader than that observed with methane-oxygen. Tests using 6-mm-diameter cores to form a 2-mm-gap showed spinning waves could be established with both hydrogen and methane fuels, however, the intense heat transfer to the inner cores resulted in their erosion and deformation with run durations of approximately 500 ms. Data from a 10-mm-diameter combustor in its coreless and 2-mm-gap configurations with cores fabricated from copper, molybdenum, and tungsten are presented.