Nonintrusive stabilization of a conical detonation wave for supersonic combustion

Theoretical and experimental studies are undertaken of the feasibility of an air-breathing supersonic combustor based on a stabilized, conically configured (oblique) detonation wave. The conical wave is the result of the interaction of a train of spherical detonation waves, each directly initiated by a brief, localized deposition of energy from a very-rapidly-repeated pulsed laser. The laser is tightly focused on a fixed site (in the combustor) where there is a steady uniform supersonic stream of combustible gas. Simple analysis of the requirements for (nonintrusive) direct initiation of an individual spherical detonation wave by a single laser pulse relates the pulse-energy and pulse-duration parameters. Then, an estimate is given of the entropy production associated with the early-time interaction of spherical detonations created in a supersonic reactive stream by a train of laser pulses. The entropy production, which arises from reflected shocks in the already detonated mixture, is reduced by increasing the repetition rate of the laser. Finally, the fuel/air mixing is inevitably imperfect in practical high-speed combustors. We investigate that portion of the throughput which is compressed, but not reacted, during transit of the conical detonation wave, because of imperfect mixing. Specifically, we estimate the spatial scale of the cold-mixture inhomogeneity that still permits diffusive burnup, prior to exhaust from the nozzle of the combustor.