Dual-Mode Combustion of Hydrogen in a Mach 5, Continuous-Flow Facility

C. E Goyne,* J. C. McDaniel, t T. M. Quagliaroli, * R. H. Krauss)and S. W. Day *University of Virginia, Charlottesville, Virginia 22904Results of an experimental and numerical study ora dual-modescramjet combustor are reported.The experimentconsisted of a direct-connect test ofa Mach 2 hydrogen-air combustor with a single unswept-ramp fuel injector. Theflow stagnation enthalpy simulated a flight Mach number of 5. Measurements were obtained using conventionalwall instrumentation and a particle-imaging laser diagnostic technique. The particle inmging was enabled throughthe development of a new apparatus for seeding fine silicon dioxide particles into the combustor fuel stream.Numerical simulations of the combustor were performed using the GASP cod_ The modeling, and much of theexperimental work, focused on the supersonic combustion mode. Reasonable agreement was observed betweenexperimental and numerical wall pressure distributions. However, the numerical model was unable to predictaccurately the effects of combustion on the fuel plume size, penetration, shape, and axial growth.NomenclatureH = normal height of ramp injectorM = Much numberP = static pressurePr = Prandtl numberSc = Schmidt numberT = temperatureX, Y, Z = Cartesian coordinates with origin at ramp baseSub.vcriptsav = averageref = reference quantity at nozzle exitt = turbulentIntroductionHE concept of a dual-mode scramjet ha.sconsiderable potentialfor transatmospheric vehicle applications. _ The dual mode ofoperation provides the capability of using a single-engine flowpathovera broad range of flight Mach numbers. At speeds of Much 5 andabove, the engine is operated as a scram jet, and the heat-release pro-cess in the combustor remains predominantly supersonic. At lowerspeeds however, the requirement of high thermal efficiency pre-scribes that the combustion process remain subsonic.'- This ramjetmode can be achieved, using the same engine geometry, by match-ing the flowpath area ratio and combustion heat release such that athermal choke is produced downstream of the point of fuel injec-tion. Provided the associated pressure rise upstream of this chokecan be effectively isolated from the engine's supersonic inlet, thedual-mode scramjet will operate at low supersonic flight speeds ina manner similar to a conventional ramjet.Of particular importance to the development of dual-mode scram-jets are the differences in the fuel-air mixing, ignition, and combus-tion processes in the supersonic and subsonic modes and in the tran-sition region between the modes. Although the dual-mode concepthas been experimentally studied since the 1960s,Z3 these processesand differences are still not fully understood. Modem computational