A major component of the research program at Taitech is integrated experimental and computational investigation of supersonic combustion ramjet (scramjet) propulsion, including innovative approaches to fuel injection, flame-holding, flow modeling, and control of combustion instabilities. 

        Over the past several years, Taitech has designed, manufactured, installed, and calibrated a direct-connect scramjet test facility.  The facility was designed in support of the Air Force Hypersonic Technologies (HyTech) program, for long-duration, steady-state combustor tests.  Research conducted in this facility will pursue technological breakthroughs in ignition, fuel injection, and flameholding for supersonic combustion, and will provide local experience in the areas of high-speed propulsion systems testing and analysis. Facility calibration is complete, and recent experiments and computations have investigated ignition and combustion of liquid and gaseous hydrocarbon fuels in supersonic flow.  In initial experiments, ignition and sustained combustion of room temperature ethylene were achieved using a cavity-based fuel-injector/flameholder.  Combustion inlet conditions simulated Mach numbers of 4-6 and dynamic pressure of 1000 psf. Temperature, thrust, and pressure measurements were made, and visual video records indicate an active combustion zone with rapid flame spreading.  In subsequent experiments, various cavity flameholders, several fuel injectors, and aerated-fuel injection have been explored as means of providing efficient fuel injection and combustion stabilization.  The aerated-fuel injection experiment is an extension of a separate experimental program researching the fundamental spray structure of aerated-liquid jets in a supersonic crossflow environment.

        These promising cavity flows and injector configurations are also the subject of an integrated program of experiments and computations on mixing and combustion. The experimental portion of this program is being performed in the supersonic mixing/combustion facility at the Air Force Research Lab. This wind tunnel is capable of continuous operation at Mach numbers up to 4.5, with peak stagnation conditions of 750 psi and 1660?R. The standard test section measures 5 x 6 inches, with allowance for boundary layer growth. The test facility is capable of probe-based measurements of species concentration, Pitot pressure, cone static pressure, and total temperature. Conventional static pressure, temperature and flowrates can also be measured. A wide array of non-intrusive optical diagnostic techniques are being developed and used, including schlieren and shadowgraph photography, laser Doppler velocimetry (LDV), particle image velocimetry (PIV), planar laser-induced fluorescence (PLIF), Mie scattering and Raman scattering.

        In an investigation of pilot configurations proposed for the Air Force HyTech program, Taitech has studied the cold-flow mixing effectiveness of single-jet, ramp, aeroramp, cascade, and strut fuel injectors. Cavity flameholders were used and the effects of a pre-combustion shock train on mixing were considered for some configurations. All of this research is performed through joint CFD and experimental efforts, with the computational and experimental programs supporting each other in the design of experiments and the interpretation of data. Further development of CFD models is crucial, given the highly complex nature of high-speed reacting flows in combustor environments and the physical, economic, and temporal limitations on experimental testing.

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Last modified: May 10, 2001