Investigation of a contoured wall injector for hypervelocity mixing augmentation

Waitz, Ian A.; Marble, Frank E.; Zukoski, E. E.

doi:10.2514/3.11723

Cited by 102 publications

(23 citation statements)

References 15 publications

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“…Finally, the helium mass fraction contours presented in Fig. 7, for the previously considered (see [18]) ramp injection in a Mach 6 air flow by Waitz et al [28] lends support to the aforementioned validation results. Note that the turbulence Schmidt number has been shown to be low and vary across the mixing layers ( [29], p. 49) and that the trend appears in the preceding results.…”

Section: Validationsupporting

confidence: 79%

Hypervelocity Fuel/Air Mixing in Mixed-Compression Inlets of Shcramjets

2006

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This paper investigates the mixing of hydrogen fuel with air in the mixing duct of a mixed-compression shockinduced combustion ramjet (shcramjet) inlet. Mixing augmentation through the use of cantilevered ramp injector arrays on opposite shcramjet inlet walls is studied and the influence of relative array locations is quantified. Studies were undertaken numerically using the WARP code that solves the Favre-averaged Navier-Stokes equations closed by the Wilcox k-! turbulence model. Air-based mixing efficiencies of up to 0.58-0.68 were achieved with thrust potential losses less than that gained from high-speed fuel injection. Shocks created from the fuel injector structures play a major role in the mixing behavior of the fuel jets on the opposing side of the mixing duct. Chemically reacting studies verified for the correct selection of spanwise displacement of the fuel injectors, an air buffer created between the fuel and walls suppresses premature ignition while still allowing for a mixing efficiency of up to 0.46-0.54. Nomenclature a = speed of sound c = species mass fraction d w = distance from wall to first inner node F pot = thrust potential F pot;ref = reference thrust potential at engine inlet k = turbulence kinetic energy M c = convective Mach number, q 1 q 2 =a 1 a 2 _ m = mass flow rate _ m air;engine = mass flow rate of air in engine p = pressure p ?= effective pressure, p 2=3k Pr t = turbulent Prandtl number q = magnitude of velocity vector r = grid size factor Sc t = turbulent Schmidt number T = temperature x 1 , x 2 , x 3 = Cartesian coordinates y = nondimensional wall distance, d w w p = m = mixing efficiency = viscosity = density w = wall shear stress = equivalence ratio ! = dissipation rate per unit of turbulent kinetic energy Subscripts b = station of interest c = station of interest reversibly expanded to constant pressure at shcramjet exit area Superscripts R = reacting S = stoichiometric

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Section: Validationsupporting

confidence: 79%

Hypervelocity Fuel/Air Mixing in Mixed-Compression Inlets of Shcramjets

2006

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“…Previous work 3,4 has suggested that mixing enhancement in fuel jets can be brought about by the baroclinic vorticity generated by the shock/jet interaction. Strong, nonuniform acceleration can also lead to shear (Kelvin-Helmholtz) and inertial (RayleighTaylor) instability.…”

Section: Introductionmentioning

confidence: 99%

“…The simplicity of this con guration aids in the study of the fundamental mixing mechanisms operative in more complicated combustor geometries. Previous work 3,4 has demonstrated the utility of using unsteady shock propagationto study mixing processes in compressible jet ows by showing that the intersection of an oblique shock wave with a steady fuel jet can be simulated, locally, by the passage of a shock wave though a stationary cylindrical region of gas.…”

Section: Introductionmentioning

confidence: 99%

Numerical Simulation of Shock-Enhanced Mixing in Nonuniform Density Turbulent Jets

Obata

Hermanson

2000

AIAA Journal

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A numerical study of the interaction of weak normal shock waves with turbulent jets was conducted. The con guration consisted of a planar jet of air, helium, or carbon dioxide situated on the centerline of a shock tube with an air co ow. The shock strengths were M s = 1:2 and 1:4. The numerical model was based on a time-dependent, Navier-Stokes approach and a two-equation q-! turbulence model. The results indicate that passage of a shock through low-density (helium) jets produces a vortexlike structure not seen for the case of the air or carbon dioxide jets. Helium jets exhibit a decrease in mean jet uid concentration due to shock interaction of up to approximately 30% at a location 30 jet exit heights downstream of the jet exit for a shock strength of M s = 1:4. The amount of mixing enhancement increases with increasing shock strength and decreases with increasing downstream distance. In comparison, the air and carbon dioxide jets show a signi cantly smaller degree of mixing enhancement. These results are qualitatively consistent with recent experimental results in axisymmetric, turbulent jets subject to normal shock passage.

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“…The RM instability occurs in several problems of interest, such as inertial confinement fusion studies of deuterium-tritium targets, 7-10 natural phenomenon like supernova collapse, 11,12 pressure wave interaction with flame fronts, 13 and supersonic and hypersonic combustion. [14][15][16] The dynamics of the flow driven by the RM instability is extremely complex. As a result, these flows are studied experimentally, analytically, and computationally through various simplified test problems.…”

Section: Introductionmentioning

confidence: 99%

Stretching of material lines in shock-accelerated gaseous flows

et al. 2005

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A Mach 1.2 planar shock wave impulsively accelerates one of five different configurations of heavy-gas ͑SF 6 ͒ cylinders surrounded by lighter gas ͑air͒, producing one or more pairs of interacting vortex columns. The interaction of the columns is investigated with planar laser-induced fluorescence in the plane normal to the axes of the cylinders. For the first time, we experimentally measure the early time stretching rate ͑in the first 220 s after shock interaction before the development of secondary instabilities͒ of material lines in shock-accelerated gaseous flows resulting from the Richtmyer-Meshkov instability at Reynolds number ϳ25 000 and Schmidt number ϳ1. The early time specific stretching rate exponent associated with the stretching of material lines is measured in these five configurations and compared with the numerical computations of Yang et al. ͓AIAA J. 31, 854 ͑1993͔͒ in some similar configurations and time range. The stretching rate is found to depend on the configuration and orientation of the gaseous cylinders, as these affect the refraction of the shock and thus vorticity deposition. Integral scale measurements fail to discriminate between the various configurations over the same time range, however, suggesting that integral measures are insufficient to characterize early time mixing in these flows.

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Investigation of a contoured wall injector for hypervelocity mixing augmentation

Cited by 102 publications

References 15 publications

Hypervelocity Fuel/Air Mixing in Mixed-Compression Inlets of Shcramjets

Hypervelocity Fuel/Air Mixing in Mixed-Compression Inlets of Shcramjets

Numerical Simulation of Shock-Enhanced Mixing in Nonuniform Density Turbulent Jets

Stretching of material lines in shock-accelerated gaseous flows

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