Investigation of a contoured wall injector for hypervelocity mixing augmentation
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Waitz, Ian A.↗
Engineering topics
Marble, Frank E.
Publications and source records attributed to Marble, Frank E..
Vorticity generation by contoured wall injectors
A class of contoured wall fuel injectors was designed to enable shock-enhancement of hypervelocity mixing for supersonic combustion ramjet applications. Previous studies of these geometries left unresolved questions concerning the relative importance of various axial vorticity sources in mixing the injectant with the freestream. The present study is a numerical simulation of two generic fuel injectors which is aimed at elucidating the relative roles of axial vorticity sources including: baroclinic torque through shock-impingement, cross-stream shear, turning of boundary layer vorticity, shock curvature, and diffusive flux. Both the magnitude of the circulation, and the location of vorticity with respect to the mixing interface were considered. Baroclinic torque and cross-stream shear were found to be most important in convectively mixing the injectant with the freestream, with the former providing for deposition of vorticity directly on the fuel/air interface.
Waitz, Ian A.↗
A systematic experimental and computational investigation of a class of contoured wall fuel injectors
The performance of contoured wall fuel injectors for scramjet engine applications is considered. These fuel injectors were aimed at augmenting mixing through axial vorticity production arising from interaction of the fuel/air interface with an oblique shock. The effects of incoming boundary layer height, injector spacing, and injectant to freestream pressure and velocity ratios are examined. Results from 3D flow field surveys and Navier-Stokes simulations are presented.
Waitz, Ian A.↗
An investigation of a contoured wall injector for hypervelocity mixing augmentation
An experimental and computational investigation of a contoured wall fuel injector is presented. The injector was aimed at enabling shock-enhanced mixing for the supersonic combustion ramjet engines currently envisioned for applications on hypersonic vehicles. Three-dimensional flow field surveys, and temporally-resolved planar Rayleigh scattering measurements are presented for Mach 1.7 helium injection into Mach 6 air. These experimental data are compared directly with a three-dimensional Navier-Stokes simulation of the flow about the injector array. Two dominant axial vorticity sources are identified and characterized. The axial vorticity produced strong convective mixing of the injectant with the freestream. Shock-impingement was particularly effective as it assured seeding of baroclinic vorticity directly on the helium/air interface. The vorticity coalesced into a counter-rotating vortex pair of a sense which produced migration of the helium away from the wall. The influences of spatial averaging on the representation of the flow field as well as the importance of the fluctuating component of the flow in producing molecularly-mixed fluid are addressed.
Waitz, Ian A.↗
Shock enhancement and control of hypersonic mixing and combustion
Experimental and computational analyses of the possibility that shock-enhanced mixing can substantially increase the rate of mixing between coflowing streams of hydrogen and air are discussed. Numerical computations indicate that the steady interaction between a weak shock in air with a coflowing hydrogen jet can be approximated by the two-dimensional time-dependent interaction between a weak shock and an initially circular region filled with hydrogen imbedded in air. Experimental results obtained in a shock tube and contoured wall injector are presented. It is shown that the shock impinging process causes the light gas cylinder to split into two parts; one of these mixes rapidly with air and the other forms a stably stratified vortex pair which mixes more slowly. The geometry of the flow field and the mixing process and scaling parameters are assessed.
Marble, Frank E.↗
Effect of the NACA Injection Impeller on the Mixture Distribution of a Double-row Radial Aircraft Engine
For the normal range of engine power the impeller provided marked improvement over the standard spray-bar injection system. Mixture distribution at cruising was excellent, maximum cylinder temperatures were reduced about 30 degrees F, and general temperature distribution was improved. The uniform mixture distribution restored the normal response of cylinder temperature to mixture enrichment and it reduced the possibility of carburetor icing, while no serious loss in supercharger pressure rise resulted from injection of fuel near the impeller outlet. The injection impeller also furnished a convenient means of adding water to the charge mixture for internal cooling.
Marble, Frank E.↗