The structures of spray plumes from 0.5-mm waterjets injected into a subsonic crosse ow were experimentally investigated using phase Doppler particle anemometry. Droplet size, axial velocity, and volume e ux were measured across the spray plume at several axial distances downstream of the injector exit. Results indicate that large droplets can be found in the central portion of the spray plume for cases with small liquid/air momentum e ux ratios and in which the momentum exchange between column waves and the airstream is signie cant. For cases with large-momentum e ux ratios, the droplet size distribution exhibits a concave-layered structure, with the peak on the centerline and large droplets at the top. Droplets were found to concentrate in a small area within the spray plume, which indicates that the liquid mass distribution is not uniform. The height of the maximum volume e ux locations, an indicator of the location of the highest concentration of droplets, was measured and correlated with momentum e ux ratios and axial distances. It was found that more droplets are distributed toward the upper portion of the spray plume for larger momentum e ux ratios. Spray penetration, spray width, penetration-to-width ratio, and spray cross-sectional area were also found to increase with the momentum e ux ratio.

Spray Structures of Liquid Jets Atomized in Subsonic Crossflows

Review of combustion stabilization for hypersonic airbreathing propulsion

The ine uence of different injector geometries on the mixing behavior of planar supersonic jets is investigated. Hydrogenisinjectedinthee owdirectionthroughthebluntendofastrut.Differentlipthicknessesattheinjectorend induce different extents of recirculation zones. Additionally, changes are caused within the shock-wave/expansion fan pattern at the injector exit that have an important ine uence on loss in total pressure. The accuracy of the used numerical scheme is demonstrated for one injector geometry by comparison with experimental data. Based on this cone guration, modie cations in lip thickness and injection Mach number are investigated numerically and are assessed using several calculated performance parameters. Results show that the chosen lip thickness has a much stronger ine uence on loss in total pressure than moderate modie cations in injector length and height. For the very thin hydrogen jets that were investigated, the mixing efe ciency is nearly independent on injector lip thickness.

Numerical Investigation of Hydrogen Strut Injections into Supersonic Airflows

A method for estimating the axial distribution of thrust performance potential in a supersonic combustor is described. A complementary technique for illustrating the spatial evolution and distribution of thrust potential and loss mechanisms in reacting flows is developed. A wall jet case and swept ramp injector case for Mach 17 and Mach 13.5 flight enthalpy inflow conditions, respectively, are numerically modeled and analyzed using these techniques.

Investigation of scramjet injection strategies for high Mach number flows

In this paper, we present our experimental and numerical results for the supersonic mixing and combustion control. Our strategy of enhancing supersonic mixing is to use streamwise vortices. The reasons are (1) that in supersonic flows streamwise vortices can be generated quite easily and almost without additional losses in total pressure such as those due to shock waves, (2) that their breakdown into smaller scale, which is essential for mixing enhancement, can be controlled by their geometry in spanwise row configurations and by various combinations of their scales, intensity of circulation and rotational directions, and (3)that the hydrogen fuel can be injected into their core region. Several kind of alternating wedge struts are tested to examine the effects of the cited various combinations on the mixing enhancement. By presenting those results, we will discuss the formation mechanism of streamwise vortices and their downstream development, in particular the interaction between themselves in spanwise row configurations, their eventual breakdown into turbulent eddies. Firing tests are also carried out and the results for alternating wedge strut will be presented together with the results for a generic fuel injection strut for comparison. The results show the effectiveness of the present streamwise vortices for supersonic mixing enhancement and combustion control.

Supersonic mixing and combustion control using streamwise vortices

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A. Nejad

Papers

Fuel-vortex interactions for enhanced mixing in supersonic flow