Evolution of Large-Scale Structures Generated by a Strut Injector in a Mach 2.5 Flow

Vergine, Fabrizio; Maddalena, Luca

doi:10.2514/6.2012-332

Cited by 12 publications

(9 citation statements)

References 21 publications

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“…The very first action of these vortices is to change the morphology of the plume due to the imposed flowfield, as has been already proved in supersonic cold flow studies conducted by the authors [14,15]. In those works it was pointed out that, for the flow to be dominated and, therefore, controlled by the streamwise vortices, their strength must be larger than that of the spanwise structures convecting in the close layer in which they evolve.…”

Section: Introductionmentioning

confidence: 88%

“…In the simulations, the initial position of the cores of the vortices in the CVP forming downstream of the ramps was set at two-thirds of the total ramp height to account for downwash, which was found to be a good approximation during the cold flow studies previously conducted [14,15]. The vertical distances of the vortices were made to coincide with the width of the ramps in use, the extent of which was chosen after a set of simulations was performed to find configurations that resulted in peculiar flow physics.…”

Section: Experiments Designmentioning

confidence: 99%

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Supersonic Combustion of Pylon-Injected Hydrogen in High-Enthalpy Flow with Imposed Vortex Dynamics

Vergine

Crisanti

Maddalena

et al. 2015

Journal of Propulsion and Power

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The ignition and combustion characteristics of the hydrogen plume issued from two pylon-type injectors in a Mach 2.4, high-enthalpy airflow are presented. Specifically, the focus of the study is on the effects of the imposed interaction and subsequent dynamics of a system of selected supersonic streamwise vortices on the reacting plume morphology and its evolution. The design phase of the experimental campaign was carried out with a reduced-order model, with the goal of identifying peculiar interactions among streamwise vortical structures introduced in the flow of interest. Two vortex interaction modes have been selected and later implemented using ramp-type vortex generators positioned symmetrically and asymmetrically on the pylon injectors, as prescribed by the results of the simulations reported here. Hydrogen/air combustion experiments, aimed at investigating the selected cases, were conducted in the expansion tube facility of the High-Temperature Gas Dynamics Laboratory at Stanford University. Stagnation enthalpy of 2.8 MJ∕kg, static temperature of 1400 K, and static pressure of 40 kPa were the chosen test conditions. Hydrogen at 300 K was delivered with two different total injection pressures. The supersonic combustion, ignition, and flameholding characteristics were documented with schlieren photography, OH chemiluminescence, and instantaneous OH radicals planar laser-induced fluorescence. The evolution of the reactive vortical system was probed in cross-sectional planes at a distance of 1.8, 4.3, 7.6, and 10.7 cm from the fuel exit plane. The results are thoroughly analyzed and the marked difference in the plume morphology between the two cases is explained. The similarities between the injectant's predicted plumes and the measured distribution of OH radicals across the surveyed planes allow for an interpretation of the results based on supersonic vortex dynamics considerations.

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Section: Introductionmentioning

confidence: 88%

Section: Experiments Designmentioning

confidence: 99%

Supersonic Combustion of Pylon-Injected Hydrogen in High-Enthalpy Flow with Imposed Vortex Dynamics

Vergine

Crisanti

Maddalena

et al. 2015

Journal of Propulsion and Power

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“…However, for the purpose of obtaining a more accurate value to use during the design stage of experiments involving more complex vortical systems, an experiment with a single ramp was performed to characterize the actual strength of the resulting CVP. 24 During this initial investigation, it was also found that the central positions of the cores of the vortices did not coincide exactly with the corners of the ramp. It was found that a good estimation, for the numerical simulations, was to consider the vortices as being shed at 2/3 of the ramp's height.…”

Section: A Vortx Simulationsmentioning

confidence: 93%

Vortex dynamics studies in supersonic flow: Merging of co-rotating streamwise vortices

2014

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For air-breathing propulsion systems intended for flight at very high Mach numbers, combustion is carried out at supersonic velocities and the process is mixing limited. Substantial increase in mixing rates can be obtained by fuel injection strategies centered on generating selected modes of supersonic, streamwise vortex interactions. Despite the recognized importance, and potential of the role of streamwise vortices for supersonic mixing enhancement, only few fundamental studies on their dynamics and interactions have been conducted, leaving the field largely unexplored. A reduced order model that allows the dynamics of complex, interacting, supersonic vortical structures to be investigated, is presented in this work. The prediction of the evolution of mutually interacting streamwise vortices represents an enabling element for the initiation of an effective, systematic experimental study of selected cases of interest, and is an important step toward the design of new fuel injection strategies for supersonic combustors. The case presented in this work is centered on a merging process of co-rotating vortices, and the subsequent evolution of a system composed of two counter-rotating vortex pairs. This interaction was studied, initially, with the proposed model, and was chosen for the peculiarity of the resulting morphology of the vorticity field. These results were used to design an experimental investigation with the intent to target the same specific complex flow physics. The experiment revealed the same peculiar features encountered in the simulation.

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“…This approach is the scope of work by Maddalena et al 13 in which a reduced order model, is used in order to target selected modes of vortex interaction and amalgamation via imposed ramp configurations. This approach has been proven to be successful in both cold flow 14,15 and reacting flow 16 in that the plume morphology predictions of the reduced order model have been verified experimentally for both one (1 CVP), two (2 CVPs), three (3 CVPs), and four (4 CVPs) ramp injector configurations for both merging and non-merging scenarios.…”

Section: Introductionmentioning

confidence: 92%

Experimental and Numerical Investigation of the Flow Characteristics of a Strut Injector for Scramjets

Ground

Vergine

Maddalena

et al. 2014

19th AIAA International Space Planes and Hypersonic Systems and Technologies Conference

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A peculiar dynamical interaction of two supersonic counter-rotating vortex pairs (CVPs) has been generated by a pair of overlapping expansion ramps mounted on a strut injector in a Mach 2.5 flow. Similar CVP configurations generated by overlapping ramps on the same modular strut injector have previously been studied by the authors and experimentally corroborated the predictions based on the in-house developed reduced order model, VorTx. Two co-rotating vortices at the center of the generated structure have either merged or begun to orbit each other. However, for the case discussed in this work, experiments have revealed an additional structure; in fact, instead of the expected four streamwise vortices in the flowfield consisting of two inner co-rotating vortices and two oppositely rotating external vortices, the formation of a fifth structure, a central vorticity patch, was detected. The manuscript presents a detailed experimental characterization of the flow of interest via the use of stereoscopic particle image velocimetry and a parallel computational effort based on the solution of the Reynolds Averaged Navier-Stokes equations with the ANSYS Fluent CFD Package. The results of the CFD simulations highlight the near injector flowfield, which is unable to be characterized experimentally, in order to focus upon the mechanism that result in the formation and the effects of the central vorticity patch. Nomenclatureh = Ramp height, mm M = Mach number ω = Vorticity, s -1 Subscripts ∞ = Free-stream

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Evolution of Large-Scale Structures Generated by a Strut Injector in a Mach 2.5 Flow

Cited by 12 publications

References 21 publications

Supersonic Combustion of Pylon-Injected Hydrogen in High-Enthalpy Flow with Imposed Vortex Dynamics

Supersonic Combustion of Pylon-Injected Hydrogen in High-Enthalpy Flow with Imposed Vortex Dynamics

Vortex dynamics studies in supersonic flow: Merging of co-rotating streamwise vortices

Experimental and Numerical Investigation of the Flow Characteristics of a Strut Injector for Scramjets

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