Numerical Simulation of Injection Strategies in a Cavity-Based Supersonic Combustor

Ebrahimi, Houshang; Malo-Molina, Faure J.; Gaitonde, Datta V.

doi:10.2514/1.b34512

Cited by 42 publications

(7 citation statements)

References 25 publications

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“…It appears to that a majority of the injectant is confined within two counter-rotating vortices resulting in a primarily fuel rich recirculation region. Ebrahimi et al 26 also observed fuel pooling in the recirculation region of a cavity with parallel direct injection. The high localized fuel concentrations are indicative of fuel trapped within the cores of the counter-rotating vortices.…”

Section: A Cavity Step Injectionmentioning

confidence: 90%

Mixing and Mass Exchange for Cavities in Supersonic Flows

Barnes

Segal

2014

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

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The ability of wall-mounted cavities to facilitate flameholding is largely dependent on local conditions within the recirculation region, that are, generally, vastly different from the adjacent supersonic flow. The local stoichiometry depends on the mixing within the flameholder and the mass exchange with the core flow. These processes are integrally linked to fuel injection location and its coupling with the recirculation region flow field. In the present study planar laser-induced fluorescence (PLIF) was used to obtain a twodimensional image of the streamwise fuel distribution in a non-reacting, directly-fueled cavity in a Mach 2.2 flow. Fuel was injected from two different locations within the cavity chosen to result in parallel and counterflow mixing with respect to the primary cavity circulation. Injection from both locations resulted in a largely fuel rich recirculation region. Parallel injection from the cavity step was characterized by pooling of fuel within the cavity's trapped vortices with the majority of mixing occurring in the shear layer and along the cavity walls. Counterflow injection from the cavity floor resulted in a leaner flow field attributed to enhanced mixing with the impinging shear layer, larger quantities of fuel escaping the recirculation region and limited mass exchange between the trapped vortices. The local concentration fields generated by both fueling schemes suggested that under analogous reacting conditions the region around the shear layer would serve as the most probable flame anchoring location. Nomenclature D= cavity depth, mm L = cavity length, mm M = Mach number P inj = injection pressure, atm P 0 = stagnation pressure, atm q r = fuel-to-air dynamic pressure ratio T 0 = stagnation temperature, K V = velocity, m/s X = mole fraction in air, % θ = cavity aft ramp angle, deg. = floor injection angle, deg. = global equivalence ratio

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Section: A Cavity Step Injectionmentioning

confidence: 90%

Mixing and Mass Exchange for Cavities in Supersonic Flows

Barnes

Segal

2014

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

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“…The use of a downstream air throttle to simulate combustor backpressure resulted in significantly improved local mixing and entrainment into the cavity. Ebrahimi et al [21] performed a 3-D RANS computation of a cavity exposed to a Mach 2 freestream and examined a variety of fuel injection configurations. For the case of angled upstream injection, only a small fraction of fuel was entrained into the cavity and distinct fuel jets were still visible in the far field.…”

Section: Upstream Injectionmentioning

confidence: 99%

“…Note the lack of substantial lateral spreading, minimal fuel jet-shear layer interaction, and distinct fuel jets that persist in the far-field. Only a small fraction of injected fuel reaches the cavity recirculation zone as evidenced by its lean mixture [21]. .…”

Section: Floor Injectionmentioning

confidence: 99%

Cavity-based flameholding for chemically-reacting supersonic flows

Barnes

Segal

2015

Progress in Aerospace Sciences

180

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“…Passive methods use a specific structure inside the combustion chamber or change the configuration of the wall to form a vortex and recirculation zone in the flow, which result in improved air-fuel mixing performance for higher combustion performance. Various methods have been studied, such as pylons [3][4][5][6], cavities [7][8][9][10][11][12][13][14], hyper-mixers [15][16][17][18][19][20][21], injector locations [22], angles [23,24], and outlet shapes [25]. A pylon is a slim structure on the wall of the combustion chamber that generates a recirculation zone and vortex to promote air-fuel mixing and stabilize the flame.…”

Section: Introductionmentioning

confidence: 99%

A Numerical Study on the Characteristics of Air–Fuel Mixing Using a Fluidic Oscillator in Supersonic Flow Fields

et al. 2019

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In this study, numerical simulations were conducted to confirm the possibility of improved mixing performance by using a fluidic oscillator as a fuel injector. Three-dimensional URANS non-reacting simulations were conducted to examine air-fuel mixing in a supersonic flow field of Mach 3.38. The numerical methods were validated through simulations of the oscillating flow generated from the fluidic oscillator. The results show that the mass flow rate and momentum are reduced at the outlet because the total pressure loss increases inside the fluidic oscillator, which means that higher pressure needs to be applied to supply the same mass flow rate. The simulation showed that the flow structure varies over time as the injected flow is swept laterally. With lateral injection, the fuel distribution is long and narrow, and asymmetric vortexes are generated. However, with central injection, the fuel distribution is relatively similar to the case of using a simple injector. Compared to the simple injector, the penetration length, flammable area, and mixing efficiency were improved. However, the total pressure loss in the flow field increases as well. The results showed that the supersonic fluidic oscillator could be fully utilized as a means to enhance the mixing effect, however a method to reduce the total pressure loss is necessary for practical application.It is relatively easy to improve the mixing efficiency, but there is a disadvantage of significantly increasing the total pressure loss at a high Mach number. The cavity has been studied because it helps to mix the air-fuel and it can more effectively hold the flame in empty space where a recirculation zone can be formed on the wall [7][8][9][10][11][12][13][14]. A number of studies have been conducted on experiments or numerical simulations to observe the interaction of the cavity with flow fields in the combustion chamber [13] and derive the optimum cavity shape [7][8][9]. Recent studies have been conducted to find ways to improve the mixing performance through more diverse attempts, such as variable cavities and pylons and double cavities [10,11,14].Using the cavity, a scramjet engine can efficiently mix the air-fuel and hold the flame more easily with less total pressure loss. However, combustion instability can occur due to acoustic interference, and additional systems may be needed to compensate for this. A hyper-mixer is a system where a part of the wall of a combustion chamber has a form such as a ramp or a step. The shape generally induces a counter-rotating vortex, which helps to improve the mixing efficiency and expansion of the mixed area [15][16][17][18][19][20][21]. Studies have been carried out on adjusting the angle, arrangement, and shape of the injector [23-25] and using a swirler or counterflow nozzle [26,27].Unlike passive methods, active methods actively intervene in the flow of combustion chambers. Pulsed injection [28][29][30][31][32][33] and the Hartmann-Sprenger (H-S) tube [34,35] are examples of ways to directly affect the flow through variou...

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Numerical Simulation of Injection Strategies in a Cavity-Based Supersonic Combustor

Cited by 42 publications

References 25 publications

Mixing and Mass Exchange for Cavities in Supersonic Flows

Mixing and Mass Exchange for Cavities in Supersonic Flows

Cavity-based flameholding for chemically-reacting supersonic flows

A Numerical Study on the Characteristics of Air–Fuel Mixing Using a Fluidic Oscillator in Supersonic Flow Fields

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