Effects of Ramp Side Angle in Supersonic Mixing

Abdel-Salam, Tarek; Tiwari, S. N.; Mohieldin, T.

doi:10.2514/2.2064

Cited by 15 publications

(3 citation statements)

References 12 publications

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“…[14], [15]) or ramp (e.g. [16], [17]) injectors, but these come with the cost of increased ow entropy [18]. Overall, high heating loads and ow losses are thought likely render physical protrusions into the ow impractical at hypervelocity Mach numbers [19].…”

Section: Nomenclaturementioning

confidence: 99%

Tailored Fuel Injection for Performance Enhancement in a Mach 12 Scramjet Engine

Barth

Wise

Wheatley

et al. 2015

20th AIAA International Space Planes and Hypersonic Systems and Technologies Conference

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To investigate the potential performance benets of tailored fuel injection in a scramjet engine, ow through a rectangular-to-elliptical shape-transitioning scramjet was simulated with two dierent combustor injection geometries: one with uniformlyspaced boundary-layer fuel injection, and the other with oblique-angle porthole injectors targeting the ow structures observed in engine simulations. Both engines utilized inlet injection to promote rapid ignition and burning of the combustor-injected fuel.The simulations were compared with experimental data for validation purposes. The tailored-injection engine fueled to an equivalence ratio of 1.24 was found to have superior mixing and combustion eciencies, improving upon the 1.33 equivalence ratio symmetric engine by 7% and 2%, respectively. Tailored injection was shown to be a promising method for improving scramjet performance, potentially allowing higher fuel eciency and a shorter combustor section. Nomenclature A/A t = ratio of local cross-section area to throat cross-section area g = acceleration due to gravity, m/s 2 F thrust = thrust force, N H = stagnation (total) enthalpy, M J/kg I sp = specic impulse, ṡ m = mass ow rate, kg/s M = Mach number P ∞ = freestream static pressure, P a P/P 1 = ocal static pressure normalized to pressure behind forebody shock Q = Q-criterion, 1 2 ( Ω 2 − S 2 ) q = dynamic pressure, kP a Re unit = unit Reynolds number, m −1 S = strain tensor T = static temperature, K u = unit velocity vector U ∞ = freestream velocity, m/s x = streamwise distance from forebody leading edge, mm y + = dimensionless wall distance Y = local species mass fraction Y stoich = stoichiometric local species mass fraction η comb = Oxygen-based combustion eciency, % η mix = Oxygen-based mixing eciency, % ρ = density, kg/m 3 ∂ 1 ρ = ∇ρ ·û φ = fuel equivalence ratio Ω = vorticity tensor 2 Downloaded by UNIVERSITY OF ILLINOIS on October 1, 2015 | http://arc.aiaa.org |

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Section: Nomenclaturementioning

confidence: 99%

Tailored Fuel Injection for Performance Enhancement in a Mach 12 Scramjet Engine

Barth

Wise

Wheatley

et al. 2015

20th AIAA International Space Planes and Hypersonic Systems and Technologies Conference

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“…(Gerlinger et al, 2008), (Genin and Menon, 2010)) and ramp injectors (e.g. (Donohue et al, 1994), (Eklund et al, 1997), (Schumacher, 2000)) have been shown to be effective at mixing fuel, though at a cost of increased flow entropy (Abdel-Salam et al, 2003). Injection into a cavity (Ben-Yakar and Hanson, 2001) has similarly been shown to enhance mixing with available air, and increase fuel residence time within the engine.…”

Section: Fuel Injection and Mixingmentioning

confidence: 99%

Mixing and combustion enhancement in a Mach 12 shape-transitioning scramjet engine

Barth¹

118

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are to investigate and characterize the flow physics behind the Mach 12 REST engine's current performance, and then attempt to improve its combustion performance by tailoring the engine's fuel injection to its internal flow field without otherwise modifying the engine geometry. To meet these aims, the engine was studied both numerically and experimentally.The first-ever combusting simulations of a REST scramjet operating at Mach 12 conditions were performed for the Mach 12 REST engine using the CFD research code US3D. The simulations covered a range of conditions, including: unfuelled engine flow, inlet-fuelled flow, and various combined inlet/combustor fuelling configurations. The simulations were found to match well with the experiments they were designed to reproduce and be compared against. A comparison of simulations with experimental inflow conditions and their equivalent flight conditions on an otherwise identical engine showed that experiments in the T4 Stalker tube reproduce engine pressure and heat flux distributions well. The tunnel condition tends to capture less incoming flow than the engine at flight conditions, which leads to the ground-tested engine over-predicting the engine equivalence ratio.The Mach 12 REST inlet was found to produce a thick "bubble-shaped" boundary layer along its bodyside compression surface, due to the compression effects of the inlet sidewalls acting on a thick turbulent boundary layer ingested from the vehicle forebody. This thick boundary layer forces the majority of inlet-captured air into a high-density, high Mach number flow region along the engine cowlside wall . The inlet also produces a symmetric pair of high-temperature swept separations that enter the engine isolator along the sidewalls of the engine. When fuel is injected from the bodyside surface of the inlet, it remains trapped inside the thick, turbulent boundary layer, where it becomes well-mixed and begins to burn just upstream of the inlet throat.i As much as 50% of this fuel is burned by the time it enters the engine isolator, while its injection and burning increases the inlet's drag by less than 5%. This burning bodyside flow region thermally compresses the remaining air flow within the engine isolator, and provides a source of heat and combustion radicals for the ignition of fuel injected further downstream. Overall combustion efficiency of inlet-injected fuel at the engine exhaust plane was found to be nearly 80% at high equivalence ratios.Flow within the Mach 12 REST combustor is strongly shock-dominated. This is caused by both the cowl closure shock train transmitted from the inlet, and a strong recompression shock generated at the start of the combustor. This recompression shock is generated by the flow passing over a backward step at the entrance to the combustor, and is reinforced on the cowlside of the engine by compression caused by the engine flow path turning to realign with the nominal direction of flight. Fuel injected from the face of the combustor step was combined with inlet injection in...

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“…There are many studies focusing on transverse jet schemes that adopt different mixing enhancement devices, such as struts [9,10], ramps [11,12], pylons [13,14], and cavities [15,16]. Unfortunately, the effect of the BFS on the transverse jet mixing in supersonic crossflow has not been thoroughly and systematically investigated.…”

Section: Introductionmentioning

confidence: 99%

Effect of the Backward Facing Step on a Transverse Jet in Supersonic Crossflow

Zhang¹,

Wang²,

Sun³

et al. 2020

Energies

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A transverse jet in the supersonic crossflow is one of the most promising injection schemes in scramjet, where the control or enhancement of jet mixing is a critical issue. In this paper, the effect of the backward facing step on the characteristics of jet mixing was investigated by three-dimensional large eddy simulation (LES). The simulation in the flat plate configuration (step height of 0) was performed as the baseline case to verify the computation framework. The distribution of the velocity and pressure obtained by the LES agreed well with the experiment, which shows the reliability of the LES code. Then, two steps with a height of 1.0D and 1.58D (D is the injector diameter) were numerically compared to the non-step baseline case. The comparison of the three cases illustrates the effect of the large-scale recirculation region on the variable distribution, and shock and vortex structures in the flow field. In the windward region, the shear layers become thicker, and the convection velocity of the shear vortexes reduces. In the leeward region, the wake vortices almost disappear while the counterrotating vortex pairs (CVPs) expand in the spanwise direction. In the area upstream of the jet, the separation bubble works with the upstream large-scale recirculation zone to entrain the jet into the upstream near-wall zone. At last, a comparison of the overall mixing performance of the three cases revealed that the penetration depth and mixing efficiency increased with the step height increasing.

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Effects of Ramp Side Angle in Supersonic Mixing

Cited by 15 publications

References 12 publications

Tailored Fuel Injection for Performance Enhancement in a Mach 12 Scramjet Engine

Tailored Fuel Injection for Performance Enhancement in a Mach 12 Scramjet Engine

Mixing and combustion enhancement in a Mach 12 shape-transitioning scramjet engine

Effect of the Backward Facing Step on a Transverse Jet in Supersonic Crossflow

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