Study of Forebody Injection and Mixing with Application to Hypervelocity Airbreathing Propulsion

Axdahl, Erik L.; Kumar, Ajay; Wilhite, Alan W.

doi:10.2514/6.2012-3924

Cited by 12 publications

(12 citation statements)

References 27 publications

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“…The fuel injectors in this study were chosen among those evaluated by Axdahl et al 2 for nonreacting fuel injection and mixing on a notional Mach 12 vehicle forebody. Transverse, ramp, and strut injection were evaluated and the best performer in each category was used in this study.…”

Section: Modeling and Simulation Fuel Injector Geometriesmentioning

confidence: 99%

“…First is the ability to achieve uniform mixing of the fuel and air along the forebody without spillage from the cowl lip or significant loss in stream thrust potential. 1,2 Second is the prevention of autoignition of the fuel-air mixture as fuel enters the hot boundary layer of the forebody or as hot gas from the boundary layer is entrained into the fuel plume. 3 Third is the issue of shock wave stability due to combustion at conditions characteristic of the entrance to the combustor.…”

Section: Introductionmentioning

confidence: 99%

“…Three injection cases were considered-flush-wall, ramp, and strut injection-with the geometry of each case taken from the authors' previous study of forebody injection and mixing. 2 Regions of autoignition were identified along with the circumstances from which autoignition arises for each case. Autoignition mitigation through the use of film cooling and wall transpiration were considered as active cooling strate- gies to inhibit the presence of autoignition near the wall.…”

Section: Introductionmentioning

confidence: 99%

“…Fuel injector exit conditions by Axdahl et al2 All cases use 100% H2 at a static temperature of 390 K.…”

mentioning

confidence: 99%

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Mitigation of Autoignition Due to Premixing in a Hypervelocity Flow Using Active Wall Cooling

Axdahl

Kumar

Wilhite

2013

49th AIAA/ASME/SAE/ASEE Joint Propulsion Conference

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Preinjection of fuel on the forebody of an airbreathing vehicle is a proposed method to gain access to hypervelocity flight Mach numbers. However, this creates the possibility of autoignition either near the wall or in the core of the flow, thereby consuming fuel prematurely as well as increasing the amount of pressure drag on the vehicle. The computational fluid dynamics code VULCAN was used to conduct three dimensional simulations of the reacting flow in the vicinity of hydrogen injectors on a flat plate at conditions relevant to a Mach 12 notional flight vehicle forebody to determine the location where autoignition occurs. Active wall cooling strategies were formulated and simulated in response to regions of autoignition. It was found that tangential film cooling using hydrogen or helium were both able to nearly or completely eliminate wall autoignition in the flow domain of interest.

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Section: Modeling and Simulation Fuel Injector Geometriesmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

“…Fuel injector exit conditions by Axdahl et al2 All cases use 100% H2 at a static temperature of 390 K.…”

mentioning

confidence: 99%

See 2 more Smart Citations

Mitigation of Autoignition Due to Premixing in a Hypervelocity Flow Using Active Wall Cooling

Axdahl

Kumar

Wilhite

2013

49th AIAA/ASME/SAE/ASEE Joint Propulsion Conference

Self Cite

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“…while the mixing efficiency was defined as the ratio of the mixed fuel mass flow rate, and the total fuel mass flow rate, as adapted from Axdahl et al(2012). This ratio is defined mathematically asṁ…”

Section: Mixing and Combustion Efficienciesmentioning

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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Combustion

Bruno

2023

Airbreathing Hypersonic Propulsion

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Study of Forebody Injection and Mixing with Application to Hypervelocity Airbreathing Propulsion

Cited by 12 publications

References 27 publications

Mitigation of Autoignition Due to Premixing in a Hypervelocity Flow Using Active Wall Cooling

Mitigation of Autoignition Due to Premixing in a Hypervelocity Flow Using Active Wall Cooling

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

Combustion

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