Cavity-based flameholding for chemically-reacting supersonic flows

Barnes, Frank W.; Segal, Corin

doi:10.1016/j.paerosci.2015.04.002

Cited by 180 publications

(14 citation statements)

References 84 publications

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“…For supersonic combustion, typical solutions for mixing intensification are based on vorticity generation such as by struts (hypermixers), cavities, shock wave impinging the fuel jet, etc. [117][118][119][120]. Plasma-based mixing is still considered an exotic approach.…”

Section: Mixing Enhancement By Electric Dischargesmentioning

confidence: 99%

Electrically Driven Supersonic Combustion

Leonov

2018

Energies

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This manuscript reviews published works related to plasma assistance in supersonic combustion; focusing on mixing enhancement, ignition and flameholding. A special attention is paid for studies, which the author participated in person. The Introduction discusses general trends in plasma-assisted combustion and, specifically, work involving supersonic conditions. In Section 2, the emphasis is placed on different approaches to plasma application for fuel ignition and flame stabilization. Several schemes of plasma-based actuators for supersonic combustion have been tested for flameholding purposes at flow conditions where self-ignition of the fuel/air mixture is not realizable due to low air temperatures. Comparing schemes indicates an obvious benefit of plasma generation in-situ, in the mixing layer of air and fuel. In Section 3, the problem of mixing enhancement using a plasma-based technique is considered. The mechanisms of interaction are discussed from the viewpoint of triggering gasdynamic instabilities promoting the kinematic stretching of the fuel-air interface. Section 4 is related to the description of transitional processes and combustion instabilities observed in plasma-assisted high-speed combustion. The dynamics of ignition and flame extinction are explored. It is shown that the characteristic time for reignition can be as short as 10 ms. Two types of flame instability were described which are related to the evolution of a separation zone and thermoacoustic oscillations, with characteristic times 10 ms and 1 ms correspondingly.

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Section: Mixing Enhancement By Electric Dischargesmentioning

confidence: 99%

Electrically Driven Supersonic Combustion

Leonov

2018

Energies

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“…The configuration of the fuel injection greatly influences the combustion characteristics of the combustor. The injection configurations employed for cavity-based supersonic combustors are usually divided into two types: cavity wall injections (direct injections) and upstream injections (passive injections) [17]. Compared with passive injection, Gruber et al [10] found that cavity wall injection is conducive to fuel entering the cavity recirculation zone and maintaining a more stable combustion in the ignition transition process.…”

Section: Introductionmentioning

confidence: 99%

Effects of Additional Cavity Floor Injection on the Ignition and Combustion Processes in a Mach 2 Supersonic Flow

et al. 2020

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Effects of additional cavity floor injection on the ethylene ignition and combustion processes in a cavity-based scramjet combustor are investigated experimentally in a Mach 2.0 supersonic flow using flame luminosity and CH* (CH radical) spontaneous emission methods and static pressure measurements. Numerical calculation is performed to study the non-reacting flow-field structures prior to ignition. Two injection schemes, including the cavity upstream injection scheme and the combined injection scheme with an additional cavity floor injection, are compared to study the effects of the additional cavity floor injection on the ignition and combustion processes. It is found that there exists an equivalence ratio upper limit for maintaining stable combustion for the cavity upstream injection scheme. As the equivalence ratio further increases, the fuel jet penetration is improved accordingly, and thus, the interaction between the fuel jet and the cavity is weakened, which can lead to the ignition failure and flame blowout during combustion. On the contrary, although the combined injection scheme has a minor effect on combustion enhancement at the same global equivalence ratio, it can also provide a more favorable flow-field environment that enables more successful ignitions and better flame stabilizations. For the combined injection scheme, as the equivalence ratio increases, the initial flame propagations are observed to perform different routines during the ignition process, and the major combustion reaction zone tends to move further downstream the cavity shear layer. It is concluded that the advantages of the combined injection scheme with an additional cavity floor injection are more significant when the equivalence ratio is higher, as well as that the interaction between the fuel jet and the cavity becomes weaker.

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“…The problem of flame-holding, along with the understanding of the mechanisms of flame stabilization and flame extinction, are thus key elements in the development of a future reliable scramjet engine. Among the different strategies to trap the fuel and air in recirculation zones [1,2], the use of cavity has been viewed as a promising solution [3] since it reduces drag, lowers total pressure losses and minimizes aerodynamic heating [4]. Resolving problems related to cavity scramjets requires the treatment of various problems such as the effect of cavity geometry and fuel injection parameters which ultimately condition the impact of heat release on the structure and the dynamics of the shear layer above the cavity, the recirculation zones, the flame regimes or the conditions of flame blowout.…”

Section: Introductionmentioning

confidence: 99%

Stabilisation and extinction mechanisms of flames in cavity flameholder scramjets

Ruan

Ribert

Domingo

2020

Combustion Theory and Modelling

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Stabilizing a flame in scramjet engines is a current technological challenge. Indeed, the residence time in the combustion chamber is very short, thus limiting the mixing efficiency and consequently, the combustion. This problem is presently addressed by simulating the scramjet combustor of the U.S Air Force Research Laboratory in which ethylene is injected from the back of a slanted cavity to react with the supersonic airflow. Large-Eddy Simulations (LES) are performed for different cases showing a dependence of the combustion regimes encountered in the scramjet cavity with the fuel flow rate. For a medium-high flow rate, a mix of lean and rich premixed reaction zones is found along with non-premixed flames. At medium flow rate, rich premixed flames disappear but the flame remains stable in the cavity. The mechanism of flame stabilization is detailed and the LES tool has proven its efficiency in such challenging configuration. Finally, a mechanism of extinction is proposed when the fuel flow rate is further reduced.

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Cavity-based flameholding for chemically-reacting supersonic flows

Cited by 180 publications

References 84 publications

Electrically Driven Supersonic Combustion

Electrically Driven Supersonic Combustion

Effects of Additional Cavity Floor Injection on the Ignition and Combustion Processes in a Mach 2 Supersonic Flow

Stabilisation and extinction mechanisms of flames in cavity flameholder scramjets

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