The flow physics of inlet-fueled, low-compression scramjets

Gehre, Rolf

doi:10.14264/uql.2015.772

Cited by 4 publications

(15 citation statements)

References 154 publications

(399 reference statements)

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“…In the present simulations, a 33 equation, 13 species Hydrogen-Air oxidation model is used based on the work of Jachimowski. 12 This model has performed reasonably well in comparative testing, 10 and was believed to be a good compromise between expense and accuracy. Thermal non-equilibrium between TranslationalRotational and Vibrational temperature modes is modelled using the Landau-Teller relaxation formula, with relaxation times drawn from the literature 18,8 whenever the classical Millikan-White method is inadequate.…”

Section: Cfd Methodologymentioning

confidence: 93%

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Simulation of Laser-Induced-Plasma Ignition in a Hypersonic Crossflow

Gibbons

Gehre

Brieschenk

et al. 2015

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

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A numerical study of a laser-induced-plasma ignition system in a scramjet-like geometry is conducted. Simulations are based on experiments in which hydrogen is injected into hypersonic air-crossflow, compressed by a 9 • ramp from a freestream Mach number of 8 to below hydrogen autoignition conditions. Ignition of the jet is conducted using a laser pulse, modelled in the simulations as a small region of high temperature and pressure corresponding to the energy input measured in the experiments. To capture the highly unsteady nature of the fuel-air interface and its coupling with the dynamics of the expanding laser spark, Wall-Modelled Large Eddy Simulations are used to resolve the majority of turbulent motion. Detailed non-equilibrium thermochemistry models are included in the calculations. Simulations have revealed that the cloud of hydroxyl radicals detected in the experiments is created by the blast wave which forms from the expanding plasma kernel merging with the jet's bow shock. This event raises the temperature and pressure in the upstream mixing layer and spontaneous ignition of the fuel is observed. Shortly after this ignition, combustion ceases due to hostile conditions for flame anchoring. Downstream of the jet, the simulations suggest that the plasma kernel remains can initiate some radical formation in the wake region, but no stable flame forms due to nominally low pressures in the experimental condition studied.

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Section: Cfd Methodologymentioning

confidence: 93%

“…More quantitative analysis is obtained using the resolution criterion in Ref. 10, in which the fraction of resolved turbulent kinetic energy (TKE) compared to an estimated sub grid TKE is presented. The average resolved turbulent kinetic energy has been computed using:…”

Section: Iva Meshing Considerationsmentioning

confidence: 99%

Simulation of Laser-Induced-Plasma Ignition in a Hypersonic Crossflow

Gibbons

Gehre

Brieschenk

et al. 2015

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

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“…Only through experimental investigation is it possible to gain better understanding of the underlying processes. [4] (red area), [56] (blue area), [9] (green area), [10] (purple dot) and [27] (orange dots), compiled by [42]. (c) Large-Eddy Simulations of combustion regimes in a scramjet engine [42].…”

Section: Turbulent Combustion Regimesmentioning

confidence: 99%

“…The SCHOLAR experiment and other results are discussed in more detail on Section 2.2.3. Finally, results for LES performed on a complete scramjet engine by Gehre [42] are shown in Fig. 2.8c.…”

Section: Turbulent Combustion Regimesmentioning

confidence: 99%

“…This process is usually modelled in simulations. The simplest way to treat turbulence-chemistry interaction is by considering laminar chemistry, also referred to as the quasi-laminar modelling which Gehre [42] used. This approach has no dedicated modelling of turbulence-chemistry interactions, using finite-rate chemistry to close the chemical source term in the equations (see Section 3.2.5).…”

Section: Turbulent Combustion Regimesmentioning

confidence: 99%

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Investigation of supersonic turbulent combustion in a Mach 10 scramjet engine

Moura¹

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A doctorate is by definition an individual project, but it would be hard to argue it is done on one's own. It's been four years of ups and downs and there are many people who supported me directly or indirectly: partner, friends, co-workers. Having moved into a new country with no one but my partner, these people have played an important role. Too important for the brief words I dedicate to them here. Most important of all I'd like to thank my partner, Luciana, for her support throughout this period. This experience would not have been as good if not for her being around to support me, especially when things seemed like they would fall apart. And when I had no confidence in myself, she did. Thank you for everything. Thank you to my parents, Dolores and Paulo, and my sister, Mariana, who supported me from across the world and were patient and understanding of mine coming here. Particularly my father, who I know was hit hardest by the distance. Thank you for supporting me through this career choice. Thank you to my supervisors, Ingo Jahn, Vince Wheatley and Tim McIntyre for the support and guidance over these years, and for the opportunity. Thank you to the new friends I made here in Australia for the fun times you made sure I had. Some moved on already to pastures new, some are still around. You know who you are. I hope we can keep in touch as our lives take us to different places. I'd like to thank Andreas, Juan and Pierpaolo, closest and constant over these years, those "hyperfools". They'll get it. Thank you to the T4 crew: Eric, Jens, Keith, Ryan, the other Ryan, Sam, Tristan, Will, Zac. Some of you operated the tunnel for me, all of you taught me something and helped me when I needed. You made my experiments possible, in both small and big ways. Thank you for the support. Many thanks to Wilson Chan and Michael Smart. Your help was the most invaluable when I was in the tunnel and helped me successfully concluded my experiments. Not enough can be said about your support. Lastly, but certainly not least, thank you to Nicholas Gibbons for his support with the simulations, particularly the LES. You've always been extremely supportive and never denied help, even towards the end when I was annoying you daily with small problems. Thank you very much for all the help. ix Financial support This thesis was completed with financial support from the Brazilian National Council of Scientific and Technological Development-CNPq.

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Numerical and experimental investigation of hypersonic streamwise vortices and their effect on mixing

Gomez¹,

Ramón²

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Scramjet propulsion is a promising technology that could lead to substantial improvements in cost and flexibility for access to space for satellite placement into Low Earth Orbit. However, scramjet development is hindered by different technological issues. Amongst these, fast and efficient fuel-air mixing, and heat management, are key areas. By increasing mixing rate, the combustor can be shortened while keeping a high combustion efficiency. This reduces drag and heat losses, highly improving the feasibility and viability of scramjet engine designs. Several techniques have been proposed to increase mixing rate in scramjets, such as hypermixers and strut injectors. However, these techniques improve mixing at the expense of increased losses and local heat loads.For this reason, the use of naturally occurring vortices in scramjet flowfields for mixing enhancement came into consideration. Most scramjet geometries inherently generate streamwise vortices. Therefore, there are no increased losses when using these vortices for mixing enhancement. However, these vortices are weaker than those generated by hypermixers or struts.Hence, the ability of these vortices to effectively enhance mixing rate has to be evaluated.This work addresses the study of the interaction between streamwise vortices in scramjet flowfields and fuel injected through an inclined porthole injector to establish optimum arrangements for scramjet performance. The analysis of this interaction is performed numerically and experimentally. Numerical RANS simulations are used as the principal tool to analyse and describe the vortex-injection interaction. In addition, experimental data was gathered to assess the validity of the numerical approach. Scramjet flows are highly complex. To study the effect of the vortex in isolation, a simplified, canonical geometry, consisting of a flat plate with a normal fin is used. The swept shock generated by the fin interacts with the flat plate boundary layer, inducing the formation of a vortex. The features of this vortex are equivalent to those of vortices present in real scramjet flowfields. Moreover, this geometry allows to control the vortex intensity by modifying the fin compression angle. The flat plate incorporates a porthole injector, from which Hydrogen fuel is injected into the vortex. The interaction between the injected fuel and the streamwise vortex was studied focusing on its effect on mixing. Moreover, its effects on maximum wall heat flux, and fuel combustion were also analysed.

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The flow physics of inlet-fueled, low-compression scramjets

Abstract: Flow features for transverse sonic injection into supersonic crossflow. . 2.4Williams diagram for premixed and non-premixed turbulent combustion regimes adapted from [44,166,230] with additional experimental/numerical data.

Cited by 4 publications

References 154 publications

Simulation of Laser-Induced-Plasma Ignition in a Hypersonic Crossflow

Simulation of Laser-Induced-Plasma Ignition in a Hypersonic Crossflow

Investigation of supersonic turbulent combustion in a Mach 10 scramjet engine

Numerical and experimental investigation of hypersonic streamwise vortices and their effect on mixing

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