Scramjet test flow reconstruction for a large-scale expansion tube, Part 2: axisymmetric CFD analysis

Gildfind, David; Jacobs, Peter A.; Morgan, Richard G.; Chan, W. Y. K.; Gollan, Rowan

doi:10.1007/s00193-017-0786-9

Cited by 20 publications

(15 citation statements)

References 14 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…It has been noted by McGilvray [74] and Sancho Ponce [119] that scramjet conditions in expansion tubes are characterised by the undesirable feature of a steady pressure gradient that can be observed in the Pitot pressure traces (in addition to the flow disturbances already illustrated in the previous sections). The pressure is seen to gradually increase across the nominal test time, and CFD simulations confirm that static pressure, density, and temperature keep rising, while velocity and Mach number decrease [129]. As an example, this phenomenon can be observed in Fig.…”

Section: Test Flow Unsteadinessmentioning

confidence: 75%

“…Gildfind et al [129] carried out an analysis for a somewhat different scope that, however, helps in confirming this prediction with a suggested explanation. The proposed mechanism is that, across the acceleration gas/test gas interface, a recirculation zone is created, which pushes test gas into the boundary layer.…”

Section: Shock Tube Length/diaphragm Locationmentioning

confidence: 77%

“…More recently, Gildfind et al [129] carried out full facility simulations, well-supported by experimental data, of the X3 expansion tube. It was observed that, unlike Mirels theory, if the acceleration tube is long enough (in that case an additional 10 m long section was added to the simulation), there is an eventual collapse of the test gas core flow, leading to no usable test time.…”

Section: Mirels and Viscous Effectsmentioning

confidence: 96%

“…The transient flow coming from the acceleration tube has a thick, but varying boundary layer, causing the core flow to see a changing nozzle area as it progresses further along, such that the gas that arrives later (and that in the acceleration tube was the under-expanded test gas) undergoes a bigger expansion. Additionally, as discussed in [129], the increase in the duct area simply facilitates the unsteady expansion process in a boundary layer limited expansion-tube flow.…”

Section: Inflow Velocitymentioning

confidence: 98%

“…The flow in an expansion tube is time-varying and radially non-uniform, and full facility simulations are necessary to provide detailed insight into the nozzle inflow properties. At the time of this project, work towards full facility simulations of X3 was being carried out in a separate study (later published [129]), where hybrid simulations of a Mach 10 condition were used to estimate the flow through the acceleration tube and nozzle. These simulations, although done for a different condition, are similar to the intended Mach 12 condition.…”

Section: Expansion Tube Nozzles: Simplifying Hypothesesmentioning

confidence: 99%

See 4 more Smart Citations

Free-jet testing of a Mach 12 scramjet in an expansion tube

Toniato¹

View full text Add to dashboard Cite

Scramjet technology has the theoretical potential to provide air-breathing propulsion as a more efficient alternative to conventional rocket propulsion. Since the vehicle captures its oxidiser from the atmosphere -as opposed to carrying it like a rocket -the specific impulse can theoretically be increased by an order of magnitude, thereby increasing payload mass fractions. In this context, threestage hybrid rocket-scramjet-rocket launch systems have shown to potentially provide a cost-effective and flexible solution for satisfying the requirements of the small-satellites market. However, to be economically feasible, the proposed scramjet-powered second stage would be reusable.Rectangular-to-Elliptical-Shape-Transitioning (REST) engines have shown to be a viable concept that can be integrated into access-to-space vehicles operating between Mach 5 and 12. The half-scale Mach 12 REST engine is a research scramjet specifically designed to operate in the last part of the ascent trajectory. Previous studies have demonstrated the ability of this design to successfully operate at equivalent flight conditions of Mach 11.6, 30 kPa dynamic pressure. However, tests have never been performed in freejet mode at the design conditions, as the facility which was used -the T4 reflected shock tunnel -was limited, like all RSTs by the extreme total pressure requirements of a Mach 12 flight. These limitations are aggravated by the even higher pressure necessary for pressure-length scaling, used to conserve the flow similarity between the half-scale experimental model and the flight engine.To overcome these limitations and allow freejet testing with pressure-length scaling, the use of expansion tubes has been proposed. These are currently the only kind of facility capable of producing these high-pressure requirements. Currently, the University of Queensland operates the X3 expansion tube, which is one of the few facilities worldwide with the potential to produce both the required total pressures and sufficiently long test times (up to 1.5 ms) to test an engine such as the Mach 12 REST engine.

show abstract