A Computational Investigation of Unstart in a Dual-Mode Scramjet

Riley, Logan P.; Hagenmaier, Mark A.; Donbar, Jeffrey M.; Gaitonde, Datta V.

doi:10.2514/6.2016-1901

Cited by 6 publications

(4 citation statements)

References 42 publications

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“…Such supersonic duct flows have been studied using both experimental and computational [22][23][24][25][26][27][28][29][30][31][32][33][34][35][36][37] approaches. The experimental studies have mainly used pressure measurements, laser Doppler velocimetry, and schlieren images to reconstruct the shocktrain structure.…”

Section: Introductionmentioning

confidence: 99%

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Numerical Investigation of Shock-Train Response to Inflow Boundary-Layer Variations

et al. 2017

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A dataset of normal shock trains in a rectangular cross-section channel has been created from direct numerical simulations in an effort to quantify the impact of inflow confinement ratio on the shock-train structure. To this end, the inlet boundary-layer momentum thickness was varied while the bulk inflow and outflow conditions remained constant. The simulations show that the shock train is displaced upstream as the inflow confinement ratio increases. Also, an increase in boundary-layer momentum thickness results in a reduction of the normal-like portion of the lambda-shock structures in the channel core. This leads to more numerous but weaker bifurcating shocks as well as an increase of the shock-train length. When the inflow boundary-layer thickness is varied temporally, the complex shocktrain response depends on the excitation frequency. A resonant frequency is observed when different components of the shock train exhibit the highest amplification in terms of pressure jumps. Further, the domain upstream of the leading shock acts as a low-pass filter, which has the end result of limiting the axial shock-train motion. Nevertheless, even a small oscillation in boundary-layer momentum thickness of 0.45 mm (0.6% of the channel height) is seen to increase the shock-train length by two orders of magnitude (4 cm).

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Section: Introductionmentioning

confidence: 99%

“…Other studies [12,[17][18][19]36,37] have focused on the physics of the unstart process, where the shock train is completely dislodged by an unsupportable pressure rise across the isolator section. Such instability can be caused either by upstream (change of flight conditions) or downstream (unstable combustion) perturbations.…”

Section: Introductionmentioning

confidence: 99%

Numerical Investigation of Shock-Train Response to Inflow Boundary-Layer Variations

et al. 2017

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“…Recent computational analyses of unstart have been extended to the HIFiRE-2 configuration (Riley et al 2016). Further analyses of unstart may be of interest, including reduced-order modeling based on LES results along with the deployment of flow control techniques to mitigate unstart and to formulate reliable procedures for engine restart.…”

Section: Unstart In Scramjet Enginesmentioning

confidence: 99%

Supersonic Combustion in Air-Breathing Propulsion Systems for Hypersonic Flight

Urzay

2018

Annu. Rev. Fluid Mech.

407

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Great efforts have been dedicated during the last decades to the research and development of hypersonic aircrafts that can fly at several times the speed of sound. These aerospace vehicles have revolutionary applications in national security as advanced hypersonic weapons, in space exploration as reusable stages for access to low Earth orbit, and in commercial aviation as fast long-range methods for air transportation of passengers around the globe. This review addresses the topic of supersonic combustion, which represents the central physical process that enables scramjet hypersonic propulsion systems to accelerate aircrafts to ultra-high speeds. The description focuses on recent experimental flights and ground-based research programs and highlights associated fundamental flow physics, subgrid-scale model development, and full-system numerical simulations.

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“…Additionally, steady-state and transient CFD calculations in two and three dimensions were conducted by Hoeger [9] to characterize the effect of backpressure on the shock train development and unstart in a separate rectangular inlet/isolator configuration. Riley et al [10,11] and Yentsch and Gaitonde [12,13] studied inlet unstart and mode transition of dual-mode ramjets with fixed geometry using transient CFD solutions.…”

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confidence: 99%

Computational Analysis of Unstart in Variable-Geometry Inlet

Reardon

Schetz

Lowe

2021

Journal of Propulsion and Power

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Computational fluid dynamics was used to study the flow through a scaled, mixed-compression, high-speed inlet with a rotating cowl at Mach 4.0 conditions. First, steady Reynolds-averaged Navier-Stokes computations were undertaken with a range of popular turbulence models including the Spalart-Allmaras model, the realizable k-ε model, the cubic k-ε model, and the Menter shear stress transport (SST) model to assess the impact on the inlet operating state. It was found that two models, the Spalart-Allmaras model and the Menter SST model, predicted the inlet to become unstarted at a cowl angle where the experimental data indicated the inlet remained started. Next, steady-state flow structures were studied at three discrete cowl positions, identifying highly three-dimensional flow features including regions of separated flow and spanwise gradients that became stronger as the cowl opened. Finally, the study culminated with the development of the new transient model, which allowed for time-accurate investigation into the unstart, restart, and hysteresis. The evolution of the separation bubbles was shown to be a major factor in the hysteresis, causing the inlet to restart at an angle different from where it unstarted. The utility of unsteady Reynolds-averaged Navier-Stokes computations to capture the complex time-dependent details of such flows was demonstrated.

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A Computational Investigation of Unstart in a Dual-Mode Scramjet

Cited by 6 publications

References 42 publications

Numerical Investigation of Shock-Train Response to Inflow Boundary-Layer Variations

Numerical Investigation of Shock-Train Response to Inflow Boundary-Layer Variations

Supersonic Combustion in Air-Breathing Propulsion Systems for Hypersonic Flight

Computational Analysis of Unstart in Variable-Geometry Inlet

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