Numerical study of gaseous reactive flow over a ram accelerator projectile in subdetonative velocity regime

Bengherbia, Tarek; Yao, Yufeng; Bauer, Pascal; Knowlen, C.

doi:10.1051/epjap/2011100087

Cited by 4 publications

(1 citation statement)

References 25 publications

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“…Quasi-steady and unsteady one-dimensional modeling of the thermally choked ram accelerator in a SBRA showed that in the Mach range of 3 to 4, thrust estimates of the unsteady one-dimensional model agree with the experimental results [21]. Standard quasi-steady model for simplicity is briefly described in this section and the details of unsteady one-dimensional modeling are shown by Bundy et al and Bengherbia [22,23].…”

Section: Theorymentioning

confidence: 79%

Transient computational fluid dynamic modeling of baffled tube ram accelerator

Daneshvaran

Knowlen

2017

55th AIAA Aerospace Sciences Meeting

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The minimum entrance Mach number that allowed supersonic projectile transit through a baffled tube filled with inert gas and the thrust generated in reactive flow were examined. The primary parameters considered were chamber-to-projectile diameter ratio, projectile geometry, baffle thickness, baffle spacing and baffle geometry. Axisymmetric and three-dimensional simulations used a dynamic mesh for a projectile moving at constant Mach (ranging from 1.8 to 5.1) through stationary baffles. The maximum baffle thickness and minimum baffle spacing at velocities near the minimum allowable entrance Mach number were both found to be ~53% of the projectile diameter. Further reducing the baffle spacing resulted in the projectile pushing a normal shockwave ahead of it like in a jet engine unstart. It was also found that thicker baffles and closer baffle spacing increased the projectile drag coefficient. Reactive flow phenomena were investigated by first establishing the combustion on the projectile in a smooth bore tube before it entered the baffled-tube section. A key finding from premixed methane and oxygen propellant simulations was that aftward-slanted baffles generated higher thrust than when the baffles were normal to the projectile or forward-slanted. This increase in thrust was associated with more complete propellant combustion in the annular baffle chambers around the tail and base sections of the axisymmetric projectile, as well as immediately behind it. It was also determined that residence time of the propellant during combustion process in the vicinity of the projectile at any given baffle, influences the overall thrust production. As the projectile Mach increases, both the propellant residence time and overall thrust level decrease. 6. Baffled tube parameters include chamber-to-projectile diameter ratio (dc/dp), baffle thickness (tb), and chamber width (wc

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Section: Theorymentioning

confidence: 79%

Transient computational fluid dynamic modeling of baffled tube ram accelerator

Daneshvaran

Knowlen

2017

55th AIAA Aerospace Sciences Meeting

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The Ram Accelerator: Review of Experimental Research Activities in the U.S.

Bruckner

Knowlen

2016

Hypervelocity Launchers

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Improved One-Dimensional Unsteady Modeling of Thermally Choked Ram Accelerator in Subdetonative Velocity Regime

Bengherbia

Yao

Bauer

et al. 2011

Journal of Applied Mechanics

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The subdetonative propulsion mode using thermal choking has been studied with a one-dimensional (1D) real gas model that included projectile acceleration. Numerical results from a control volume analysis that accounted for unsteady flow effects established that the thrust coefficient versus Mach number profile was lower than that obtained with a quasi-steady model. This deviation correlates with experimental results obtained in a 38-mm-bore ram accelerator at 5.15 MPa fill pressure. Theoretical calculations were initially carried out with the assumption that the combustion process thermally choked the flow about one projectile length behind the projectile base. Thus the control volume length used in this 1D modeling was twice the projectile length, which is consistent with experimental observations at velocities corresponding to Mach number less than 3.5. Yet the choice of the length of the combustion zone and thus the control volume length remains a key issue in the unsteady modeling of the ram accelerator. The present paper provides a refinement of the unsteady one-dimensional model in which the effect of control volume length on the thrust coefficient and the projectile acceleration were investigated. For this purpose the control volume length determined from computational fluid dynamics (CFD) as a function of projectile Mach number was applied. The CFD modeling utilized the Reynolds-averaged Navier-Stokes (RANS) equations to numerically simulate the reacting flow in the ram accelerator. The shear-stress transport turbulence and the eddy dissipation combustion models were used along with a detailed chemical kinetic mechanism with six species and five-step reactions to account for the influence of turbulence and rate of heat release on the length of the combustion zone. These CFD computational results provided Mach number dependent estimates for the control volume length that were implemented in the 1D modeling. Results from the proposed improved 1D unsteady modeling were compared and validated with ram accelerator experimental data with significant improvements in terms of the predicted thrust dependence on Mach number.

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Numerical study of gaseous reactive flow over a ram accelerator projectile in subdetonative velocity regime

Cited by 4 publications

References 25 publications

Transient computational fluid dynamic modeling of baffled tube ram accelerator

Transient computational fluid dynamic modeling of baffled tube ram accelerator

The Ram Accelerator: Review of Experimental Research Activities in the U.S.

Improved One-Dimensional Unsteady Modeling of Thermally Choked Ram Accelerator in Subdetonative Velocity Regime

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