Unsteady-State Simulation of Model Ram Accelerator in Expansion Tube

Steady- and unsteady-state numerical simulations have been carried out to investigate the ram accelerator flowfield that had been studied experimentally using an expansion tube facility at Stanford University. Navier-Stokes equations for chemically reactive flows were used for the modeling with a detailed hydrogen-air combustion mechanism. The governing equations were analyzed using a fully implicit and time-accurate total variation diminishing scheme. As a result, steady-state simulation reveals that the near-wall combustion regions are induced by aerodynamic heating in the separated flow region. This result agrees well with experiments in the case of the 2H 2 + O 2 + 17N 2 mixture but fails to reproduce the centerline combustion in the case of the 2H 2 + O 2 + 12N 2 mixture. To investigate the reason for this disagreement in the flow establishment process, unsteady-state simulations have been carried out, and the results show the detailed process of flow stabilization. The centerline combustion is revealed to be an intermediate process during flow stabilization. It is induced behind a Mach stem formed by the intersection of strong oblique shock waves at an early stage of the flow stabilization process

[1]  J. Driscoll,et al.  Shock-wave-enhancement of the mixing and the stability limits of supersonic hydrogen-air jet flames , 1996 .

[2]  S. Yungster,et al.  Reacting Flow Establishment in Ram Accelerators: A Numerical Study , 1998 .

[3]  E. Oran,et al.  Detonation structures generated by multiple shocks on ram-accelerator projectiles , 1997 .

[4]  Michael J. Nusca,et al.  Reacting Flow Simulation for a Large-Scale Ram Accelerator. , 1996 .

[5]  A. Hertzberg,et al.  Ram accelerator - A new chemical method for accelerating projectilesto ultrahigh velocities , 1988 .

[6]  Adam P. Bruckner,et al.  High acceleration experiments using a multi-stage ram accelerator , 1998 .

[7]  Seokkwan Yoon,et al.  Numerical study of chemically reacting flows using a lower-upper symmetric successive overrelaxation scheme , 1989 .

[8]  Kazuyoshi Takayama,et al.  Operation tests of a 25-mm-bore ram accelerator , 1996 .

[9]  R. Hanson,et al.  Expansion tube investigation of ram-accelerator projectile flowfields , 1996 .

[10]  In-Seuck Jeung,et al.  Numerical study of scram accelerator starting characteristics , 1998 .

[11]  Elaine S. Oran,et al.  Stability of Projectiles in Thermally Choked Ram Accelerators , 1996 .

[12]  P. A. Thibault,et al.  Studies on Detonation Driven Hollow Projectiles , 1994 .

[13]  David W. Bogdanoff.  Ram accelerator direct space launch system - New concepts , 1992 .

[14]  Adam P. Bruckner,et al.  Hollow projectile operation in the ram accelerator , 1996 .

[15]  Jeong-Yeol Choi,et al.  Numerical investigation of ram accelerator flow field in expansion tube , 1998 .

[16]  A. Hertzberg,et al.  In-Tube Photography of Ram Accelerator Projectiles , 1995 .

[17]  Shaye Yungster,et al.  Numerical study of shock-wave/boundary-layer interactions in premixed combustible gases , 1992 .