Abstract
This paper presents advancement on one–dimensional (1–D) unsteady modelling of a ram accelerator (RAMAC) in the sub–detonative velocity regime by including real–gas equations of state (EoS) in order to account for the compressibility effects of the combustion products. Several equations of state based on generalised empirical and theoretical considerations are incorporated into a 1–D computer code TARAM. The objective of this work is to provide the best available formulations in order to improve the unsteady 1–D model and make the TARAM code a useful tool to predict the performance of the RAMAC in the sub–detonative velocity regime, without having to resort to more complicated 2–D or 3–D computational schemes. The calculations are validated against experimental data from 38–mm and 90–mm–bore facilities and good agreements have been achieved. Yet, the results demonstrate the need for further CFD studies involving the scale effect.
Highlights
The ram accelerator (Hertzberg et al 1988), referred to, as RAMAC for brevity, is a propulsion concept based on using shock-induced combustion processes to accelerate projectiles up to very high velocity at a supersonic speed in a tube prefilled with a gaseous combustible mixture
Among a series of equations of state (EoS), the 1-D modelling of TARAM code is capable of using the ideal gas, Boltzmann, or Becker Kistiakowsky and Wilson (BKW) EoS; which were validated by comparison with experimental CJ speeds (Bauer et al 1991, 1996)
Whereas the BKW results over predict performance for this situation. This latter result is not unexpected since the CJ speed predicted for this propellant by BKW EoS is about 10% higher than that measured in experiments at this fill pressure
Summary
The ram accelerator (Hertzberg et al 1988), referred to, as RAMAC for brevity, is a propulsion concept based on using shock-induced combustion processes to accelerate projectiles up to very high velocity at a supersonic speed in a tube prefilled with a gaseous combustible mixture. The RAMAC technology is a multi-discipline investigation domain where several types of expertise are required, including aerodynamics, chemistry, thermodynamics, and material behavior The performance of such a device is dependent upon its physical configuration, i.e. RAMAC tube diameter and length, projectile dimensions, cross-section shapes, and the length-to-diameter ratio (L/D). In the sub-detonative mode, the thrust is generated by the high projectile base pressure resulting from a normal shock system that is stabilized on the body by thermal choking of the flow at the full tube area behind the projectile as shown in Fig. 1 (Hertzberg et al 1991)
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