Numerical refinement of the 1D modeling of ram accelerator in sub-detonative propulsion mode
- Paper number
IAC-06-C4.5.08
- Author
Mr. Tarek Bengherbia, Kingston University, United Kingdom
- Coauthor
Dr. Yao Yufeng, Kingston University, United Kingdom
- Coauthor
Prof. Pascal Bauer, France
- Year
2006
- Abstract
Several modes of ram accelerator propulsion have been investigated experimentally and theoretically. One important feature is the thermally choked sub-detonative mode, which operates at Mach numbers ranging from 2.5 to 4 with projectile velocities below the Chapman-Jouguet detonation speed. The thrust is thus provided by high projectile base pressure resulting from a normal shock that is stabilized on the body. Earlier studies were based on one dimensional control-volume modeling of the flow. Result from this theory has showed good agreement with test data derived from experiments conducted in the sub-detonative mode. Besides, it has been observed that given mixture composition could have various behaviors ranging from the non-initiation to the direct onset of the detonation, namely, the projectile shape, and more specially the shape of the fins and the sabot downstream. Numerical investigations dealing with this type of combustion are numerous and they have often been used to validate numerical codes. More recently, a thorough analysis by present authors has taken account of the whole projectile including the fins and sabot downstream. The predicted thermal choking pressure point performed in success numerically for the first time and agrees fairly well with both the experimental data and a quasi one-dimensional theoretical estimation. Moreover at initial pressures beyond 10 MPa, the acceleration is such that the quasi-steady 1D modeling is no longer valid. Instead, a non-steady modeling has to be considered as previous did by Bauer. It involves the thermodynamic description of the flow change between entry and exit of a control volume that includes the projectile and the reaction zone behind the projectile. This control volume is a key element in the modeling and there is no available theoretical data that helps defining it precisely. Based on our previous experience of numerical simulation of ram acceleration, this paper will extend the study by merely focusing on providing a series of data that show the Mach number influence on the control volume length. Besides the determination of the induction length, this investigation requires the correlation of the combustion zone length to the incoming Mach number. As a next step, the calculation of the acceleration of the projectile is required in order to provide the appropriate validation against the test results. A generic RAMAC configuration will be adopted for this purpose, similar to that adopted in previous work.
- Abstract document