| Popis: |
Experiments have shown that the self-adjustment mechanism of supersonic flow in scramjetsis due to the spontaneous appearance of shock waves of variable strength at the entrance to the combustion chamber. In order to model this mechanism, one must find a criterion for the selection of the proper physical solution, since no equation is available to compensate for the additional degree of freedom due to the variable shock strength. In this paper the variation of the combustion efficiency—rather than the change in static pressue employed by Billig, Dugger and coworkers—is used for closing the system of equations that governs the flow. This variation is assumed to be affected by the initial shock strength. It is also postulated that, among all the mathematical solutions, the flow will choose the one giving the smallest entropy increase between the initial and final states of the flow (entrance to and exit from the combustion chamber, respectively). A computer program, based on this model, is presented and good agreement with measurements is demonstrated for a set of experimental data. Some preliminary conclusions, resulting from a parametric investigation of the flow behaviour in a supersonic combustor, are also presented. |
