Computation of a Nonequilibrium Expansion Flow in a Single Expansion Ramp Nozzle

Kurzfassung

The simulation of the flow inside the propulsion system is of essential interest, for the design of airbreating hypersonic vehicles. To compute accurately the expansion flow of a hydrogen/air mixture at high temperatures, the chemical and vibrational nonequilibrium effects must be taken into account. A finite element code is used to model chemical reactions considering finite-rate chemistry and vibrational relaxations according to the Landau-Teller theory (Landau, L., and Teller, E., "Zur Theorie der Schalldispersion", Physikalische Zeitschrift der Sowjetunion, Vol. 10, No. 1, 1936, pp. 34-43). The computational domain is discretized by applying unstructured adaptive grids. Different test cases are computed, and the results are compared with measured and numerical data. In one test case, a remarkable difference between the rotational and vibrational temperature of a hydrogen/air nozzle flow is seen. This difference in the experiment is also supported by the computation. Because the applied relaxation rates are small compared to other data given in literature, the thermal nonequilibrium effects gain more importance.