No abstract

Elastic and plastic deformation of tubes to internal detonations and the shock waves produced by their reflection were investigated. The study included experimental measurements as well as computational modeling. Tests with stoichiometric ethylene-oxygen mixtures were performed at various initial pressures and strain was measured on thin-walled mild-steel tubes. The range of initial pressures covered the span from entirely elastic to fully plastic deformation modes. A model for the pressure load on the tube wall was developed and tested against experimental measurements. This model was applied as a boundary condition in both a single degree of freedom model of the tube cross section and a finite element model of the entire tube. Comparison of computational and experimental results showed reasonable agreement if both strain-rate and strain-hardening effects were accounted for. A unique mode of periodic radial deformation was discovered and explained through modeling as the result of flexural wave interference effects.

No abstract

A rotating detonation engine (RDE) at the Air Force Research Lab (AFRL) has been modified to allow optical access to the annulus while in operation. High speed video of chemiluminescence was taken for three operating conditions to characterize the RDE flowfield. Two-dimensional representations of the entire RDE are presented to show basic flow structure. Detonation height, detonation angle, oblique shock wave angle, shear layer angle, and contact surface angle were measured. Average value for each of these measurements did not change drastically over the range tested, but large deviations of the values were observed. These considerable deviations of the flowfield point toward device variation as a major factor to be understood.