Detonation loading of tubes in the modified shear wave speed regime
We performed experiments and numerical simulations on a thin-wall aluminum tube with internal gaseous detonation loading in the modified shear wave speed regime. Strain gauges were used to determine the time-dependent hoop strain on the surface of the tube. The experimental results were compared with analytical models and numerical simulations with explicit finite element computation treating the detonation as a traveling load. Hoop strain amplification factors (defined as the ratio of the dynamic strain to the equivalent static strain) close to two were obtained both in the present experiments and simulations. No resonance phenomena in the hoop strain were found in either experiments or simulations. Computations reveal the existence of a resonance in the shear strain.
3D numerical simulation of the gas detonation forming of aluminum tubes considering fluid-structure interaction and chemical kinetic model
Abstract The present study deals with the numerical simulation of the dynamic response of the pure aluminum AA1050 tube under internal gas mixture detonation loading. This practical topic involves structural large plastic deformation, fluid motion, and chemical reaction, and detonation wave/structure interaction. Therefore, the Fluid-Structure Interaction (FSI) with finite-rate chemistry in compressible Conservation Element/Solution Element (CESE) solver with the Immersed Boundary Method (IBM) was used to model the real situation of the whole forming process. The numerical model was verified with existing experimental data for aluminum tubes under internal gas detonation of H2+O2 in terms of the pressure-time history and deformation pattern. Moreover, the simulation results were also compared to those numerical ones in the open literature. It is found that the current numerical modelling approach reproduces the experimental observations very well, and it has a more accurate prediction capability in comparison to the reported study. Hence, the present numerical approach can be used for the design of pressure vessels and piping systems subjected to internal gas detonation loading and also further studies on hazard analysis of pipeline explosion accidents. Moreover, the effect of ignition point location, double ignition points, initial pressure, and repeated loading on the response was investigated. The results show that an experimental setup with double ignition points gives a uniform distribution for plastic deformation in the longitudinal direction of the tube while the ignition point is located at a distance of 1/6 length of the tube from both ends. Furthermore, the double gas detonation loading at the low initial pressure of 0.85 MPa gives the same result obtained for single loading at the moderate initial pressure of 1.2 MPa.
THE PERFORMANCE OF STEADY DETONATION ENGINES
Propulsion systems driven by steady normal detonations are studied. The practical di‐culties associated with stabilizing a detonation wave are highlighted. The requirement on the freestream total enthalpy is considered in parallel with efiects such as condensation or auto-ignition of the fuel-air mixture and limitations associated with fuel sensitivity to detonation. A criterion for detonation stabilization is formulated and applied to an analytical treatment of a detonation ramjet and a detonation turbojet, which are the respective analogs of the ramjet and the turbojet using detonative combustion. The performance of these engines is evaluated and compared to the ideal ramjet and turbojet models for hydrogen and JP10. A limitation is placed on the maximum total temperature allowed in the combustor, based on material considerations. The results show that steady detonation engines have a small thrust-producing range, due to the requirements for detonation stabilization. Their performance is always lower than that of the conventional ramjet and turbojet because of the total pressure loss across the detonation.