A compact shock-focusing geometry for detonation initiation: Experiments and adjoint-based variational data assimilation

A shock-focusing geometry is proposed for a pulse detonation combustor, which exhibits a very short length for detonation initiation. This characteristic is imperative for the practical integration of such a combustor into a gas turbine. Experimental investigations are conducted in order to gain more understanding of the underlying processes and confirm the reliability of the geometry with respect to the success rate of the deflagration-to-detonation transition (DDT). The pressure evolution is measured at various locations in the detonation tube. Based on these data, a numerical simulation governed by the reactive, compressible Navier-Stokes equations is adapted by means of an adjoint-based data assimilation, where Arrhenius and diffusion parameters are adjusted. The resulting numerical model reproduces the experimental results very well and is used to obtain even more detailed information.