Analysis of Acoustic Modes in Solid Fuel Ramjet Cavities

Acoustic perturbation in ramjet cavities affect both the performance and the structural integrity of the combustion chamber. In the proposed research we investigate the role of near wall processes on the formation and sustainment of acoustic modes in the ramjet combustion and mixing chambers. We focus on the presence of melt layers over fuel walls and their effect on the diffusion flames and the acoustic field they support. We perform high-order computational simulations of the ramjet combustion with regressing fuel walls using a novel discontinuous Galerkin approach, which allows us to obtain a fully conjugate solution of thermal field. Preliminary results show a good agreement of cold flow simulations against measurements from an experimental campaign conducted at Virginia Tech. We investigate the acoustic energy distribution using spectral proper orthogonal decomposition of the pressure field. We will present results of fuel injection from walls with and without cavity regression and compare them against new experimental measurements. We will discuss the role of changes in cavity shape on the acoustic frequencies and energy distribution.