Low-order model studies of combustion instabilities in a DVRC combustor

Experimental and numerical studies on Discrete Variable Resonant Combustor (DVRC) are presented with the main objective of investigating the acoustic role of oxidizer manifold. In the experimental set up the longitudinal single element combustor is characterized by the unchoked interface between oxidizer manifold and the combustor. The numerical study is carried out with two different approaches. One is based on linearized Euler equations, the other is based on quasi-1D Euler equations and allows to introduce perturbation on different quantities, i.e. mass flow rate boundary condition or heat release source term. Resonant frequencies and modal shapes are computed with both approaches and show good agreement with experimental data, provided that the perturbation, in the second approach, is applied within the combustion chamber and thus the manifold damping effect is limited. The manifold damping effect is clearly observed in the nonlinear regime which is discussed by the analysis of the solution obtained with the quasi-1D solver forcing with large perturbation different quantities.