Low order investigation on longitudinal combustion instability in a variable geometry single element combustor

Longitudinal high frequency combustion instability is the focus of the present work with particular attention to the CVRC single element combustor, characterized by the variable length of the oxidizer post. Three different geometrical configurations of CVRC combustor are examined and simulated through a quasi-1D Eulerian model, considering three different lengths of the post. The obtained flow field in the three cases is discussed and the limit cycle is described for all the configurations. Qualitative agreement with high fidelity numerical data and experimental data in the literature is obtained, showing marginal instability for the short post configuration and instability for the intermediate and long post. A detailed comparison of limit cycle obtained with high fidelity simulations and quasi-1D analysis is carried out, showing that the latter is characterized by pressure waves of higher intensity.