Comprehensive Analysis of the CVRC Test Case using Low-Order Modeling of Combustion Instability

This study explores the application of an in-house low-order numerical tool to analyze and predict longitudinal high-frequency combustion instabilities in a single-injector setup. A non-linear Eulerian model for multi-species reactive flows is employed for this purpose. The numerical tool adopts a physics-based response function formulation to replicate the behavior of shear coaxial injectors, which have recently been shown to exhibit cyclic fuel accumulation and release in response to acoustic perturbations. In this model, pressure waves are linked to unsteady fuel mass flow rate supplied by the injectors, preserving a possible physical causality between acoustic perturbations and unsteady heat release, relationship which is at the base of thermo-acoustic phenomena. The investigation is focused on the entire CVRC dataset. This test case, which shows combustion instability at the first longitudinal mode of the chamber (1L), is of particular interest as it presents limit cycle features for 17 different injector lengths, and as it includes both stable and unstable conditions, allowing us to thoroughly test the predictive capabilities of the employed numerical tool. Results show a good agreement with experimental data, particularly in terms of limit cycle frequency. The model successfully predicts variations in limit cycle features in response to changes in injector length and proves its capabilities in differentiating between stable and unstable load points, also offering valuable insights into their phenomenologies.