Advanced Boundary Conditions for Thermoacoustic Solvers
by Nicolas de Jong and Wolfgang Polifke
Motivation
The transition toward a climate-neutral energy system places new demands on gas-turbine technology. Modern low-emission combustors must remain stable and efficient under variable operating conditions and when fueled with CO2 -neutral alternatives such as hydrogen. However, such flexibility increases the risk of thermoacoustic combustion instabilities, self-excited oscillations caused by feedback between unsteady heat release and acoustic pressure waves.
Although numerical tools for predicting these instabilities have advanced significantly, they remain limited by simplified acoustic boundary conditions. In particular, existing solvers can not accurately model the stabilizing effect of acoustic dampers such as Helmholtz resonatorsor multi-perforated plates (MPPs) used in combustor liners.
The scientific goal of this project is therefore the development, implementation, and validation of advanced acoustic boundary and coupling conditions, formulated in a state-
space representation, that allow physically consistent and computationally efficient simulation of liners, resonators, and similar damping elements.
Objectives
- Develop a flexible state-space formulation of acoustic boundary and coupling conditions.
- Implement these formulations in the open-source solver Nektar++ for multiple linearized perturbation equation systems (Wave, APE, LNSE).
- Validate the new models against experimental data from the Rolls-Royce SCARLET test facility.
- Apply the framework to analyze the thermoacoustic stability of two industrially relevant combustor variants.
Expected Impact
- Improved prediction of thermoacoustic instabilities and liner damping performance.
- Validated, open, and extensible simulation framework for frequency-dependent acoustic boundary modeling.
- Earlier detection and mitigation of thermoacoustic risks, reducing development costs.
- Dissemination through peer-reviewed publications and conference presentations.
- Education of qualified researchers and doctoral candidates in thermoacoustics and hydrogen combustion technologies.
Acknowledgement
This Project is a collaboration with Rolls-Royce under AG-Turbo