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ThermoacOustic instabilities contRol in sequential Combustion cHambers

Periodic Reporting for period 2 - TORCH (ThermoacOustic instabilities contRol in sequential Combustion cHambers)

Reporting period: 2021-03-01 to 2022-08-31

A new type of combustor architecture for large gas turbines has emerged in recent years: sequential combustion systems operated at constant pressure. This major technology change results from the need for more operationally and fuel flexible gas turbines, for future sustainable energy networks. A gas turbine equipped with such combustor produces several hundred megawatt of electricity, and this new architecture enables clean combustion of Hydrogen at high efficiency and high power output, which was out of reach a few years ago. As for regular gas turbines, the risk of combustor breakdown due to thermoacoustic instabilities is a major challenge. While the harmful consequences of these instabilities in novel sequential combustors can be as dramatic as in conventional systems, the associated physics is considerably complexified, because the two flames not only “talk” together via sound waves, but also via entropy waves. Our aim is to propose, investigate and develop novel active and passive control technologies, tailored for this new generation of combustors, in order to suppress their thermoacoustic instabilities. It brings significant scientific challenges in fluid mechanics, acoustics, combustion, nonlinear dynamics and control theory.
The project TORCH is on track. Many steps were successfully taken, including 1) the recruitment of all the members of the project team, 2) the conception of the prototype combustor, the manufacturing and testing of all its modules at atmospheric condition, 3) the adaptation of the laboratory infrastructure for the TORCH project to enable experiments at elevated pressure, and 4) several key scientific objectives of the project were attained.
We address the problem of controlling the thermoacoutic instabilities on two unexplored fronts:
First, we significantly move forward the state-of-the-art in passive control of combustion instabilities, by creating acoustic metamaterials with unprecedented thermoacoustic damping properties, and capable of long term operation in harsh environments. A new passive control concept has been developped from scratch and it is currently subject to intense research for demonstrating its capabilities at relevant conditions and explain the details of the underlying physics.
Second, we address scientific challenges, required to successfully achieve active combustion control in sequential combustors, by distributing non-equilibrium plasma discharges to locally and dynamically enhance the autoignition chemistry. The plasma-based active control has been already demonstrated at atmospheric condition, and new models of plasma and combustion kinetics have been developped to simulate the complex turbulent reacting flow.