Session: 04-43 Combustion dynamics - modeling I

Paper Number: 124263

124263 - Model-Based Inference of Flame Transfer Matrices From Acoustic Measurements in an Aero-Engine Test Rig 

Flame dynamics in the form of a flame transfer matrix (FTM) is not directly measurable in an experimental test rig, but must be deduced from transfer matrix measurements of the entire combustion system. The established approach for estimating the FTM is based on local pressure signals from two microphone arrays located upstream and downstream of the combustor. It combines acoustic transfer matrix measurements in non-reacting and reacting conditions, where the latter implicitly includes the flame. A simple matrix operation then yields the FTM. However, this approach assumes that there is loss-free wave propagation at constant speed of sound with no change in cross-sectional area between the microphone location and the burner/flame. The present work demonstrates the limitations of these assumptions when applied to a test rig with more complex features such as effusion cooling, bypass annulus, and downstream end contraction. To remedy the shortcomings of the established approach, this work proposes a generalized method to infer the FTM for arbitrarily complex combustors by combining reactive transfer matrix measurements of the entire combustor with an accurate low-order thermoacoustic network model (LOM) of the test rig. This generalized method yields the established approach as a special case.

Throughout this work, the Rolls-Royce Scaled Acoustic Rig for Low Emission Technology (SCARLET) is used as an exemplary complex combustor to analyze the capabilities of the proposed model-based inference method and the limitations of the established approach. In a first step, a LOM based on the geometry and operating point of SCARLET is created using a synthetic FTM. This synthetic model is used to visualize the limitations of the established method in terms of different physical and geometrical parameters. Subsequently, the sensitivity of the proposed inference method with respect to measurement and modeling errors is analyzed using Monte Carlo simulations. Finally, experimental measurement data is used to deduce the FTM of SCARLET using the proposed approach.

Presenting Author: Alexander J. Eder Technical University of Munich

Presenting Author Biography: Alexander J. Eder is a research associate and PhD candidate in the research group of Prof. Wolfgang Polifke at the Technical University of Munich (TUM). His research focuses on the modeling of entropy waves and dynamics of partially premixed flames in aero-engine combustors using low-order modeling and high-fidelity numerical simulation. This research is carried out in close collaboration with Rolls-Royce Deutschland Ltd & Co KG and ETH Zurich within the framework of a DFG transfer project.

Authors:

Alexander J. Eder Technical University of Munich
Moritz Merk Technical University of Munich
Thomas Hollweck Technical University of Munich
André Fischer Rolls-Royce Deutschland
Claus Lahiri Rolls-Royce Deutschland
Camilo F. Silva Technical University of Munich
Wolfgang Polifke Technical University of Munich