Aug 26 2015 02:00 PM
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Aug 26 2015 03:00 AM
On Wednesday, 26 August 2015, a seminar on the
'Thermoacoustic Instabilities in Annular Combustion Chambers: Linear and
Non-Linear Phenomena' by Prof. Jonas Moeck was hosted at the Clean
Combustion Research Center. The abstract of the seminar is given below:
Abstract
Thermoacoustic
instabilities frequently appear in various combustion systems in the form of
high-amplitude pressure oscillations. This undesirable dynamic phenomenon that
originates from the interaction of unsteady heat release rate and the acoustic
modes of the combustion chamber has been particularly plaguing for the
development of low-emission gas turbine technology. After a brief introduction
to the topic, Prof. Moeck discussed some aspects that are specific to annular
combustion chambers, as they are found in aeroengines and in most gas turbines
for power generation. These combustors exhibit some special dynamical features
associated with their discrete rotational symmetry. After introducing the key
aspects of the linear properties of thermoacoustic modes in this type of
system, he presented a new, efficient modeling approach that fully exploits
the discrete rotational symmetry to compute linear stability properties. This
technique is applied to determine thermoacoustic modes in an industrial gas
turbine combustor and gives results in excellent agreement with a full
computation. At finite amplitude, when the flame response saturates, additional
phenomena appear, such as the existence of multiple limit cycle solutions or
the nonlinear interaction of modes in the form of synchronized two-mode oscillations;
the latter is shown to give rise to a slanted mode pattern, which was recently
observed in experiments. These phenomena can be qualitatively modeled using
coupled nonlinear oscillator models. He also presented some recent results
based on this approach.
Bio
Jonas
Moeck is an Assistant Professor of combustion dynamics at the Technical
University of Berlin. He received his engineering degree and PhD also from the
Technical University Berlin and had a postdoc position at Ecole Centrale,
Paris. His research focuses on flame dynamics, active control of combustion
instabilities, and low-order modeling and stability analysis.