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|Besides adherence to the legally prescribed pollutant emission levels, one of the major problems in designing and optimising new combustion systems is reliably guaranteeing a stable combustion process over the entire control range. During the design, the current state of knowledge does not allow reliable predictions about the stability behaviour of burner/combustion chamber components. Consequently, the occurrence of periodic combustion instability often causes expensive and time-consuming investigations and modifications to the original version during commissioning.|
These self-sustaining, i.e. self-excited pressure/flame oscillations in a closed feedback circuit are characterised by time-periodic correlated fluctuations in the global fuel-reaction turnover of the flame and the static pressure in the combustion chamber, as well as in the upstream and downstream plant sections.
According to knowledge acquired at the chair for combustion technology, the formation and reaction of coherent, turbulent swirl structures is to be seen as the key exciting/sustaining mechanism in technical combustion systems (with swirl or bluff body stabilised premixing and diffusion flames) for the occurrence of self-excited pressure/flame oscillations.
Within this research focus the following research projects are associated:
The project is funded in the framework of Marie Skłodowska-Curie Actions as Innovative Training Network (ITN).
Air transportation is expected to grow persistently over the next decades. Clean combustion technology for aircraft engines is a key enabler to reduce the impact of this growth on ecosystems and humans’ health. The vision for European aviation is shaped by the Advisory Council for Aviation Research and Innovation in Europe in the Flight Path 2050 goals, which define stringent regulations on pollutant emissions.
To meet these goals, the major engine manufacturers develop lean premixed combustors operated at very high pressure. This development introduces a large risk for reduced reliability and lifetime of engines: pressure oscillations in the combustor called thermoacoustics.
Aviation industry encounters currently the fourth industrial revolution: cyber-physical systems analyze and monitor technical systems and take automated decisions. This industrial revolution is known as “Industry 4.0” in Germany and “Industrial Internet” in the USA. An essential enabler of the fourth industrial revolution is Machine Learning.
The ITN MAGISTER will utilize Machine Learning to predict and understand thermoacoustics in aircraft engine combustors, and to lead combustion research to a revolutionary new approach in this area.
Within this research focus in the past the following research projects were associated:
Improvement and optimisation of PERM system (together with AVIO, UNI FI, CIAM)
It has been shown that the commonly used surface radiation models without consideration of chemical reaction (combustion models) and without turbulence and soot formation models have to be re-considered. Instead, fluid dynamically driven coherent structures and CFD simulations of interacting fires have to be considered using the above mentioned sub models which partly have to be developed.
In particular, the knowledge about the interaction phenomena between two or even more pool fires will be investigated both, experimentally and numerically using CFD simulations. Additionally the knowledge about the length of the so-called clear combustion zone, which is not covered by black sooting regions, has to be deepened. Also the knowledge on the specific radiation (SEP) of single and interacting black sooting fires needs to be extended.
Of high importance and a pre-requisite for success of the above mentioned goals the knowledge on the elementary chemical reactions in peroxide pool flames has to be deepened, especially with respect to soot formation in such hydro-carbon pool flames. For this, mechanisms of soot formation will be improved and reaction mechanisms for the combustion of organic peroxides will be developed and integrated into CFD tools. Such tools can be flamelet models, which will be used int the present research work.
The current project aims to calculate quantitatively the generation mechanism and propagation of noise caused by turbulent combustion. Fully compressible Large Eddy Simulations (LES), hybrid CFD (Computational Fluid Dynamics)/CAA (Computational Aero-Acoustics) and Direct Numerical Simulation (DNS) are chosen as computational tools. The UTFC combustion model based on a TFC (Turbulent Flame Speed Closure) approach and a FGM (Flamelet Generated Manifold) tabulation procedure has been developed during this project which is used together with compressible LES for turbulent flames. This enables the direct computation of combustion noise from the resolved large scale fluctuations. The DNS will then be applied for investigation of noise within the sub grid scale. The project is connected with three other project partners from TU Darmstadt (Prof. J. Janicka), TU AAchen (Prof. W. Schröder) and TU Berlin (Prof. C.O. Paschereit) who make inkompressible LES, CAA-computation and measurement for the same burner configuration.
More information can be found on this page.