Berechnung der Lärmemission von turbulenten Flammen mittels kompressibler Grobstruktursimulation und Direkter Numerischer Simulation

• Antragsteller: Professor Dr.-Ing. Henning Bockhorn
• Fachliche Zuordnung: Energieverfahrenstechnik
• Förderung: Förderung von 2010 bis 2019
• Projektkennung: Deutsche Forschungsgemeinschaft (DFG) - Projektnummer 135863701

• Erstellungsjahr: 2020

Zusammenfassung der Projektergebnisse

Large eddy simulations have been performed to study the generation of combustion noise from a generic lean premixed burner system. Although the time-averaged quantities from differnt modeling concepts are comparable, fluctuations of heat release rates and sound pressures in the spectral domain are under-estimated by LES compared with measured data, particularly in the high frequency range. The reason is attributable to the use of turbulence and combustion models on an under-resolved grid, which leads to an enhanced numerical diffusion and modified flame structures. The effect of grid resolution in LES has been extensively studied, where an increase in grid resolution results in an higher fluctuations of turbulent heat release rate and noise level in the high frequency. In order to study the effect of combustion modeling in a more systematical way, the same formulations used by LES for the mean rate are applied to an excited plane-jet flame using equidistant grid cells and forced inflow conditions, thereby excluding the influence of varying grid resolution and broadband turbulent fluctuations. This setup is specifically tailored for a detailed analysis of flame response to flow unsteadiness and grid resolution. The formulation of the reaction rate according to the turbulent flame-speed closure (TFC) approach results in a considerably thicker flame compared to results obtained from the dynamically thickened flame (DTF) model and direct numerical simulation, even on a sufficiently fine mesh Therefore, the DTF formulation of the reaction rate shows overall stronger responses of heat release rates to forced fluctuations than the TFC formulation. Differences are smaller in the low-frequency range, indicating a stronger damping of heat release fluctuations with increasing frequency for the TFC formulation. Coarsening the grid leads to a much stronger damping of heat release fluctuations in the DTF formulation compared with the TFC formulation, so that the benefit of the DTF formulation decreases with decreasing grid resolution. This reflects the different sensitivity behavior of these models with respect to unsteady flows and grid resolutions, which is of great importance for computing thermoacoustic problems with LES, for example, combustion noise. Based on further direct numerical simulation (DNS) of 3D turbulent flames, a first-order estimation for the prediction of combustion-generated noise from turbulent premixed flames has been proposed. The method is based on Lighthill’s acoustic analogy and uses experimental data from high-speed imaging of chemiluminescent emissions as input. To determine the noise-generating source, i.e., the overall heat release rate from the measured chemiluminescence signals, DNS have been carried out fo 3D turbulent freely propagating flames, employing detailed transport model and reaction mechanism including the full reaction chain of the chemiluminescent hydroxyl radical (OH*). It has been shown that the local generation of OH* correlates strongly with the heat released from the chemical reaction, especially in the fuel-lean range. As the chemiluminescence measurement gathers light only along the viewing direction, the line-of-sight summed values of heat release rate and OH* concentration have been evaluated from the 3D simulation and a quasilinear relationship has been identified for these integral values. Hence, a linear relation has been applied for the computation of the integral heat release from measured chemiluminescence intensity. An analytical solution of Lighthill’s wave equation serves as a transfer function, which takes fluctuations of the total heat release rate or light intensity as input to calculate the sound radiation in the far field. This approach has been applied to the generic burner experimentally studied at TU Berlin. Good quantitative agreement is obtained between the sound pressures derived from the chemiluminescence measurement and microphone data, which justifies the potential of the analytical model for applications to more complex flame configurations.

Projektbezogene Publikationen (Auswahl)

• Impact of Grid Refinement on Turbulent Combustion and Combustion Noise Modeling with Large Eddy Simulation, in High Performance Computing in Science and Engineering ’13, Wolfgang E. Nagel, Dietmar H. Kröner, Michael M. Resch (ed.), Springer International Publishing, 259-274, 2014
  F. Zhang, H. Bonart, P. Habisreuther, H. Bockhorn
  
• Direct Numerical Simulation of Chemically Reacting Flows with the Public Domain Code OpenFOAM. In High Performance Computing in Science and Engineering ’14, Nagel, Wolfgang E. and Kröner, Dietmar H. and Resch, Michael M. (ed.), Springer International Publishing, 221-236, 2015
  F. Zhang, H. Bonart, T. Zirwes, P. Habisreuther, H. Bockhorn, N. Zarzalis
  
• Numerical Simulation of Turbulent Combustion with a Multi-Regional Approach. In High Performance Computing in Science and Engineering ’15, Nagel, Wolfgang E., Kröner, Dietmar H., Resch, Michael M. (ed.), Springer International Publishing, Cham, 267-280, 2016
  F. Zhang, T. Zirwes, P. Habisreuther, H. Bockhorn
  
• A DNS Analysis of the Correlation of Heat Release Rate with Chemiluminescence Emissions in Turbulent Combustion. In High Performance Computing in Science and Engineering ’16, Nagel, Wolfgang E., Kröner, Dietmar H., Resch, Michael M. (ed.), Springer International Publishing, 2017
  F. Zhang, T. Zirwes, P. Habisreuther, H. Bockhorn
  
• Combustion generated noise: an environment related issue for future combustion systems. Energy Technol 5, 1045-1054, 2017
  F. Zhang, T. Zirwes, H. Nawroth, P. Habisreuther, H. Bockhorn, C.O. Paschereit
  
• Effect of unsteady stretching on the flame local dynamics. Combust Flame 175, 170-179, 2017
  F. Zhang, T. Zirwes, P. Habisreuther, H. Bockhorn
  
• Towards Reduction of Computational Cost for Large-Scale Combustion Modeling with a Multi-Regional Concept. Prog Comput Fluid DY 18 (6) 333-346, 2018
  F. Zhang, T. Zirwes, P. Habisreuther, H. Bockhorn
  
• Impact of Combustion Modeling on the Spectral Response of Heat Release in LES. Combust Sci Technol 191(9) 1520-1540, 2019
  F. Zhang, T. Zirwes, P. Habisreuther, H. Bockhorn, D. Trimis, H. Nawroth, C.O. Paschereit
  
• LES of Combustion Noise from a Turbulent Premixed Flame. 17th International Conference on Numerical Combustion, 6.-8. May 2019, Aachen, Germany
  F. Zhang, T. Zirwes, P. Habisreuther, H. Bockhorn, D. Trimis
  
• Noise sources of lean premixed flames, Flow. Turbul. Combust. 103(3), 773–796, 2019
  K. Pausch, S. Herff, F. Zhang, H. Bockhorn, and W. Schröder
  
• Quasi-DNS Dataset of a Piloted Flame with Inhomogeneous Inlet Conditions, Flow. Turbul. Combust. (2019)
  T. Zirwes, F. Zhang, P. Habisreuther, M. Hansinger, H. Bockhorn, M. Pfitzner, D. Trimis
  
• Spectral response of heat release in LES combustion modeling. 17th International Conference on Numerical Combustion, Aachen, Germany, 6.-8. May 2019
  F. Zhang, T. Zirwes, P. Habisreuther, H. Bockhorn, D. Trimis