Investigation of the Effect of Surface Roughness on the Pulsating Flow in Combustion Chambers with LES

Pritz, Balázs; Magagnato, Franco; Gabi, Martin

doi:10.1007/978-3-540-85190-5_6

Cited by 5 publications

(4 citation statements)

References 12 publications

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“…Recently the Discrete Element Method (DEM) was implemented in our research code in order to model the effect of surface roughness. The simulations with DEM showed a good agreement with the experimental results [12].…”

Section: Introductionsupporting

confidence: 75%

A novel approach to predict the stability limits of combustion chambers with large eddy simulation

Pritz¹,

Magagnato²,

Gabi³

2010

J. Therm. Sci.

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Lean premixed combustion, which allows for reducing the production of thermal NOx, is prone to combustion instabilities. There is an extensive research to develop a reduced physical model, which allows -without time-consuming measurements -to calculate the resonance characteristics of a combustion system consisting of Helmholtz resonator type components (burner plenum, combustion chamber). For the formulation of this model numerical investigations by means of compressible Large Eddy Simulation (LES) were carried out. In these investigations the flow in the combustion chamber is isotherm, non-reacting and excited with a sinusoidal mass flow rate. Firstly a combustion chamber as a single resonator subsequently a coupled system of a burner plenum and a combustion chamber were investigated. In this paper the results of additional investigations of the single resonator are presented. The flow in the combustion chamber was investigated without excitation at the inlet. It was detected, that the mass flow rate at the outlet cross section is pulsating once the flow in the chamber is turbulent. The fast Fourier transform of the signal showed that the dominant mode is at the resonance frequency of the combustion chamber. This result sheds light on a very important source of self-excited combustion instabilities.Furthermore the LES can provide not only the damping ratio for the analytical model but the eigenfrequency of the resonator also.

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Section: Introductionsupporting

confidence: 75%

A novel approach to predict the stability limits of combustion chambers with large eddy simulation

Pritz¹,

Magagnato²,

Gabi³

2010

J. Therm. Sci.

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“…9. A detailed investigation of the pulsating flow is shown in (Pritz, 2010). In this section the resonance characteristics of the combustion chamber obtained from experiments and computations are compared by means of the amplitude and phase transfer functions.…”

Section: Comparison Of the Resultsmentioning

confidence: 99%

“…Damping is provided by the bulk viscosity during the pressure-volume work, the laminar viscosity in the oscillating boundary layer in the resonator neck, the vortex shedding at the ends of the resonator neck at the inflow and outflow and the dissipation of the kinetic energy through turbulence generation. Which source is dominating in the pulsating flow in the combustion system is discussed in (Pritz, 2010).…”

Section: Helmholtz Resonatormentioning

confidence: 99%

Stability Investigation of Combustion Chambers with LES

Pritz¹,

Gabi²

2012

Advanced Fluid Dynamics

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“…In swirl combustion, Al-Fahham et al [20] considered the use of biomimetic microsurfaces in a burner nozzle to enhance boundary layer flashback resistance, observing a reduction in the thickness of the near-wall velocity gradient, a reduction in boundary layer turbulence intensity, and a positive shift in the flashback equivalence ratio, u. Finally, Pritz et al [21] found improved agreement between experimental results and large eddy simulation which included surface roughness along selected geometric boundaries versus smooth walls, confirming that surface roughness can influence flow and flame stability. Thus, with the recent emergence of ALM as a tool for gas turbine combustor components, the need for and cost of postprocessing the components, and the potential for novel surface finishes, the impact of surface roughness on combustion systems requires further systematic study.…”

Section: Introductionmentioning

confidence: 99%

Characterization of Additive Layer Manufacturing Swirl Burner Surface Roughness and Its Effects on Flame Stability Using High-Speed Diagnostics

Runyon

Giles

Marsh

et al. 2020

Journal of Engineering for Gas Turbines and Power

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In this study, two Inconel 625 swirl nozzle inserts with identical bulk geometry were constructed via additive layer manufacturing (ALM) for use in a generic gas turbine swirl burner. Further postprocessing by grit blasting of one swirl nozzle insert results in a quantifiable change to the surface roughness characteristics when compared with the unprocessed ALM swirl nozzle insert or a third nozzle insert which has been manufactured using traditional machining methods. An evaluation of the influence of variable surface roughness effects from these swirl nozzle inserts is therefore performed under preheated isothermal and combustion conditions for premixed methane-air flames at thermal power of 25 kW. High-speed velocimetry at the swirler exit under isothermal conditions gives evidence of the change in near-wall boundary layer thickness and turbulent fluctuations resulting from the change in nozzle surface roughness. Under atmospheric combustion conditions, this influence is further quantified using a combination of dynamic pressure, high-speed OH* chemiluminescence, and exhaust gas emissions measurements to evaluate the flame stabilization mechanisms at the lean blowoff and rich stability limits. Notable differences in flame stabilization are evident as the surface roughness is varied, and changes in rich stability limit were investigated in relation to changes in the near-wall turbulence intensity. Results show that precise control of in-process or postprocess surface roughness of wetted surfaces can positively influence burner stability limits and NOx emissions and must, therefore, be carefully considered in the ALM burner design process as well as computational fluid dynamics (CFD) models.

show abstract

Investigation of the Effect of Surface Roughness on the Pulsating Flow in Combustion Chambers with LES

Cited by 5 publications

References 12 publications

A novel approach to predict the stability limits of combustion chambers with large eddy simulation

A novel approach to predict the stability limits of combustion chambers with large eddy simulation

Stability Investigation of Combustion Chambers with LES

Characterization of Additive Layer Manufacturing Swirl Burner Surface Roughness and Its Effects on Flame Stability Using High-Speed Diagnostics

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