0
Gas Turbines: Combustion, Fuels, and Emissions

Effects of Outlet Boundary Conditions on the Reacting Flow Field in a Swirl-Stabilized Burner at Dry and Humid Conditions

[+] Author and Article Information
Steffen Terhaar1

 Chair of Fluid Dynamics Hermann-Föttinger-Institut, Technische Universität Berlin, Müller-Breslau-Str. 8, 10623 Berlin, Germanysteffen.terhaar@tu-berlin.de

Bernhard C. Bobusch, Christian Oliver Paschereit

 Chair of Fluid Dynamics Hermann-Föttinger-Institut, Technische Universität Berlin, Müller-Breslau-Str. 8, 10623 Berlin, Germany

1

Corresponding author.

J. Eng. Gas Turbines Power 134(11), 111501 (Sep 20, 2012) (9 pages) doi:10.1115/1.4007165 History: Received June 18, 2012; Revised July 06, 2012; Published September 20, 2012

During the design and testing process of swirl-stabilized combustors, it is often impractical to maintain identical outlet boundary conditions. Furthermore, it is a common practice to intentionally change the acoustic boundary conditions of the outlet in order to suppress thermoacoustic instabilities. In the presented work the susceptibility of the reacting flow field to downstream perturbations is assessed by the application of an area contraction at the outlet. Since combustion and fuel composition are shown to be important parameters for the influence of the boundary conditions on the flow field, highly steam diluted flames are investigated in addition to dry flames at different equivalence ratios and degrees of swirl. The applied measurement techniques include particle image velocimetry, laser doppler velocimetry, and emission analysis. The results reveal a clear correlation of the susceptibility of the flow field to downstream perturbations to both the inlet swirl number and the amount of dilatation caused by the flame. The concept of an effective swirl number downstream of the flame is applied to the results and is proven to be the dominating parameter. A theoretical explanation for the influence of this parameter is provided by the usage of the well known theory of subcritical and supercritical swirling flows, where perturbations can propagate upstream solely in subcritical flows via standing waves. Knowledge of the flow state is of particular importance for the evaluation of combustion tests with differing exit boundary conditions and the results emphasize the need for realistic exit boundary conditions for numerical simulations.

Copyright © 2012 by American Society of Mechanical Engineers
Your Session has timed out. Please sign back in to continue.

References

Figures

Grahic Jump Location
Figure 1

(a) Generic burner and (b) movable block swirl generator

Grahic Jump Location
Figure 2

Sketch of the experimental setup for the LDV measurements

Grahic Jump Location
Figure 3

Measured and calculated flame temperatures

Grahic Jump Location
Figure 4

Isothermal flow field at S=0.7 measured with PIV. Velocity vectors superimposed on the normalized turbulence intensity. Solid lines are the isocontours of zero axial velocity. Dashed lines show measurement locations of LDV measurements.

Grahic Jump Location
Figure 5

Radial velocity profiles at isothermal conditions (S=0.7) with and without area contraction. Measured with LDV.

Grahic Jump Location
Figure 6

Reacting flow fields at S=0.7 with area contraction. (a) Flow field type 1 and (b) flow field type 2. Solid lines are the isocontours of zero axial velocity.

Grahic Jump Location
Figure 7

Radial velocity profiles for various swirl numbers at combustion conditions (Tin=527 K; φ=0.49; Ω=0) without area contraction

Grahic Jump Location
Figure 8

Radial velocity profiles (x/Dh=10) at S=1.5 without area contraction at the outlet for three density ratios

Grahic Jump Location
Figure 9

Reacting flow fields at S=1.2, with area contraction. Solid lines are the isocontours of zero axial velocity.

Grahic Jump Location
Figure 10

Radial velocity profiles at S=1.5 for high acceleration due to heat release

Grahic Jump Location
Figure 11

Radial velocity profiles at S=1.5 for low acceleration due to heat release

Grahic Jump Location
Figure 12

Influence of the density ratio on the parameters px and pΘ at different swirl numbers and combustor operating conditions

Grahic Jump Location
Figure 13

Influence of the effective swirl number on the parameters px and pΘ at different swirl numbers and combustor operating conditions

Grahic Jump Location
Figure 14

NOx emissions for premixed flame at subcritical conditons (Seff=0.45–0.58)

Grahic Jump Location
Figure 15

Criticality parameter κ for different effective swirl numbers. Dashed line divides subcritical from supercritical flow.

Grahic Jump Location
Figure 16

Influence of the criticality parameter κ on the parameters px and pΘ

Tables

Errata

Discussions

Some tools below are only available to our subscribers or users with an online account.

Related Content

Customize your page view by dragging and repositioning the boxes below.

Related Journal Articles
Related eBook Content
Topic Collections

Sorry! You do not have access to this content. For assistance or to subscribe, please contact us:

  • TELEPHONE: 1-800-843-2763 (Toll-free in the USA)
  • EMAIL: asmedigitalcollection@asme.org
Sign In