English (United Kingdom)

https://curated-unify.zendy.io/wp-json/zendy-region/v1/featured_content/oa?rat=en

https://curated-unify.zendy.io/wp-json/zendy-region/v1/highlighted_journal/

Global: Zendy Plus annual

Presents the access of premium content as premium feature

Premium Content

Presents the keyphrase highlighting as premium feature

Keyphrase Highlighting

Presents the summarisation as premium feature

Summarisation

Insights

Presents the pdf analysis as premium feature

PDF Analysis

Presents the zaia usage as premium feature

ZAIA

Global: Zendy Tools annual

Global: Zendy Free Plan

Global: Zendy Tools monthly

Global: Zendy Plus monthly

This paper presents recent research activities on coherent structures in combustor flows employing linear hydrodynamic stability theory. Large-scale coherent structures play an important role in swirling combustor flows. On the one hand isothermal swirling jets undergoing vortex breakdown are susceptible to self-excited flow oscillations. They manifest in a precessing vortex core and synchronized growth of large-scale helical vortical structures. On the other hand, thermoacoustic oscillations are often related to axisymmetric flow structures that are driven by the acoustic field. Despite the qualitative difference between the self-excited helical instabilities and the acoustically forced axisymmetric instabilities, the linear analysis is capable to describe both phenomena with an astonishing accuracy. The proposed theoretical framework allows for a systematic analysis of the dominant flow dynamics in the turbulent combustor flow and their interplay with the flame. This is demonstrated by considering two examples: a swirl-stabilized flame featuring a precessing vortex core that becomes suppressed when changing from steamdiluted to dry conditions, and a swirl-stabilized flame subjected to strong axial forcing mimicking thermo-acoustic oscillations. Application of linear hydrodynamic stability analysis to reacting swirling combustor flows Received 10 July 2014 1. Nomenclature ReD Reynolds number based on Dh Ret Reynolds number with eddy viscosity S swirl number K normalized coherent velocity fluctuation intensity A amplitude ratio νt eddy viscosity ν kinematic viscosity Dh hydraulic diameter of the burner OH∗ OH-chemiluminescence intensity α = αr + iαi complex axial wave number ω = ωr + iωi complex frequency ω0 = ω0,r + iω0,i complex local absolute frequency ωg = ωg,r + iωg,i complex global frequency m azimuthal wave number t time f frequency φ complex eigenfunctions x = (x, y, z) Cartesian coordinates x = (x, r,Θ) cylindrical coordinates