https://cyberleninka.org/article/n/1384319.pdf

Combustion instability of pilot flame in a pilot bluff body stabilized combustor

The pilot flame’s effects on dynamic stability have been investigated in a pilot bluff-body stabilized combustor at atmospheric pressure. During the experiment, the pilot fuel proportion increased from 6 to 20% with an interval of 2%, while the total equivalence ratio remained unchanged. Simultaneous dynamic pressure and unsteady heat release rate measurement and analysis were used to identify and characterize combustion instability modes. Combustion dynamics were captured by a high-speed camera. High-speed images were further analyzed by using proper orthogonal decomposition. With the increase of pilot fuel proportion, the transition between combustion instability modes of 33 and 130 Hz was observed. Based on acoustic mode analysis, the 33 and 130 Hz modes corresponded to the first and second longitudinal acoustic mode, respectively. The results show that the pilot fuel proportion affects the local equivalence ratio distribution in the shear layer and the recirculation zone. As a result, it has significa...

Combustion Instability Mode Transition in a Pilot Bluff-Body Stabilized Combustor

Acoustic waves in gas flows with sound speed discontinuities

: Combustion instability manifests itself by the coupling of heat release and chamber acoustics. These instabilities can be present in any type of combustion system, including gas turbine engines, scramjet engines, and industrial furnaces and boilers. Much research has been conducted on the coupling of acoustics and heat release for lean-burning systems. Historically, models of these systems assume the flames to be short and the mean fields to be incompressible. Proposed here is a new approach to coupling dynamics. If the governing equations are considered to be compressible, then a relationship among acoustics, vorticity, and pressure can be derived. In this study the relationship among vortex shedding, flame dynamics, and acoustics is explored for a bluff-body-stabilized flame using high-speed flame images and high-speed pressure transducers. It is demonstrated that the flame radiates sound over a broad spectrum and that thermoacoustic coupling occurs when the flame sound radiation couples with one of the modes of the combustion chamber.

Nick Parr

Papers

The Influence of Stoichiometry and Flame-Holder Shape on Flame Dynamics and Acoustics (Preprint)