The Structure and Dynamics of Turbulent, Interacting Flames
In many modern combustion devices, multiple closely-spaced flames interact with each other. These combustion devices include jet engine combustors and augmentors, power generation gas turbine combustors, and industrial boilers and furnaces. For example, modern gas turbine engines for power generation utilize can-type combustor geometries, where flame-interaction is observed. The development of these practical combustion devices requires a detailed understanding of combustion processes occurring in these devices. Computational fluid dynamics has become a popular tool used in the design process for these devices. However, simulating real flames in these combustors is challenging and the ability to capture all physical processes involved has not yet reached its pinnacle. Flame-flame interaction is one such process that is yet to be completely captured in simulating modern combustors, as this can directly affect these flames by changing the flame structure, flame propagation, flame stability, and emissions production. The interaction between the flow-fields and scalar-fields in these devices changes the structure and dynamics of these flames. Understanding these effects is of crucial importance as it will help in creating a foundational understanding that can enhance the design and operation of combustion devices.
The objective of this research is to understand the impact of flame interactions on flame structure and propagation for the development of turbulent combustion models. To achieve this objective, we are investigating the fundamental understanding of flame interaction events, and the sensitivity of flame interaction behavior to a number of key operational parameters. This will help in characterizing the relative impact of flame interaction events on flame structure and propagation over a wide operating range. The main goals of this project include: 1) better understand flame interactions and how operational parameters – including turbulence intensity, turbulent length scales, turbulence anisotropy, Lewis number, and flame shape – alter flame interaction processes, 2) determine the differences between flame-flame and turbulence-flame interactions, particularly the impact that flame-flame interactions have on key properties that determine flame structure and propagation, including flame area (or flame surface density), flame stretch, flame heat release rate, and combustion efficiency, and 3) describe the relative importance of flame-flame vs. turbulence-flame interaction processes on both local and global flame characteristics as a function of operating parameter to determine in what regimes it is critical to incorporate flame-interaction effects in combustion models. High-speed diagnostic techniques, such as, 10 kHz stereoscopic-particle image velocimetry (S-PIV), OH-planar laser induced fluorescence, and CH* chemiluminescence are utilized to capture the dynamic behavior of these flames.
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