Analysis of V-Gutter Reacting Flow Dynamics Using Proper Orthogonal and Dynamic Mode Decompositions

Yang Yang,Zhihao Zhang,Xiao Liu

doi:10.3390/en13184886

Abstract

The current work is focused on investigating the potential of data-driven post-processing techniques, including proper orthogonal decomposition (POD) and dynamic mode decomposition (DMD) for flame dynamics. Large-eddy simulation (LES) of a V-gutter premixed flame was performed with two Reynolds numbers. The flame transfer function (FTF) was calculated. The POD and DMD were used for the analysis of the flame structures, wake shedding frequency, etc. The results acquired by different methods were also compared. The FTF results indicate that the flames have proportional, inertial, and delay components. The POD method could capture the shedding wake motion and shear layer motion. The excited DMD modes corresponded to the shear layer flames’ swing and convect motions in certain directions. Both POD and DMD could help to identify the wake shedding frequency. However, this large-scale flame oscillation is not presented in the FTF results. The negative growth rates of the decomposed mode confirm that the shear layer stabilized flame was more stable than the flame possessing a wake instability. The corresponding combustor design could be guided by the above results.

Highlights

Lean premixed combustion is of interest due to the fact that it has been widely used in modern gas turbine combustors to control nitrogen oxides (NOx) emission
(2) The mean x-velocity in the recirculation zone increases with an increase in the equivalence ratio but it decreases with increases in the opening angle and inflow velocity
The 3rd–4th modes exhibit a high fluctuating product formation rate (PFR) value, which is symmetrical and located downstream of the stable recirculation zone between the shear layer flame, which is the shedding wake motion induced by Bérnard von Karman (BVK) instability

Summary

Introduction

Lean premixed combustion is of interest due to the fact that it has been widely used in modern gas turbine combustors to control nitrogen oxides (NOx) emission. When the dry low NOx (DLN) combustion system in the FT8 engine was first developed, the frequency of the dynamic pressure fluctuation showed a 200–400 Hz range [1]. This pulsation has been damped by adding additional acoustic resonators [2] while more complicated designs should be considered, such as the cooling of resonators. The thermoacoustic issue is caused by a combination of the heat release rate (HRR) and the pressure fluctuation. Such unsteady heat release is one of the manifestations for flame dynamics. If the phase between the pressure fluctuation and the heat release rate (HRR) fluctuation is less than π/4, and the integral of their product’s volume is larger than the damping of the system, the thermoacoustic issue occurs [4]

Objectives

Methods

Results

Conclusion