Session: 04-44 Combustion dynamics - modeling II

Paper Number: 127023

127023 - On the Optimum Distribution of Multiple Helmholtz Resonators for Annular Combustors 

The combustors of many modern land-based gas turbines and aero-engines are annular, and lean-burn premixed combustion is used to reduce pollutant emissions. This kind of combustors often suffer from thermoacoustic oscillations, with the occurrence of mostly the circumferential first-order, second-order and third-order oscillation modes in the annular combustion chamber. This could cause severe oscillations in the combustion chamber, affecting the stable operation of the engine. What's more, they may damage the structure of the combustion chamber and ultimately cause irreversible damages to the unit. To solve this problem, a passive control method is usually adopted – adding Helmholtz resonators (HRs). Targeting different circumferential modes, these HRs will have different arrangement design solutions, and a good  design is the key to solve this problem. In this paper, three types of HRs with the same number (7 for each type so a total of 21; these numbers can be adjusted according to actual requirements) and equidistant distribution along the circumferential direction are considered in the form of equivalent impedance to suppress these oscillation modes. Firstly, a simple annular duct with arbitrary distributions of these HRs is studied by using an analytical method. Based on the results of the analytical method, the impact of the HRs on the acoustic modes of the combustion chamber is studied. These mainly include two aspects: the splitting and damping of the original  circumferential acoustic modes. Based on this study, the optimum arrangement of multiple resonators is obtained. This arrangement usually gives a small mode splitting strength and a good damping effect. Finally, we apply the optimum arrangement to damp the thermoacoustic modes that have been captured by numerical simulation for a real annular combustor. We use numerical simulations based on solving the 3D Helmholtz equation in COMSOL to verify the feasibility of the optimum arrangement.

Keywords: Helmholtz resonator, Optimum distribution, Thermoacoustic instability, Annular combustor

Presenting Author: Hongwei Chen Southern University of Science and Technology

Presenting Author Biography: Master student, currently studying at Southern University of Science and Technology, Department of Mechanics and Aerospace Engineering.
The main research direction is: thermoacoustic oscillation in annular combustion chambers.
Graduate Supervisor: Dong Yang.

Authors:

Hongwei Chen Southern University of Science and Technology
Liming Yin Southern University of Science and Technology
Xiaopei Liu Shanghai Electric Gas Turbine Co., Ltd.
Mingmin Chen Harbin Engineering University
Dong Yang Southern University of Science and Technology