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Combustion Instability Analysis of a Model Gas Turbine by Application of Dynamic Mode Decomposition
Yuangang Wang(왕위엔강),Jinwoo Son(손진우),Chae Hoon Sohn(손채훈),Jisu Yoon(윤지수),Jinhyun Bae(배진현),Youngbin Yoon(윤영빈) 한국연소학회 2019 한국연소학회지 Vol.24 No.1
Dynamic mode decomposition (DMD) technique is applied to analyze combustion instabilities in a model gas turbine combustor. The flame transfer function (FTF) obtained by the DMD method agrees with the experimental results qualitatively. However, FTF results show that the perturbation frequency with the largest gain is 100Hz, which contradicts the 1000Hz with the largest amplitude in the fast Fourier transform (FFT) results. In order to figure out this, gains and damping coefficients of all resonance frequencies are calculated by DMD technique. Results show the possibility that the model combustor has high-frequency instabilities as a results of coupling between flame and chamber responses. Another finding is that to obtain a pure FTF, the combustor must be removed to exclude coupling of chamber response with flame response.
Yuangang Wang(왕위엔강),Junho Park(박준호),Chae Hoon Sohn(손채훈) 한국연소학회 2020 한국연소학회지 Vol.25 No.4
Two factors that affect NOX emission of swirl premix burner are investigated numerically in the present study. The first one is air fuel ratio which is changed from 31.7 to 38.7 by keeping the air flow rate and decreasing the fuel flow rate. As the air fuel ratio increases, the mixing is enhanced and temperature of a model combustor decreases. Then, the NOX emission decreases. The second factor is the air slit area of the burner. Air slit area is reduced by changing the width of slit with 3 methods depending on the position, i.e., width decrease in the upper-side, the lower-side, and both sides. The velocity of air inflow increases as the air slit width decreases. Then, unmixedness inside the burner will be reduced, which results in reduction of NOX emission. This strong correlation between unmixedness and NOX emission verifies that NOX reduction can be attained by mixing enhancement of fuel and air inside the burner.
A Numerical Study on Gas Mixing Time in a Low-Pressure (Driven) Section of a Shock Tube
YuanGang Wang(왕위엔강),Cheon Hyeon Cho(조천현),Chae Hoon Sohn(손채훈),Youngbin Yoon(윤영빈) 한국연소학회 2017 한국연소학회지 Vol.22 No.3
The fuel and oxidizer mixing process in the shock tube driven section is simulated numerically. The boundary condition is set based on an shock tube experimental condition. The objective is to predict the gas mixing time for experiments. In the experiment, the amount of fuel to be injected is determined in advance. Then, according to duration of fuel injection, 5 cases with the same fuel mass but different fuel mass flow rate are simulated. After fuel is injected into the driven section, the fuel and air will be mixed with each other through convection and diffusion processes. The mixing time is predicted numerically for experiments.
YuanGang Wang(왕위엔강),Chul Jin Kim(김철진),Chae Hoon Sohn(손채훈),In-Seuck Jeung(정인석) 한국연소학회 2016 한국연소학회지 Vol.21 No.4
Pressure and temperature variations in a shock tube have been studied numerically by changing the diameter ratio of a driven part to a driver part . There are five cases where the adopted diameter ratios are 40%, 50%, 60%, 80%, and 100% respectively. The diameter of the driver part remains unchanged meanwhile the shock tube driven part diameter increases from 40% to 100% of the driver part. In the 100% ratio case, the driver part and driven parts have the same diameter of 66.9 mm. As the diameter ratio decreases, the pressure in the shock tube and available test time are increased.