표제지
목차
Abstract 6
Ⅰ. 서론 11
1.1. 연구 배경 11
1.2. 연구동향 13
1.2.1. 희박 예혼합 연소 (Lean Premixed Combustion) 13
1.2.2. 열-음향 불안정성 (Thermo-acoustic instability) 16
1.2.3. 대칭성파괴 (Symmetry breaking) 21
1.3. 연구 목적 24
Ⅱ. 실험장치 및 방법 25
2.1. 환형연소기 (Annular combustor) 25
2.2. 측정 장치 30
2.3. 실험조건 및 측정방법 33
Ⅲ. 결과 및 고찰 39
3.1. 대칭성파괴 현상 39
3.1.1. 당량비에 따른 대칭성파괴 현상 39
3.1.2. 대칭 노즐 배치에 따른 대칭성파괴 현상 46
3.1.3. 비대칭 노즐 배치에 따른 대칭성파괴 현상 51
3.2. 2D-FFT(Pixel to pixel FFT) 57
3.3. Hysteresis cycle phenomenon 60
Ⅳ. 결론 65
참고문헌 67
Table 1. Specification of devices for calibration of flow rate. 29
Table 2. Specification of devices for acquiring pressure signal data. 32
Table 3. Operating conditions 36
Fig. 1. NOx, CO and HC with equivalence raio 15
Fig. 2. Image of gas turbine system damaged by instability. 19
Fig. 3. Stability map with instability mode. 20
Fig. 4. PDF of A- and A+ with equivalence ratio. 20
Fig. 5. Symmetry breakdown due to arrangement of nozzles with different shapes. 23
Fig. 6. 2D (pixel-to-pixel) FFT results. 23
Fig. 7. Schematics diagram of annular combustor. 27
Fig. 8. Combustor dump plane. 28
Fig. 9. Schematic diagram of swirler for calculating the swirl number. 28
Fig. 10. Schematic diagram of swirler for calculating the swirl number. 32
Fig. 11. Schematic diagram with the nozzle number. 37
Fig. 12. Schematic diagram with the nozzle arrangements. 38
Fig. 13. Schematic diagram with the nozzle arrangements. 38
Fig. 14. Dependence of normalized pressure amplitude on pressure oscillations. 43
Fig. 15. Time series and FFT correspondence of combustor pressure signals. 45
Fig. 16. Pressure fluctuation analysis of representative conditions of phase space reconstruction plot. 45
Fig. 17. Symmtrey arrangement contour maps in symmetry beaking of normalized combustor pressure amplitude, normalized heat release rate,... 50
Fig. 18. Asymmtrey arrangement contour maps in symmetry beaking of normalized combustor pressure amplitude, normalized heat release rate,... 54
Fig. 19. A4 nozzle arrangement condition with FFT, Recurrence plot, phase space reconstruction plot. 55
Fig. 20. A3a2 nozzle arrangement condition with FFT, Recurrence plot, phase space reconstruction plot. 56
Fig. 21. 5 second interval time signal (Ramp time = 5s). 59
Fig. 22. 2D FFT results on phase (first), amplitude (second) 59
Fig. 23. Hysteresis in frequency response between increasing (decreasing) 𝜙₂ path for 𝜙₁ 0.9. 62
Fig. 24. Hysteresis in frequency response between increasing (decreasing) 𝜙₂ path for 𝜙₁ 1.2. 62
Fig. 25. A hysteresis of the frequency response to 𝜙₂ for 𝜙₁ 0.9, 1.2 with the injector arrangement of A4. 63
Fig. 26. Limit cycle of the frequency response between increasing(decreasing). 63
Fig. 27. FFT in chugging mode. 64
Fig. 28. Frequency in chugging mode in all nozzle arrangement. 64