표제지
초록
Abstract
목차
제1장 서론 23
1.1. 연구 배경 23
1.2. 기존 연구 31
1.2.1. 통합 설계 및 건전성 평가 기술 31
1.2.2. 가스터빈 해석 기술 36
1.3. 연구 목표 41
제2장 고온고압 환경에서 금속 재료 거동 44
2.1. 개요 44
2.2. 재료의 탄성과 소성 변형 45
2.3. 주기 소성 51
2.3.1. 등방 경화 모델 51
2.3.2. 이동 경화 모델 53
2.3.3. 복합 경화 모델 57
2.4. 시간 의존적(Time-dependent) 주기 소성 58
2.4.1. 통합 점소성 모델 58
2.5. 고온 환경에서 금속 재료의 거동 62
2.5.1. IN738LC 63
2.5.2. 시험데이터 비교 69
2.6. 피로 수명 평가 78
2.6.1. IN738LC의 피로 수명 평가 78
2.6.2. 저주기 피로(Low cycle fatigue) 수명 평가 81
2.6.3. 열-기계적 피로(Thermo-Mechanical Fatigue) 수명 평가 85
2.6.4. 가스터빈 블레이드 해석에서 점소성 모델의 필요성 91
2.7. 요약 92
제3장 리엔지니어링을 위한 블레이드 형상 획득 93
3.1. 개요 93
3.2. 가스터빈 블레이드의 구조 94
3.2.1. 일반적인 가스터빈 블레이드의 냉각 유로 94
3.2.2. 가스터빈 블레이드의 구조가 받는 하중 97
3.2.3. 대상 가스터빈 블레이드 99
3.3. 터빈 블레이드의 형상 획득 101
3.3.1. 3차원 스캐너를 활용한 형상 획득 과정 101
3.3.2. CAE(Computer Aided Engineering) 모델링 106
3.4. 요약 108
제4장 터빈 블레이드 유체-구조 연계해석을 위한 복합열전달 축약 모델 109
4.1. 개요 109
4.2. 차수 축소 방법의 종류 110
4.2.1. 적합 직교 분해법 110
4.2.2. 머신러닝 115
4.2.3. 크리깅(Kriging) 117
4.3. 가스터빈 블레이드의 복합열전달 축약 모델 120
4.3.1. 임무 지점 선정 122
4.3.2. 복합열전달 해석을 위한 전산유체해석 모델링 125
4.3.3. 크리깅을 이용한 축약 모델 생성 131
4.3.4. 복합열전달 축약 모델 135
4.4. 요약 143
제5장 복합열전달 축약 모델을 활용한 터빈 블레이드 열구조 해석 144
5.1. 개요 144
5.2. 열유동 축약 모델을 활용한 열구조 연계해석 145
5.2.1. 가스터빈 블레이드 유한요소모델 145
5.2.2. 가스터빈 블레이드의 하중 조건 모델링 146
5.2.3. 열구조 해석 절차 150
5.3. 실제 운전조건을 고려한 블레이드 열구조 해석 151
5.3.1. 열전달해석 결과 152
5.3.2. 구조해석 결과 157
5.3.3. 수명 평가 171
5.4. 고온 운전조건에서 블레이드 열구조 해석 174
5.4.1. 열전달해석 결과 175
5.4.2. 구조 해석 결과 178
5.4.3. 수명 평가 190
5.5. 가스터빈 급속 가동에 따른 영향 192
5.5.1. 운전 조건 정의 192
5.5.2. 열전달해석 결과 194
5.5.3. 구조해석 결과 196
5.5.4. 수명 평가 200
5.6. 블레이드 열차폐코팅(TBC)의 변화 따른 영향 202
5.6.1. 모델 구성 203
5.6.2. 열전달해석 결과 206
5.6.3. 구조 해석 결과 212
5.7. 요약 213
제6장 결론 215
6.1. 고온 환경에서 금속의 거동 연구 215
6.2. 터빈 블레이드 형상 취득 216
6.3. 복합열전달 축약 모델 연구 216
6.4. 복합열전달 축약 모델 기반의 열구조 연계해석 연구 217
6.5. 기대 효과 219
APPENDIX 1. 터빈 블레이드 리엔지니어링 220
A.1.1. 개요 220
A.1.2. 리엔지니어링 221
A.1.3. 블레이드의 냉각 유로 변화에 따른 영향 224
A.1.4. 기존 블레이드 성능 개선 방법 232
참고 문헌 234
Table 2-1. Density, Young's modulus and Poisson's ratio 64
Table 2-2. Coefficient of thermal expansion 64
Table 2-3. Isotropic hardening and viscoplasticity 65
Table 2-4. Kinematic hardening with static recovery term 66
Table 2-5. Conductivity and Specific heat 67
Table 2-6. Ramberg-Osgood model (IN738LC, 850℃) 80
Table 2-7. LCF life estimation results (LCF01) 85
Table 2-8. LCF life estimation results (LCF02) 85
Table 2-9. IP and OP-TMF test results 86
Table 2-10. TMF-IP life estimation results (TMF-IP01) 89
Table 2-11. TMF-IP life estimation results (TMF-IP02) 89
Table 2-12. TMF-IP life estimation results (TMF-IP03) 89
Table 2-13. TMF-IP life estimation results (TMF-IP04) 90
Table 4-1. Boundary conditions of Mission points 123
Table 4-2. Boundary conditions of Mission points(considering dynamic temperature) 124
Table 4-3. Material properties of Thermal barrier coating (Density, Thermal properties) 128
Table 4-4. Material properties of Air 129
Table 4-5. Boundary conditions at mission points for verification 136
Table 4-6. RMSE and MAPE calculated from predicted values (ROM) and actual values (CFD) (E01) 139
Table 4-7. RMSE and MAPE calculated from predicted values (ROM) and actual values (CFD) (E02) 142
Table 5-1. Material properties of TBC 145
Table 5-2. Types of mechanical loads considered by references 146
Table 5-3. Types of thermal/mechanical loads acting on the blade 146
Table 5-4. Analysis cases to determine the effect of mechanical load 147
Table 5-5. LCF Life estimation (Gas turbine blade, Actual operating profile) 173
Table 5-6. TMF Life estimation (Gas turbine blade, Actual operating profile) 173
Table 5-7. TMF Life estimation of gas turbine blade (High temp. operating condition vs. Original operating condition) 191
Table 5-8. Accumulated plastic strain after 5 cycles (Ramp Rate 6.5 MW/min vs. Ramp Rate 26 MW/min, Viscoplastic) 198
Table 5-9. Amplitude of equivalent mechanical strain at 5 cycle (Ramp Rate 6.5 MW/min vs. Ramp Rate 26 MW/min, Viscoplastic) 199
Table 5-10. TMF Life estimation of gas turbine blade (Ramp Rate 6.5 MW/min vs. Ramp Rate 26 MW/min, Viscoplastic) 201
Table 5-11. TMF Life estimation of gas turbine blade (Ramp Rate 6.5 MW/min vs. Ramp Rate 26 MW/min, Plastic) 201
Table 5-12. Boundary conditions of additional analysis (Thickness of TBC) 203
Table 5-13. Boundary conditions of additional analysis (Thickness of TBC) 205
Table A-1. Number of cooling holes and TBC thickness in simple blade models 224
Table A-2. Boundary conditions of Mission points (Simple blade model) 226
Table A-3. Maximum temperature at key hotspots (Model_v1 vs. Model_v3) 229
Figure 1-1. World consumption (Exajoules) 23
Figure 1-2. Total energy supply by fuel and CO2 emissions by scenario 25
Figure 1-3. Shares of global primary energy 26
Figure 1-4. Final assembly of the large gas turbine for power generation 27
Figure 1-5. Fractured blade accident 29
Figure 1-6. Flow chart of conjugate transient thermal analysis process 31
Figure 1-7. Lifing methodology principle 32
Figure 1-8. Aero-thermal Procedures for 1st Stage Cooled Blade 32
Figure 1-9. Example of Tip and Platform Cracking of W501FC 1st Stage Blade 33
Figure 1-10. Simplified LCF analysis procedures 34
Figure 1-11. Procedure of Life Calculation 35
Figure 1-12. Surface temperature distributions of the original and improved blades 36
Figure 1-13. Rotor FEM model 37
Figure 1-14. Crack and erosion of first blade W501F 38
Figure 1-15. Temperature distribution on PS and SS Blade surface 39
Figure 1-16. Von mises stress variation within one cycle 39
Figure 1-17. Von mises stress distribution of Blade 40
Figure 1-18. Flow chart of gas turbine blade Re-engineering 41
Figure 2-1. Stress-Strain curve 45
Figure 2-2. Bauschinger effect 47
Figure 2-3. Shakedown 49
Figure 2-4. Ratchetting 50
Figure 2-5. Stress relaxation 50
Figure 2-6. Schematic representation of isotropic hardening on the deviatoric plane and in tension-compression test conditions 52
Figure 2-7. Schematic representation of kinematic hardening in deviatoric plane and in tension-compression test 53
Figure 2-8. Schematic representation of saturated stress represented by the nonlinear kinematic hardening model 55
Figure 2-9. The stress-strain curve obtained from the superposition of three kinematic hardening variables 56
Figure 2-10. Example of Thermal fatigue 62
Figure 2-11. Finite element model of IN738LC specimen 67
Figure 2-12. Boundary conditions and loading conditions assigned to IN738LC specimen for uniaxial tensile simulation 68
Figure 2-13. Stress-strain response of IN738 LC at 850℃ and uniaxial tension 69
Figure 2-14. Stress-strain response of IN738 LC at 450℃ and uniaxial tension 70
Figure 2-15. Stress-strain response of IN738 LC at 950℃ and uniaxial tension 71
Figure 2-16. Stress relaxation behavior after uniaxial tension at 450℃ 72
Figure 2-17. Stress relaxation behavior after uniaxial tension at 850℃ 72
Figure 2-18. Uniaxial Creep at 850℃ 73
Figure 2-19. Uniaxial Creep at 950℃ 73
Figure 2-20. Test conditions of isothermal cycle 74
Figure 2-21. Stress-strain hysteresis loop (850℃, △ε = 0.983%, Nf = 11)[이미지참조] 75
Figure 2-22. Stress-strain hysteresis loop (850℃, △ε = 0.608%, Nf = 46)[이미지참조] 75
Figure 2-23. Stress-strain hysteresis loop (850℃, △ε = 0.573%, Nf = 84)[이미지참조] 76
Figure 2-24. Stress-strain hysteresis loop (850℃, △ε = 0.475%, Nf = 150)[이미지참조] 76
Figure 2-25. Test conditions of TMF-IP 77
Figure 2-26. Stress history of TMF-IP (△ε = 1.17%) 77
Figure 2-27. Process of converting elastic strain to true strain using Neuber's Rule 79
Figure 2-28. Comparison of Ramberg-Osgood model and specimen test results (IN738LC, 850℃) 81
Figure 2-29. Strain-Life curve of IN738LC 83
Figure 2-30. Stress and temperature conditions for simulation (LCF Test) 84
Figure 2-31. Strain amplitude-fracture cycle curves (IP and OP TMF) 86
Figure 2-32. Stress and temperature conditions for simulation (TMF-IP01, TMF-IP02) 87
Figure 2-33. Stress and temperature conditions for simulation (TMF-IP03) 88
Figure 2-34. Stress and temperature conditions for simulation (TMF-IP04) 88
Figure 3-1. Gas turbine blade cooling schematic [55] (a) External cooling; (b) Internal cooling 94
Figure 3-2. Turbine start/stop cycle - firing temperature changes 97
Figure 3-3. Position of in-phase and out of phase in the cross section of a turbine blade 98
Figure 3-4. Gas turbine blade 99
Figure 3-5. Cooling holes on the blade surfaces 100
Figure 3-6. 3D scanning procedure 101
Figure 3-7. Interior and exterior geometries obtained with a 3D scanner 102
Figure 3-8. Before and after CAD modeling of internal channel 104
Figure 3-9. Assembly of internal channel and external geometry (Left: Original scan data, right: Modified CAD model) 105
Figure 3-10. CAD model of Gas turbine blade 105
Figure 3-11. Finite element model and CAD model of gas turbine blade 106
Figure 3-12. Boundary conditions and contact conditions 107
Figure 3-13. Load conditions and symmetry boundary conditions 108
Figure 4-1. Scheme for creating reduced order model 120
Figure 4-2. Operating profile 122
Figure 4-3. Fluid/solid domain of computational fluid analysis model 125
Figure 4-4. Grid in fluid/solid domain 126
Figure 4-5. Boundary conditions set in Fluent model 127
Figure 4-6. Pressure distribution (CASE 101) 130
Figure 4-7. Temperature distribution (CASE 101) 130
Figure 4-8. Creation and analysis procedures of reduced order model 131
Figure 4-9. Input parameters of the reduced order model. 132
Figure 4-10. Pressure distribution comparison in CFD and ROM(E01) 137
Figure 4-11. Temperature distribution comparison in CFD and ROM(E01) 137
Figure 4-12. HTC distribution comparison in CFD and ROM(E01) 138
Figure 4-13. Comparison of relative error between predicted value (ROM) and actual value (CFD) (E01) 139
Figure 4-14. Pressure distribution comparison in CFD and ROM(E02) 140
Figure 4-15. Temperature distribution comparison in CFD and ROM(E02) 140
Figure 4-16. HTC distribution comparison in CFD and ROM(E02) 141
Figure 4-17. Comparison of relative error between predicted value (ROM) and actual value (CFD) (E02) 142
Figure 5-1. Gas turbine blade model 145
Figure 5-2. Stress contour for mechanical load influence analysis case 147
Figure 5-3. Stress contour for CASE-PAV 148
Figure 5-4. Loading conditions applied to the blade finite element model 149
Figure 5-5. Thermal-structural analysis procedure using reduced order model 150
Figure 5-6. Actual operating profile 151
Figure 5-7. Heat transfer analysis results considering actual operating profiles 152
Figure 5-8. Streamline of cooling flow 153
Figure 5-9. Temperature contours of the blade on the pressure side 154
Figure 5-10. Temperature contours of the blade on the suction side 155
Figure 5-11. Temperature contours from CFD analysis and comparison with actual blade (Suction side) 155
Figure 5-12. Temperature contours at the top of the platform 156
Figure 5-13. Temperature contours in different spans of the blade 157
Figure 5-14. Structural analysis results considering actual operating profiles 157
Figure 5-15. Stress contours (Actual operating profiles, Base load) 158
Figure 5-16. Stress contours in different spans of the blade 159
Figure 5-17. Accumulated plastic strain contours (Actual operating profiles, N=1) 160
Figure 5-18. Accumulated plastic strain contours (Actual operating profiles, N=5) 161
Figure 5-19. Determination of hot spots through thermal-structural analysis results 162
Figure 5-20. Determination of hot spots through thermal-structural analysis results 162
Figure 5-21. Strain-Temperature map (Actual operating profile, Shank, N=1,5) 163
Figure 5-22. Stress, temperature, and strain histories (Actual operating profile, Shank) 163
Figure 5-23. Strain-Temperature map (Actual operating profile, Platform: Suction side, N=1, 5) 165
Figure 5-24. Stress, temperature, and strain histories (Actual operating profile, Platform: Suction side) 165
Figure 5-25. Strain-Temperature map (Actual operating profile, Platform: Pressure side, N=1, 5) 167
Figure 5-26. Stress, temperature, and strain histories (Actual operating profile, Platform: Pressure side) 167
Figure 5-27. Strain-Temperature map (Actual operating profile, Blade tip, N=1, 5) 168
Figure 5-28. Stress, temperature, and strain histories (Actual operating profile, Blade tip) 168
Figure 5-29. Strain-Temperature map (Actual operating profile, Cooling hole on trailing edge, N=1, 5) 170
Figure 5-30. Stress, temperature, and strain histories (Actual operating profile, Cooling hole on trailing edge) 170
Figure 5-31. Hotspots of gas turbine blade 171
Figure 5-32. Differences between original operating conditions and high temperature operating conditions 174
Figure 5-33. Heat transfer analysis results (High temp condition vs. original condition) 175
Figure 5-34. Comparison of temperature contours at various view (High temp condition vs. original condition, Base load) 177
Figure 5-35. Comparison of temperature contours in different spans of the blade (High temp condition vs. original condition, Base load) 178
Figure 5-36. Structural analysis results (High temp condition vs. original condition) 179
Figure 5-37. Comparison of stress contours in different spans of the blade (High temp condition vs. original condition) 180
Figure 5-38. Comparison of accumulated plastic strain contours according to the number of cycles 181
Figure 5-39. Comparison of accumulated plastic strain contours in the blade cross section 181
Figure 5-40. Strain-Temperature map (High temp condition vs. original condition, Shank, N=1, 5) 183
Figure 5-41. Plastic strain histories (High temp. condition vs. original condition, Shank) 183
Figure 5-42. Strain-Temperature map (High temp condition vs. original condition, Platform: Suction Side, N=1,5) 184
Figure 5-43. Plastic strain histories (High temp condition vs. original condition, Platform: Suction Side) 185
Figure 5-44. Strain-Temperature map (High temp condition vs. original condition, Platform: Pressure Side, N=1,5) 186
Figure 5-45. Plastic strain histories (High temp. condition vs. original condition, Platform: Pressure Side) 186
Figure 5-46. Strain-Temperature map (High temp. condition vs. original condition, Blade tip, N=1,5) 187
Figure 5-47. Plastic strain histories (High temp. condition vs. original condition, Blade tip) 187
Figure 5-48. Strain-Temperature map (High temp condition vs. original condition, Cooling hole on trailing edge, N=1,5) 188
Figure 5-49. Plastic strain histories (High temp. condition vs. original condition, Cooling hole on trailing edge) 189
Figure 5-50. Operating profiles (top: 6.5MW/min, bottom: 26MW/min) 192
Figure 5-51. Operating profiles (RPM) 193
Figure 5-52. Comparison of operating profiles according to ramp rate 194
Figure 5-53. Comparison of heat transfer results according to ramp rate 195
Figure 5-54. Comparison of stress contours according to ramp rate (Base load) 196
Figure 5-55. Comparison of accumulated plastic strain contours according to ramp rate and material (N=5) 197
Figure 5-56. Thermal Barrier coating of gas turbine blade 202
Figure 5-57. Input parameters of the reduced order model (TBC Thickness) 204
Figure 5-58. TBC04 model 205
Figure 5-59. Comparison of heat transfer results according to TBC thickness (Ramp rate 6.5 MW/min, 255min) 206
Figure 5-60. Comparison of heat transfer results according to TBC thickness (Ramp rate 6.5 MW/min, 278min) 208
Figure 5-61. Comparison of heat transfer results according to TBC thickness (Ramp rate 6.5 MW/min, 400min) 209
Figure 5-62. Average temperature change of the blade according to TBC thickness 210
Figure 5-63. Maximum temperature change at hotspots depending on TBC thickness 211
Figure 5-64. Accumulated plastic strain change at hotspots depending on TBC thickness 212
Figure A-1. Framework of Re-engineering 221
Figure A-2. Simple blade models and location of cooling holes 225
Figure A-3. Boundary conditions set in Fluent model (Simple blade model) 226
Figure A-4. History of the average temperature of the blade 227
Figure A-5. Comparison of heat transfer results at base load (Model_v1, v2, and v3) 228
Figure A-6. History of the average accumulated plastic strain of the blade 230
Figure A-7. Comparison of accumulated plastic strain results after 1 cycle (Model_v1, v2, and v3) 231
Figure A-8. Final improved model of gas turbine blade (Add cooling holes) 232
Figure A-9. Final improved model of gas turbine blade (Modified TBC) 233