Shaft Alignment and Whirling Vibration
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The document discusses the performance prediction of shafts, particularly focusing on problems related to shaft alignment and whirling vibrations. It emphasizes the impact of bearing stiffness on bearing loads and shaft slopes in marine propulsion systems, with case studies revealing how variations in stiffness affect system performance. Furthermore, the document introduces a study on lateral vibrations and the importance of understanding natural frequencies in the context of maintaining optimal operational conditions.
![Discussion of results
B‐ Slope of the shaft inside propeller bearing.
B Slope of the shaft inside propeller bearing
Slope mismatch between the shaft and the bearing is more interesting, So
the slope of the bearing it self is important as well.
BEARING REACTIONS IN VERTICAL - OPERATING CONDITION 1 (GB-COLD-STATIC)
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Position Load Pressure Offset Slope
[cm] [kN] [bar] [mm] [mm/m]
Bearing 1 244 182 5 -0 221
0.221 0.669
0 669
Bearing 2 284 129 5 -0.060 0.511
Bearing 3 803 5 0 0.000 -0.163
Bearing 4 1325 78 5 0.719 0.447
Lubricant White metal Bearing 5 1436 59 4 1.223 0.474
238 -1.074 7.340E-004 235233 15 -220
244 -1.036 7.200E-004 246710 16 -221
244 -1.035 7.200E-004 246930 16 -221
249 -1.000 7.050E-004 248883 16 -39
254 -0.964 6.910E-004 250869 16 -40
259 -0.930 6.770E-004 252888 16 -40
264 -0.896
-0 896 6 620E-004
6.620E-004 254940 17 -41
269 -0.863 6.470E-004 257025 17 -42
274 -0.831 6.320E-004 259143 17 -42
279 -0.799 6.170E-004 261294 17 -43
284 -0.769 6.020E-004 263463 17 -44
292 -0.723 5.790E-004 256819 17 84
DNV Software User Conference 17
Busan July 2012](https://image.slidesharecdn.com/berg-shaftalignmentandwrhilingvibration-120920061109-phpapp02/85/Shaft-Alignment-and-Whirling-Vibration-16-320.jpg)
Shaft Alignment and Whirling Vibration
- 1. Consequence of detailed modelling into shaft performance prediction q g p p Shaft Alignment and Whirling vibration
- 2. Problem? A proper Shaft Analysis report issued. Practical alignment verfication muserments shows a recognaizable variation! Why ?! In some of the cases it is subjected to the tools used. But there is some other reasons! One of these reasons is the cosequence of the system components stiffness into: One of these reasons is the cosequence of the system components stiffness into: 1‐Bearing loads and Shaft slope inside propeller bearing 2‐Propeller shaft lateral vibration. 2 Propeller shaft lateral vibration This will explain some of the other reasons meanwhile it helps to investigate the most reliable working domain for new projects. li bl ki d i f j t DNV Software User Conference 3 Busan July 2012
- 3. Model of the case study Propeller ASTB FSTB AGB FGB ASTB=Aft Sterntube Bearing FSTB=Fwd Sterntube Bearing AGB=Aft Gearbox Bearing FGB=Fwd Gearbox Bearing GB= Gearbox (OR Main Engine first E i fi two bearings). b i ) DNV Software User Conference 4 Busan July 2012
- 4. Bearing stiffness External Bearing E t lB i Calc. Tool Shaft Bearing Oil Film Calculation Bearing Material Practical or theoretical Model assumption Bearing Foundation DNV Software User Conference 5 Busan July 2012
- 5. Part 1‐ Alignment Case No.1‐ Variation of FSTB Stiffness Case No 1 Variation of FSTB Stiffness Working Domain: ‐Variation of Forward Sterntube Bearing stiffness from 5.0E7 N/m to 5.0E10 N/m. ‐GAP & SAG are kept constant at all analysis Propeller points. GB ASTB FSTB ‐All other bearings assumed stiffness kept constant. ‐GB bearings offsets changed at each analysis point in order to maintain the same GAP‐SAG figures. fi DNV Software User Conference 6 Busan July 2012
- 6. Case No.1‐ Variation of FSTB Stiffness Results: A‐ Bearing loads. FSTB Stiffness variation effect on Bearing Loads FSTB Stiffness variation effect on Bearing Loads 120 ASTB/10 FSTB AGB FGB 100 80 kN) 60 Load (k 40 20 0 4.00E+07 4.00E+08 4.00E+09 4.00E+10 Stiffness (N/m) DNV Software User Conference 7 Busan July 2012
- 7. Case No.1‐ Variation of FSTB Stiffness Results: B‐ Slope of the shaft inside Aft Sterntube bearing. FSTB Stiffness variation effect on Shaft Slope at ASTB FSTB Stiffness variation effect on Shaft Slope at ASTB 0.53 0.525 0.52 0.515 mm/m) 0.51 Shaft Slope at ASTB p Slope (m 0.505 0.5 0.495 0.49 4.00E+07 4.00E+08 4.00E+09 4.00E+10 Stiffness (N/m) DNV Software User Conference 8 Busan July 2012
- 8. Case No.2‐ Variation of ASTB Stiffness Working Domain: ‐Variation of Aft Sterntube Bearing stiffness from 3.0E8 N/m to 5.0E10 N/m. ‐GAP & SAG are kept constant at all analysis Propeller points. GB ASTB FSTB ‐All other bearings assumed stiffness kept constant. ‐GB bearings offsets changed at each analysis point in order to maintain the same GAP‐SAG figures. fi DNV Software User Conference 9 Busan July 2012
- 9. Case No.2‐ Variation of ASTB Stiffness Results: A‐ Bearing loads. ASTB Stiffness variation effect on Bearing Loads ASTB Stiffness variation effect on Bearing Loads 90 ASTB/10 FSTB AGB FGB 80 70 60 Load (kN) 50 40 30 20 10 0 2.00E+08 2.00E+09 2.00E+10 Stiffness (mm/m) DNV Software User Conference 10 Busan July 2012
- 10. Case No.2‐ Variation of ASTB Stiffness Results: B‐ Slope of the shaft inside Aft Sterntube Bearing. ASTB Stiffness variation effect on Shaft Slope at ASTB ASTB Stiffness variation effect on Shaft Slope at ASTB 0.75 0.7 0.65 Shaft Slope at ASTB Slope(mm/m) 0.6 0.55 0.5 0.45 0 45 0.4 2.00E+08 2.00E+09 2.00E+10 Stiffness (N/m) DNV Software User Conference 11 Busan July 2012
- 11. Case No.3‐ Variation of GB Bearings Stiffness. (OR Main Engine foundation stiffness) fo ndation Working Domain: ‐Variation of Gearbox Bearings stiffness from 2.0E7 N/m to 1.0E11 N/m. ‐GAP & SAG are kept constant at all analysis Propeller points. GB ASTB FSTB ‐All other bearings assumed stiffness kept constant. ‐GB bearings offsets changed at each analysis point in order to maintain the same GAP‐SAG figures. fi DNV Software User Conference 12 Busan July 2012
- 12. Case No.3‐ Variation of GB Bearings Stiffness. (OR Main Engine foundation stiffness) fo ndation Results: A‐ Bearing loads. GB bearings Stiffness variation effect on Bearing Loads 100 ASTB/10 FSTB AGB FGB 90 80 70 60 Load (kN) 50 L 40 30 20 10 0 2.00E+07 2.00E+08 2.00E+09 2.00E+10 Stiffness (N/m) Stiffness (N/m) DNV Software User Conference 13 Busan July 2012
- 13. Case No.3‐ Variation of GB Bearings Stiffness. (OR Main Engine foundation stiffness) fo ndation Results: B‐ Slope of the shaft inside Aft Sterntube Bearing. GB bearings Stiffness variation effect on Shaft Slope at ASTB GB bearings Stiffness variation effect on Shaft Slope at ASTB 0.538 0.536 0.534 Shaft Slope at ASTB 0.532 mm/m) Slope (m 0.53 0.528 0.526 0.524 1.00E+07 1.00E+08 1.00E+09 1.00E+10 1.00E+11 Stiffness (N/m) ( / ) DNV Software User Conference 14 Busan July 2012
- 14. Discussion of results A‐ Bearing loads. A Bearing loads It is of importance to advice a well reliable stiffness range for the bearings (Foundation & Material) in order to ensure a more reliable loads into the bearing. 120 100 90 90 100 80 80 70 70 80 60 60 60 50 50 40 40 40 30 30 20 20 20 10 10 0 0 0 4.00E+07 4.00E+08 4.00E+09 4.00E+10 2.00E+08 2.00E+07 2.00E+08 2.00E+09 2.00E+10 2.00E+09 2.00E+10 Case 1 C Case 2 C Case 3 Variation of FSTB Stiffness Variation of ASTB Stiffness Variation of GB B. Stiffness DNV Software User Conference 15 Busan July 2012
- 15. Discussion of results B‐ Slope of the shaft inside propeller bearing. B Slope of the shaft inside propeller bearing Is the slope of the shaft inside the propeller bearing (only) is judgeable ? 0.53 0.75 0.538 0.525 0.7 0.536 0.52 Shaft Slope at ASTB 0.65 0.534 0.515 0.6 0.532 0.51 Shaft Slope at ASTB 0.55 0.53 0.505 0.5 0.528 0.5 05 Shaft Slope at ASTB f 0.495 0.45 0.526 0.49 0.4 0.524 4.00E+07 4.00E+08 4.00E+09 4.00E+10 2.00E+08 2.00E+09 2.00E+10 1.00E+07 1.00E+08 1.00E+09 1.00E+10 1.00E+11 Case 1 Case 2 Case 3 Variation of FSTB Stiffness Variation of ASTB Stiffness Variation of GB B. Stiffness DNV Software User Conference 16 Busan July 2012
- 16. Discussion of results B‐ Slope of the shaft inside propeller bearing. B Slope of the shaft inside propeller bearing Slope mismatch between the shaft and the bearing is more interesting, So the slope of the bearing it self is important as well. BEARING REACTIONS IN VERTICAL - OPERATING CONDITION 1 (GB-COLD-STATIC) ----------------------------------------------------------------------------------- ---- Position Load Pressure Offset Slope [cm] [kN] [bar] [mm] [mm/m] Bearing 1 244 182 5 -0 221 0.221 0.669 0 669 Bearing 2 284 129 5 -0.060 0.511 Bearing 3 803 5 0 0.000 -0.163 Bearing 4 1325 78 5 0.719 0.447 Lubricant White metal Bearing 5 1436 59 4 1.223 0.474 238 -1.074 7.340E-004 235233 15 -220 244 -1.036 7.200E-004 246710 16 -221 244 -1.035 7.200E-004 246930 16 -221 249 -1.000 7.050E-004 248883 16 -39 254 -0.964 6.910E-004 250869 16 -40 259 -0.930 6.770E-004 252888 16 -40 264 -0.896 -0 896 6 620E-004 6.620E-004 254940 17 -41 269 -0.863 6.470E-004 257025 17 -42 274 -0.831 6.320E-004 259143 17 -42 279 -0.799 6.170E-004 261294 17 -43 284 -0.769 6.020E-004 263463 17 -44 292 -0.723 5.790E-004 256819 17 84 DNV Software User Conference 17 Busan July 2012
- 17. Discussion of results B‐ Slope of the shaft inside propeller bearing. B Slope of the shaft inside propeller bearing Then a traditional evaluation of the oil fils stiffness can be checked. DNV Software User Conference 18 Busan July 2012
- 18. Part 2‐Lateral vibration study. Introduction‐ Introduction Basics Vibration: Is a harmonic motion. Vib ti I h i ti Stiffness: Is the rigidity of an object Damping: Is the resistance to the motion. System response: Is the amount of the object deflection based on stiffness and damping (Local/Global). damping (Local/Global) DNV Software User Conference 19 Busan July 2012
- 19. Part 2‐Lateral vibration study. Introduction‐ Lateral vibration mode shapes Introduction Lateral vibration mode shapes Amplitude and stiffness components. λ4 λ3 λ2 λ1 λ1 > λ2 > λ3 > λ4 Ω1 < Ω2 < Ω3 < Ω4 wave lengths vibrating frequencies DNV Software User Conference 20 Busan July 2012
- 20. Part 2‐Lateral vibration study. Introduction‐ System response amplification factor with related damping. Introduction System response amplification factor with related damping 5 4 η=0 η=0.1 or η 0.2 η=0.2 plification facto η=0.3 3 η=0.4 η=0.5 η=1 Amp 2 η=1.5 η=2 η=7 1 0 0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 Ω/Ωn DNV Software User Conference 21 Busan July 2012
- 21. Part 2‐Lateral vibration study. Introduction‐ Lateral vibration and whirling. Introduction Lateral vibration and whirling Real life whirling case Real life whirling case Whirling case during test System stiffness diagram in lateral Whirling case during test System stiffness diagram in lateral DNV Software User Conference 22 Busan July 2012
- 22. Case study‐ Variation of ASTB Stiffness Working Domain: ‐Variation of Aft Sterntube bearing stiffness from 3.0E8 N/m to 5.0E10 N/m. ‐GAP & SAG are kept constant at all analysis Propeller points. GB ASTB FSTB ‐All other bearings assumed stiffness kept constant. ‐GB bearings offsets changed at each analysis point in order to maintain the same GAP‐SAG figures. fi DNV Software User Conference 23 Busan July 2012
- 23. Case study‐ Variation of ASTB Stiffness Results: ASTB Stiffness variation effect on ASTB Stiffness variation effect on ASTB Stiffness variation effect on ASTB Stiffness variation effect on Shaft natural frequency (order1) Propeller natural frequency (order4) 800 190 750 180 M) 700 170 Speed (RPM Speed (RPM) ) 650 160 150 600 Shaft natural frequency (order1) 140 550 Propeller natural frequency (order4) p q y( ) 130 500 120 2.00E+08 2.00E+09 2.00E+10 2.00E+08 2.00E+09 2.00E+10 Stiffness (N/m) Stiffness (mm/m) 1‐ Lateral vibration 2‐ Lateral vibration Shaft natural frequency. Propeller blades natural frequency. DNV Software User Conference 24 Busan July 2012
- 24. 1‐ Lateral vibration, Shaft natural frequency. How it Built? What is the Natural frequency and Excitation frequency ? What is the mode shapes? Clear mode shapes. Cl d h Integrated mode shapes. DNV Software User Conference 25 Busan July 2012
- 25. 1‐ Lateral vibration, Shaft natural frequency How to handle? Most determined mode shapes: Cantliver , First bending. Direction of the local/global response. Damping: Have a slight effect on the D i H li ht ff t th 5 cantiver mode and almost no effect on 4 the first bending (Global response 3 direction is linear toward the maximum direction is linear toward the maximum 2 bending without resistance). 1 0 0 0.5 1 1.5 General conclusion: Running close to reasonance have to be avoided. DNV Software User Conference 26 Busan July 2012
- 26. 2‐ Lateral vibration, Propeller blades natural frequency How it built? DNV Software User Conference 27 Busan July 2012
- 27. 2‐ Lateral vibration, Propeller blades natural frequency What is the Natural frequency and Excitation frequency ? What is the mode shapes? 190 Propeller natural frequency (order4) 180 170 160 150 140 130 120 2.00E+08 2 00E+08 2.00E+09 2 00E+09 2.00E+10 2 00E+10 5 4 3 2 1 0 0 0.5 1 1.5 DNV Software User Conference 28 Busan July 2012
- 28. 2‐ Lateral vibration, Propeller blades natural frequency How to handle? How to handle? Diametrical Damping 2.1) Shaft impact (Direct impact) Propeller shaft Most determined mode shapes: response to vibration Cantliver , First bending. Cantliver First bending Direction of the local/global response. Propeller damping (Resistance) effect due to this applied vibration motion have to be considered 5 as it is very effctive (Propeller diametrical damping). 4 3 So far the damping is effective, then a view 2 of the excitation force is important as well. f th it ti f i i t t ll 1 The system response of this vibration motion 0 0 0.5 1 1.5 should be followed up as it is an excitation force should be followed up as it is an excitation force for another vibration motion‐‐‐‐ > DNV Software User Conference 29 Busan July 2012
- 29. 2‐ Lateral vibration, Propeller blades natural frequency How to handle? How to handle? 2.2) ASTB impact (indirect impact) Aft Sterntube bearing vibration, (Consequence of main propeller (Consequence of main propeller viberation). Bending variation leads to load variation into the bearing. bearing Is the bearing damping able to dominate Bearing Damping capability. the new intreduced harmonic load? Is the viberation motion charctrestics acceptable ? DNV Software User Conference 30 Busan July 2012
- 30. Questions and discussion ! BERG PROPULSION PRODUCTION AB BERG PROPULSION PRODUCTION AB Mohamed Zeid Naval Architect ‐ Rotordynamics Specialist Direct: +46 31 30 10 736 Mobile: +46 761 175 022 E‐mail: mohamed.zeid@bergpropulsion.com @ gp p www.bergpropulsion.com DNV Software User Conference 31 Busan July 2012