Shaft Alignment and Whirling Vibration

Consequence of detailed modelling into shaft performance predictionq g p pShaft Alignment and Whirling vibration

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 vibration2‐Propeller shaft lateral vibration.

This will explain some of the other reasons meanwhile it helps to investigate the most

li bl ki d i f j treliable working domain for new projects.

3DNV Software User Conference Busan July 2012

Model of the case study

Propeller

FGBFSTBASTB AGB

ASTB=Aft Sterntube BearingFSTB=Fwd Sterntube BearingAGB=Aft Gearbox BearingFGB=Fwd Gearbox BearingGB= Gearbox (OR Main E i fi b i )

DNV Software User Conference Busan July 2012

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Engine first two bearings).

Bearing stiffness

E t l B i

Shaft

External Bearing Calc. Tool

Oil Film Bearing Calculation

Bearing Material

Practical or theoretical Model

Bearing

assumption

Bearing Foundation


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Part 1‐ AlignmentCase No 1 Variation of FSTB StiffnessCase No.1‐ Variation of FSTB Stiffness

Working Domain:‐Variation of Forward Sterntube Bearing stiffness from 5.0E7 N/m to 5.0E10 N/m.

Propeller‐GAP & SAG are kept constant at all analysis points.

GBFSTBASTB‐All other bearings assumed stiffness kept constant.

‐GB bearings offsets changed at each analysis point in order to maintain the same GAP‐SAG fifigures.


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Case No.1‐ Variation of FSTB Stiffness

Results:A‐ Bearing loads.

FSTB Stiffness variation effect on Bearing Loads

100

120

FSTB Stiffness variation effect on Bearing Loads

ASTB/10 FSTB AGB FGB

60

80

kN)

40

60

Load

(k

0

20

4.00E+07 4.00E+08 4.00E+09 4.00E+10


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Stiffness (N/m)

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

0.525

0.53

FSTB Stiffness variation effect on Shaft Slope at ASTB

0.51

0.515

0.52

mm/m

)

Shaft Slope at ASTB

0.495

0.5

0.505

Slop

e (m

p

0.494.00E+07 4.00E+08 4.00E+09 4.00E+10

Stiffness (N/m)


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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.





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ASTB Stiffness variation effect on Bearing Loads

70

80

90

ASTB Stiffness variation effect on Bearing Loads

ASTB/10 FSTB AGB FGB

50

60

70

(kN)

20

30

40Load

0

10

20

2.00E+08 2.00E+09 2.00E+10


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Stiffness (mm/m)


Results:B‐ Slope of the shaft inside Aft Sterntube Bearing.

ASTB Stiffness variation effect on Shaft Slope at ASTB

0.7

0.75

ASTB Stiffness variation effect on Shaft Slope at ASTB

0.6

0.65

(mm/m

) Shaft Slope at ASTB

0 45

0.5

0.55

Slop

e

0.4

0.45

2.00E+08 2.00E+09 2.00E+10

Stiffness (N/m)


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Case No.3‐ Variation of GB Bearings Stiffness. (OR Main Engine fo ndation stiffness)(OR Main Engine foundation stiffness)

Working Domain:‐Variation of Gearbox Bearings stiffness from 2.0E7 N/m to 1.0E11 N/m.


GBFSTBASTB

‐All other bearings assumed stiffness kept constant.



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Case No.3‐ Variation of GB Bearings Stiffness. (OR Main Engine fo ndation stiffness)(OR Main Engine foundation stiffness)


100GB bearings Stiffness variation effect on Bearing Loads

70

80

90ASTB/10 FSTB AGB FGB

50

60

70

Load

(kN)

20

30

40

L

0

10

2.00E+07 2.00E+08 2.00E+09 2.00E+10

Stiffness (N/m)


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Stiffness (N/m)

Case No.3‐ Variation of GB Bearings Stiffness. (OR Main Engine fo ndation stiffness)

Results:

(OR Main Engine foundation stiffness)

Results:B‐ Slope of the shaft inside Aft Sterntube Bearing.

GB bearings Stiffness variation effect on Shaft Slope at ASTB

0.536

0.538

GB bearings Stiffness variation effect on Shaft Slope at ASTB

0.532

0.534

mm/m

)

Shaft Slope at ASTB

0.528

0.53

Slop

e (m

0.524

0.526

1.00E+07 1.00E+08 1.00E+09 1.00E+10 1.00E+11

Stiffness (N/m)


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( / )

Discussion of results

A Bearing loadsA‐ 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.

12090 100

60

80

100

50

60

70

80

50

60

70

80

90

20

40

60

10

20

30

40

10

20

30

40

50

04.00E+07 4.00E+08 4.00E+09 4.00E+10

0

10

2.00E+08 2.00E+09 2.00E+10

02.00E+07 2.00E+08 2.00E+09 2.00E+10

C 1 C 2


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Case 1Variation of FSTB Stiffness

Case 2Variation of ASTB Stiffness

Case 3Variation of GB B. Stiffness


B Slope of the shaft inside propeller bearingB‐ Slope of the shaft inside propeller bearing.

Is the slope of the shaft inside the propeller bearing (only) is judgeable ?

0.52

0.525

0.53

0.65

0.7

0.75

0.534

0.536

0.538

Shaft Slope at ASTB

0 5

0.505

0.51

0.515

Shaft Slope at ASTB

0.5

0.55

0.6

f0.528

0.53

0.532

0.49

0.495

0.5

4.00E+07 4.00E+08 4.00E+09 4.00E+100.4

0.45

0.5

2.00E+08 2.00E+09 2.00E+10

Shaft Slope at ASTB

0.524

0.526

1.00E+07 1.00E+08 1.00E+09 1.00E+10 1.00E+11

Case 1Variation of FSTB Stiffness

Case 2Variation of ASTB Stiffness

Case 3Variation of GB B. Stiffness


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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 0 669

Lubricant White metal

Bearing 1 244 182 5 0.221 0.669Bearing 2 284 129 5 -0.060 0.511Bearing 3 803 5 0 0.000 -0.163 Bearing 4 1325 78 5 0.719 0.447 Bearing 5 1436 59 4 1.223 0.474

238 -1.074 7.340E-004 235233 15 -220244 -1.036 7.200E-004 246710 16 -221244 -1.035 7.200E-004 246930 16 -221249 -1.000 7.050E-004 248883 16 -39254 -0.964 6.910E-004 250869 16 -40259 -0.930 6.770E-004 252888 16 -40264 -0 896 6 620E-004 254940 17 -41264 -0.896 6.620E-004 254940 17 -41269 -0.863 6.470E-004 257025 17 -42274 -0.831 6.320E-004 259143 17 -42279 -0.799 6.170E-004 261294 17 -43284 -0.769 6.020E-004 263463 17 -44292 -0.723 5.790E-004 256819 17 84


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Then a traditional evaluation of the oil fils stiffness can be checked.


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Part 2‐Lateral vibration study.

Introduction BasicsIntroduction‐ Basics

Vib ti I h i tiVibration: Is a harmonic motion.

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).


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Introduction Lateral vibration mode shapes Amplitude Introduction‐ Lateral vibration mode shapes and stiffness components.

λ4

λ1

λ2

λ3

λ1 > λ2 > λ3 > λ4 Ω1 < Ω2 < Ω3 < Ω4

wave lengths vibrating frequencies


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Introduction System response amplification factor with related damping

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Introduction‐ System response amplification factor with related damping.

4

or

η=0

η=0.1

η=0.2

3

plification

facto η 0.2

η=0.3

η=0.4

η=0.5

η=1

1

2

Amp

η=1.5

η=2

η=7

00 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6


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Ω/Ωn


Introduction Lateral vibration and whirlingIntroduction‐ Lateral vibration and whirling.

System stiffness diagram in lateralWhirling case during testReal life whirling case System stiffness diagram in lateralWhirling case during testReal life whirling case


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Case study‐ Variation of ASTB Stiffness

Working Domain:‐Variation of Aft Sterntube bearing stiffness from 3.0E8 N/m to 5.0E10 N/m.





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Case study‐ Variation of ASTB Stiffness

Results:

ASTB Stiffness variation effect on ASTB Stiffness variation effect on

700

750

800

M)

ASTB Stiffness variation effect on Shaft natural frequency (order1)

170

180

190

)

ASTB Stiffness variation effect on Propeller natural frequency (order4)

550

600

650

700

Speed (RPM

Shaft natural frequency (order1)

130

140

150

160

170

Speed (RPM

)

Propeller natural frequency (order4)

5002.00E+08 2.00E+09 2.00E+10

Stiffness (N/m)

120

130

2.00E+08 2.00E+09 2.00E+10Stiffness (mm/m)

p q y ( )

1‐ Lateral vibrationShaft natural frequency.

2‐ Lateral vibrationPropeller blades natural frequency.


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1‐ Lateral vibration, Shaft natural frequency.

How it Built?What is the Natural frequency and Excitation frequency ? What is the mode shapes?

Cl d hClear mode shapes. Integrated mode shapes.


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1‐ Lateral vibration, Shaft natural frequency

Most determined mode shapes: Cantliver , First bending.

How to handle?

D i H li ht ff t th

Direction of the local/global response.

Damping: Have a slight effect on the cantiver mode and almost no effect on the first bending (Global response direction is linear toward the maximum 2

3

4

5

direction is linear toward the maximum bending without resistance).

0

1

2

0 0.5 1 1.5

General conclusion: Running close to reasonance have to be avoided.


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2‐ Lateral vibration, Propeller blades natural frequencyfrequency

How it built?


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180

190 Propeller natural frequency (order4)

What is the Natural frequency and Excitation frequency ? What is the mode shapes?

150

160

170

180

120

130

140

2 00E+08 2 00E+09 2 00E+102.00E+08 2.00E+09 2.00E+10

4

5

1

2

3


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00 0.5 1 1.5


How to handle?Diametrical Damping

Propeller shaft response to vibration

How to handle?2.1) Shaft impact (Direct impact)

Most determined mode shapes: Cantliver First bendingCantliver , First bending.

Direction of the local/global response.Propeller damping (Resistance) effect due to this applied vibration motion have to be considered as it is very effctive (Propeller diametrical 5

damping).

So far the damping is effective, then a view f th it ti f i i t t ll

2

3

4

The system response of this vibration motion should be followed up as it is an excitation force

of the excitation force is important as well.

0

1

0 0.5 1 1.5


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should be followed up as it is an excitation force for another vibration motion‐‐‐‐ >

2‐ Lateral vibration, Propeller blades natural frequency

How to handle?

frequency

Aft Sterntube bearing vibration, (Consequence of main propeller

How to handle?2.2) ASTB impact (indirect impact)

(Consequence of main propeller viberation).Bending variation leads to load variation into the bearingbearing.

Bearing Damping capability.

Is the bearing damping able to dominate the new intreduced harmonic load?

Is the viberation motion charctrestics acceptable ?


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Questions and discussion !

BERG PROPULSION PRODUCTION ABBERG PROPULSION PRODUCTION ABMohamed ZeidNaval Architect ‐ Rotordynamics Specialist

Direct: +46 31 30 10 736Mobile: +46 761 175 022E‐mail: [email protected]@ gp p

www.bergpropulsion.com

31DNV Software User Conference

Busan July 2012

Shaft Alignment and Whirling Vibration

Technology

Transcript of Shaft Alignment and Whirling Vibration