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This is a description of a short course that our president and chief engineer, Mark A. Corbo, P.E., teaches at the client’s site. Depending on the amount of audience interaction that takes place, the short course lasts for about 6 to 7 hours. The short course is split into two halves of approximately equal length. The first half consists of a general primer on the fundamentals of torsional vibration and a generic design procedure that can be used for all rotating equipment. The second half focuses exclusively on marine propulsion systems and the specific manner in which they should be handled from a torsional analysis standpoint.

An approximate agenda for the short course is as follows:

  1. Introduction

  2. Torsional Vibration Fundamentals
    1. General Description of Free and Forced Torsional Vibration
    2. Preparation of Lumped Parameter Models
    3. Undamped Torsional Vibration Analysis
    4. Coupling Modes vs. Shaft Modes
    5. Methods for Checking Computer Results by Hand
    6. Generation of Campbell Diagrams
    7. Torsional Vibration Excitation Sources
    8. Synchronous Motor Startups
    9. Types of Variable Frequency Drives
    10. Torsional Problems Associated With Variable Frequency Drives
    11. Determination of Interference Points
    12. Elimination of Interference Points by Inspection
    13. Representative Excitation Torque Magnitudes
    14. Common Damping Sources
    15. Determination of Damping Coefficients
    16. Steady-State Damped Response Analysis
    17. Transient Torsional Vibration Analysis
    18. Short Circuit Analysis
    19. Determination of System Adequacy
    20. Shaft Endurance Limit Determination
    21. Detailed HCF and LCF Fatigue Life Analysis Procedures
    22. Methods for Eliminating Problems
    23. Elastomer-in-Compression Couplings
    24. Hydraulic Couplings
    25. Overall Analysis Procedure
    26. Case Studies

  3. Torsional Vibration of Marine Propulsion Systems
    1. Typical Marine Propulsion Systems
    2. Need to Assess Multiple Operating Modes
    3. Modeling of Diesel Engine Crankshafts, Connecting Rods, and Reciprocating Parts
    4. Added Mass Effects in Propellers
    5. Typical Mode Shapes in Marine Propulsion Systems
    6. Diesel Engine (Gas Pressure & Inertia) Excitations
    7. Diesel Engine Fourier Coefficients
    8. Diesel Engine Major & Minor Orders
    9. Diesel Engine Damping
    10. Propeller Excitations & Damping
    11. Handling of Variable Pitch Propellers
    12. Forced, Damped Response Analysis Plots
    13. Determination of FC and FT Stress Limits for Intermediate & Propeller Shafting
    14. Barred Speed Ranges
    15. Effect of Changing Diesel Engine Loading Conditions
    16. Diesel Engine Misfire Condition
    17. Reciprocating Equipment Criteria for Acceptability
    18. Methods for Eliminating Problems
    19. Viscous Dampers
    20. Overall Analysis Procedure
    21. Coupling Between Torsional & Longitudinal Vibrations
    22. Case Studies

  4. Conclusion

Some of the benefits a client’s personnel receive from taking this short course include the following:

1. A greater familiarity with torsional vibration fundamentals, which would allow them to communicate more effectively with experts in the field.

2. A better understanding of the meaning and validity of torsional vibration results obtained from consultants and/or in-house computer codes.

3. An appreciation that, contrary to the approach of most engine manufacturers, torsional analysis is not a trivial task that can be handed to any junior engineer with a computer code.

4. A better understanding of the torsional vibration causes of common problems in marine propulsion systems which would assist them when trying to troubleshoot field problems.

5. A better feel for which components in a marine system play an important role in torsional vibration behavior and which ones have little impact. This would be valuable when evaluating potential design changes.

6. An appreciation that torsional vibration analysis can be performed in a practical and timely manner and does not require a "research project."

7. An appreciation for the large role that torsional vibration behavior plays in the reliability of marine propulsion systems and for the importance of evaluating that behavior in the design stage.

The short course is presented using multi-color Power Point presentation software. Each employee the client sends to the short course receives a complimentary copy of our paper, "Practical Design Against Torsional Vibration," and a pdf file containing all the slides presented in the short course.


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