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Vibration dampers

by | Jan 31, 2024 | INSIGHT

The periodic combustion cycles of 2-stroke and 4-stroke engines create torque fluctuations that cause torsional vibration to be passed down the ship's propulsion system. Therefore, when developing a damper, the objective is to isolate as much of the propulsion system as possible from the torsional vibration caused by the engine's rotating mass.
Vibration dampers INSIGHT feature image
Vibration damper live sketch

What is damping in vibration?

Damped vibrations occur when the energy of a vibration diminishes over time, eventually coming to a complete stop. These vibrations involve a periodic motion of an object, characterized by a reduction in amplitude due to the presence of a resisting force.

Vibration damper live sketch

What is the function of a vibration damper?

The functioning principle of a dumper is simple yet efficient. The vibration torque range is moved to a lower resonance speed range due to the additional mass on the transmission input shaft. Moreover, this ensures excellent damping of engine vibration even at idle speeds.

DAMPING OF TORSIONAL VIBRATIONS OF CRANKSHAFTS OF SHIP ENGINES

For many years, for the damping of torsional vibrations of ship engine crankshafts, the following kinds of dampers have been used:

  • frictional dampers
  • rubber dampers
  • viscous dampers
  • spring dampers

Further, among the above-mentioned group of dampers, the viscous one is the most popular and successfully used for controlling the vibration level of ship large-power medium-speed engines.

Nevertheless, before commencing the design of a viscous torsional vibration damper, its designer should obtain an appropriate set of necessary data from the engine producer.

The data should contain the information on:

  • Kind of fuel (petrol, diesel oil)
  • Number of cylinders
  • Type of the engine (two-stroke, four-stroke)
  • Minimum rotational speed of the engine
  • Maximum rotational speed of the engine
  • Range of operational speed of the engine (if not constant)
  • Ignition sequence
  • Main journal diameter
  • Crank journal diameter
  • Cylinder diameter
  • Mean indicated pressure
  • Total weight of masses in reciprocating axial motion
  • Torsional stiffness of shaft between cylinders
  • Permissible value of the twist angle of the shaft
  • Limitations for damper gabarites

As written above, 2-stroke marine drivetrain systems must deal with several challenges influencing a system’s dynamic behavior and torsional vibrations.

Markedly, the Geislinger Damper is a finely tuned torsional vibration damper equipped with steel springs that optimize the natural frequency of a system, effectively mitigating the most critical resonances. Tailored for applications demanding high performance, compact design, and cost-effectiveness, the Geislinger Damper maintains constant stiffness and high damping throughout its service life.

Similarly, Geislinger VDAMP® and VDAMP®XT are viscous dampers designed to safeguard engine camshafts and crankshafts, preventing potential damage from torsional vibrations and avoiding barred speed ranges. These dampers convert vibration energy into heat, dissipating from the damper’s surface into the surrounding air.