AN EXAMINATION OF THE EFFECTS OF VARIABLE INERTIA ON THE TORSIONAL VIBRATIONS OF MARINE ENGINE SYSTEMS

The analysis of torsional vibrations in the running gear of reciprocating engine systems is normally carried out by neglecting the variation in inertia torques of the system arising from the motion of the reciprocating parts. When the variable inertia effect is allowed for the equation of motion taking into account the effect is non-linear. Assuming small displacements, the equation can be linearized to predict important characteristics of the motion. Such an equation when solved by numerical methods using a digital computer predicts the regions of instability and the manner in which the amplitude and frequency vary with the speed of rotation of the engine. The responses of the system show a modulation of amplitude and frequency at definite rotational speeds. The occurrence of such a modulation in amplitude and frequency is established by use of the process given by Wentzel, Kramers, Brillouin and Jeffreys generally known as the WKBJ approximation. The first order term in the equation and the forcing term which represents the outer impulse from the reciprocating parts, are investigated for their effect on the waveforms of the responses of the system. Futher investigations of the effect of lower order external excitations on the characteristics of the motion are given. Theoretical results are compared with solutions of the equation obtained from an analogue computer. A discussion of some actual cases from engines in service is included.

• Availability:
  • Find a library where document is available. Order URL: http://worldcat.org/issn/03093948
• Corporate Authors:

  Institute of Marine Engineers

  Memorial Building, 76 Mark Lane
  London EC3R 7JN,   England 
• Authors:
  • Carnegie, W
  • Pasricha, M S
• Publication Date: 1972

Media Info

• Pagination: p. 160-165
• Serial:
  • Institute of Marine Engineers Transactions
  • Volume: 84 P
  • Issue Number: t6
  • ISSN: 0309-3948

Subject/Index Terms

• TRT Terms: Engines; Inertia (Mechanics); Inertial forces; Torsion; Vibration
• Old TRIS Terms: Engine vibration; Torsional vibration
• Subject Areas: Marine Transportation; Materials; Vehicles and Equipment;

Filing Info

• Accession Number: 00035222
• Record Type: Publication
• Source Agency: United States Merchant Marine Academy
• Files: TRIS
• Created Date: Oct 27 1972 12:00AM