Tuesday, June 23, 2020

Derating of engine

  • A vessel’s engine and propeller are optimized and designed for a given operational and max. speed.
  • If the operational speed of the vessel is generally lower than the one originally optimized for, it may be beneficial to consider derating of the main engine and propeller.
  • Derating as a retrofit product offers reduction of the total fuel consumption by improving the match between the operational speed and optimization speed.
  • Derating is usually an attractive option for fuel oil savings if a reduction of 10-15% of the max. speed at SMCR can be accepted.
  • It is a techno-commercial concept done at the time where shipping industry is in bad shape
Methods:
  • Readjusting fuel timing
  • Decreasing compression ratio
  • Fuel nozzle size
  • Turbocharger matching
  • t/c, propeller and shaft matching
Fuel saving originates from
  • Optimisation of the engine and propeller layout to the actual operational speed
  • Utilisation of the latest engine tuning methods
  • Utilisation of state-of-the-art high efficiency propeller design.
Derating projects includes
  • Specification of new operating/optimisation speed and max. speed of the vessel
  • Engineering
  • Design of new propeller
  • Derating of the engine
  • Rematching of turbocharger(s)
  • On board NOx measurements (parent engine)
  • New technical file
  • Torsional vibration calculation report
  • Shaft alignment calculation report.
RATE SHAPING
  • A fuel injection rate shaping control system is provided which effectively controls the flow rate of fuel injected into the combustion chamber of an engine to improve combustion and reduce emissions by controlling the rate of pressure increase during injection.
  • The injection rate shaping control system includes a rate shaping control device including a rate shaping transfer passage having a predetermined length and diameter specifically designed to create a desired injection pressure rate shape.

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