Friday, January 31, 2014

Marine gas turbine (GT)

In the name of Allah (The most supreme knowledge)

An aircraft can use the energy in the gas stream directly to provide the propulsive power eg in a jet. In the marine environment this is not feasible because of the very nature of the surroundings , the noise, the requirement to reverse and limitations imposed by the construction of the ship. The GT must be used to drive a propeller/water jet/generator. Because of this requirement we may consider the marine GT to be split into two main parts.

·         The gas generator- that providing the high energy gas stream.
·         The power producer- that converting the energy in the stream into a useful form of power eg shaft power(power turbine)

Hence it is possible to adapt an aircraft engine for  marine use by the addition of a power turbine eg Olympus SMIA.
In addition marine GTs are not nearly so restricted for space as the aero versions and therefore it is theoretically possible to attempt to improve the performance by using one or more of the following:

  • Intercooling
  • Reheat
  • Heat exchanger
  • Water injection
  • Waste heat recovery


REASONS FOR THE ADOPTION OF GAS TURBINE

  1. The aim to be able to explain the reasons why the royal navy and other navy is adopted gas turbines as main propulsion units in major surface warships, the typical problems associated with running them at sea and their solutions.

  1. The resons for using gas turbine in warships:

·         High power/weight ratio.
·         Quick startup capability
·         Comparatively low development cost.(benefits from aero engine development)
·         Low onboard maintenance requirement.
·         Ease of upkeep by exchange of critical parts.
·         Reduced watchkeeping manpower.
·         Good SFC at high power.
·         Availability
·         Reduced underwater noise(fewe hull openings)


  1. Typical problems and solutions

·         Distortion of combustion chambers- ongoing design effort, regular inspection.
·         Combustion of naval fuels-redesign of combustion system.
·         Compressor fouling-air filtration, regular washing.
·         Surge and rotating stall- air bleeds, variable geometry blades.
·         Turbine Disc failures – Design effort, defined service life.
·         Bearing failures- Uprated bearings, earlier detection of possible failure.
·         Fuel consumption at part load- multispool variable geometry engines, higher operating temperature.
·         Practical problem of a complex cycle- no solutions at present.


·         Poor life of aero types –rapid engine change capability-comprehensive repair/rebuild facilities, life continually being upgraded.