Numéro : 2566 - Year : 2009
The different evolutions of gas turbines for military ship propulsion, fuel consumption and emissions
Dominique MIGNOTTE, DCNS Bu Propulsion
Bertrand LARS, DCNS Bu Propulsion
Celia CONSONETTI, DCNS Bu Propulsion
Symposium on the marine pollution regulations until 2012
The development of naval gas turbines occurs mainly after the Second World War from the said turbines “aero derivatives” which its very low ratio mass/power in regard to Diesel engine is the major characteristic. Several propulsion architectures have been designed all along the time COGOG, COGAG, then CODAG, CODOG, and more recently CODLOG, CODLAG, etc. Mass is an important data for installation, nevertheless the other parameters as inlet and exhaust and auxiliaries shall be taken into account. The development of these turbines has followed the jets engines’ one without reaching the competitive level of diesel fuel consumption. The specific fuel consumption is a handicap for the use of gas turbine so gas turbine with recuperator has been developed as the WR 21 and used on board of Britannic T45 frigates. Another way to reduce fuel consumption concerns the propulsion architectures evolution towards an association of Diesel engines for the low and cruising speeds and the gas turbines for high speed becomes a propulsion standard.
The Navy ships use commonly gas oil as fuel, the exhaust pollutant emissions are limited to NOx (SOx are emitted at a very low level due to the very low level of sulphur content in gas oil used by navy ships at NATO standards). Only Siemens Company continues to develop a marine gas turbine non aero derivative able to burn heavy fuel.
Gas turbines are not subject today to follow the exhaust pollutant emissions limitations (i.e. IMO rules). If there will be an important evolution of the rules the use of said dry “DLE” combustors to reduce NOx emissions can be used on board of navy ships. However if considering the NOx emissions at the gas turbine exhaust which are much lower than Diesel one’s adversely the CO2 are much higher.
The FREMM frigates propulsion in building process (first tests planed for 2010) developed by DCNS become therefore as the good compromise of a clean ship and economical between the use of Diesel electric to minimize the fuel consumption in transit speeds and the use of a unique cross connected gas turbine for high speeds.
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