3 CHOOSING THE RIGHT GAS TURBINE AIR INTAKE FILTRATION SYSTEM Regional conflicts and growing international security concerns more generally are prompting the world’s navies to expand their operational fleets. Gas Turbine (GT) propelled surface vessels and marine warships are at the heart of many of these taskforces, helping deliver an advanced capability to manoeuvre and to quickly engage and pursue targets at sea. Modern naval vessels are moved through the water using powertrain combinations of either reciprocating engines, electric motors and/or gas turbines to provide the propeller rotating forces necessary. In many instances when GTs are employed, they are engaged only when additional speed is required, perhaps in pursuit of criminal gangs or during evasive manoeuvres, or when the vessel is close to shore and combustion exhaust emissions are more stringent. A reliable propulsion system, however, is always critical to the vessel’s function and the primary power sources employed simply cannot be allowed to fail to operate when called upon. It is difficult to envisage any single characteristic more important to a naval marine surface vessel engaged in combat operations than the reliability and availability of its propulsion system. Image 1 below shows some common powertrain configurations available for propeller driven naval surface vessels. Gas Turbines ingest enormous amounts of ambient air as part of their combustion process. Air that left untreated will contain all manner of airborne contaminants, all of which will do serious damage, erosion, corrosion and fouling of the highly optimized GT internals. Harsh weather conditions, high levels of small airborne particulate in the form of sand, dust, airborne hydrocarbons and salt aerosols, added to the concentration seasonality of these contaminants are just some of the challenges faced by a gas turbine air intake filtration system operating at sea. The offshore environment is brutal for any piece of equipment, let alone one that needs to continuously run in the face of harsh storms, sea spray, mist, fog and almost every other type of water challenge. Naval marine vessels can also be located anywhere in the world, near or far from the shoreline. These systems therefore need to be designed to be able to remove sand and particulate blown seawards from the land as well as the corrosive salts churned up from the ocean. Image 1 – Common naval propulsion system configurations Reduction gearboxes Reduction gearbox Diesel generators Reduction gearboxes Diesel engines Diesel engine Gas turbine Gas turbine High speed gas turbine Multispeed gearboxes Electric motor Cruise gas turbine Gas turbine Clutches Clutches Clutches Clutches Diesel generator Crossconnect gearbox Gearbox Gearbox Controllable pitch propeller Propeller Propeller Propeller CODAG Combined Diesel and GT COGAG Combined GT and GT IEP Integrated Electric Propulsion CODOG Combined Diesel or GT CODLOG Combined Diesel Electric or GT COGOG Combined GT or GT Gearboxes Propeller Propeller Reduction gearboxes Electric motor Gas turbines Gas turbine
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