GE's M a r i n e Gas Turbine Family Expanding To Satisfy The Markets

It was 1974 when the first of GE's advanced-technology marine gas turbines, the LM2500, entered naval service aboard the U.S. Navy's USS Spruance (DD-963). Since that time, the LM 2500 has been selected by 17 other navies, GE has introduced other marine gas turbines, and the served market for GE's engines has continued to expand every year. The shift to marine gas turbines for surface combatants for all worldwide navies is virtually complete, and now the trend appears to be a broadening of the served market (see Figure 1).

The U.S. Navy was not the first major navy to shift to gas turbines for its primary propulsion system for a major ship class; however, since that original commitment, the USN has been steadfast in its use of gas turbines for all subsequent classes of surface combatants short of their supercarriers. The overwhelming success of the Spruance Class lead to the Perry Class frigate, Pegasus Class hydrofoil, Kidd Class destroyer, Aegis Class cruiser, and now the newest class, the Burke Class destroyer. Today there are more than 100 LM2500-powered ships in service in the U.S. Navy.

The widespread use of the LM2500 marine gas turbine is attributable to the simplicity, compactness, and unprecedented availability of the propulsion system. Moreover, maintenance requirements on the LM2500 have been far below original expectations and reliability continues to grow each year. During a recent Navy League meeting in Washington, an admiral expressed the U.S. Navy's experience with the LM2500 very succinctly and accurately as "...The only thing we ever did that exceeded our expectations." The acceptance by international navies of the LM2500 has closely paralleled the U.S. Navy except that the international navies have hastened to adapt the engine to a much broader range of ship classes and sizes. For many of these navies, operational requirements dictate a much higher level of mobility to cope with local conditions. This has resulted in the general acceptance of the CODOG propulsion system configuration by many of these navies.

In this system, the high-speed diesel engines are used to provide excellent endurance, and the gas turbine( s) provides sprint capability for reacting to emergencies and responding to conflicts. Overall, the system is very compact and lightweight so that ship payload factors are not influenced by this added mobility. In fact, the growth in the popularity of the high-speed corvette and lightweight frigate has been fostered in part by the availability of these highly efficient designs.

Marine gas turbines are used extensively from corvettes of less than 1,000 tons up to aircraft carriers (see Figure 2). With the availability of advanced-technology smaller gas turbines and the growing demand for more mobility, i.e., responsiveness, power availability, and speed, the use of gas turbines in standard hulls less than 500 tons (e.g., the Stanflex 300) as well a unconventional hull forms, such as SESs, ACVs, etc., is expanding. This trend has been boosted with the emergence of a series of small, compact, and very efficient marine gas turbines which are currently offered by GE (see Figure 3). Capitalizing on the unprecedented success of the LM2500 in marine service, these engines are destined to open a variety of new markets to marinized/indus- trialized aircraft gas turbines. As an example, the LM120 has been selected as the prime mover for the marine propulsion system demonstrator for the U.S. Marine Corps' new high-speed amphibious assault vehicle.

The shift to marine gas turbines in international navies has not been limited to high-speed, lightweight patrol craft. LM2500-based marine propulsion systems are powering the largest naval ships recently commissioned, e.g., the Italian Navy's aircraft carrier Garibaldi and the Spanish Navy's aircraft carrier Principle de Asturias. Moreover, this same pattern is emerging in the U.S. Navy with the selection of an LM2500-based propulsion system for the AOE-6 fast support ship (displacement 55,000 tons) and apparent recommendation of the same system for the LHD-5 amphibious assault ship (displacement 43,000 tons). The merits of marine gas turbine propulsion of design simplicity, lower first cost, higher system availability, and lower life-cycle costs are now recognized to be applicable to all classes of naval ships from fast patrol boats to large aircraft carriers and support ships. Additionally, the U.S. Navy is now reaping major logistics benefits from its standardization to the LM2500.

The marine gas turbine has been responsible for the emergence of another market, i.e., propulsion system modernization. With the escalation in the cost of replacing ships, many navies are planning to modernize current ships and thus extend their life by 15 or 20 years. The first major step in this direction will be the re-engining of an aircraft carrier with LM2500 gas turbines. The compactness of gas turbines plus the availability of fluid couplings that permit the retention of shafting, propellers and gearboxes make virtually any steam propulsion system amenable to modernization with current marine gas turbines.

Broader consideration of this concept is anticipated as new ship prices continue to rise exponentially- The future for marine gas turbines in naval ships appears very bright as the emphasis on design flexibility, system availability, and life-cycle costs continues to dominate the propulsion system selection process. The combined development of electric-drive transmission systems and an intercooled regenerative gas turbine should further heighten the commitment of naval ship designers and operators to gas turbine propulsion.

It remains to be seen when marine gas turbines will challenge the dominance of the ubiquitous diesel in the commercial marine market.

The demand for speed, the value of space, and the value of on-charter time, i.e., ship availability, are militating in favor of the high-power density and reliability of marine gas turbines. These factors coupled with the proven performance of engines like GE's LM2500 would suggest that gas-turbine-powered cruise liners, containerships, and car/passenger ferries may be just over the horizon.

For free literature detailing the full line of marine gas turbine engines offered by GE for both naval and commercial applications, Circle 8 on Reader Service Card

Maritime Reporter Magazine, page 82,  Apr 1989 Washington

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