This article reviews that twenty-first century passengers on the Royal Caribbean International and Celebrity Cruises are set to make history in style. Up to six of Royal Caribbean’s Voyager- and Millennium-class vessels will be the first cruise ships ever powered by General Electric’s gas turbines. In addition to reducing engine-room noise and vibration and cutting emissions, this propulsion system—a departure from the traditional diesel engine—will make it possible for ships to set sail with a reduced maintenance crew and smaller parts inventory. Royal Caribbean International currently operates a fleet of 12 ships. In the Royal Caribbean application, the GE gas turbine will be used to drive generators that will provide electricity to propeller motors. The steam turbine will recover heat from the gas turbine exhaust for other uses. This combined gas turbine and steam turbine integrated electric drive system represents a departure from diesel engines in more than one respect.
Twenty-First Century passengers on the Royal Caribbean International and Celebrity Cruises are set to make history in style: Up to six of Royal Caribbean's Voyager-and Millennium-class vessels will be the first cruise ships ever powered by General Electric's gas turbines. In addition to reducing engine-room noise and vibration and cutting emissions, this propulsion system-a departure from the traditional diesel engine-will make it possible for ships to set sail with a reduced maintenance crew and smaller parts inventory.
"We have designed these to be the most environmentally sensitive cruise ships in the world," said Richard D. Fain, chairman and chief executive officer of Royal Caribbean Cruises, Ltd., in Miami, Fla.
"This technology introduces a new era in cruise-ship design, and marks the first partnership between a major American technology company and foreign-flagged cruise lines."
Royal Caribbean International currently operates a fleet of 12 ships. These ships hosted more than 1.4 million guests in 1998 and brought them to such diverse locales as Alaska, the Bahamas, the Caribbean, Europe, Hawaii, Mexico, New England, and the Panama Canal.
The company has long been a trendsetter in cruise ship design. In 1970, Royal Caribbean launched the Song of Norway, the first ship purposely built for warm-weather cruising. Among the vessel's design innovations was a cocktail lounge cantilevered from the rear of the smokestack.
By 1978, when the demand for cruise ships outstripped supply, Royal Caribbean marine engineers scored another coup: By cutting the Song of Norway in half, they were able to add an 85-foot section. This was the first lengthening of a major cruise ship, but not the last for Royal Caribbean, which extended its Nordic Prince in 1980.
In this decade, Royal Caribbean designed its Vision-class ships, each capable of berthing 11,508 passengers. Two of these vessels are equipped with 18-hole miniature golf courses for the seagoing duffer.
Aeroderivative Gas Turbines
Typically, cruise ships use four or five medium-speed (500 revolutions per minute), 8-to-10-megawatt diesel-fueled generator sets, according. to Carl Brady, manager of advanced marine programs at GE Marine Engines, Even-dale, Ohio. Brady is also a member of the American Society of Mechanical Engineers International Gas Turbine Institute Marine Technical Committee. Brady said that, as far as is known in maritime circles, the Royal Caribbean ships will be the first cruise vessels equipped with gas turbines.
Royal Caribbean managers considered using turbine technology on the company's cruise ships for several years, and later worked with their counterparts at General Electric to develop a cruise ship power application.
Each ship will be equipped with a pair of GE Marine Engines' LM2500+ aeroderivative gas turbines and a single steam turbine from an as-yet unspecified manufacturer. In the Royal Caribbean application, the GE gas turbine will be used to drive generators that will provide electricity to propeller motors. The steam turbine will recover heat from the gas turbine exhaust for other uses.
This combined gas turbine and steam turbine integrated electric drive system (COGES) represents a departure from diesel engines in more than one respect. Ship builders customarily approach a variety of suppliers to provide power system equipment. Royal Caribbean, however, used a single company-S&S Energy Products, a GE Power Systems business based in Houston-to package the gas turbines and integrate the propulsion system. S&S engineers will place the gas turbines into acoustic enclosures along with the requisite control, fuel and lube oil systems, piping, and associated equipment.
A major advantage of the COGES power plant is that it will lower noise and vibration levels. This should improve the comfort of all passengers, particularly those in cabins aft of the ship. In addition, turbine technology minimizes a ship's environmental impact. Turbines produce reduced air emissions, sludge, and oil waste in comparison with diesel engines, according to William K. Reilly, an Environmental Protection Agency administrator. Reilly also serves on Royal Caribbean's board of directors and advises the company on its environmental operations. "Emssions of nitrous oxides are lowered 80 percent and sulfur oxide 98 percent, resulting in much lower emissions than from typical diesel engines," said Reilly. Using gas turbines also eliminated the need for the selective catalytic-reduction equipment and special exhaust-treatment systems that would be required by diesels.
The compactness of the COGES machinery is another plus, according to Brady of GE Marine Engines. "The power density of a modern aeroderivative gas turbine is about 1,500 kilowatts per cubic meter, compared [with] only about 80 kilowatts per cubic meter for a marine, medium speed diesel engine," he said. When the gas turbine is packaged in an acoustically and thermally insulated enclosure, as is typical of a shipboard installation, its power density is reduced to about 400 kW per cubic meter. Despite the reduction, this power density is still five times that of its diesel counterpart. The gas turbine auxiliary equipment support systems are also more compact than diesels. This saved space can be converted into additional passenger rooms, or public rooms and activity areas.
The energy recovered by the COGES power plant offers other benefits. "By utilizing the waste heat from the turbine's exhaust, we're able to produce a major portion of the electricity for the ship services, from heating water to air conditioning, and it eliminates the need for additional energy-depleting machinery," noted Harri Kulovaara, senior vice-president of marine operations at Royal Caribbean. "The gas and steam turbine arrangement will also reduce the size of the maintenance crew and parts inventory," he added.
GE engineers created the LM2500+ by improving upon the GE LM2500 aeroderivative gas turbine. The LM2500 was adapted from the GE's CF6 family of commercial aircraft engines and the TF39 military engine.
The LM2500+ was designed as a more powerful version of its predecessor with lower life-cycle costs. GE engineers increased the turbine's compressor airflow 23 percent with a minimal increase (approximately 35 degrees C) in combustor firing temperature. This raised the power of the turbine while maintaining reliability and availability.
The LM2500+ is a 3,600 revolution machine that provides 39,000 brake horsepower, with a simple-cycle thermal efficiency of 39 percent. The LM2500+ is rated at 25,000 kilowatts output power at the generator terminals over an ambient temperature range from 0 degrees C to 32 degrees C at the installed inlet and exhaust. Depending on the amount of steam required for on-board services, the LM2500+ will achieve a combined-cycle thermal efficiency of roughly 45 to 50 percent.
The first two 85,000-ton Millennium ships destined for Celebrity service are due in June 2000 and January '2001. These will be built by Chantiers de l' Atlantique in St. Nazaire, France. The first of Royal Caribbean's Voyager-class ships is scheduled for completion in February 2001 by Meyer Werft in Papenburg, Germany. The cruise line has options to build an additional three ships by 2003. If people are as eager for stress-free, sumptuous, and environmentally conscious travel as they were in the 20th century, prospects are good for these quieter and greener luxury craft.