R&D

R&D SPECTRE Closed Cycle Diesel

The Netherlands' RDM submarine shipyard offers its "Spectre" Closed Cycle Diesel  as an AIP option for the yard's 1,800-ton Moray 1800 H submarine; none have been built yet, but RDM estimates that a hybrid-powered Moray could remain submerged for 20 days while cruising at two knots. 

On this page you will find some articles explaining the Closed Cycle Diesel system

Karen Winzoski, Mar 24 2000.

. . . . . .Perhaps the simplest of AIP conversions is the closed-cycle diesel (CCD). A CCD engine works like a regular diesel engine, except that it does not need to draw in atmospheric oxygen for the combustion of the diesel fuel. A CCD carries around its own oxygen, stored as liquid oxygen (LOX) in a cryogenic tank. Before entering the diesel generator the stored oxygen is mixed with an unreactive gas like argon in order to control the rate of combustion. The exhaust produced by the combustion of oxygen and diesel fuel.

leaves the diesel engine outlet with a temperature of approximately 350 to 400 (degrees Celsius) and a pressure of up to 5 bar. After being cooled down by a spray cooling system to approximately 80 (degrees Celsius) the gas is fed into the absorber. The absorber is a rotating scrubbing mechanism, consisting of a rotor which mixes the exhaust gas with seawater. The required amount of seawater is supplied by the water management system, in a way which enables the CCD to operate depth independently. The system is designed for a maximum operation depth of 500m and a maximum seawater flow of 50 litres per second.(75)

CCD allows a submarine to increase its submerged endurance by a factor of five. CCD meets many of the desired criteria set forth in the previous section. The system can eject exhaust up to 500m, which just meets our requirement for depth independence. CCD will also allow the submarine to operate at the same speed as a regular diesel engine. Because the CCD system uses a regular diesel engine to provide propulsion, little in the way of new maintenance facilities or extensive training for crews and support staff will be necessary. (Although the construction of a shore-based cryogenics plant will be necessary for the storage of LOX.) Since the system uses regular diesel fuel, submarines powered by CCD can refuel at ports anywhere around the world, or use fuel supplies carried by any number of AORs. Although there are no large engineering firms currently producing CCD motors in Canada, research on CCD has taken place here, and it would probably be possible to find a Canadian engineering consortium to build a CCD propulsion system. Finally, because the CCD system uses a normal diesel-electric motor, which has been refined for well over half a century, it is an extremely robust and reliable system.

The CCD system does have some drawbacks. Although its developers are currently working to overcome this necessity,(76) as it stands, CCD requires a 'plug-in' section to contain the argon and oxygen tanks and other components of the CCD system. As already discussed, this may adversely influence the boat's manoeuvrability. Furthermore, the CCD operates just as noisily and produces just as much heat as a regular diesel-electric motor. This makes it just as detectable by sonar and infrared means as an unmodified SSK. The CCD also ejects dissolved exhaust, which may be detectable by chemical means. Finally, the CCD can only offer performance similar to what a regular diesel-electric engine offers. While this seems quite beneficial right now, after all most AIP systems can't offer anywhere near the same kind of speed as a diesel engine, we must remember that engineers hope that other AIP technologies will one day offer performance many times better than standard diesel-electric propulsion systems. This lack of future potential has prevented the Closed-Cycle Diesel from receiving the attention it would otherwise deserve.

Research on CCD has taken place in many countries, including Canada. However, the world leaders in CCD technology are definitely Germany's Thyssen Nordseewerke (TNSW) and RDM submarines of the Netherlands. They have been working on CCD since the late 1980's and have produced a 300kW power plant known as SPECTRE, which stands for Submarine Power for Extended Contact Trailing and Range Enhancement.(77) In 1988, TNSW installed the SPECTRE system in a decommissioned German Navy submarine, the ex- U1, for sea trials in the Baltic. (webmaster: In the early 1990s RDM installed a CCD system on board the decommissioned Dutch submarine Zeehond (3) ).  Although TNSW and RDM have actively marketed the SPECTRE system to the Argentinean Navy, the Royal Netherlands Navy, the German Navy, and the South Korean Navy, so far they have had no success finding a buyer.(78) This is a shame. CCD offers speeds superior to what any other AIP system can currently offer or will likely be able to offer within the next decade, and it does so with minimal changes to interoperability or support infrastructure.. . . . .

(76) Ibid., 36.
(77) Scott, "Power Surge," 27.
(78) Ibid., 27.

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Edward C. Whitman, Fall 2001.

. . . . . .Typically, a closed-cycle diesel (CCD) installation incorporates a standard diesel engine that can be operated in its conventional mode on the surface or while snorkelling. Underwater, however, it runs on an artificial atmosphere synthesized from stored oxygen, an inert gas (generally argon), and recycled exhaust products. The engine exhaust - largely carbon dioxide, nitrogen, and water vapour - is cooled, scrubbed, and separated into its constituents, with the argon recycled back to the intake manifold. The remaining exhaust gas is mixed with seawater and discharged overboard. Generally, the required oxygen is stored in liquid form - LOX - in cryogenic tanks.

CCD systems have been developed by a number of firms in Germany, Britain, the Netherlands, and a few other countries. However, except for a 300-horsepower demonstration system refitted onto the German Navy's ex-U 1 in 1993, no modern CCD systems have entered naval service. England's Marconi Marine recently acquired CCD pioneer Carlton Deep Sea Systems and is marketing a CCD retrofit package for existing conventional submarines, such as South Korea's nine Type 209s. Although one key advantage of CCD systems is their relatively easy backfit into existing submarine engineering plants, there have been no takers. Despite the additional supply complication of needing regular replenishment of cryogenic oxygen and inert gas, there are logistics advantages in retaining standard diesel engines and using normal diesel fuel.. . . . . .

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