Kockums To Retrofit Swedish Sub With Air-Independent Stirling Engine

Kockums AB of Malmo, Sweden, has been awarded a contract by the Swedish Navy to install its airindependent propulsion system, based on the Stirling principle, in an existing conventional submarine.

The combat efficiency will increase with an increase in submerged endurance, allowing the submarine to operate in highly troublesome areas with a minimum of risk of being detected. Conventional submarines are vulnerable to detection when showing the snorkel to recharge the batteries. The new air-independent Stirling propulsion system developed in Sweden will increase the sub's submerged endurance from days to weeks.

The Stirling engine is an externally heated, continuous combustion motor. For combustion, fuel oil is provided from the ordinary onboard bunker oil supply, and oxygen from liquefied oxygen (LOX) storage tanks. The Stirling generators will provide the necessary electrical energy for the extended submerged endurance that will be limited only by the size of the LOX tanks.

As the Stirling engine is extremely quiet, and the exhaust from the overpressure combustion chamber is dissolved in the seawater, the airindependent machinery could be used whenever submerged. The Stirling has been developed for use at slow speeds; for high speeds the storage batteries will be used.

The Swedish Navy order at Kockums will involve cutting an existing conventionally powered submarine and lengthening it with the neutrally buoyant Stirling section containing the air-independent propulsion system with its LOX supply. The system was developed by the Swedish submarine design authority and Kockums, in cooperation with United Stirling AB for the engine and AGA for the LOX system.

For further information on Kockums, Circle 67 on Reader Service Card For free literature on the Stirling engine, Circle 68 on Reader Service Card

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