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Submarine Stirling Engine

The first domestic basic prototype of a large-bore Stirling engine was successfully completed at the China Shipbuilding Corporation 711 Institute in late 2021. The basic prototype has a rated power of 320kW and a thermal power conversion efficiency of 40%. It is currently known as the largest single engine power in the world. The successful development of the basic prototype indicates that China has made an important breakthrough in the key technology and manufacturing process of large-bore Stirling engines, laying a good foundation for the development of subsequent megawatt-level Stirling engines.

Robert Stirling patented the first practical example of a closed-cycle hot air engine in 1816, and it was suggested by Fleeming Jenkin as early as 1884 that all such engines should therefore generically be called Stirling engines. The concept of mechanically manipulating the ideal gas laws to convert heat into motion or vice-versa was first patented by Robert Stirling. Since that time several designs, most utilizing multiple pistons, have emerged including some designs utilizing pressure waves in lieu of a displacer with only a single piston.

The basic Stirling engine includes a trapped gas that is heated or cooled which then expands or contracts (according to the ideal gas laws) which pushes or pulls on a piston which then drives a crankshaft. The crankshaft is typically coupled to a flywheel and an output shaft. The output shaft delivers usable mechanical force relative to the initial temperature differential and amount of heat transferred.

Current commercial designs utilize a piston style displacer to move the working gas from a heating chamber to a cooling chamber and back. Common designs use multiple internal seals and two or more pistons. Current designs are complex and difficult to manufacture making them relatively high cost. The greater efficiency, reliability, lifespan, cleanliness, and flexibility that Stirling engines demonstrate compared to internal combustion engines has previously been sacrificed in favor of the faster start up, control response, greater power density, and ease of manufacture of competing engines. However, the inherent advantages of the Stirling engine allows it to compete successfully in various specialty niches of the engine market, such as satellite power production, waste heat recovery, cryogenics, solar power conversion, space craft, and submarines, where faster start up, control response, greater power density, and ease of manufacture are not the critical criteria in engine selection.

The Stirling engine is a closed-cycle reciprocating power machine, and its theoretical efficiency is equal to that of the Carnot cycle, which is the highest efficiency that can be achieved by all thermodynamic cycles. At the same time, as a closed-cycle power machine with external heating, the Stirling engine can be combined with any heat source such as conventional energy and nuclear energy. The structure is flexible and changeable. It has a compact structure and simple system within the range of megawatt power levels. Fast start-up, modular layout and other significant advantages. Especially in combination with metal reactors such as sodium-cooled fast reactors, it can fundamentally eliminate the risk of sodium-water reaction in the traditional sodium-cooled fast reactor power generation system, and has inherently high safety.

In 1975, the older generation of scientific researchers founded the Stirling Engine Laboratory at the Seven-Eleven Institute. It is more efficient and has wider energy applicability, and possessing this technology is of great significance to the country. At that time, only a few countries in the world were developing this type of engine. After ten years, they did not give up and finally developed a small solar Stirling prototype, taking a solid first step.

In another ten years, their team of fifteen or six people achieved technological breakthroughs by relying on meagre scientific research funds. They developed my country’s first engine with a power of 10 horsepower, and reached the same level of technology of developed countries, which used dozens of years and spennt a lot of money.

In the next ten years, in the continuous self-denial and independent innovation, they solved more than ten key technologies such as sealing, combustion, heat exchange, opened up all technical bottlenecks, broke the foreign technology blockade, successfully developed engineering prototypes, and realized The product trial was completed. From scratch, from small to large, from large to refined, from fine to practical, from practical to industrial development, the scientific research team of the 71st Research Institute is always struggling and continues to concentrate on "China Power".

The Stirling engine is known for its application on submarine propulsion. Swedish Gotland-class submarines feature Stirling engine air-independent propulsion (AIP) systems, enabling them to avoid going to the surface to charge the batteries, and thus increasing the submerged endurance from days to weeks. Sweden's A19 Gotland class submarines, with a submerged displacement of 1647 Tons, are equipped with two MTU diesel engines and two Kockums V4-275R Stirling Air Independent Propulsion units. The Stirling engines each provide up to 75 kW, giving the submarine the capacity for two weeks of air independent propulsion at a speed of 5 knots without snorting.

The Stirling engine is quiet and vibration free, so no vibrations spread out to the hull making the submarine silent in the water and therefore difficult to find. The CSSC did not mention the potential application of the Chinese Stirling engine on submarines. The basic prototype with a rated power of 320kW is about double that to the pair of Stirling engines on the Gotland, suggesting it might be sized for a 3,300 ton submarine, or roughly that of the Type 039 series Yuan-class attack submarines. A pair of such engines [as used on the Gotland] might power the Type 032 Qing should it enter series production.

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Page last modified: 24-12-2021 18:52:30 ZULU