Anonymous in Comments on November 5, 2018 has kindly provided details discussing the

Kockum's Mark 5 Stirling engine that will likely be incorporated into the



The SAAB A26 and SAAB-Damen Walrus concept, will likely have an evolution of the current (in Gotland class) Kockums Mark 3 Stirling engine v4-275R Mark 3 [4]. The evolution-next version being likely the Mark 5 [1], but there is little information on the Mark 5. The Mark 5 evolution is discussed at [2] and [3]. The evolution may provide increased diving depth and a longer submerged period.



[1]

R. Bitzinger and Haris Vlavianos

“Emerging Critical Technologies and Security in the Asia-Pacific” 2016,

Page 100, “Sweden’s next generation submarine, Kockums A26-currently in development, will incorporate the latest and most modern and refined Stirling AIP technology-MK 5 version.”



[2] ibid, bars, which limits the submarine’s depth to 200m, unless power consuming and potentially noisy exhaust gas intensifier is used.” Page 101, “Stirling engine operates at a pressure of 20, which limits the submarine’s depth to 200m, unless power consuming and potentially noisy exhaust gas intensifier is used.”



[3]



Scrolling down half way to “Air Independent Propulsion” you come to the diagrams, reproduced below.













- diagram on left (above) is the current

Kockums Stirling Mark 3

(on Gotland class)





- diagram on right (above) is the

Kockums

Stirling

Mark 5 to be fitted on the future A26s.

The c

ombustor and insulator are omitted from this right diagram. For the Mark 5 to

achieve higher

efficiency are improvements in:

= The heater (cylindrical pipes (inside of engine) connected top of piston cylinder)

improves heat

transfer.



= The

heat insulation has presumably reduced heat loss, thus elevating combustion temperature

and pressure. If the Mark 5 can tolerate pressure increases from 20 bars to 25 bars, the A26's

depth at which it

can operate the AIP increases from

200m to 250m. This improvement will

provide a longer submerged period. But an significant increase in speed is not expected,

because speed is proportional to square-cubes of AIP output.



The Mark 5's generator is omitted (in the middle figure), but, the size of the generator does not seem to have changed. If the Mark 5's combuster size has not changed, the size of the Mark 5 AIP's (engine + generator) will not have significantly changed.





[4] Sweden's Sweden's Gotland class submarines each use two v4-275R Stirling engines (each rated at 75kW)

s

.

While Japan's Soryu Mark 1s use four Kawasaki Kockums

V

China's Type 039A Yuans may use three or four

Kockums

V





More recent and detailed data on Kockum's Mark 5 Stirling engine may well alter this current appreciation.





Anonymous (with Pete translating into standard English)

ee this4-275R.4-275R.