Does the reference below to Chinese use of Stirling engines for air independent propulsion (AIP) mean:
1. Kockums sold its Stirling engine technology (see http://www.kockums.se/en/products-services/submarines/stirling-aip-system/) to China? or
2. Did China acquire Stirling technology covertly from current users - Sweden, Japan (Soryu Class) or Singapore (Archer Class)? or
3. Did China develop Stirling indigenously with the help of open source information - like the Kockums Stirling photo above?
Perhaps China used all three methods.
According to http://www.globalsecurity.org/military/world/china/yuan.htm in March 2007 Jane's Navy International reported that the Yuan class was fitted with an AIP system developed by the No.711 Ship Research Institute. Yuan is using an AIP engine of 100 kw in power, and is probably equipped with 2 such AIP engine. Sweden's Gotland Class submarines use 2 V4-275R stirling AIP units (each rated 75 kw). The larger Yuan obviously needs more powerful AIP units.
http://en.wikipedia.org/wiki/Type_041_submarine#Propulsion advises "Recent rumors stated that the [Type 041 Yuans] utilize a Stirling cycle engine, but this cannot be confirmed. It is also unclear if the incorporation of air-independent propulsion system has become the standard or just for evaluation purposes. Since the air-independent propulsion systems on board western submarines usually rate at 150 kW to 300 kW, so it is safe to assume that similar systems on board Chinese submarines would also be consisted of at least two units just like its western counterpart."