The TKMS Type 212CD - MTU12V4000s vs current MTU16V396s

Thanks to Anonymous's 2 comments of 20 December 2017 on which this Submarine Matters article is based. Following a Norway-German government-to-government agreement signed in June 2017 Norway and mainly Germany’s TKMS are producing 6 new Type 212CDs. CD means Common Design. Earlier, in February 2017, the 212CD purchase decison was referred to a Type 212NG.

This article discusses the pros and cons of having an extra diesel engine for the new Type 212CD.

Naval Today, on November 1, 2017 reported “According to TKMS, the class 212CD will combine the low signatures of the class 212A with extended range, speed and endurance to allow worldwide operations.”

A German language Kieler Nachrichten article of December 7, 2017 (once translated) reported “…..it is planned that six identical submarines of the new class 212CD will be procured [4 for Norway and 2 for Germany]. The [German Navy’s] 1st submarine squadron currently has six Class 212A boats. Through the cooperation with the Norwegians, the [German Navy’s numbers will increase] to eight submarines. The first new addition is scheduled for 2027.”

An increase in a submarine's speed may be achieved by reduction of hydrodynamic resistance and increase in propulsive power. As 212CDs are based on 212As (which already have very low hydrodynamic resistance) greater speed can be mainly achieved by increased propulsive power.

Possible propulsive measures include more powerful diesels, motor and lithium-ion batteries (LIBs).

-    The 212CD may use the Type 214's 2 x MTU 16V-396 diesels (amounting to 3.96 MW) much higher than the Type 212A's 1.2MW (see Table page 3) diesel

-   these 2 diesels could work to a Type 214's 2.85MW Siemens Permasyn Motor. This would be an

    increase over the 212A’s existing 1.7MW  Siemens Permasyn Motor, and

-  Lithium Iron Phosphate LIBs may be relied on to give 212CDs high power when fully submerged.

-  A low power fuel cell AIP may be retained or dispensed with.

So, the single diesel generator on the 212A (though it permits miniaturisation in the Baltic) may be replaced by a more powerful two diesel generator arrangement. Favouring two diesels is:

-  Extra power necessary to generate enough electricity for LIBs. 

-  Two diesels are more reliable if one breaks down. 

-  Two also provide the option of servicing one diesel at sea while the other continues to operate.

The trade offs of using different one or two diesel generators arrangements are as follows:

-  Current beam (6.8m)/ one generator [low power] but keeps the 212 usefully compact

-  Current beam (6.8m)/ parallel two generators [lack of repair "elbow" room - bad for

    maintainability]
-  Current beam (6.8m)/ tandem two generators [extends length of whole submarine]
-  Wider beam/ parallel two generators [requires redesign of whole submarine]

Using MTU12V4000 instead of current MTU16V396

Although a major change to two diesels was canvassed above, a less radical solution may be the use of just one MTU12V4000. Just one diesel is an important requirement of the German Navy to keep 212s small enough to handle or exploit Baltic conditions. For example a 212 only 57m long can sit in to smaller holes in the Baltic seafloor than a 214 that is 65m long. A shorter submarine can also turn more sharply on its axis (without hitting rock obstructions) than a longer submarine.

A 212CD equipped with one MTU12V4000 not two MTU16V396s may be still LIBs capable. Having just one MTU12V4000 diesel also makes it easier to adopt a TKMS's future Methanol Reforming FC AIP. Many common features and spare parts between 212As and 212CDs also means lower through life costs

Comparing the MTU12V4000 and MTU16V396

MTU12V4000s are more powerful than MTU16V396s. Increased power is particularly important given the higher-faster charging capabilities of LIBs.

For the quotes below try opening http://www.tognum.com/fileadmin/fm-dam/tognum/press/2011/MTU_Submarine_Charging_Unit_12V_4000.pdf  which reports:
-  “A submarine charging unit with a 12V4000 submarine engine does have smaller dimensions

    compared to a 16V 396 SE design. However, the mechanical power [of a MTU12V4000] is

    noticeably increased to 1,300 kilowatts (kW) at 1,800 rpm.”

-  “Another major design objective was the reduction of the specific fuel consumption [sfc] 

   [of MTU12V4000s] in combination with greater operating flexibilities for different scenarios.”

-  “The new engine foot for [the MTU12V4000] includes an integrated shock limiter. Its compact and

    easy to install design results in very low effects of the foot’s dynamic behavior on the structure-

   borne noise signature of the engine.”

Alternatively open BMT Defence Services Ltd’s “SUBMARINE POWER AND PROPULSION: BALANCING THE ENERGY ELEMENTS” https://www.bmtdsl.co.uk/media/6097995/BMTDSL-Sub-Power-and-Propulsion-Confpaper-Pacific-Jan12.pdf and especially note the tables in the first 3 pages.

Pete Comment

If the MTU12V4000 in operational practice proves as powerful, efficient and reliable as hoped it will be a good replacement for the MTU16V396 and other diesels.

Mainly Anonymous and (a bit) Pete