January 11, 2018

Australian Future Subs Diesel Generator Requirements PART 0.5

This article is a necessary Prequel, which, in retrospect, I should have written before I wrote Australian Future Subs Diesel Generator Requirements PARTs ONE and TWO

Basically greater definition of the diesel problems are required before assessments of diesel remedies can be made.

In the beginning Australia was well served, from 1967 to 1999 by the long UK developed military-off-the-shelf (MOTS) Oberon class submarine. This included the mature, (used since 1959?) Admiralty Standard Range V16 diesel. The Oberon's diesels were apparently used long enough on submarines to detect and resolve deficiencies. Comments from readers who actually worked with Oberon diesels are welcome.

Without the benefit of long UK experience Australia embarked from the late 1970s, on studies and then development of locally built Collins class submarines. The UK Royal Navy had long experience of operating submarines in Indian and Pacific Ocean conditions while the Swedes had not. 

There begins the unhappy tale of the Garden Island-Hedemora (GI-H) diesel and most of the other components of the Collin's drive-train. 

The UK headquartered, but international Royal Institute of Naval Architects (RINA) have published  a very useful  paper titled "Technical Meeting - 3 February 2016" which is partly on the GI-H, see https://www.rina.org.uk/iqs/dbitemid.1665/rp.2/sfa.view/Section_News1.html

In 1987, Australia, hoping for a “off-the-shelf or low-risk” diesel for the Collins submarine, selected the Hedemora V18B14SUB diesel. At that time, nothing else was judged to have met Australia’s stringent, high power, diesel specifications. Unfortunately the Swedish Hedemora Diesel company declined and Australia's Hedemora diesels became Australia Only orphan technology.

"Now [Australia has] all of the 19 Hedemora V18B14SUB engines in the world [just for all 6 of Australia's Collins subs]! The V indicates the vee configuration, the 18 is the number of cylinders, the B is the larger bore (210×210 mm), the 14 is the speed (1400 rpm), and the SUB category is the monolithic engine (not bedplate mounted) for submarines." 

“Hedemora had demonstrated the V12B configured for snorting, and promised that the V18B would work as well giving 1.4 MWe. However, they had never actually built a turbocharged V18B14SUB, but had built lots of V18B engines for industrial power and marine generator sets, and had tested a V12B against submarine-type conditions. They had built a number of V12A (smaller bore) submarine engines for the Royal Swedish Navy, the latest examples being turbocharged."

"Therefore the V18B14SUB was accepted as an off-the-shelf design, which it really wasn’t. But then, nothing else seems to have met the specification either [no MAN, MTU diesels met Australia's criteria and Japan was nowhere near contemplating exporting arms].”

Looking to the Australian future submarine the paper goes on to comment:

"Safety Issues
With fuel supply at around 2000 bar (200 Pa), containment is critical. All components, including pumps, need to be safely contained. MTU have developed (or are developing) a submarine variant of their 4000 series engine (it is mentioned on their website). However, many in the submarine community remain nervous of such high pressure systems.

Performance Issues
Such an engine would require significant work on the control system and turbocharging arrangements. The control system would need load control, not just the conventional speed control. MTU are well capable of this, but one would need to be reassured that they were applying it to cope with open-ocean sea states. Likewise for the Pielstick engines, which may be favoured by a French supplier, although Pielstick is now back in the MAN stable after many years in French hands."

So several issues need to be kept in mind: 

1.  What is a military-off-the-shelf (MOTS) submarine diesel? 

2.  Is MOTS the structure of a still unmodified diesel?

3.  Must a MOTS diesel be proven by being used for years in submarines? Is prior use on a
     locomotive or surface ship beneficial?

4.  Can turbocharging or supercharging a diesel disrupt the reliability or other 
     characteristics of the diesel?

5.  How extensive can modifications to the structure or use of a MOTS diesel be before it is
     no longer MOTS? Hence becoming risky?

Reader comments made here January 5 to 10, 2018, will be added to two "Australian Future Subs Diesel Generator Requirements PART..." per week.

Pete

7 comments:

Anonymous said...

Hi Pete

According to ex-submarine Commander, Rear Admiral Kobayshi, in LABs-submarine, one hour-ventilation by using diesel generator (DG) is needed after charge to release hydrogen generated by charge. Based on this information, indiscretion ratio (IR) of following five model submarins was reviewed and very roughly estimated for operation period 70 days (surveillance 50days, transition 10days x 2) and output (hotel load + propulsion) 250kW:
Case I (length 84m, LABs, 100MW- AIP, 2 x 2MW-generators, model Soryu MK I) IR =7%;
Case II (length 84m, LIBs, 2 x 2MW-generators, model Soryu MK II) IR=6%;
Case III (length 90m, LIBs, 4 x 2MW-gnerators) IR=2.5%;
Case IV (length 96m, 100MW-AIP, LIBs, 4 x 2MW-gnerators) IR=2%;
Case V (length 96m, 100MW-AIP, LABs, 4 x 1MW-generators) IR=7%.

Comparison of Cases I and V shows that IR is determined by slow charge rate of LABs for LAB-submarine. Comprison Cases II, III an IVshows that output of DG shows critical effects on IR for LIB-submarine.
Performance at low speed which means IR is Case IV>= Case III >>Case II >Case V = Case I.
Performance at high speed which depends on batteries is Case III>= Case IV >>Case II >Case V = Case I.
The facts that depletion of LOx means end of operation for AIP-submarine and that LIBs are better than LABs shows flexibility of operation of each cases: Case III>= Case II >Case IV> Case V=Case I.

Superiority of AIP-LIBs- or simple LIBs-submarine depends on its operation and DGs play critical role in both LIBs-submarines within certain range of diesel exhaust.

I think future of LAB-submarine is dark whether with or without AIP and recent tragedy shows LABs are not safe.

Regards

Anonymous said...

Hi Pete

(Continued from 13/1/18 1:35 AM)

IR was very roughly estimated as follows :

In daily base, balance of supplied energy [Es] to batteries and consumed energies [Ec] form batteries and AIP is described in equation (1)
Es = Ec --- (1)
Es = Energy from diesel generator [Ed] + Energy from AIP [Ea] --- (2)
Ec = Energy for propulsion [Ep] + Energy for hotel load [Eh] --- (3)

Indiscretion ratio (IR) which snorkeling period [ts] per day (=24h) is desctibed in eq (4)
IR = ts/24 x 100 (%) = (tg + th)/24 x 100 (%) --- (4)
ts = snorkeling period for diesel generation [tg] + snorkeling period for hydrogen release [th] --- (5)
Where, th =1h for LABs with hydrogen generation, and th = 0h for LIBs without hydrogen generation.

Charge of batteries (capacity X (MWh)) with Y of C rate, Ed for ts is described in (6)
Ed = 1000XYtg --- (6)
Daily energy from Z (MWh)-AIP for 50days-opertion is described (7)
Ea =1000Z/50 =20Z --- (7)

From (2), (6) and (7), Es =1000XYtg + 20Z --- (8)
If 250 kW of energy is consumed in an hour, then, Ec = 250 x {24-(tg + th)} --- (9)

From (1), (8) and (9), 1000XY tg+ 20Z = 250 x {24-(tg + th)} --- (10)

From (4) and (10), IR =[1-{(1000XY tg+ 20Z)/(250x24)}]x100=(tg + th)/24 x100 --- (11)
Where, tg = (250 x24-20Z-250 th)/(1000XY+250)


IR from eq (11)
10MWh-LAB, non-AIP, 0.2 C rate, 2MW-diesel: X=10, Y=0.2, Z=0, th =1, IR=14.8%
10MWh-LAB, 100MWh-AIP, 0.2 C rate, 2MW-diesel: X=10, Y=0.2, Z=100, th =1, IR=11.1%
20MWh-LIB, non-AIP, 0.2 C rate, 4MW-diesel: X=20, Y=0.2, Z=0, th =0, IR=5.8%
20MWh-LIB, non-AIP, 0.4 C rate, 8MW-diesel: X=20, Y=0.4, Z=0, th =0, IR=3.0%
20MWh-LIB, 100MWh-AIP, 0.2 C rate, 4MW-diesel: X=20, Y=0.2, Z=0, th =0, IR=3.9%
20MWh-LIB, 100MWh-AIP, 0.4 C rate, 8MW-diesel: X=20, Y=0.4, Z=0, th =0, IR=2.0%

Though estimation is based on many assumpition and rough, result clearly shows superiorty of LIBs to LABs. I believe LIBs are indispensable to maintain regional superiority by covensional submarine.

Regards

Anonymous said...

Correction

Before
20MWh-LIB, 100MWh-AIP, 0.2 C rate, 4MW-diesel: X=20, Y=0.2, Z=0, th =0, IR=3.9%
20MWh-LIB, 100MWh-AIP, 0.4 C rate, 8MW-diesel: X=20, Y=0.4, Z=0, th =0, IR=2.0%

After
20MWh-LIB, 100MWh-AIP, 0.2 C rate, 4MW-diesel: X=20, Y=0.2, Z=100, th =0, IR=3.9%
20MWh-LIB, 100MWh-AIP, 0.4 C rate, 8MW-diesel: X=20, Y=0.4, Z=100, th =0, IR=2.0%

Anonymous said...

Hi Pete

(Continued from 15/1/18 1:47 AM)

One of key assumpitions in this esiamtion is that intake and exhaust system of diesel engine functions properly at snorkeling by using high power diesel generation. If resistance against intake and exhaust is too high, generation system does not function well resulting in poor output. Though effectiveness of intake and exhaust system has been proven for Japanese submarine which equips with nearly 4MW-generators, the effectiveness of the intake and exhaust system with 8MW-generators is not reported.

Here, this issue is discussed using SEA-1000 Japanese submarine (SEA-J) as a concept model. SEA-J is based on Soryu MKI in figure [1], does not equips with AIP and 6m longer than Soryu MKI. Soryu MKI, which is notorious in poor endurance, still provides individual bed to 65 crews, and huge LOx tanks AIP ((9) and (10) sections in the 4th coumpartment shown in figure [1]). Though the improvement of endurance and addition of batteries in (9) and (10) for SEA-J can be explained well, meaning of 6m elongation is not clear. In SEA-J without AIP, new section (7th section) for diesel generators may be introduced between 5th and 6th sections to improve the indiscretion ratio (IR) by using 8MW-generation system.This may suggest that the intake and exhaust system with 8 MW-generators is effective.

[1] http://gentleseas.blogspot.jp/2015/10/diagram-inside-soryu-submarine.html

Regards

Peter Coates said...

Hi Anonymous

Thanks for all the comments above.

I'll turn them into two articles this week:

- First for Tuesday 16 January

- Second for Thursday 18 January.

Regards

Pete

Anonymous said...

Given that a submarine has to do lots of accelerating/decelerating in order chase/listen how does a lithium ion design perform in these terms?

Peter Coates said...

Hi Anonymous [at 17/1/18 7:00 AM]

Good question.

The performance of Lithium-ion batteries (LIBs) on submarine has been tested by the Japanese Navy over 10 years to that Navy's satisfaction.

The real test will be on the first operational fully LIBs Japanese submarine known as 27SS. (see Table at http://gentleseas.blogspot.com.au/2018/01/soryu-labs-vs-libs-aip-and-indiscretion.html ).

27SS may be launched this year (2018). Then its LIBs performance will be rigorously tested until it is commissioned around 2022. If the Japanese Navy fully publicises 27SS's LIBs performance (without battery fire or explosion) that will answer your question.

Regards

Pete