Comments, Friday, May 21, 1999

integrated generation system supplying both propulsion and ship service loads. Sigdicant ship impacts are seen with this integrated approach. Therefore, the generator and phased controlled rectifier are replaced with a trans- former phased controller rectifier.

For the SSCM technology, the feasibility of incorporat- ing soft-switching dc-dc buck choppers has been accom- plished with the delivery of the PCM-1 from PSG, SPD Technologies, Inc. to the IPS Land Based Test Site in Philadelphia. With the increased performance character- istics of IGBT‘s over the last five years, we would like to ask the author’s their opinion on the advantages of soft versus hard switching for the power converters.

AUTHOR’S RESPONSE

The authors wish to sincerely thank Mr. Hegner and Mr. Desai for their efforts and comments. The reviewers are correct in emphasizing the lmk between DC ZEDS and the IPS program. An IPS system integrating DC ZEDS will possess many advantages in terms of weight/volume over a conventional drive with DC ZEDS (specifically, con- sidering the reduction in the number of prime movers). We regret not makmg this point more apparent. As such, it is also true that it would be more accurate to replace the rectifier modules in our DC ZEDS diagram by a trans- former-rectifier combination (PCM-4), thus clearly iden- hfymg the ac generator output as being avdable for the propulsion motor converter module.

In response to Mr. Hegner and Mr. Desai’s question regarding soft-switching dc-dc converters, the authors have recently conducted a literature search regarding ad- missible topologies and have investigated a number using simulation tools. The principle advantages of most of these topologies are that switching semiconductor device stresses are sigtufxantly reduced and switchmg losses are minimized, enabling higher switching frequencies. The higher switching frequencies facilitate higher control band- widths (faster-acting units) and smaller magnetic compo- nents. In addition, if the switching frequency of the soft- switchmg unit is maintained at the same value as the hard- switched unit, the softer switch transitions will result in considerably less EMI. Otherwise as the switchmg fre- quency of the soft-switching unit is increased, the EM1 benefits begin to diminish. Currently, hard-switched dc- dc converters a t the 200 kw power level are being switched at 4 kHz. Equivalent soft-switching units should be able to extend the switching frequency to approximately 20 Mz. Exactly how much benefit can be derived will be a function of the particular topology considered. Also, higher effective switching frequencies can be realized by interlacing the outputs of multiple dc-dc converters. The authors would also like to point out the recent important work in multi-level converters that may also pay dividends in future versions of the SSCM. This clearly illustrates one of the important advantages of the DC ZEDS archi-

tecture nestled in the IPS. The system has been set forth in a very functional manner. Any upgrades to the SSCM (using soft-switching technology or multi-level converters) is r eady integrated into the system.

Improved Navy Ship Fuel Systems H i l h y McGowen and L. Nilsen Abstract The forward deployment of a naval task force is dependent upon the performance of the Underway Replenishment (UNREP) systems, especially Fueling At Sea (FAS). A series of Office of Naval Research (ONR) sponsored de- velopments are reviewed that will help Navy ships to achieve current and future FAS requirements with re- duced manning, Life Cycle Cost (LCC), and risk of pollu- tion. The following developments are presented: H DDG 51 class Improved Fuel Fill Control System

(IFFCS) development and DDG 57 at sea demonstra- tion.

H Combat Logistic Force (CLF) Fuel Transfer Recordmg System and the AOE 8 Installation and operating ex- perience.

H CV/CVN Fuel Tank Monitoring and Display System de- velopment.

H Improved UNREP Phone, Distance, and Data Link System development.

4 Tensioned Hose Fueling At Sea System (THFASS) De- velopment. Improvements of the Navy’s fuel systems are necessary

to help meet current and future operational, LCC, man- ning, and environmental requirements. The improvements provided by these developments illustrate the COTS tech- nologies and hardware can have a significant impact on the Fleet’s FAS and storage systems.

COMMENTS BY

Edwin Matthews The paper starts with introduction and background sec- tions, which are substantially correct. The paper then presents five different developments. Each of these devel- opments will be discussed separately

1. DDG 51 Class Improved Fuel Fill Control System (IFFCS) Development and DDG 57 At-Sea Demonstra- tion.

Concur that this system for receiving ships, promises to improve fuel fill operations in several ways. Reduced alongside time, risk of pollution, inventory control, and workload are all improved. Further development and fleet implementation is warranted. Additionally, establishmg a data link and developing control algorithms with the oiler could further automate the fuel fill evolution.

2. CLF Fuel Transfer Recordmg System and the AOE 8 Installation and Operating Experience.

92 September 1999 NAVAL ENGINEERS JOURNAL

Comments, Friday, May 21, 1999

Concur that this system improves CLF fuel accounting and operation. Further development and Fleet implemen- tation is warranted. This fuel transfer accounting system is useful for fueling U.S. ships and can be very important when fueling foreign naval ships. Again, establishing data link and control algorithms between the oiler and receiving ship could further automate fuel fill operations and account- ability

3. CV/CVN Fuel Tank Monitoring and Display System Development.

Concur that this system improves fuel accountability and maintenance, and reduces operator workload. Further development and implementation is warranted. Again, es- tablishing data link and control algorithms between the oiler and CV/CVN could further automate fuel fill and ac- countability 4. Improved Phone, Distance, and Data Link System

Development. Concur that this system has the potential to reduce

workload, improve safety, and dramatically improve fuel fill efficiency and accountability This development ties di- rectly with each of the earlier discussed developments and can be a technology enabler for them. Further development and Fleet implementation is dehtely warranted.

5. Tensioned Hose Fueling At-Sea System (THFASS) Development.

Existing fuel delivery systems provide efficient and high performance fueling at-sea capabilities. THFASS not only does not improve fuehg, it cannot be rigged at sea with current systems. This system, although conceptually in- teresting, should not be pursued.

AUTHOR’S RESPONSE

The authors appreciate the review comments of Mr. Mat- thews (SEA 03P8) regarding the paper. The goal of the paper was to review a series of developments where state- of-the-art COTS technologies and hardware can be em- ployed to improve the Fleet’s FAS capability What has been demonstrated is that improved sensors and controls can be used to provide the oiler and receiving ship a much improved man-machine interface, a predictive status of the system, realistic real-time operator training. and the op- portunity to reduce manning. Future improvements in- clude hydrocarbon sensors and a data link that can be employed to sigmficantly reduce the risk of pollution and to further improve FAS capabilities.

The reviewer highlighted that the Improved Phone, Distance, and Data Link has the potential to reduce man- ning, improve safety, fuel fill efficiency, and accountability It was noted that thls development is a technology enabler for a series of FAS improvements.

Out of the five developments discussed in the paper, the reviewer did not support further development of the Tensioned Hose Fueling At-Sea System (THFASS), stating that the existing FAS delivery system was adequate. Over

the years, the R&D community has had a difference of opinion concerning THFASS development. The reviewer pointed out that THFASS cannot be rigged with current systems. This was a reference to the large diameter THFASS where the interface at the receiving ship for the STREAM fuel probe-receiver has not been developed. However, a small diameter rig was tested at-sea and per- formed very well. It should be noted that the anticipated mission of THFASS has not been on oilers and AOEs whose primary mission is to fuel other ships, but has been on ships with a secondary mission to provide fuel if re- quired. Important features of the small diameter THFASS are that it is a simple, affordable rig with the ability to refuel smaller ships with greater ship-to-ship separation. An additional feature of THFASS would be its modularity for the rapid installation on any Navy or merchant ship capable of providing fuel to other ships. In this augmen- tation role, the THFASS can replace the astern refuehg rigs to enable fueling by a safer alongside method.

T R A C K

2 Future Ship Designs

It’s In the Bag: Submarine Plastic Waste Management Douglas S. kughters, Todd M. Olson, Sean E. Gill, and Laurie A. (Devlin) Wagner Abstract The National Defense Authorization Act for Fiscal Year 1994 prohibits the discharge of plastic waste from U.S. Navy submarines after December 31, 2008. This wdl re- quire the Navy submarine community to develop an effec- tive method for handling and storing plastic waste aboard for eventual return to port. Paramount objectives include volume reduction, sanitary packaging of the waste, and locating suitable storage spaces on each submarine class. Carderock Division of the Naval Surface Warfare Center conducted a review of all potential plastic waste processing options. The submarine trash compactor unit and Navy odor barrier bags were selected for detailed investigation. A process was developed whereby plastic waste was com- pacted directly into high strength odor barrier bags called submarine plastic waste containment bags. Potential stor- age locations for compacted plastic waste have been iden- tified aboard the Los Angela (SSN 688), Ohio (SSBN 726), and SeuwoEf (SSN 21) classes. Plastic Waste Man- agement Demonstrations will be conducted on each sub- marine class to evaluate the suitability and effectiveness of the proposed plastic waste management solutions.

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