Showing papers in "Naval Engineers Journal in 2005"

5 MW High Temperature Superconductor Ship Propulsion Motor Design and Test Results

Abstract: American Superconductor has designed, built, tested and delivered to the U.S. Navy's Office of Naval Research (ONR) a 5MW, 230-RPM, 6-pole high temperature superconductor (HTS) ship propulsion motor. The motor uses an air core armature winding and first generation HTS wire (BSCCO-2223) field winding. The goal of the motor development project was to validate the technologies required to design and build larger HTS ship propulsion motors, as well as to develop a motor production process that streamlines development time and minimizes cost. A commercial variable frequency drive is used to power the motor. The HTS field winding is cooled with G-M coolers with gaseous helium as the cooling medium in a closed cycle. The armature is cooled by MideP. The motor was delivered to the U.S. Navy in July 2003 and met or exceeded requirements in operation (up to the facility's testing limit of 2.5MW). The motor demonstrated both full torque and full speed operation in separate tests.

A military effectiveness analysis and decision making framework for naval ship design and acquisition

Abstract: This paper describes research that develops a new framework for performing military effectiveness analyses and design tradeoff decisions. It provides an extensive survey of literature for effectiveness analysis and multi-criteria decision making to develop a single consistent philosophy for such analyses. This philosophy is applied to a requirements and effectiveness analysis case study of a conventional submarine that is performed using response surface methods to facilitate design space visualization and decision maker interaction. Measures of merit are developed and applied to the case study. The resulting requirements space and methods to visualize and explore it in a decision making context are presented and discussed. Lastly, a framework is proposed that would facilitate the concurrent consideration of requirements and effectiveness analyses with design and technology forecasting to create a unified tradeoff environment that would provide decision makers with pertinent information to facilitate better informed requirements derivation and design selection.

Flow Visualization Studies of Exhaust Smoke-Superstructure Interaction on Naval Ships

Abstract: The problem of ship funnel exhaust is often studied through flow visualisation using smoke in a wind tunnel. It is a very useful tool for the naval architect to ensure that the funnel exhaust will not interfere during operation. Naval ships are particularly prone to the problem of smoke nuisance because they tend to favor short funnel heights because of competition for topside space. This paper presents the flow visualization studies undertaken to understand the interaction between a bluff body air wake (of the funnel and superstructure/mast) and the ship's exhaust on naval ships. As a first step, the analysis of the exhaust smoke-superstructure interaction was carried out in a wind tunnel for a generic frigate shape. Four variants of the superstructure configuration with progressive introduction of the structures on the topside (i.e. the superstructure/mast upstream and downstream of the funnel) were investigated in the wind tunnel at two velocity ratios through flow visualization studies to understand their effect on the exhaust plume path. Apart from providing an insight into the process of plume dispersion in the vicinity of the funnel and other structures on topside of naval ships, the results of the flow visualization studies presented can also be used for validation of the computational fluid dynamics (CFD) simulations (including particle tracing) of the exhaust smoke-superstructure interaction for cruise vessels, ferries, yachts, as well as naval ships.

The Navy and Asbestos Thermal Insulation

Abstract: Asbestos was once used in U. S. Navy shipboard pipe and machinery thermal insulation and in many other shipboard products. It was also used throughout the country in thousands of commercial products and in some products it remains in use today. The health hazards of asbestos have resulted in an increasing number of lawsuits that involve, among many others, manufacturers of Navy hardware. The plaintiffs in these lawsuits include many who were exposed to asbestos while serving in Navy ships built during and following WWII. Because the materials are dry, friable, and easily accessible, the most likely source of their Navy shipboard exposures was thermal insulation. In this article the evolution of thermal insulation systems in WWII and post-WWII ships is described, Navy and national asbestos consumption patterns are compared, the asbestos industrial hygiene environment of the times are described, and a perspective on asbestos concerns from a hardware manufacturers' standpoint is provided. The liability situation regarding asbestos may be seen as a pattern causing Navy manufacturers to seek some form of waiver of liability or other relief from the Government for all hazards arising from their Navy work. Naval engineers have a responsibility to understand the background surrounding the use of asbestos, particularly as they continue to deal with new systems and materials that could potentially impact the future health of those who come in contact with them.

Design and development of a two- megawatt, high speed permanent magnet alternator for shipboard application

Abstract: Conventional gas turbine generator sets consist of a high speed turbine coupled to a low speed alternator through a speed reduction gearbox. This is required to maintain the alternator output frequency at 50 Hz or 60Hz, as output frequency is directly proportional to speed. Since power is also directly proportional to speed, the conventional system is bulky and possesses a very large footprint. The advent of solid-state inverters with their unique ability to efficiently and cost effectively change the alternator output frequency has made it possible to eliminate the need to link the alternator speed to the required 50/60 Hz output frequency. This output can be produced with a high-speed alternator, eliminating the need for a gearbox and greatly reducing the size, complexity, and weight of the machine by trading speed for torque. A direct drive system in which an alternator is coupled directly to a gas turbine is much more compact and highly efficient and requires much less maintenance. In this paper we will review the design and development of a high-speed permanent magnet alternator in an advanced cycle gas turbine system for shipboard applications. In addition to the alternator's design features, we will discuss design considerations including electromagnetic design, thermal design and structural design of high speed electrical machines, and review the alternator development including risk mitigation.

Operating Speed Profles and the Ship Design Cycle

Abstract: One key, but little documented and empirically supported, input in the ship design cycle is the expected operating speed profile. This real-world constraint affects many decisions regarding hull form and power systems, from fuel tanks to main propulsion and ship's service machinery selection and operation. These decisions, in turn, ripple through the design of a ship in ways that are often hard to discern, but clearly impact acquisition and life cycle costs. Recent studies of DDG 51 operating speed profiles demonstrate that the Navy regularly operates with speed profiles considerably different than used to design the ship. In general, warships operate in standard engine order telegraph increments (e.g., Ahead 2/3) and at lower speeds than designed for.

Modeling Ship Motion Effects on Human Performance for Real Time Simulation

Abstract: Modeling the effects of ship motions on human task performance is an emerging technology, and implementing these models in real time distributed simulation for virtual naval platforms is a new discipline. The environmental, ship and computer technologies embodied in the virtual naval platform concept are summarized. The types and severity of human performance problems related to ship motions are reviewed and task performance issues are discussed. Requirements for modeling fatigue, motion sickness, biodynamic problems and task performance are discussed, and existing models are described. Recommendations are made for developing new performance models and for enhancing existing models.

Practical Hydrodynamic Design of Bulbous Bows for Ships

Abstract: Although in modern times, bulbous bows have become an integral part of commercial ships, the hydrodynamic design of bulbous bows is still difficult because of costly tank tests and patent-driven knowledge banks. The design of a bulbous bow is needed even at the preliminary design level to predict speed and power. In this work, a design method is presented that combines and extends two famous theories i.e., Kracht (1978a) and Yim (1980) for a particular set of requirements within a narrow range of parameters. The method uses a reanalysis of an approximate linear theory with sheltering effect for resistance estimation, and re-correlation with statistical analysis via a non-linear multivariate regression analysis from existing literature and tank test results available in the public domain. The optimization of design parameters has been done for the design speed. The effect of change in the speed has been discussed and suitably incorporated in the design process. In the present work, the effect of production constraints on the design of bulb parameters has also been briefly examined. The results of this study are presented in the form of design parameters related to main hull parameters for a set of input data in a narrow range. The first six parameters have been derived by re-correlation with statistical analysis and the seventh parameter by reanalysis of an approximate linear theory with sheltering effect for resistance estimation. Finally, a design example, which includes tank test results, of an additive bulbous bow for a container ship has been presented.

Developing an HLA-based naval maneuvering simulation

Abstract: This paper discusses the main issues involved in developing a high level architecture (HLA)-based distributed simulation while presenting an application called Naval Surface Tactical Maneuvering Simulation System (NSTMSS), which is intended to serve as a testbed for HLA and distributed interactive simulation (DIS) research. NSTMSS provides a networked virtual environment (NVE) for naval surface actions in which new formations can be evaluated and tested and present ones can be practiced and analyzed. This paper also describes a development lifecycle for HLA-based distributed interactive simulations and reflects best practices.

Development of Metal Fiber Electrical Brushes for 500 kW SSMG Sets

Abstract: The effort that this paper reports began in 1996 as a Team Submarine sponsored Navy SBIR N96-103, and expanded into a multi-year NAVSEA (SUB-RT) sponsored, Phase III, applied research and development project. Therein a combined government, university and industry partnership are designing, building, integrating and testing metal fiber electrical brushes for the AC (slip ring end) and DC (commutating end) of a 500 k W Ship's Service Motor Generator set and other submarine DC motors. These revolutionary brushes are being designed and laboratory-tested, then transitioned toward Navy use via the submarine MG set land based test facility, and later at sea on US Navy submarines. The metal fiber brush project was previously reported on at the ASNE sponsored Navy Electric Machines Conference in 1999.

High Torque Density Propulsion Motors

Abstract: The size and weight of electric drive components are primary considerations in their successful integration into various Naval platforms. Direct drive propulsion motors are of particular importance due to their requirement of developing full power at low shaft speed. As such, their torque density (ft-lbs of motor torque developed per lb of motor mass) is the key defining metric. Torque density projections of existing and future technology machines require thorough understanding of the constituent mass elements that comprise an electrical machine and their specific scaling relationships. Such models can be used to compare machine performance across a wide range of objective torques and technologies. Liquid-cooled permanent magnet motors typify current state of the art propulsion motors. The torque density of such motors at ˜ 2Mftlbs is roughly 8 ft-lbs/lb which represents a twofold increase over the prior generation of air-cooled induction motors at ˜ 4 ft-lbs/lb. The next generation of propulsion motors technology, advanced PM motors and high temperature superconductivity motors, are targeting >16 ft-lbs/lb as achievable goals.

A Network‐Centric Approach to Maritime Domain Awareness

Abstract: The Integrated Deepwater System's C4ISR (command, control, communications, computers, intelligence, reconnaissance, and surveillance) system is a critical element in the U.S. Coast Guard's efforts to modernize its aging force structure and implement its maritime strategy for homeland security. >> Conceived during the 1990s, the fully implemented Deepwater program will consist of three classes of new cutters and their associated small boats, a new and upgraded fixed-wing manned aircraft fleet, a combination of new and upgraded helicopters, both cutter-based and land-based unmanned aerial vehicles (UAVs), and highly improved systems for C4ISR and advanced logistics capabilities. Integrated Coast Guard Systems (ICGS, a joint venture between Lockheed Martin and Northrop Grumman) is Deepwater's partner in industry and systems integrator. >> Deepwater's C4ISR capability improvements will contribute to higher levels of maritime domain awareness (comprehensive information, intelligence, and knowledge of all relevant entities within the U.S. maritime domain, and their respective activities, that could affect U.S. security, safety, economy, or environment). The Integrated Deepwater System (IDS) will play an important role in transforming the Coast Guard to meet the nation's 21st-century maritime-security requirements

Counter-Capsizing a Battleship

Abstract: The new Italian battleship Leonardo Da Vinci suffered a severe fire in 1916 resulting in the ship capsizing in Taranto harbor. The ship was not destroyed but upside down. The Italian Navy thought she could be salvaged and returned to service. The chosen approach was to refloat the ship upside down. Superstructure was cut away under water and the turrets dropped to bottom of the harbor in order to reduce the draft enough to get the ship into a dry-dock. In drydock, the still bottom-up ship was prepared for being turned upright. The ship was taken out of the drydock and by weight additions plus selective flooding the ship was capsized again but this time coming upright. Two appendices to the paper describe other ships floating upside down and other approaches to righting capsized ships.

A Statistical Examination of Sea Valve Failure Rates

Abstract: This paper presents the results of a study that targeted identification of statistical methods to characterize the failure rates and related probability distributions of sea valves across a broad range of hull classes. Beginning with maintenance records from sea valve assessment, the paper demonstrates the application of various statistical tools and the related strengths and weaknesses of each. These tools involve maximum likelihood estimators, empirical methods, and hypothesized distributions. Using these methods, failure rates and confidence intervals are estimated and compared. Finally this information is combined to formulate a cohesive view that allows a high level of confidence in predicting sea valve failure. This paper demonstrates use of statistical models as a tool to validate and improve maintenance systems, costs, and strategic maintenance management programs.

Engineering the Total Ship: A System Perspective on Warships

Abstract: This paper describes warships as manmade systems. A discussion of systems in terms of their characteristics and behavior is given and used as a foundation for a perspective of a warship as an integrated whole and an element of the naval force. The symposium series titled "Engineering the Total Ship" is used as a source of technical material to describe warships, naval operations, and the Navy organization. A system perspective is provided that defines warships as an integrated whole made up of interacting parts. The relationship of the Navy organization to the characteristics of warships is discussed.

A Fault Resilient IPM Motor Drive for Wide Speed Range Operation

Abstract: Interior permanent magnet motors are superior to surface mount permanent magnet motors due to some of their inherent characteristics such as higher torque density These motors enjoy an extended flux weakening region because of their reluctance torque and ruggedness of the rotor which is an important factor in high speed applications The above mentioned advantages of the IPM motor depend on the saliency ratio of the motor In order to obtain high performance motor drives, modern control strategies like field oriented control should be employed These techniques are inherently dependent on the proper operation of measurement devices, or feedback sensors (current sensors, position sensor or even voltage sensors) In this paper, in order to guarantee a reliable drive, a fault resilient system with soft sensors and automatic controller reconfiguration is designed These soft sensors substitute the actual sensors in case of sensor failure such that the motor continues operating safely over the whole speed range Theoretical and experimental results will be presented to validate the proper operation of the proposed back up system