Military

April 2002 Excerpt

Machinery Systems and Components
—An Overview

By Arnold N. Ostroff , reprinted from NSWCCD Tech Digest

PHILADELPHIA—Since the early 1900s, NSWCCD has served as the Navy’s leader in the development, evaluation, and integration of marine machinery systems and components. From formative work in naval fuel oils and machinery standards to today’s developments in electric drive and fuel cells, the Division has been at the forefront in advancing naval machinery technology and providing systems that enable the Navy to maintain its military dominance.

Machinery systems and components represent the most diverse and numerous equipment installed on a modern warship. They include items such as engines, boilers, gears, shafting, bearings, pumps, air compressors, hydraulics, piping and valves, distillation plants, heat exchangers, heating and refrigeration systems, electric motors and generators, electric power conversion and control systems, electric distribution systems, elevators, conveyors, cranes, steering systems, underway replenishment, habitability, and hull outfitting systems.

Today’s machinery systems and components are more complex and intelligent as a result of automation, network connectivity, and built-in diagnostics. They interact with other ship systems and are designed to meet stringent requirements that often relate to other ship design disciplines such as signature and silencing systems, structures and materials, and vulnerability and survivability systems. This article describes several current technology areas that demonstrate the diversity and sophistication of today’s machinery systems. They represent enabling technologies that are expected to significantly influence future ship machinery systems applications.

Fuel Cells

Recent advances in fuel cell technology make fuel cells increasingly attractive for electric power generation on naval ships, as well as in commercial marine applications. These include significant increases in cell and stack power density, the development of compact fossil fuel reformers, and emerging commercialization efforts. A significant technology push over the last decade by the U.S. Department of Energy and commercial partners may soon enable fuel cells to compete with commercial diesel and gas-turbine-powered generators. In 1997, the Office of Naval Research (ONR) initiated an advanced development program to demonstrate a ship service fuel cell (SSFC) power generation module. When completed, this program will provide the basis for new fuel cell based ship service power systems that will be a viable and attractive option for future U.S. Navy surface ships.

During the initial phase of the ONR SSFC program, competitive conceptual designs of 2.5 MW power plants were prepared, as were critical component demonstrations designed to reduce development risk. Two fuel cell systems were tested—a molten carbonate system and a proton exchange membrane (PEM) system. After critical review of both designs, the molten carbonate system was chosen to advance in the second phase of the program, which includes the construction of a nominal 500-kW fuel cell module. This system will be land based tested at the Division’s Philadelphia site in 2003. After testing, the module will be installed aboard a ship for an at-sea demonstration the following year. Further development of PEM systems is underway to advance technology for diesel fuel reforming.

Quiet Electric Drive

The objective of the ONR-sponsored Quiet Electric Drive (QED) program is to demonstrate signature reduction technologies applicable to ship electric drive propulsion and auxiliary systems and to enhance warfighting effectiveness, commonality, and affordability across platforms. The concept being pursued is integrated hydrodynamic, hydroacoustic, and structural acoustic signature control through the use of electric drive propulsion. The ONR Electrical Systems Task supports this advanced development program. In this task, contributing technologies are investigated, developed, and transitioned to the QED program for demonstration in a direct Fleet application. There are significant strategic naval payoffs associated with the QED program.

• Reduced acoustic signature over the full range of submarine operating speeds.
  
  
• Improved affordability through increased propulsion system modularity, simplification, and a reduced need for machinery isolation.
  
  
• Additional signature reduction when this technology is applied to auxiliary systems, such as main seawater pumps, secondary propulsion motors (see photo on page 20), and other submarine machinery.
  

Thermal Management

Non-chlorofluorocarbon chillers developed by NSWCCD are being installed on U.S. Navy surface ships and submarines. They are efficient, environmentally friendly, and exhibit reduced fuel consumption, acoustic signatures, and equipment footprint. As effective as these new chillers are today, they may prove to be unsuitable for future cooling requirements because auxiliary systems of the future are being designed for decentralized and autonomous operation. The new architectures will require cooling systems that are also decentralized, programmable, and capable of operating in a zonal configuration. Furthermore, the transition from mechanical to electrical auxiliary equipment will result in significantly increased power density and heat dissipation. Increasing the number of cooling units (smaller, more efficient, and localized) may prove to be the means to provide a suitable environment for the crew and equipment. Some alternative cooling technologies being investigated are listed below.

• Thermoelectric Air Conditioning—Recent breakthroughs in thin-film thermoelectric materials have the potential for efficient solid-state cooling with no environmental impact.
  
  
• Magnetic Refrigeration—This is an emerging technology that offers the potential for high-energy and efficiency with minimal environmental hazard. It is based on the use of an active magnetic regenerator to produce chilled water efficiently.
  
  
• Thermoacoustic Cooling—This employs sound waves to produce cooling. Pennsylvania State University is building a 3-ton cooling system that will be tested in the near future.
  
  New heat exchanger designs using novel methods and materials to remove heat passively are being explored as well.
  
  
• Dry sump heat exchangers that use heat pipe technology to eliminate closed-water loops, external heat exchangers, and piping arrangements.
  
  
• Waste heat recovery systems that turn the unwanted heat back into useful energy that could power secondary equipment or even be used to produce supplemental cooling.
  
  
• Through-the-hull heat exchangers that eliminate the need for large, bulky freshwater-to-seawater heat exchangers.
  

Composite Construction Materials for Naval Machinery and Equipment

During the last two decades, the Navy has demonstrated the feasibility of propulsion and auxiliary machinery made of fiber-reinforced thermosetting resins (e.g., epoxies, vinylesters, and fire-resistant phenolics) in a number of shipboard applications—propulsion shafting, piping systems, centrifugal pumps, ball valves, heat exchangers, and supply-intake ventilation ducting (see figure below).

Composite machinery components offer a number of advantages, such as corrosion/erosion-resistance, galvanic compatibility with metals, reduced life-cycle cost, improved structural efficiency, and reduced weight. Furthermore, composites are well suited to support numerous applications in future ship and autonomous vehicle concepts because of advances in the development of conductive reinforcing agents, as well as conductive polymer matrices. As a result of successful at-sea trials, long-term development investments, and growing commercial use of composite construction materials in the United States, a wide variety of composite machinery components are becoming available for consideration in surface ship design and construction. Current efforts to expand the application of composite machinery are directed toward the identification of appropriate commercial specifications, standardization strategies, and design guidance to ensure compliance with performance and safety standards.

Electric Actuators for Submarines

The use of electric actuators on submarines is a potential enabling technology that will reduce manning via the eventual replacement of maintenance intensive hydraulic actuators and fluid distribution systems. These systems operate several hundred valves, control surfaces, weapons handling, and other equipment in today’s submarines. Their output torques range from 2.5 in-lb (small 1/4-turn valves) to tens of millions of in-lb (control surfaces). At present, ONR and NAVSEA (SEA 93R) are developing electric actuator technology to address the wide range of actuation demands and satisfy all of the submarine service requirements.

Submarine actuator system performance requirements include minimal acoustic signature, resistance to shock and vibration, electromagnetic interference emissions and susceptibility, corrosion resistance, power density, fail-safe operation, back-up power, reliability, and maintainability. A wide variety of electric actuator systems are available or under development. Mature configurations such as electric motor and geared speed reducer are common in commercial and aerospace applications, but have not been qualified to satisfy submarine service requirements. New types of electric actuators (such as piezo-electric, magnetostrictive, electrohydrostatic, and shape-memory alloy) are being developed and show promise. The wide range of actuator output torque requirements suggests that a variety of electric actuator systems eventually will be needed for submarine actuator applications.

Integration of electric actuators on submarines is expected to be a long-term effort. The qualification program for electric actuator systems must include laboratory and shipboard tests to demonstrate satisfactory performance for long-term submarine service. Initially, they would be installed to replace hydraulic actuators in non-vital, non-sea-connected systems to obtain operating, reliability, and maintenance data. The submarine community has relied on hydraulic actuators for over 50 years. As confidence in the performance and reliability of electric actuator systems increases, they could replace the hydraulic fluid system, and the anticipated maintenance and manpower savings would be realized.

Machinery Automation and Control

Many of the machinery and auxiliary systems on Navy ships rely heavily on human intervention to operate the system and perform damage control functions. With the goal to reduce manning on the next generation of Navy ships, affordable and survivable automation technology is being investigated to replace the crew function through its deployment. Some of the major issues associated with implementing an automation system for a naval warship include:

• Ensuring that the system is highly survivable.
  
  
• Integrating multiple automated control systems at the ship control level.
  
  
• Designing an affordable system to optimize control and fight-through capability.
  

Under the sponsorship of NAVSEA (SEA 05R), ONR, and the DD 21 Program Office, the Division developed, tested, and demonstrated control technologies to meet the manning reduction initiatives. Efforts focused on the development of highly distributed control systems and networks for improved survivability and automation to reduce manpower requirements for both machinery systems and distributed auxiliary systems. Recent research and development tasks used distributed control and network technology to accomplish the following.

• To demonstrate the techniques to detect and isolate leak and rupture damage from a warhead event and to reconfigure the highly distributed fluid system to regain the maximum capability possible with the remaining resources.
  
  
• To operate and manage the resources and distribution of a highly distributed closed- loop fluid system using control algorithms that also are distributed to all of the system components with no central controller.
  
  
• To demonstrate advanced network healing technology on a small Navy surface ship using advanced distributed control algorithms.
  

Advanced Sensors and Networks

The research and development of advanced sensors is a multidisciplinary field serving machinery, damage control, and materials applications. Recently, the technologies employed by the Division to serve Fleet needs included fiber optics, and ultrasonic and microelectro-mechanical systems (MEMS). Under programs primarily directed by ONR, the Division develops sensors and data acquisition systems that provide advanced capabilities in the measurement of flow, pressure, proximity, current, temperature, strain, material damage, wear, and other parameters. Current development efforts are shown below.

• An ultrasonic hull damage sensor array that locates and estimates, in real time, the size of hull penetrations due to damage.
  
  
• A Bragg grating fiber optic strain sensor array that measures strain in absolute units (allowing for removal and reattachment of electronics) and allows real time/long-term monitoring.
  
  
• A fiber optic bearing wear sensor that remotely measures the wear of outboard water-lubricated propulsion bearing staves.
  
  
• Integrated fiber optic current and temperature sensors to measure such parameters within electrical components.
  

To operate with a reduced crew, a ship must have a reliable, accurate, and timely information system to monitor vital environmental, structural, machinery, and personnel conditions. An ONR-sponsored advanced technology demonstration called Reduced Ship-crew by Virtual Presence (RSVP) is investigating the necessary technologies. The RSVP program will demonstrate elements of key high-risk technology areas in the implementation of a Navy shipboard wireless sensor network to support reduced ship manning. The program has defined three major areas of high-risk technology application development.

• Advanced sensors in a high-density configuration.
  
  
• Wireless shipboard intra-compartment networks.
  
  
• Data fusion and advanced reasoning to support situational awareness.
  

Land-based evaluation of prototype components on full-scale naval machinery has been completed; at-sea tests commenced late in 2001. The DD(X) shipbuilder will use information provided by the RSVP program to select technologies that will support a reduced crew size.

Future Machinery Technology Developments

In January 2000, the Secretary of the Navy announced that the new Land Attack Destroyer (DD(X)) would be the Navy’s first ship class designed and built during the 21st century to be powered by electric drive, featuring an integrated power architecture. Integrated power is a flexible, open-architecture approach that permits any generating unit to supply propulsion or ship service power to support ship operational priorities. Looking beyond DD(X), there is strong interest to make future ships all-electric, thereby eliminating pneumatic, hydraulic, and other maintenance-intensive auxiliary systems. All-electric ships will also enable the deployment of high-energy weapons for long-range fire support. Operation of these weapons systems requires huge amounts of power over a very short time period, and depends on sophisticated high-power solid-state switching and pulse-forming networks. Greater dependency on
integrated power systems and the expanded use of electric power throughout the ship places a greater demand on the technologies that provide and maintain electrical distribution systems and their availability, survivability, and power quality.

It is anticipated that future electric power systems will operate at higher voltage levels and use superconducting electric machines and energy storage systems. Superconductive machinery offers the advantages of reduced size and weight, high efficiency, design simplicity, and reduction of components that contribute to the platform’s signature.

Intelligent systems, advanced sensors, and the greater use of electromechanical actuators are beginning to play a major role in the design of future machinery systems and equipment. The systems are becoming more modular, with “plug and play” capability, and will be logically interconnected and distributed via advanced ship-wide networks, thus enabling unmanned decision-making and reconfiguration. Other future developments include more energy-dense and environmentally compliant propulsion systems, decentralized auxiliary systems, enhanced shaftline components, and advanced machinery for autonomous vehicles. Fuel cells are expected to be a significant source of shipboard electricity, especially for zonal power generation. In the near term, hydrogen for the fuel cells will be obtained from liquid hydrocarbon fuels; however, future developments will focus on the extraction of hydrogen from seawater to reduce dependence on fossil fuels. Advances in machinery technology cannot be made without attention given to the reduction of noise signatures. Future machinery designs for submarines and surface ships will demand improved stealth via reduced acoustic and electromagnetic signatures without degradation of performance levels.