N101-063 TITLE: Robust Rotary Union for High Speed, High Power Density Rotating Electrical Machines

TECHNOLOGY AREAS: Ground/Sea Vehicles

ACQUISITION PROGRAM: PMS 320, Electric Ship Office

OBJECTIVE: Develop and demonstrate robust rotary union designs suitable for shipboard application to high speed, high power density rotating machines being developed by the Navy for Next Generation Integrated Power Systems (NGIPS).

DESCRIPTION: Increased shipboard electrical power requirements, needed to enable future weapon systems and electric drive propulsion systems, necessitate improvements to component power densities. Improved component power densities maximize installed power, and accommodate the necessary power conversion equipment within ship machinery arrangement constraints (ref 1).

For rotating electrical machines, including prime power generators, significant power density improvements are achievable through high speed operation and liquid cooling of the generator rotor (ref 2). High speed operation enables direct coupling to prime movers (engines) and elimination of the otherwise necessary reduction gearbox. Liquid cooling of generator rotors enables increased flux densities through more effective thermal management of rotor electrical losses. Alternately, high-temperature super conducting generators and motors enable significant increases in power density by virtually eliminating rotor losses (ref 3). Both high-speed, liquid-cooled generators and high-temperature superconducting generators require rotating couplings (i.e. rotary unions) to transfer the rotor cooling medium from the stationary equipment skid to the rotating shaft. Current commercial rotary unions do not meet the combinations of flow capability, speed capability, durability and reliability required by critical naval systems.

This topic seeks to explore innovative, affordable, advanced concepts and technologies to develop robust high speed rotary union designs suitable for application in advanced liquid cooled and high temperature superconducting generators. The technical challenges are providing a rotary union that operates satisfactorily in a high speed generator application at the flows and pressures required, specifically: zero or minimal leakages through seals, dynamically stable-with no modes excited by a dynamically active generator rotor, long life/durability (i.e. 12,000 hour time between overhaul or repair), reliability (i.e. 3000 hours mean time between failure), and graceful degradation (i.e. failure modes are not catastrophic and do not preclude generator from operating at reduced capability). Proposed concepts should be able to withstand severe shipboard environments (vibration, shock, and duty cycle).

PHASE I: Demonstrate the feasibility of innovative, affordable, advanced concepts and technologies that will result in the development of robust high-speed rotary union design(s) suitable for application in advanced liquid-cooled and high-temperature superconducting generators. Develop an initial conceptual design and establish performance goals and metrics to analyze the feasibility of the proposed solution. Develop a test and evaluation plan that contains discrete product development milestones for verifying performance and suitability.

PHASE II: Develop and demonstrate the prototype(s) as identified in Phase I. Through laboratory testing, demonstrate and validate the performance goals as established in Phase I. The prototype must meet Navy Shock and Vibration requirements (refs 4-5). Refine and demonstrate the capabilities of the system. Conduct life cycle and environmental testing. Develop a cost benefit analysis and a Phase III testing, qualification and validation plan.

PHASE III: The small business will work with the Navy and commercial industry to transition a full-scale system into advanced naval power systems demonstrations and tactical design development programs.

PRIVATE SECTOR COMMERCIAL POTENTIAL/DUAL-USE APPLICATIONS: Rotary unions are featured in several commercial applications including machine tools, mills, crude oil processing, and chemical industry. Advances in rotary union designs for naval applications will provide enhanced capability directly applicable to commercial applications, resulting in improved performance, higher reliability, increased durability, and graceful degradation.

REFERENCES:
1. Doerry, Norbert "Next Generation Integrated Power System (NGIPS) Technology Development Roadmap", Naval Sea Systems Command, Ser 05D/349, 30 Nov 2007.

2. Ray M. Calfo, Matt B. Smith, John E. Tessaro, "High-Speed Generators for Power-Dense, Medium-Power, Gas Turbine Generator Sets", Naval Engineers Journal, Volume 119, Issue 2, October 2007, Pages: 63-81.

3. Stephen D. Umans, "Transient Performance of a High-Temperature-Superconducting Generator", 2009 International Electric Machines and Drives Conference, Miami, Florida, May 3-6, 2009.

4. Doerry, Norbert, "Next Generation Integrated Power System (NGIPS) Technology Development for the Future Fleet", IEEE Electric Ship Technologies Symposium Baltimore, MD, April 21, 2009, http://ewh.ieee.org/conf/ests09/ESTS-2009%20Capt%20Doerry.pdf

5. MIL-S-901D, Military Specification Shock Tests H.I (High-Impact) Shipboard Machinery, Equipment, And Systems, Requirements, http://www.dcfp.navy.mil/library/dcpubs/MIL-S-901D.pdf

KEYWORDS: high-temperature super conducting; water-cooled generator; power density; electric ship; electric drive; NGIPS; rotary coupling

** TOPIC AUTHOR (TPOC) **

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