REVERSE TURBO BRAYTON CYCLE CRYOCOOLERDEVELOPMENT FOR LIQUID HYDROGEN SYSTEMS

(http://www2.mmae.ucf.edu/~mini)(Department of Mechanical, Materials and Aerospace Engineering)

Dr. Louis Chow – Project DirectorDr. Jayanta Kapat – Project Co-directorDrs. Q. Chen (MMAE); L. An (AMPAC); C. Ham (FSI); K. B. Sundaram (ECE), T. Wu (ECE). Partners: Dr. Neelkanth Dhere (FSEC); Dr. Nagaraj Arakere (UF); Dr. Dan Rini (Rini Technologies, Inc.); Mr. Jay Vaidya (Electrodynamics Associates, Inc.); Mr. Bill Notardonato (NASA KSC) and Mr. George Haddad (NASA KSC).

1. Project Goals2. Importance and Benefits to NASA3. Key Issues to be Resolved for Project Success4. Past, Current and Future Work5. Time Line

PROJECT GOAL

TO DESIGN AND BUILD AREVERSE TURBO BRAYTON CYCLE CRYOCOOLER

Affordability & Reliability

High-Efficiency Compactness

Light in weight 20-30 W Cooling Power at 18 K

70%

85%

90%

75%

95%

GPGPaa

55%

IMPORTANCE & BENEFITS TO NASA

Motor/Compressor unit

Heat regenerator, Flexible lines,

Cold head

Cryomech G-M Cryocooler Cryomech G-M Cryocooler AL330AL330

(40W @ 20K)(40W @ 20K)

UCF Miniature RTBC UCF Miniature RTBC CryocoolerCryocooler

(20–30W @ 18K)(20–30W @ 18K)

The rest of the cryocooler

Motor/Compressor unit

Ceramic micro-channel heat recuperator,

Cold head,Expander/Alternator

119-176 kg

24 kg

10 kg

12 kgThe rest of the cryocooler

143-200 kg 22 kgTotal weight Total weightCOP 0.005 COP 0.01

All of the previous attempts of flight cryocoolers have cooling capacities less than 2 W at liquid hydrogen temperature. There are commercially available cryocoolers that have higher cooling powers but their weight

restricts their possible usage for in-space applications.Long term propellant storage

Propellant losses

Propellant management and stocking

Zero Boil-Off (ZBO)

Key Issue

Prevention

Solution

The proposed design can significantly contribute to NASA

efforts on densification and ZBO storage of cryogenic propellants for missions to

Mars.

KEY ISSUES

• Miniature High-speed Centrifugal Compressor Development,

• High-speed, High-efficiency Motor Development, and• Integration and Testing of Compressor and Motor

The integrated compressor/motor is key to RTBC, and is useful for many NASA and non-NASA applications.

Examples include,• Durable, light-weight cryogenic (liquid hydrogen) propellant storage and feed systems for the development of Unmanned Air Vehicles (UAV) and transport aircraft and,• Future aircraft propulsion systems driven by electric power,where cryogenic and non-cryogenic high power density electric motors are useful.

March 2004 NASA Panel Advice: To reduce the scope and develop a much improved compressor/motor over the current

state-of-the-art

DevelopmentOf

Gas Foil BearingAnd

Heat Recuperator

De-scoped from the project

CURRENT WORK FUTURE WORK

Design and Fabrication of Miniature Centrifugal Compressor

Design, Fabrication and Testingof High-Speed, High-Efficiency PMSM

PAST WORK

Miniature Centrifugal Compressor Design Verificationby Numerical Simulation and Testing

5. Integration and Preliminary Testing5. Integration and Preliminary Testingof Motor/Compressor Test Assemblyof Motor/Compressor Test Assembly

6. 5.4 kW PMSM Design6. 5.4 kW PMSM Design

7. Two-stage 7. Two-stage Centrifugal Compressor DesignCentrifugal Compressor Design

Fabrication and Integrationof the 5.4 kW Motor/Two-stage

Compressor Assembly

Overall System Optimization

Coupler

Motor

Cooling water

Compressor Collector

Design:• Rotordynamic study based on the two-impellermounted shaft structure using FEA

Design:Completed test rig design with features like single rotor, spring loaded bearing, closed gas passage structure and precision impeller tip clearance control mechanismSome Parts Fabricated:Bearing Loader, Gas Passage, Inlet Guide Vane and Top Plate

Design:• Slotless stator and high energy density permanent magnet lead to low electrical losses and high efficiency.• Cylindrical structure with a large thickness hollow shaft design optimized to provide minimal rotor imbalance and high overall structural stiffness, thereby, preventing the shaft super-critical operation.

Overall Project Schedule/Tasks List Task 1. Design and Fabrication of Miniature Centrifugal Compressor Task 2. Design of a High-speed, High-efficiency PMSM Task 3. Fabrication and Testing of PMSMTask 4. Miniature Centrifugal Compressor Design Verification by Numerical Simulation and Testing

(with appropriate scaling) Task 5. Integration and Preliminary Testing of the Motor/Compressor Assembly (by December 2005)Task 6. 5.4 kW Permanent Magnet Synchronous Motor (PMSM) – Design (by August 2005)Task 7. Two-stage Centrifugal Compressor – Design (by August 2005)Task 8. Fabrication and Integration of the 5.4 kW PMSM/Two-stage Compressor Assembly Task 9. Overall System Optimization – Systematic Testing of the Motor/Compressor Assembly, Evaluation, Possible Design Changes

TIME LINE

Overall Project Milestones: Phase IIIM1 – 12/31/04: Design verification of miniature centrifugal compressor by numerical simulation and testing (with appropriate scaling) (completed)M2 – 02/28/05: Design of the motor/compressor assembly test rig (completed)M3 – 07/30/05: Fabrication and integration of the motor/compressor assembly test rig (under progress)M4 – 08/31/05: Design of the 5.4 kW PMSM (under progress)M5 – 08/31/05: Design of the two-stage 313,000-rpm centrifugal helium compressor (under progress)M6 – 12/31/05: Preliminary testing of the 2 kW motor/one-stage compressor assembly