Design and Fabrication of Gas Foil Journal Bearing For High Speed Small Turboexpander Used

in Cryogenic Application

Suraj Kumar Behera Ranjit Kumar Sahoo Sunil Kumar Sarangi Trilok Singh

Application of Turboexpander in Cryogenic

2

Modified Claude Liquefaction cycle

Anatomy of Cryogenic Turboexpander

3

Anatomy of Cryogenic Turboexpander

4

Brake Compressor

Expansion Turbine

Upper Thrust Bearings

Upper Journal Bearings

Lower Journal Bearings

Rotor Collar

Lower Thrust Bearings

Experimental prototype of turboexpander for cryogenic application.

• Analysis of GAS FOIL JOURNAL BEARING(GFJB) system, An alternate gas

bearing system for high speed small turboexpander

• Design and fabrication of gas foil Journal bearings for the prototype

turboexpander.

Objective

5

Gas Bearings for Small Turboexpander

Advantages of gas bearings over other Bearings • Oil free as process gas can be used as lubricants. • Gases are more stable at extreme temperatures and speeds (no lubricant

vaporization, cavitations, solidification, or decomposition). • No Scheduled Maintenance. • Small friction losses. • High speed. • Long Life.

Types gas bearings 1. Aerodynamic ( Self Acting )

2. Aerostatic ( Externally pressurized) 6

Justification Current advancements in turboexpander, turbochargers and midsize gas turbines are need of proven gas bearing technology to procure compact units with improved efficiency in an oil-free environment.

Aerodynamic Spiral groove bearings

Available Gas Bearing Technologies for turboexpander

Aerodynamic Tilting pad journal bearing

Aerostatic Thrust bearings Aerodynamic Herringbone grooved bearing

• Precision fabrication process • Low load capacity , stiffness and damping

NICH Center, Tohoku University

NIT Rourkela NIT Rourkela

• Performance is good. • Repeated start and stop is not an issue. •5% to 10% of process gas is used in external pressure system

• Precision fabrication of tilting pad • Selection of tilting pad materials.

NIT Rourkela

•Repeated start and stop is an issue. •Rigid bearing bush

Top Foil Bump Foil Gas Film

Bearing Block

Rotor Spinning

Gas Foil Bearings

Journal Gas foil bearing ISOMETRIC VIEW 8

1. Tension Dominated foil bearings - Tape Type - Leaf Type 2. Bending dominated foil bearings - Bump type

Major Types of Foil Bearings

Working Principle of Bump Type Gas Foil Bearings

Journal foil bearing

• Bump foil Gas bearings consist of three parts: a. Smooth Top foil b. Bump foil structure c. Bearing Block

9

•Aerodynamic pressure generation between the runner and the smooth top foil due to wedging action.

•Aerodynamic pressure determines the load carrying capacity of shaft .

•Aerodynamic pressure deforms the top foil and bump foil to prevent contact between rotor and bearing, which results zero wear of the bearings.

•The bump foil structure gives flexibility to tolerate significant amounts of misalignment and distortion that would otherwise cause a rigid bearing to fail.

•Micro-sliding between the top foil and bump foil also the bump foil and the housing generates Coulomb damping which can increase the dynamic stability of the rotor-bearing system.

Gas Foil Bearings Development History Generation I

Generation II Generation III

10

Bumps are uniform both radially and circumferentially .

Circumferential slits cut in Bump Foil. Complex support structures

of bump Foil.

Two kinds of new compliant foil bearing for small cryogenic turbo-expander

Institute of Cryogenic Engineering, Xi’an Jiaotong University, China,2003

Available Gas Foil Bearing Technologies for turboexpander

School of Energy and Power Engineering, Xi’an Jiaotong University, China

Thrust foil dynamic gas bearing with elastic hemispherical convex dots Foil Bearings to helium turbo compressor at Fermi

National Accelerator Laboratory,Batavia,Illinois

NASA

Korea University, Seoul, South Korea

Proceedings of the 30th Turbomachinery Symposium, Texas A & M University,

11

Available Gas Foil Bearing Technologies for turboexpander

Foil Bearing Air Cycle Machine After 7,500 Start-Stops of Air Force B-2 Stealth bomber

12

Proceedings of 30th turbomachinery s symposium

Use of Foil Bearings in high speed machinery

Foil Bearing Air Cycle Machine After 13,000 Hours in Saudia Aircraft

Finite Difference Approximation

Simplified Dimensionless Reynolds Equation for Compliance bearing

Aerodynamic Formulation of Gas Foil Journal bearings The Standard Compressible Reynolds Equation in 2 Dimension for Journal Bearings in polar form neglecting time variant:

23 3( ) ( ) ( )p D pph ph ph

L y yθ θ θ∂ ∂ ∂ ∂ ∂ + = Λ ∂ ∂ ∂ ∂ ∂

Air Film Thickness Bearing number Compliance number

22 2 2 22 2

2 2 3 2

3 1p D p p h D p h p D p h pL y h L y y p L y h phθ θ θ θ θ θ

∂ ∂ ∂ ∂ ∂ ∂ ∂ ∂ Λ ∂ Λ ∂ + = − + − + + + ∂ ∂ ∂ ∂ ∂ ∂ ∂ ∂ ∂ ∂

From Taylor series

21, , 1, , 1 , , 1

2 2

2 2L.H.S.= i j i j i j i j i j i jp p p p p pD

L yθ+ − + −− + − + + ∆ ∆

22 2 2

, ,

3 2, , ,

R.H.S.=

3 1

i ii j i jj ji j

ii j i j i ji

p h D p h p D ph L y y p L y

h ph p h

θ θ θ

θ θ

∂ ∂ ∂ ∂ ∂ ∂ − + − + ∂ ∂ ∂ ∂ ∂ ∂ Λ ∂ Λ ∂ + + ∂ ∂

21, , 1,

2 2

2, 1 , , 1

2 2 2

2

2

i j i j i j

i j i j i j

p p pp

p p ppy y

θ θ+ −

+ −

− +∂=

∂ ∆− +∂

=∂ ∆

1 cos ( 1)h pε θ α= + + − 206

a

Rp Cωµ Λ =

( )

322 1aP s l

CE tα ν = − (Heshmat et al., 1983, Walowit et al., 1975).

13

Aerodynamic Analysis of Gas Foil Journal bearings

14

Result of Aerodynamic analysis

Pressure distribution of 3600 bump type gas foil journal bearing.

Rotodynamic analysis of Turboexpander rotor

15

Results:

2. Mode shapes.

1. Critical Speed

NO Critical Speed(Hz) Critical Speed(r/min)

1 314 18,869

2 405 24,313

3 4165 2,49,894

4 10197 6,11,823

Rotodynamic analysis of Turboexpander rotor

16

Results: 3. Unbalance Response

Selection of Bump Foil and Die for Bump foil

where: Ri, Rf: initial and final bend radii respectively, mm Y: Yield strength, Gpa E: Young’s modulus, Mpa t: Sheet thickness, mm

To estimate spring back, the following formula can be used:

Manufacturing processes by S. Kalpakjian and S. Schmid

Foil Material Ri/Rf

Inconel 0.923

K monel 0.891

Phosphorous Bronze 0.862

Beryllium-Bronze 0.793

3

4 3 1. .

i i i

f

R RY RYR E t E t

= − +

17 Die for Journal bump foils:

Important Dimension and material chosen are : 1. Smooth top foil thickness: 0.1 mm 2. Bump foil thickness: 0.1 mm 3. Bump Height: 0.60 mm 4. Bump Pitch : 4.20 mm 5. Top foil Material: Phosphor Bronze 6. Bump foil material: Phosphor Bronze

18

Fabrication of Bump foil

Die for bump foil

smooth foil with slits

Rubber Sheet

Punch

Bump foil formation under hydraulic press

Design of Gas foil journal bearings

Important Dimension and material chosen are : 1. Smooth top foil thickness: 0.1 mm 2. Bump foil thickness: 0.1 mm 3. Bump Height: 0.51 mm 4. Bump Pitch : 3.17 mm 5. Top foil Material: Phosphor Bronze 6. Bump foil material: Phosphor Bronze

19

Journal Foil Bearing Fabrication and Assembly

Deburr Deburr

Press Bumps: at 200Mpa Die punch set up

Cut to shape by wire EDM

Cut to shape by wire EDM

Roll to approximate shape

Roll

Assemble with pins or spot weld

20

Roll at end, for fixing with bearing base

21

Journal Foil Bearing Assembly

Bearing Housing and Assembly of Bearings

22 Assembly of Bearings in housing

Schematic Diagram of Turboexpander set up

23

Reference

Ref No

Details of reference

1 Gross, W. A. (1962), Gas Film Lubrication, John Wiley and Sons,New York.

2 Giri L. Agrawal,1997, ”Foil Air/Gas Bearing Technology ,An Overview” ASME,Publication 97-GT-347

3 I.A.Davydenkov,1992”Development of Cryogenic Turboexpander with gas Dynamic foil Bearings”, Cryogenic 1992 vol 32 ICEC.

4 Christopher DellaCorte,2011,”Oil-Free Shaft support system rotodynamic: Past ,Present and Future Challenge and oppertunities” ,NASA/TM-2011-217003

5 Yao, H., Quan, H. and Chen, C. Development of Foil Journal Bearing for Small High Speed Cryogenic Turboexpander Proceedings of the Sixteenth International Cryogenic Engineering Conference (1996) 233-236

6 DellaCorte, C., and Valco, M. J. ,2000, “Load Capacity Estimation ofFoil Air Journal Bearings for Oil-Free Turbomachinery Applications,” Trib.Trans., 43(4), 795-801.

7 Heshmat, H., Walowit, J. A., Pinkus, O., 1983, “Analysis of Gas Lubricated Foil Journal Bearings”, Journal of Lubrication Technology, 105, 647-655.

8 Manish kumar,2009”Static performance of hydrostatic bump foil bearings “Tribology international,43, 752-758

9 Rathanraj K.J and Ravikumar R.N, 2011,”A Research trends in air foil thrust bearings used in micro turbines and aircraft machines.”Int Journal of ETED”,Issue1, Volume 2

24

Reference

Ref No

Details of reference

10 Christopher DellaCorte, Kevin C. Radil , Robert J. Bruckner & S. Adam Howard,2008,”Design, Fabrication, and Performance of Open Source Generation I and II Compliant Hydrodynamic Gas Foil Bearings” Tribology Transactions, 51: 254-264

11 Brian Dykas,Robert Bruckner,Christopher DellaCorte,Brian Edmonds,and Joseph Prahl,2009,"Design, Fabrication, and Performance of Foil Gas Thrust Bearings Micro turbomachinery Applications", Journal of Engineering for Gas Turbines and Power,131,1-8

12 H.Ming Chen, Roy Howarth, Bermard Geren,Jay C. Theilacker and William M Soyars,2010” Application of foil bearings to Helium Turbo compressor.”Proceedings of the 30th turbomachinery symposium.

13 Christopher DellaCorte,Antonio R. Zaldana, Kevin C. Radil ,2003“A Systems Approach to the Solid Lubrication of Foil Air Bearings for Oil-Free Turbomachinery”, ASME J of Tribol., 126, 200-207.

14 Christopher DellaCorte,2011,”Oil-Free Shaft support system rotodynamic: Past ,Present and Future Challenge and oppertunities” ,NASA/TM-2011-217003

15 Oscar De Santiago and Luis San Andres,2011,”Parametric study of bump foil gas bearings for industrial Application”, Proceeding of ASME Turbo expo 2011

16 Crystal A. Heshmat,David S. Xu,Hooshang Heshmat ,2000 “Analysis of Gas Lubricated Foil Thrust Bearings Using Coupled Finite Element and Finite Difference Methods”, Journal of Tribology., 122, 199-204. 25

Thank You

26