Air-Riding Seal Technologies for Advanced Gas Turbines

Jake MillsSenior Systems Design Engineer

Florida Turbine Technologies, Inc.561-427-6439

[email protected] 2014, Florida Turbine Technologies, Inc. All Rights Reserved

Air-Riding Seal Technologies for Advanced Gas Turbines

University Turbine Systems Research WorkshopOctober 22, 2014

Copyright 2014, Florida Turbine Technologies, Inc. All Rights Reserved

OutlineOutline

• Air Riding Seal Concept• Phase I

– Design– Testing

• Application• Future Development

2


ConceptConcept

3

• Non-contacting static to rotating seal • Hydrostatic balance of forces• Ability to follow rotor to maintain close clearances

0

Clearance

Desired Gap

Bal

anci

ng F

orce

Restorative Forces Outer

Seal Land

Pocket

Inner Seal Land

Seal Clearance

Rotating Surface

Secondary Seals

Piston

Secondary Seal

Outer Seal Land

Inner Seal Land

Piston

Pocket Static Housing


4

PhAh

Pl Al

Pl Al

Equilibrium ΣFx = 0

PcAc

Pl AlPh Ah + = Pc Ac

Reduced Clearance ΣFx =

Pl AlPh Ah + < Pc Ac

Increased Clearance ΣFx =

Pl AlPh Ah + > Pc Ac

ARS Concept


Phase IPhase I

5

Analytical ModelsRig Design Seal Testing

Simple low cost rig used for initial evaluation of the ARS seal concept

RoutersRotating Disk

Drive side Seal

Non-drive side Seal

Gearbox

Seal Body

Static Seal Face

Rotating Seal Face

Rotating Disk

Non-drive side housing

Drive side housing

Non-drive side seal

Drive side seal

Support Bearings


Proximity Probe

Pocket Pressure Tap

Set Screw

Upstream Pressure Tap

Left Seal(closed) Right Seal

(open)

Pocket Pressure Measurement

Video Recording

Proximity Probe

Speed Sensor

Supply Temp. Measurement

Phase IPhase I

6


Simple low cost rig used for initial evaluation of the ARS seal concept


Phase IPhase I

7


15 pieces of instrumentation used to accurately measure seal performance

( p )

Compressed Air Tank(110 psi)

Cashco w/ TestcomConrollerVenturi

Type K

AI 0 (mVDIFF

)

AO 1 (4‐20mA)

wT

dPTPw

TemperaturePressureFlow Rate

Px Prox ProbeS Speed (rpm)

PT

PxPS

2 x

2 x

P P


Phase IPhase I

8

• Simple 1D models used to study design variables• More complex CFD models used for more accurate physical

representation• Analytical models then anchored to test data


Predicted seal clearance is 0.0030” to 0.0035”


Phase IPhase I

9

• CFD Model


Cells = 1.3E6 Shear Stress Transport (SST)

• Heat Transfer

Total Energy• Adiabatic walls• Advection Scheme

Tetrahedral grid with prism layers to resolve boundary layer


Phase IPhase I

10

• CFD Model

Pmax=21.92 psiaPmax=21.87 psia

Static Rotating

Seal is fundamentally hydrostatic


Results are periodic, a simplified sector model can be used


Phase IPhase I

11

• 3D Periodic CFD Model– Studied clearances

• 0.001”• 0.002”• 0.003”• 0.005”• 0.010”

– Inlet pressures• 95 psi• 50 psi• 20 psi

0.010” Gap 0.005” Gap 0.003” Gap 0.002” Gap 0.001” Gap

On the rig, clearance of 0.005” and less led to uniform pocket pressures



Phase IPhase I

12

• CFD Model– Manually run for the five clearances

at the three inlet pressures


0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

0 0.001 0.002 0.003 0.004 0.005 0.006 0.007 0.008 0.009 0.01 0.011

Seal Discharge Coe

fficient

Physical Clearance

Inner/outer seal Discharge Coefficient @ 95 psia supply Cd‐Outer Cd_Inner

CDs from CFD model used to improve the accuracy of the 1D model

CFD predicted seal clearance is 0.0030” to 0.0033”


Phase IPhase I

13


• Test matrix developed to measure seal performance over a range of speeds and pressures

• For each test speed the supply pressured was varied from atmospheric to 95 psig while holding the downstream pressure at atmospheric

Test Number

Shaft Speed(rpm)

Face Speed(ft/s)

∆P(psid)

Low

Spe

ed

01a 0 0 20

01b 0 0 40

01c 0 0 60

01d 0 0 80

02a 10,450 200 20

02b 10,450 200 40

02c 10,450 200 60

02d 10,450 200 80

03a 20,900 400 20

03b 20,900 400 40

03c 20,900 400 60

03d 20,900 400 80

Test Number

Shaft Speed(rpm)

Face Speed(ft/s)

∆P(psid)

Hig

h Sp

eed

04a 31,350 600 20

04b 31,350 600 40

04c 31,350 600 60

04d 31,350 600 80

05a 41,800 800 20

05b 41,800 800 40

05c 41,800 800 60

05d 41,800 800 80

Rig failure occurred during high speed testing. However low speed data indicates seal performance is independent of speed


Phase IPhase I

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• Test data compares favorably to analytical predictions

Linear relationship between supply pressure and flow rate

Non-dimensionalized pressure remains constant for a given design


Phase IPhase I

15


Analytical models provide an accurate representation of the seal

• Friction plays a role in the steady state operating clearance

• Seal design should minimize friction forcesInitially Open

Initially Closed


Phase IPhase I

16



ARS ApplicationARS Application

17

Compressor Interstage

Seals

Turbine Interstage

Seals

Bearing Compartment

Seals

Compressor Bleed Seal

• ARS technology applicable to a variety of rotating to static seals

• Large utility scale engine performance model created to assess benefits of retrofitting an engine with the ARS technology [1]


ARS ApplicationARS Application

18

• ARS replacing labyrinth interstage seals

Leakage Location Baseline ARS ∆FlowRotor 1 Upstream 1.903% 0.89% -1.013%Rotor 1 Downstream 0.755% 0.357%* -0.398%Rotor 2 Upstream 0.769% 0.239%* -0.53%Rotor 2 Downstream 1.019% 0.357%* -0.662%Rotor 3 Upstream 0.175% 0.138%* -0.037%Total Key Leakages 4.621% 1.981% -2.64%

*limited by min purge flow requirement

Benefit in the Turbine

Benefit in the Compressor• Increased compressor efficiency

estimated from data correlating stage efficiency increase due to reduced leakage [2]

• Stage efficiency benefit weighted by pressure ratio to arrive at on overall compressor efficiency increase

• Potential increase of compressor isentropic efficiency of 0.34% points

Additional Power Output 11910 kWOperating Hours per Year 6000 hrAverage Florida Residential Electricity Rate 0.12 $/kWhAdditional Annual Revenue per Engine $8,574,725

Power Revenue $8,574,725Fuel Expense $1,370,743Net Annual Profit per Engine $7,203,982

Baseline T&C ARSNormalized CO2 Emissions per kilowatt-hour (lb CO2/kWh)

0.784 0.773


Continued Development

Phase II SBIR• Design for specific engine application• Rig test in engine-like environment

Beyond Phase II• Partner with OEM• Conduct engine testing

Technology Maturation Items• Design variations

– Tolerances, surface finish

• Operating anomalies– Rotor coning, non-symmetrical BCs

• System response

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Technology Development RoadmapTechnology Development Roadmap

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TRL1 TRL2 TRL 3 TRL 4 TRL 5 TRL 6 TRL 7 TRL 8 TRL 9

Basic Technology

Research to Prove Feasibility

Technology Development

Technology Demonstration System/Subsystem

Development

System Test, Launch & Operations

Product

SBIR Phase I SBIR Phase II OEM Partnership

Concept Test Rig

Engine Like Test Rig Low Risk Engine Test

Demo Engine Test

Large Engine Test

Pro

duct

FTT RigFTT Rig

Completed Working


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[1] Pequot Publishing Inc., “Gas Turbine World 2005 Performance Specs”, January 2005, Vol. 34 No. 6[2] Lakshminarayana, B. (1970). Methods of Predicting the Tip Clearance Effects in Axial Flow Turbomachinery. ASME: Journal of Basic Engineering, 92(3), 467-480.

Acknowledgments

References

Travis Shultz – DOE Program Manager

Todd Ebert – CFD and Sealing ExpertJustin Cejka – Performance Engineer

Air-Riding Seal Technologies for Advanced Gas Turbines

Documents

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