CFM Low Pressure Turbine Module

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February 2002 WTT face to face CFMI / Boeing Proprietary Information - Unauthorized Disclosure, Use, or Export are Prohibited 1
Low Pressure Turbine Module
February 2002 WTT face to face CFMI / Boeing Proprietary Information - Unauthorized Disclosure, Use, or Export are Prohibited 2
Stage 1 Blade Failure (DAC Issue)
Low Pressure Turbine Module
• Background
• Root Cause - Failure Scenario
• Design Improvement
• Fleet Management Program
• Summary
February 2002 WTT face to face CFMI / Boeing Proprietary Information - Unauthorized Disclosure, Use, or Export are Prohibited 3
LPT Stage #1 blade separation events :
 Found following N1 vibration level reports or during start phases
 Seven (7) CFM56-7B/2 (DAC Engines)
– TSN/CSN : 1222/912
– TSN/CSN : 2042/1639
– TSN/CSN : 2785/2207
– TSN/CSN : 3122/2404
– TSN/CSN : 1251/1748
– TSN/CSN: 1778/2379
– TSN/CSN: 433/337
Stage 1 Blade Failure (DAC Issue)
Low Pressure Turbine Module
February 2002 WTT face to face CFMI / Boeing Proprietary Information - Unauthorized Disclosure, Use, or Export are Prohibited 4
LPT blade T.E.
lower span failure Impact
(FOD/DOD)
Blade excitation
Loss of damping
or shroud support
Tip shroud HARD COAT
wear
Tip shroud HARD COAT
liberation
Tip shroud twist
decrease
Blade excitation
(HPT unbalance, nozzles, ........)
Combustor
excitation 20/2^5
No impact before
LPT stage #1 blades
APVS quality
Tip shroud re-twist
Material characteristics/Defects
Hard coat defect
Geometry
High
Medium
Low
Eliminated
Manufacturing deviation
Stage 1 Blade Failure (DAC Issue)
Root Cause confirmed by instrumented Engine test
Low Pressure Turbine Module
February 2002 WTT face to face CFMI / Boeing Proprietary Information - Unauthorized Disclosure, Use, or Export are Prohibited 5
Reinforced Blade
• P/N 338-108-206-0
• Improved platform / airfoil T/E transition radius
• Better resistance to dynamic stress
• SB 72-286 for CFM56-7B
• On SAC and DAC engines
• NO BLADE LIFE LIMITATION
 Assurance Engine test completed
 No blade life limitation confirmed since
Dec 2001
Modified
area
Stage 1 Blade Failure (DAC Issue)
Since March,2001 all new production (DAC) Engine deliveries get
reinforced Blades
Low Pressure Turbine Module
February 2002 WTT face to face CFMI / Boeing Proprietary Information - Unauthorized Disclosure, Use, or Export are Prohibited 6
Stage Blade Final Fix
• P/N 338-108-208-0
• Eliminate blade vib response
• No increase in blade weight
• No performance loss
• Improved blade damping
• Certification test in progress
• Availability in production
 For Field retrofit Apr 2002
 On DAC Engines Jun 2002
 On SAC Engines Sep 2002
Cross section area increase
and
Cambering increase
Cambering decrease
Root fillet decrease
at leading edge
Airfoil length increase by 0.5 mm
to adjust flow path
Trailing edge rotation
by 2° for
optimization
with vane leading
edge
Stage 1 Blade Failure (DAC Issue)
Low Pressure Turbine Module
February 2002 WTT face to face CFMI / Boeing Proprietary Information - Unauthorized Disclosure, Use, or Export are Prohibited 7
Stage 2 Nozzle Cracking Issue
• Hardware overview : LPT stage 2 vanes (72-54-08)
• Cracking mode failure
• Experience
 Development engine
 Field finding
• Field behavior
• New design
• Sampling Program
• Summary
Low Pressure Turbine Module
February 2002 WTT face to face CFMI / Boeing Proprietary Information - Unauthorized Disclosure, Use, or Export are Prohibited 8
Repairs
• ESM 72-54-08 inspections (at piece part) :
 Visual
 Dimensional
 FPI
• ESM 72-54-08 repairs :
 Repair 001 : blend repair of the
airfoils
 Repair 005 : touch up of protective
coating
 Repair 018 : replacement of the
abradable honeycomb liner
Stage 2 Nozzle Cracking Issue
Low Pressure Turbine Module
February 2002 WTT face to face CFMI / Boeing Proprietary Information - Unauthorized Disclosure, Use, or Export are Prohibited 9
Cracking Failure Mode
• LPT stage 2 vane is loaded per :
 Air flow
 Thermal gradients
 Vibratory excitation
• Root cause :
 High thermal gradient during
transients related to thickness
variation along the vane airfoil
profile
 Sum of loading conduct to
unacceptable stress level in airfoil
hot
Trailing Edge : cold
Leading Edge : cold
Thermal behavior during deceleration :
Thermal stress
Thermal stress
Crack location
Stage 2 Nozzle Cracking Issue
Root cause understood
High thermal gradient between LE - airfoil middle - TE
Low Pressure Turbine Module
February 2002 WTT face to face CFMI / Boeing Proprietary Information - Unauthorized Disclosure, Use, or Export are Prohibited 10
Cracking Failure Mode (cont’d)
• Phenomenon simulation :
 State of the art calculation confirmed :
– Critical area
– Unacceptable stress level
• LPT stage 2 vane mode failure :
 LPT stage 2 vane airfoils cracking
 Airfoils cutting
 Inner platform liberation (DOD)
 High cost shop visit
Stage 2 Nozzle Cracking Issue
Low Pressure Turbine Module
February 2002 WTT face to face CFMI / Boeing Proprietary Information - Unauthorized Disclosure, Use, or Export are Prohibited 11
Experience on Development SAC Engines
• 750 cycles  28% of cracked vanes
• 1,500 cycles  50% of cracked vanes
• 4,500 cycles  90% of cracked vanes
Experience on Development DAC Engines
• CFM56-5B/P, 779-193/05 : 6,000 cycles
 100% of LPT stage 2 vane above ESM 72-54-08 crack limit
 2 airfoil fractures reported
• CFM56-5B/2P, 779-011/08 : 4,000 cycles :
 60% of LPT stage 2 vane above ESM 72-54-08 crack limit
 No airfoil cutting reported
Stage 2 Nozzle Cracking Issue
Cracking phenomenon observed on development engines
Potential risk of early replacement of LPT stage 2 vane
Analytical models predict similar behavior between SAC and DAC
Low Pressure Turbine Module
February 2002 WTT face to face CFMI / Boeing Proprietary Information - Unauthorized Disclosure, Use, or Export are Prohibited 12
Experience on Field Engines
• PCA engine 874-120 (6,145 cycles) : No cracks
• During DAC LPT stage 1 blade retrofit
Stage 2 Nozzle Cracking Issue
Field Data Do Not Put in Evidence Quick Nozzle
Deterioration
LPT stage 2 vane airfoil crack lenght
0
2
4
6
8
10
12
14
16
0 2000 4000 6000 8000 10000 12000
CSN
cracklenght (mm)
7B/2P
5B/2P
ESM limit
Low Pressure Turbine Module
February 2002 WTT face to face CFMI / Boeing Proprietary Information - Unauthorized Disclosure, Use, or Export are Prohibited 13
Current
profile
Proposed profile
- Life at crack initiation is increased
by 8
- Weight impact: + 2 lb
Design Improvement
• Change rationale :
 Increase of the leading edge thickness to reduce the axial thermal
gradient between the L.E. and the middle of the airfoil
• Production introduction targeted by end of 2002
Stage 2 Nozzle Cracking Issue
Design Improvement Released Based on Development Findings
Low Pressure Turbine Module
February 2002 WTT face to face CFMI / Boeing Proprietary Information - Unauthorized Disclosure, Use, or Export are Prohibited 14
Sampling Program
• Objectives
 Collect field hardware evidence for better assessment of cracking
phenomenon severity
 Validate inspection procedure through LPT 1 blades
• Engines candidates to this sampling :
 SAC engines 5BP or 7B in Shop visit
 Results by mid 2002
 High cycle engines
 No removal on purpose
Stage 2 Nozzle Cracking Issue
Sampling program required to assess development findings
CSM will contact Customers when engines identified
Low Pressure Turbine Module
February 2002 WTT face to face CFMI / Boeing Proprietary Information - Unauthorized Disclosure, Use, or Export are Prohibited 15
Summary
• New design available by 4Q 2002
• Sampling program needed to confirm cracking vs TSN/CSN
Stage 2 Nozzle Cracking Issue
In-service Containment Action, If Necessary,
To Be Defined by 4Q 2002
Low Pressure Turbine Module
February 2002 WTT face to face CFMI / Boeing Proprietary Information - Unauthorized Disclosure, Use, or Export are Prohibited 16
Stage 2 / Stage 3 Nozzle Segments
Overspeed Modifications
• Background
 Nne LPT overspeed event on ESN 874-313 in Dec 1998
– Same LPT configuration on CFM56-5B/P
• Corrective Actions
 HMU upgrade to P07 to correct event root cause (PS3 pulsation / HMU
excitation) => Retrofit complete
 New design nozzle 2 and 3 introduced in production 1Q2000
– Intro. ESN 87T-327 (SAC); 87T-720 (DAC); (T=6or7)
– Reinforced capability to reduce rotor speed in case of LPT shaft rupture
• Field Recommendation
 Rework of nozzle 2 and 3 recommended at first piece part exposure per
SB 72-241 (issued May 2000)
 Airworthiness Directive released Jan 02 reinforces compliance of SB with
deadline = 31 Oct 2008
Low Pressure Turbine Module

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CFM Low Pressure Turbine Module

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