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作者: kinran 时间: 2011-6-4 23:24:43
