1. Issues in Mechanical Diagnostics of Jet Engines
Dr. Renata Klein
R.K. Diagnostics
14th Israeli Symposium on Jet Engines and Gas Turbines
November 5, 2015

2. Agenda Health monitoring systems Diagnostic stages
Jet Engines Diagnostics
Example
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Jet Engine Diagnostics

3. End users Data base Maintenance Diagnostic Center 5/11/2015
Jet Engine Diagnostics

4. Jet Engines Monitoring
Main engine shafts (unbalance)
Bearings
Ball/ roller bearing
Intershaft bearing
Gear & Accessory gearbox
Rotors/ Blades
Cracks & deformations
Detection of events
Stall, FOD, Rubbing, Flutter
Performance
Fuel & Oil systems
Sensors
Vibro-acoustic signatures
Rotating machinery diagnostics
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Jet Engine Diagnostics

5. PHYSICAL & STATISTICAL MODELS
Diagnostic Stages
SIGNAL PROCESSING
FEATURE EXTRACTION & TREND ANALYSIS
HEALTH CLASSIFICATION
FUSION
PHYSICAL & STATISTICAL MODELS
Components
Time
Raw Data
Failure modes
Time
Data Selection
Time
Indicators
Scores
Orders
RPM
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Jet Engine Diagnostics

6. Jet Engine Signals Problems Solutions Non-stationarity
Asynchronous shafts
Aerodynamic “noise”
Quasi-stationary segments
Time-Frequency  Speed-Order
Angular resampling
Separate angular resampling per asynchronous shaft (LP, HP)
Separation of signals classes
Dephase
Whitening
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Jet Engine Diagnostics

7. TFR  SFR
Time-Frequency
N2-Frequency
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Jet Engine Diagnostics

8. Order  Dephased Order N2-Order N2-Dephased Order 5/11/2015
Jet Engine Diagnostics

9. Dephased Order  Envelope Order
N2-Dephased Order
N2-Envelope Order
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Jet Engine Diagnostics

10. SFR  Envelope Order N2-Frequency N2-Envelope Order 5/11/2015
Jet Engine Diagnostics

11. Intershaft Bearing SFR  Dephased Order
N2-Frequency
N2-Dephased Order (N2-N1)
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Jet Engine Diagnostics

12. Questions?
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Jet Engine Diagnostics

13. Rotating Machinery Signals
𝑦 𝑡 =𝑥 𝑡 ∗ℎ 𝑡
𝑌 𝑓 =𝑋(𝑓)∙𝐻(𝑓)
Synchronous signals – shafts, gears, blades
Transmission path
Asynchronous signals – bearings (slippage)
The signal processing task is to separate between the 3 types of signals
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Jet Engine Diagnostics

14. Operating modes Detection of operating modes of the machine
The algorithm allows definition of fuzzy rules combining conditions on a configurable number of time series
Estimation of data quality: closeness to pre-defined operating modes for monitoring
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Jet Engine Diagnostics