application of ultrasonic air flow measurement to industrial gas
TRANSCRIPT
realtimepower.net
Application of Ultrasonic Air Flow
Measurement to Industrial Gas Turbines
Dr. A.R. Boucher C.Eng. MIET
Technical Director
Real Time Power, Inc.
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Outline
• Introduction
• Principle of Measurement
• System Description
• Uncertainty Analysis Example
• Results from High and Low Load Operation
• Real-Time Heat & Mass Balance
• Benefits to End Users
• Conclusions
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Introduction
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Principle of Measurement
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𝑣AB = AB
2
1
tAB−
1
tBA
𝑐AB = AB
2
1
tAB+
1
tBA
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duct factor = average velocity in plane P / average velocity along vector L
velocity direction is vertically down
(width of vector L exaggerated in this diagram)
Calculation of Duct Factor
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Ultrasonic Probes
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No detachable parts on
the inside of the duct!
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Uncertainty Analysis Example
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Probe tip to probe tip distance = 3.200 m,
Average air flow angle across path = 50°,
Average air speed = 26.5 m/s
Speed of sound = 345 m/s
Uncertainty in distance = ±2 mm
Uncertainty in timing = .±2 μs
Air speed along path = 26.5 x cos(50°) = 17.03 m/s
Upstream time of flight = 3.200 / (345 – 17.03) = 9757 μs
Downstream time of flight = 3.200 / (345 + 17.03) = 8839 μs
Time difference = 918 μs
Maximum worst case reading = 17.12 m/s (+0.48% worst case error)
Minimum worst case reading = 16.95 m/s (-0.52% worst case error)
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Accuracy Check: Speed of Sound
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Results from High & Low Load
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Air Speed v IGV Position
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Air Mass Flow Rate and CDP
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Air Mass Flow Rate v CDP
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Summary of Correlations
New Signal Existing Signal Correlation %
Air Speed
IGV Position Nonlinear 99.16%
Air Vol Flow Rate Compressor Pressure
Ratio/Density
Linear 98.42%
Air Mass Flow Rate Compressor Discharge
Pressure
Linear 98.46%
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Real-Time Mass Balance
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Accurate prediction of
exhaust gas oxygen
concentration
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Real-Time Mass Balance
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Accurate prediction of
exhaust gas oxygen
concentration
Twin gas turbines
running at same load
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Real-Time Heat Balance
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Accurate prediction of exhaust gas temperature
Exhaust gas temperature prediction validates TIT estimate
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Exhaust Gas Temperature Prediction
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Temp Limit computed from Press Ratio
Temp Pred determines when max load is reached
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Benefits to End Users
• Max Load & Heat Rate Forecasting
• Min Load & Heat Rate Forecasting
• Real-Time Performance Monitoring
• Troubleshooting Performance Issues
• Early Detection of Potentially Serious Problems
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1X1 Unit Summer Max Load Prediction
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Forecasted max load
Traders can schedule the
unit for the next 72 hours
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1X1 Unit Winter Max Load Prediction
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Unit on EGT constraint
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1X1 Unit Max MW Predictions
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Accurate prediction of ST MW
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2X1 Unit Summer Max Load Prediction
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Max load with evap coolers running
Requires accurate prediction of
evap cooler performance!
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2X1 Unit Winter Max Load Prediction
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System correctly predicts
that EGT limit would
be reached at 99% load
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2X1 Unit with Duct Burners
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System correctly predicts
maximum load with evap coolers
and duct burners running
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Conclusions
• Accurate measurement of air mass flow rate is
possible with ultrasonic technique
• Allows engine and unit performance to be
monitored and predicted with high levels of
accuracy and confidence
• Allows performance issues to easily and quickly
identified, and provides early warning of
potentially serious problems
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