Guide to Configuring a Fiber Optic Sensing System


 

Combustion Dynamics Monitoring Systems (CDMS)

Test Results

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Promotional Flyer for Davidson's Combustion Dynamics Monitoring System

CDMS System Specifications

CDMS System Configuration

Over 1,000,000 Hours of Time in Service

High-Fidelity, Stable, and Temperature-Tolerant

The following chart demonstrates the high-fidelity response of Davidson's sensors.  The signal on the top is the output of a laboratory reference laboratory calibration microphone in response to pure tones generated at 25 Hz and 65 Hz and then from 50 Hz to 950 Hz in 50 Hz increments at 0.3 psi. The signal on the bottom is the output of the Davidson GE 7FA style transducer.

Note the Davidson transducer and the reference laboratory calibration microphone are in the same acoustic chamber but at a 90° orientation relative to one another.  The Davidson transducer is faithfully reproduces the sound pressure without any falloff at either low or high frequencies.  In fact, the Davidson transducer faithfully reproduced every acoustic anomalies seen by the reference microphone.

The fidelity of Davidson's transducers are as good at the 800°F operating temperature inside the engine as the high performance laboratory calibration microphone is at room temperature.  This means all acoustic events across the spectrum will be faithfully reported by the Davidson system without any dropoff, distortion, or blind spots in the spectrum.

Comparison of Davidson Transducer with Laboratory Calibration Microphone in Laboratory Test

The test apparatus was a pure tone acoustic source that generated pure sinusoidal pressure waves at 0.25 psi. The source generated pure tones from 10 to 1000 Hz in approximately 50 Hz increments.

 

Laboratory Test Setup Generating Pure Tones from 10 to 1000 Hz

The next chart show the ultra low noise performance of the Davidson transducer.  The noise floor is uniformly less than 0.001 psi across the spectra and this provides further evidence that the Davidson system will report the actual acoustic events caused by real combustion dynamics and not false indications caused by electrical noise, thermal transients, etc.

Davidson's Ultra Low Noise Floor of 0.001 psi Provides Great Siganla to Noise

Lean blow out typically is preceded by low frequency dynamics at 25 Hz.  Davidson's system is clearly able to detect and accurately measure the low frequency dynamics providing operators and/or automated control systems with alarms to provide time to change the necessary operating conditions.

 
Field Test Results of Davidson Transducers Illustrate the
Low Frequency Precurors to a Lean Blow Out
 
In the following chart, it is obvious in the lower figures that there is something seriously wrong with the engine when operating at 164MW.  Interestingly, the signal became perfectly normal when the power was turned down to 151MW.  This chart illustrates how important it is to monitor combustion dynamics to increase the life of hot gas path components in the engine.  In this case, by cutting back power by 13 MW, the operator was able to avoid an expensive repair and possible catastrophic damage to the engine.
 
 
Field Test of Normal Combustion Dynamics at 151MW (Top Left and Right) and 
Abnormal Combustion Dynamics at164MW at 120, 240, 360, 480, 600, and 720 Hz
(Bottom Left and Right)
 
Prior to 2012, the only option for combustion dynamics monitoring systems was the use of conventional transducers that could not tolerate the heat.  Systems using the conventional technology suffered poor reliability and required complex system that involved the use of "infinite length" acoustic waveguides and all of the problems associated with condensation and nitrogen purging systems.

Davidson's system are more reliable and eliminate the need for conventional transducers, charge amplifiers, infinite tubes and all of the associated purging systems.  Davidson's CDMS systems integrates spectrum analyzers and dynamic monitoring systems with reliable, temperature-tolerant state-of-the-art  fiber optic transducers.  Davidson's fiber optic transducers can tolerate temperatures up to 1200°F continuously and are designed to be placed very near the combustion zone in the turbine without the need for any modifications to the engine.

Davidson's dynamic monitoring system continuously monitors both the health of the turbine and also the health of the transducers.  If the quality of the signal coming from any transducers degrades for any reason, the system will show a flat line response in the display for the channel with a degraded transducer.  This self-diagnostic feature provides the user with confidence that the data being reported is accurate.

Davidson's CDMS provides a more direct measurement of the combustion dynamics and generates a signal that has higher quality, fidelity, and reliability while providing the user with lower installation and maintenance cost.  Davidson's CDMS offer the best value for combustion dynamics monitoring. Davidson provides its systems as a turnkey solution including installation, commissioning, and training of site personnel. Davidson offers a line of combustion dynamics monitoring systems customized for Siemens 501 and General Electric E and F series gas turbines. These turnkey systems include all of the transducers, cabling, and signal conditioning needed for a fully integrated combustion dynamics monitoring system

 

 

 

Data Sheets for Combustion Dynamics Monitoring System

CDMS System for use in General Electric Frame 7 and 9 gas turbines

CDMS GE Frame 7 Transducer

CDMS GE Frame 9 Transducer

CDMS System for use in Siemens 501 series of gas turbines

CDMS Siemens 501 Transducer

 

 

 

 

DAVIDSON INSTRUMENTS - THE WOODLANDS, TEXAS 281-362-4900