CDMS Test Results

CDMS Test Results

Over 2,000,000 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 faithfully reproduces the sound pressure without any falloff at either low or high frequencies.  In fact, the Davidson transducer faithfully reproduced every acoustic anomaly seen by the reference microphone.

The fidelity of Davidson's transducers is 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 drop off, distortion, or blind spots in the spectrum.

Comparison of Davidson Transducer with Laboratory Calibration Microphone in Laboratory Test

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.

In the following figure, the top two charts show normal combustion signals in a Siemens 501F engine. It is obvious in the lower two charts that there is something different. In fact, the lower two charts show what a serious abnormal combustion signal looks like. Interestingly, the normal combustion dynamics signal appeared whenever the engine was generating 150MW or less and the abnormal signal appeared whenever the engine was generating 160MW or more.

If the engine had been allowed to continue running at 160MW, it would have resulted in severe damage to the turbine blades. In this case, by cutting back power by 10 MW, the alert operator avoided severe damage to the engine.

Laboratory Test Setup Generating Pure Tones from 10 to 1000 Hz

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.

The next chart shows 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 Signal 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 Precursor to a Lean Blow Out

In the following figure, the top two charts show normal combustion signals in a Siemens 501F engine. It is obvious in the lower two charts that there is something different. In fact, the lower two charts show what a serious abnormal combustion signal looks like. Interestingly, the normal combustion dynamics signal appeared whenever the engine was generating 150MW or less and the abnormal signal appeared whenever the engine was generating 160MW or more.

If the engine had been allowed to continue running at 160MW, it would have resulted in severe damage to the turbine blades. In this case, by cutting back power by 10 MW, the alert operator avoided severe damage to the engine.

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 is 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 measurement system.

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)

Data Sheets for Combustion Dynamics Monitoring System