| 摘要 |
Intensity of optical emission from a combustion flame within a gas turbine combustor is monitored through an optical window in the combustor wall by a primary detector. Because the window is susceptible to becoming coated with deposits during combustor operation, compensation for presence of a coating is achieved by directing illumination from an optical signal source, such as a silicon carbide light-emitting diode, into the window for internal reflection at an optical interface defined by the combustion side surface. A compensation detector, such as a silicon carbide photodiode, detects intensity of the internally reflected illumination as an indicator of the window coating thickness. The compensation detector is located at a non-combustion side of the window, along with a reference detector that responds to intensity of optical signal source illumination reflected from the non-combustion side surface of the window. An AC coupled differential synchronous detector circuit processes the compensation detector and reference detector output signals to compensate the primary detector output signals for the coating.
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