Quantum cascade laser sensor for SO2 and SO3 for application to combustor exhaust streams

Area of Science:

• Spectroscopy
• Environmental Science
• Aerospace Engineering

Background:

• Sulfur dioxide (SO2) and sulfur trioxide (SO3) are critical pollutants in aircraft engine emissions.
• Accurate monitoring of these gases is essential for environmental compliance and engine performance analysis.

Purpose of the Study:

• To develop and demonstrate a high-sensitivity, room-temperature sensor for detecting SO2 and SO3.
• To assess the sensor's performance under conditions simulating aircraft test combustor exhaust.

Main Methods:

• Utilized two quantum-cascade (QC) lasers to probe infrared absorption features of SO2 and SO3 at 7.50 and 7.16 micrometers, respectively.
• Employed a common dual-beam detection system for simultaneous measurement.
• Inferred noise-equivalent absorbance and determined detection limits under specific pressure, temperature, and path length conditions.

Main Results:

• Achieved a noise-equivalent absorbance of approximately 1 x 10(-4) Hz(-1/2).
• Demonstrated detection limits for SO2 and SO3 of 1-2 ppmv m/Hz(1/2) at 300 torr, elevated temperature, and ~1 m path length.
• Confirmed that the sensor's sensitivity allows for measurement of < 1 ppmv of SO2 and SO3 with signal averaging.

Conclusions:

• The developed QC laser sensor is effective for high-sensitivity, room-temperature detection of SO2 and SO3.
• The sensor's performance is suitable for monitoring emissions from aircraft test combustors.
• This technology facilitates precise measurement of low concentrations of sulfur oxides in relevant exhaust conditions.