Anderson, James Paul (2016-05). Development of a Mid-Infrared Carbon Monoxide Sensor for a High-Pressure Combustor Rig. Master's Thesis.
Carbon monoxide (CO) is a toxic byproduct of incomplete combustion in hydrocarbon-fueled systems which poses many environmental and human health hazards. Not only is CO hazardous, it also correlates to combustion efficiency. A mid-infrared (IR) CO detector has been developed to monitor the amount of CO produced by a high-pressure test rig developed by Parametric Solutions, Inc. under contract from Toshiba. The combustor rig was designed to operate using the Allam cycle, which requires methane and an oxygen/carbon dioxide blend, and operates at approximately 30MPa and 1150?C. The mid-IR system operates at the fundamental absorption band, v"=0, R(12), of CO near 4.5 ?m. The mid-IR diagnostic was constructed from a tunable quantum cascade laser produced by Alpes Lasers, an absorption cell with two window ports for monitoring CO exhaust concentration, and two IR photodetectors. Temperature and pressure sensors were mounted near the absorption cell to monitor exhaust flow conditions, and the operational wavelength of the laser was determined by a calibration process using a known mixture of CO and N2. Environmental conditions at the test facility posed significant difficulties in the data acquisition process for the IR diagnostic. Fluctuating environmental temperatures proved to be problematic when operating cryogenic photodetectors and stabilizing a quantum cascade laser designed to operate with an internal temperature of -15?C. Improvements to the IR system included elimination of problematic stagnation regions via a new absorption cell design, and an increase in the CO detection limit. During steady state conditions, the mid-IR diagnostic measured the CO concentration to be about 539.5 ? 80.6 ppm. It was discovered that during some of test runs, the CO absorption trace would be artificially raised due to unknown deposits on the inside of the cell windows. The IR diagnostic was shown to have superior CO detection response time and the ability to resolve features not detected by other CO detector counterparts.