In-situ measurements of CO, CO2, and H2O combustion emissions with diode laser sensors

Abstract

CO, CO2, and H2O emissions from a lab. flame are measured in-situ using diode laser sensors in the hot, post-flame gases and the cooler exhaust ducts. CO is a toxic regulated pollutant and CO2 is an important greenhouse gas; together these two species provide a measure of the total fuel carbon. CO2 and H2O are the major products of hydrocarbon combustion and can be used to det. combustion efficiency. Light from multiple lasers traverses the flame effluent and each species is monitored by absorption of light that is resonant with near-IR vibrational overtone transitions. Absorption spectroscopy yields path-averaged concn. measurements without intrusive probes that can perturb the gas flow or reaction chem. In-situ absorption diagnostics can provide real-time monitoring of the effluent without the inherent time lag for gas transport or risk of species conversion in extractive sampling probes. A CO detection limit <0.1 ppm/m with a 1 s measurement time is well below the 9 ppm TLV allowed for 8 h exposure, and this detection limit is sufficient for remote, on-road measurements to quantify the CO emission from the cleanest autos.