A diode-laser absorption sensor system for combustion emission measurements

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Abstract
A diode-laser sensor system has been developed to measure the concentrations of NO, O, CO, and in combustion gases using absorption spectroscopy and fast-extraction sampling techniques. Measured survey spectra of the NO 3 band (the R branch) and O lines from the band in the spectral region from 5556 to 5572 were recorded and compared with calculated spectra to select optimum transitions for detection of NO. Similarly, measured survey spectra of the O 3 band from 6535 to 6600 were used to identify optimum transitions for detection of O. High-resolution NO absorption measurements ((7.5) and (7.5) lines) were recorded in a fast-flow multipass cell containing probe-sampled combustion gases to determine NO concentrations in a laminar, premixed -air flame, seeded with . For fuel-lean conditions, the measured NO mole fractions corresponded to 68% of the injected . For fuel-rich conditions, the fraction of converted to NO decreased with increasing equivalence ratio. In additional experiments, CO, and absorption measurements (the R(13) line of the 3 band, the R(16) line of the band and the RQ(7, 8) line of the b band, respectively) were used to determine species concentrations above a laminar, premixed -air flame. Good agreement was found between measured CO, and concentrations and calculated chemical equilibrium values.