V. Nagali et Rk. Hanson, DESIGN OF A DIODE-LASER SENSOR TO MONITOR WATER-VAPOR IN HIGH-PRESSURE COMBUSTION GASES, Applied optics, 36(36), 1997, pp. 9518-9527
The design of a diode-laser sensor to monitor water vapor in high-pres
sure combustion gases is described. The sensor, which employs a multip
le-fixed-wavelength absorption strategy, has the potential to simultan
eously monitor the water mole fraction and the temperature and pressur
e in high-pressure and high-temperature environments. The conventional
scanned-wavelength strategy, employed in previous diode-laser sensors
, is shown to be ill-suited for high-pressure applications. The applic
ation of impact and additive approximations in the modeling of H2O abs
orption features at high pressures is validated experimentally for num
ber densities as high as 18 amagats. Criteria to select optimum wavele
ngth combinations for the fixed-wavelengths strategy are discussed. Op
timum wavelength combinations that meet these criteria are identified
for different temperature and pressure ranges of interest to combustio
n applications. The proposed sensor configuration and a strategy to ob
tain the baseline (zero absorption intensity) in high-pressure environ
ments are also described. Line-shape models that are appropriate for d
ifferent temperature and pressure regimes are identified. (C) 1997 Opt
ical Society of America.