ABSOLUTE LIGHT INTENSITY MEASUREMENTS IN LASER INDUCED INCANDESCENCE

摘要

The invention relates to a method and an apparatus for the determination ofparticlevolume fractions with laser induced incandescence (LII) using absolute lightintensitymeasurements. This requires a knowledge of the particle temperature eitherfrom anumerical model of particulate heating or experimental observation of theparticulatetemperature. Further, by using a known particle temperature a particle volumefraction iscalculated. This avoids the need for a calibration in a source of particulateswith a knownparticle volume fraction or particle concentration. The sensitivity of thedetection systemis determined by calibrating an extended source of known radiance and thenthissensitivity is used to interpret measured LII signals. This results in acalibrationindependent method and apparatus for measuring particle volume fraction orparticleconcentrations. A modeling process involves a solution of the differentialequationsdescribing the heat/energy transfer of the particle and surrounding gas,includingparameters to describe vaporization, heat transfer to the medium, particleheating etc.The solution gives temperature and diameter values for the particles overtime. Thesevalues are then converted to radiation values using Planck's equation.