Abstract: The method and apparatus of laser-induced incandescence (LII) to analyze characteristics of submicron-sized particles are described. LII is recognized as a good tool for determining the characteristics of small particles in a gas, e.g., volume fraction, particle size, and specific surface area. It uses the fact that the incandescence signal is proportional to the volume of the particles. It also uses the fact that transient cooling is dependent on the specific surface area of the particle, which is related to diameter of the particle. In LII, particles are heated by a pulsed laser light beam to a temperature where incandescence from the particles can be distinguished from ambient light. The temperature of particles and their volume fraction governs the incandescence. The temperature decay rate is proportional to the primary particle size. The invention uses an optical arrangement that ensures a near-uniform laser energy distribution spatial profile.

Abstract: The method and apparatus of laser-induced incandescence (LII) to analyze characteristics of submicron-sized particles are described. LII is recognized as a good tool for determining the characteristics of small particles in a gas, e.g., volume fraction, particle size, and specific surface area. It uses the fact that the incandescence signal is proportional to the volume of the particles. It also uses the fact that transient cooling is dependent on the specific surface area of the particle, which is related to diameter of the particle. In LII, particles are heated by a pulsed laser light beam to a temperature where incandescence from the particles can be distinguished from ambient light. The temperature of particles and their volume fraction governs the incandescence. The temperature decay rate is proportional to the primary particle size. The invention uses an optical arrangement that ensures a near-uniform laser energy distribution spatial profile.

Abstract: The laser-induced incandescence (LII) to analyze characteristics of submicron sized particles is described. LII is recognized as a good tool for determining the characteristics of small particles in a gas, e.g., volume fraction, particle size, and specific surface area. It uses the fact that transient cooling is dependent on the specific surface area of the particle, which is related to diameter of the particle. In LII, particles are heated by a pulsed laser light beam to a temperature where incandescence from the particles can be distinguished from ambient light. The surface temperature of particles and their volume fraction governs the incandescence. The temperature decay is proportional to the primary particle size. The invention uses an optical arrangement that ensures a near-uniform laser energy distribution spatial profile. The invention also uses a low fluence laser beam pulse to avoid evaporation of particles.

Abstract: The invention relates to a method and an apparatus for the determination of particle volume fractions with laser induced incandescence (LII) using absolute light intensity measurements. This requires a knowledge of the particle temperature either from a numerical model of particulate heating or experimental observation of the particulate temperature. Further, by using a known particle temperature a particle volume fraction is calculated. This avoids the need for a calibration in a source of particulates with a known particle volume fraction or particle concentration. The sensitivity of the detection system is determined by calibrating an extended source of known radiance and then this sensitivity is used to interpret measured LII signals. This results in a calibration independent method and apparatus for measuring particle volume fraction or particle concentrations.