An Instrument to Measure the Size, Velocity and Concentration of Particles in a Flow
A technique to measure the size, velocity and concentration of particles in a flow is discussed. An instrument to measure particles as small 0.5 μm moving at 1000 m/s was developed based on this technique. Two small beams of one color cross in the middle of two crossing larger beams of different color. The small beams, thus, define the middle of the larger beams, a region in which the intensity is almost constant. The particle size is obtained from the absolute intensity of the light scattered by particles crossing this uniform intensity region. Two velocity components are measured from the two independent fringe patterns.
The concentration is obtained from the probe volume size, and the size and velocity distributions of the particles. Results are presented for sprays of predictable characteristics and for polystyrene particles between 1.1 μm and 3.3 μm. It is shown that the method has an excellent size resolution and its accuracy is better than 10% of the particle size studied.
KeywordsProbe Volume Polystyrene Particle Small Beam Large Beam Monodisperse Droplet
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