SBIR-STTR Award

A particle sizing technique that operates in conjunction with laser velocimetry (LV) is proposed. The technique uses a nonintrusive single particle counter based on the ratio of the intensity of the scattered light at two different angles. It is expected that the required size range of 0.3 micrometers to 3 micrometers will be attainable. The technique will also identify particles larger than 3 micrometers which can produce velocity errors. Lower size limits would require ensemble measurements which cannot be readily used with laser velocimetry, since the size of each particle is necessary. The intensity ratio technique EQAS been successfully used with a single laser beam to measure soot and latex particles in the 0.2 to 3 micrometer range. It is expected that with proper development, it will work with the two laser beams normally used in LV systems, measuring also the irregularly shaped particles normally found in laser velocimetry.

A light scattering technique to measure the size of particles in addition to their velocity in laser doppler velocimetry is proposed. The studies conducted during phase I show the feasibility of the intensity ratioing technique under laboratory controlled experiments. In phase II, a working prototype will be produced and demonstrated at Wright-Patterson's facilities. Both theoretical and experimental studies have shown that the intensity ratioing technique is an excellent approach for measuring the particle size range of 0.5 micrometers to 4 micrometers. The technique measures the light scattered by particles crossing the probe volume, at two different solid angles. The ratio of these two intensities yields the particle size, while the doppler frequency yields the velocity. The phase I studies indicate that to measure the flows expected at Wright-Patterson's facilities, a more powerful laser and faster electronic processor are necessary. These elements will be part of the advanced prototype developed during phase II.