Phase Doppler Particle Analyzer

Phase Doppler particle analyzers are essentially single-particle counters because they measure one particle at a time within a small sampling volume. This volume must be kept small to minimize the probabiUty of having more than one droplet in the volume at any given instant. This probabiUty increases as the concentration of droplets becomes greater, and there is more risk of measurement errors. 

Many laser-based droplet diagnostic techniques have evolved from the fields such as spray combustion and spray drying. Phase-Doppler particle analyzer is now recognized as the most successful and advanced diagnostic instrument for spray characterization. Other proven diagnostic techniques include laser velocimetry and... 

Spray Dynamic Structure. Detailed measurements of spray dynamic parameters are necessary to understand the process of droplet dispersion. Improvements in phase Doppler particle analyzers (PDPA) permit in situ measurements of droplet size, velocity, number density, and liquid flux, as well as detailed turbulence characteristics for very small regions within the spray. 

Typically, the phase Doppler method is good for the measurement of particle sizes ranging from 1 /u.m to 10 mm with a variation by a factor of 40 at one instrument setting. As a rule of thumb, the maximum measurable concentration is 1,000 particles per cubic millimeter (mm3). Commercial instruments using this technique are available, e.g., the phase Doppler particle analyzer (PDPA) (Aerometrics) and the Dantec particle dynamics analyzer (DPDA) (Dantec Electronics). 

The laser phase Doppler particle analyzer (PDPA) simultaneously measures particle velocity, size and flux and may be considered an extension of laser Doppler velocimetry (LDV). It is particularly useful for... 

Instruments using the residence time, such as the aerodynamic particle sizers, or the particle velocity, as used by the phase Doppler particle analyzers, measure the particle size primarily based on the aerodynamic diameter. 

The time-averaged velocity field downstream of the TARS, including axial and tangential mean and turbulent velocity components, was measured using a Phase Doppler Particle Analyzer (PDPA) system. 

Sankar, S. V. and Bachalo, W.D., Response characteristics of the phase-Doppler particle analyzer for sizing spherical particles larger than the wavelength. Applied Optics, Vol. 30, 1487-1496 (1991)... 

In order to analyze the atomization mechanism of the air-shrouded injector, the atomization characteristics of the fabricated atomizer was investigated using a phase Doppler particle analyzer (PDPA). The Sauter mean diameter (SMD) and mean velocity distribution at 5 ms ASI are shown in Fig. 34.8. As the air pressure increases, the air velocity increases and the air dispersion area is enlarged proportionally. The maximum velocity achieved is 55 m/s when the air pressure is 50 kPa. The degree of atomization is greater at the center flow because the air velocity at the center flow is greater. Spray patterns for various air pressures are shown in Fig. 34.9. It can be seen that as the air pressure increases, the atomization process transitions from varicose wave to sinuous wave mode. Atomization at low air pressure and low fuel pressure can be seen to be affected by a twisted or sinuous mode. The spray angle... 

Phase doppler particle analyzer in situ frequency of Doppler-shifted scattered light 1-8000 <10 ... 

Schaub SA, Alexander DR, Barton JP (1994) Theoretical analysis of the effects of particle trajectory and structural resonances on the performance of a phase-Doppler particle analyzer. Appl Opt 33 473... 

Using the Phase Doppler Particle Analyzer for Insitu Sizing of Fine Spherical Particles... 

The phase Doppler Technique is a laser-based interferometric approach for simultaneously measuring particle size and velocity. This laser-based method is similar to the well-known laser Doppler velocimeter (LDV) and can make these measurements non-intrusively and with high accuracy. The Phase Doppler Particle Analyzer (PDPA) has been successful applied to many difilcult two-phase flow environments with spherical particles including gas-turbine and rocket fuel inlection, cavitation and bubble formation, and similar two-phase flows. ... 

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