Sizing fine particles with the phase Doppler interferometric technique

Sankar, S. V.; Weber, B. J.; Kamemoto, Derek Y.; Bachalo, W. D.

doi:10.1364/ao.30.004914

Cited by 64 publications

(24 citation statements)

References 2 publications

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“…As discussed above, APS measurements made simultaneously with the PDPA do not exhibit any evidence of nonlinearities (see Figure 7). Thus, the current results strongly indicate that the PDPA response does become rnultivalued for small droplets in the standard configuration, and the observed structure is at least similar to the Mietheory oscillations such as predicted by Sankar et al (1990). Clearly, the use of the PDPA in this configuration to measure size distributions below about 7 p m can lead to ambiguous results.…”

Section: Resultssupporting

confidence: 67%

“…Changing the receiver collection angle to 70" in addition to using the short focal length lens resulted in more scatter in PDPA response than in the other cases, without a clear reduction in the multivalued response in the < 5-pm diameter range. Thus, increasing the scattered light integration at the receiver by using a short focal length receiver lens (compared to the standard lens) resulted in significant improvement in instrument response in the small particle sizing regime as predicted by the theory of Sankar et al (1990). However, reducing the component of reflected light received by placing the receiver at the Brewster angle of the droplets had a very small effect, contrary to theory.…”

Section: Discussionmentioning

confidence: 91%

“…In contrast, Houser and Bachalo (1985) report linear PDPA response for nebulized, monodisperse polystyrene latex spheres (PSL) in the 0.54-2.88-pm range. A later study (Sankar et al, 1990) Sankar et al (1990) showed that reducing the focal length of the receiver dramatically reduces PDPA sizing uncertainty. In addition, their calculations predict that reflections from the surface of the droplet combine with refracted light to generate the oscillations in the phase-diameter relationship in the smaller diameter regime.…”

Section: Introductionmentioning

confidence: 99%

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Calibration of the Phase Doppler Particle Analyzer with Monodisperse Droplets

Ceman

Rader

O’Hern

1993

Aerosol Science and Technology

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The experimental response of the phase Doppler particle analyzer (Aerometrics, Inc., Sunnyvale, CAI to monodisperse oleic acid droplets in the 2.3-24-pm range is presented for three optical configurations. Significant nonlinearities for droplets with diameters < 20 p m were seen when using the standard configuration of a 495-mm focal length receiving lens at an off-forward scattering angle of 0 = 30". Of particular concern are response oscillations < 7 p m that lead to multivalued regions. In order to reduce these nonlinearities, two improvements to the standard receiver configuration were studied as suggested by theoretical studies reported in the literature. First, the receiver focal length was shortened to 240 mm (at 0 = 30") to increase the integration of scattered light. --As expected, the instrument response did significantly improve over the standard case, both in terms of linearity and scatter, for droplets > 5 pm. A significant departure from linearity (undersizing by 1.7 p m for a 2.3-pm indicated droplet diameter) was observed below this size, although the multivalued region of response was greatly reduced. Second, the receiving lens (focal length of 240 mm) was configured at a collection angle of 70°, close to the Brewster angle for oleic acid droplets where interference from reflected light should be minimized. Surprisingly, the performance of this configuration was comparable to the standard case (even though a shorter focal length was used), and inferior to the 240-mm/3O0 configuration.

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Section: Resultssupporting

confidence: 67%

Section: Discussionmentioning

confidence: 91%

Section: Introductionmentioning

confidence: 99%

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Calibration of the Phase Doppler Particle Analyzer with Monodisperse Droplets

Ceman

Rader

O’Hern

1993

Aerosol Science and Technology

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“…Most of the above observations are The vertical coordinate is the shifted altitude z s where the liquid water cloud top is defined as 0 m. The vertical coordinate is the shifted altitude z s where the liquid water cloud top is defined as 0 m. acquired at 40 Hz; this can then be used as-is, or averaged to 10 Hz or 1 Hz for convenience. Cloud drop size distributions are inferred from observations utilizing the Artium Flight Phase-Doppler-Interferometer (F/PDI) (Chuang et al, 2008), which measures the size of individual drops using the phaseDoppler interferometry technique (Bachalo, 1980;Bachalo et al, 1984;Sankar et al, 1991). The F/PDI and PVM-100A measurements can be used to check each other; we find during POST that the two instruments generally agree well once the difference in measured drop size range is accounted for, increasing our confidence in both data sets.…”

Section: Aircraft Observationsmentioning

confidence: 97%

Observational constraints on entrainment and the entrainment interface layer in stratocumulus

et al. 2012

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Abstract. Aircraft sampling of the stratocumulus-topped boundary layer (STBL) during the Physics of Stratocumulus Top (POST) experiment was primarily achieved using sawtooth flight patterns, during which the atmospheric layer 100 m above and below cloud top was sampled at a frequency of once every 2 min. The large data set that resulted from each of the 16 flights document the complex structure and variability of this interfacial region in a variety of conditions. In this study, we first describe some properties of the entrainment interface layer (EIL), where strong gradients in turbulent kinetic energy (TKE), potential temperature and moisture can be found. We find that defining the EIL by the first two properties tends to yield similar results, but that moisture can be a misleading tracer of the EIL. These results are consistent with studies using large-eddy simulations. We next utilize the POST data to shed light on and constrain processes relevant to entrainment, a key process in the evolution of the STBL that to-date is not well-represented even by high resolution models. We define "entrainment efficiency" as the ratio of the TKE consumed by entrainment to that generated within the STBL (primarily by cloud-top cooling). We find values for the entrainment efficiency that vary by 1.5 orders of magnitude, which is even greater than the one order magnitude that previous modeling results have suggested. Our analysis also demonstrates that the entrainment efficiency depends on the strength of the stratification of the EIL, but not on the TKE in the cloud top region. The relationships between entrainment efficiency and other STBL parameters serve as novel observational contraints for simulations of entrainment in such systems.

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“…Techniques such as Phase/Doppler measurements [2], [3] or imaging measurements that rely on separate images of droplets [4] are ineffective near the injector orifice due to multiple scattering in the overall system. Signal attenuation for ensemble light scattering techniques utilizing visible wavelengths makes these techniques of marginal use in the dense spray [5], [6].…”

Section: Motivationmentioning

confidence: 99%

Imaging and Scattering Measurements for Diesel Spray Combustion: Optical Development and Phenomenological Studies

Porter¹,

Parker²,

Duran³

2012

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The public reporting burden for this collection of information is estimated to average 1 hour per response, including the time for reviewing instructions, searching existing data sources, gathering and maintaining the data needed, and completing and reviewing the collection of information. The first successful demonstration of picosecond ballistic imaging using a greater-than-10 picosecond-pulse-duration laser in diesel sprays is reported. This technique uses an optical Kerr effect shutter constructed from a CS2 liquid cell and a 15 picosecond pulse at 532 nm. The optical shutter can be adjusted to produce effective imaging pulses between 7 and 16 picoseconds. This technique is used to image the near-orifice region (first 3mm) of diesel sprays from a high-pressure single-hole fuel injector. Ballistic imaging of dodecane ABSTRACTThe first successful demonstration of picosecond ballistic imaging using a greater-than-10 picosecond-pulse-duration laser in diesel sprays is reported. This technique uses an optical Kerr effect shutter constructed from a CS2 liquid cell and a 15 picosecond pulse at 532 nm. The optical shutter can be adjusted to produce effective imaging pulses between 7 and 16 picoseconds. This technique is used to image the near-orifice region (first 3mm) of diesel sprays from a high-pressure single-hole fuel injector. Ballistic imaging of dodecane and methyl oleate sprays are reported. The first known ballistic images of diesel injection at pre-ignition engine-like conditions are reported. Dodecane was injected into air heated to 600°C and pressurized to 20 atm. The resulting ballistic images of the near-orifice region at these diesel-engine-like conditions reveal dramatic shedding of the liquid near the nozzle, an effect which has been predicted, but to our knowledge never before imaged. Several parameters are explored including injection pressure, liquid fuel temperature, air temperature and pressure, and fuel type. Resulting trends are summarized with accompanying images. Finally, the beginings of a new ballistic scattering technique is presented with preliminary results. Names of Post DoctoratesPERCENT_SUPPORTED NAME FTE Equivalent:Total Number: Names of Faculty SupportedNational Academy Member PERCENT_SUPPORTED NAME Terry Parker 0.05 Jason Porter 0.05 0.10 FTE Equivalent: 2 Total Number: Names of Under Graduate students supportedPERCENT_SUPPORTED NAME FTE Equivalent:Total Number:The number of undergraduates funded by this agreement who graduated during this period with a degree in science, mathematics, engineering, or technology fields:The number of undergraduates funded by your agreement who graduated during this period and will continue to pursue a graduate or Ph.D. degree in science, mathematics, engineering, or technology fields:Number of graduating undergraduates who achieved a 3.5 GPA to 4.0 (4.0 max scale): Number of graduating undergraduates funded by a DoD funded Center of Excellence grant for Education, Research and Engineering:The number of undergraduates funded by your agreement who...

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Sizing fine particles with the phase Doppler interferometric technique

Cited by 64 publications

References 2 publications

Calibration of the Phase Doppler Particle Analyzer with Monodisperse Droplets

Calibration of the Phase Doppler Particle Analyzer with Monodisperse Droplets

Observational constraints on entrainment and the entrainment interface layer in stratocumulus

Imaging and Scattering Measurements for Diesel Spray Combustion: Optical Development and Phenomenological Studies

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