Phase-Doppler measurements

Qiu, H.-H., Sommerfeld, M. and Durst, F., High resolution data processing for phase-Doppler measurements in a complex two-phase flow. Measurement Science and Technology, Vol. 2, 455-463 (1991)... 

Qiu, H.-H. and Sommerfeld, M., The impact of signal processing on the accuracy of phase-Doppler measurements. Proc. 6th Workshop on Two-Phase Flow Predictions, Erlangen 1992, (Ed. Sommerfeld, M ), Bilateral Seminars of the International Bureau Forschungszentrum Julich, 421-430 (1993)... 

Albrecht, H. E., Borys, M., Damaschke, N., and Tropea, C. Laser Doppler and Phase Doppler Measurement Techniques. Berlin Springer, 2003. 

The breakup parameter, Kbu, in the bag breakup and the stripping breakup regime is proportional to the characteristic breakup frequencies suggested by [5]. The characteristic breakup frequency for the catastrophic breakup regime is derived from the study of the RT instability by Bellman and Pennington [21] as reported by Patterson and Reitz [11]. The constant k = 0.05 has been determined such that the drop radii match the phase Doppler measurements of Schneider [22], whereas the values for the constants ki and k are chosen such that Kbu is continuous at the regime-dividing Weber numbers, Web,s and Wcg c-... 

Albrecht H, Borys M, Damaschke N, Tropea C (2003) Laser-Doppler and phase-Doppler measurement techniques. Springer, Heidelberg... 

Figure 8.5. Naqwi has used Phase Doppler measurement to acquire the size distributions of various powders, a) The Phase Doppler system used by Naqwi. b) Comparison of the volume size distribution of an alumina powder obtained from a Coulter counter, to Phase Doppler measurements made by Naqwi. (Drawing and data provided by A. A. Naqwi and used by permission of TSI Inc.)...

A. A. Naqwi C. W. Fandery, Phase Doppler Measurements of Irregular Particles and Their Inversion to Velocity-Resolved Size Distributions , Powder Handling and Processing, 9 1 (Jan-March 1957) 45 and 51. 

In Table 4 the results of the phase-Doppler measurement applied to 2000 particles and of the photography are summarized. 

It was impossible to get results by phase-Doppler measurements for a droplet 150 fim in diameter with an ink concentration of 12 per cent, because the visibility of the signals was very low as can also be seen by theory (Figure 9). 

Hollow Sprays. Most atomizers that impart swid to the Hquid tend to produce a cone-shaped hoUow spray. Although swid atomizers can produce varying degrees of hoUowness in the spray pattern, they aU seem to exhibit similar spray dynamic features. For example, detailed measurements made with simplex, duplex, dual-orifice, and pure airblast atomizers show similar dynamic stmctures in radial distributions of mean droplet diameter, velocity, and Hquid volume flux. Extensive studies have been made (30,31) on the spray dynamics associated with pressure swid atomizers. Based on these studies, some common features were observed. Test results obtained from a pressure swid atomizer spray could be used to iUustrate typical dynamic stmctures in hoUow sprays. The measurements were made using a phase Doppler spray analyzer. 

The phase Doppler method utilizes the wavelength of light as the basis of measurement. Hence, performance is not vulnerable to fluctuations in light intensity. The technique has been successfully appHed to dense sprays, highly turbulent flows, and combustion systems. It is capable of making simultaneous measurements of droplet size, velocity, number density, and volume flux. 

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. 

The phase-Doppler method is capable of accurately measuring particle size distribution and velocity J655] The most recent models ofphase-Doppler particle analyzer (PDPA) can generate data of droplet size and velocity simultaneously as a function of time, from that droplet drag can be calculated and clustering phenomenon can... 

A two-color pyrometer has been used along with the phase-Doppler anemometer to simultaneously measure the local velocity and size of kerosene droplets and the temperature of burning soot mantle in a swirl burner.[648] The measurements were conducted within the flame brush that develops in the shear layer of a swirl-stabilized, gas-supported kerosene flame with a swirl number of about 0.19 and potential heat releases of 10.6 and 15.5 kW, respectively. The results showed that the maximum burning fraction of the droplets occurs adjacent to the region denoted as gas flame but the value ranges from 20 5 to 40 5% depending on the axial station, and decreases sharply across the shear layer. The flame mantle temperature was found to be independent of droplet diameter, which agrees with previous results in the literature. 

Methods for analysis of the particle size distribution in the aerosol cloud include techniques such as time of flight measurement (TOE), inertial impaction and laser diffraction. Dynamic light scattering (photon correlation spectroscopy) is confined to particles (in suspension) in the submicron range. In addition to the size distribution, the particle velocity distribution can be measured with the Phase Doppler technique. 

A two-component phase Doppler interferometer (PDI) was used to determine droplet size, velocity, and number density in spray flames. The data rates were determined according to the procedure discussed in [5]. Statistical properties of the spray at every measurement point were determined from 10,000 validated samples. In regions of the spray where the droplet number density was too small, a sampling time of several minutes was used to determine the spray statistical characteristics. Results were repeatable to within a 5% margin for mean droplet size and velocity. Measurements were carried out with the PDI from the spray centerline to the edge of the spray, in increments of 1.27 mm at an axial position (z) of 10 mm downstream from the nozzle, and increments of 2.54 mm at z = 15 mm, 20, 25, 30, 35, 40, 50, and 60 mm using steam, normal-temperature air, and preheated air as the atomization gas. 

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. 

When a spherical particle enters the crossing volume of two laser beams, a Doppler effect occurs not only in frequency shift but also in phase shift of the scattered light. The frequency shift yields the velocity of the sphere, whereas the phase shift gives the particle size. The phase Doppler principle has been employed to measure the size and size distributions of spheres in addition to the particle velocity. The phase Doppler principle was first reported by Durst and Zare (1975) and became a viable measurement tool one decade later [Bachalo and Houser, 1984]. 

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). 

Durst, F. and Zar6, M. (1975). Laser Doppler Measurements in Two-Phase Flows. Proceedings of LDA Symposium, Copenhagen. 

Tadrist, L., and Cattieuw, P. Analysis ofTwo-Phase Flow in a Circulating Fluidized Bed—Local Measurements by Using Phase Doppler Analyzer, in Circulating Fluidized Bed Technology IV (Amos A. Avidan, ed.), pp. 702-707. Somerset, Pennsylvania (1993). 

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