Particle Size Distribution Measurements Research Articles

Estimating optimum launch velocity of electrostatically detached dust particles over sunlit locations on Moon

ABSTRACT Microscopic fluctuations over sunlit locations on Moon due to dominant photoelectric charging might induce a sufficient fluctuating electric field that can electrostatically detach the overlying charged dust by overcoming surface adhesion and lunar gravity. A formulation based on the dynamical evolution of the statistical variables, viz., the mean charge and the variance, at microscopic scale is established to calculate the local charge and electric field fluctuations and illustrate this effect. The formulation has been coupled with the charged particle dynamics to derive the optimum launch velocity of the dust particles near the surface just after detachment. Fowler's treatment of the photoemission, dominant Extreme Ultraviolet Lyman α radiation of the solar spectrum and subsequent collection of the emitted photoelectrons, measured particle size distribution of the regolith sample, and typical solar wind plasma have been consistently accounted for illustrating the concept. Our analysis suggests that the intense fluctuations in the electric field locally detach the submicron-charged particles with a launch velocity of a few ms−1–for instance, the charge fluctuations might induce ∼ 10 Mv m−1 field that can launch 100 nm particles with a speed of ∼5 m s−1.

Extending traceability in airborne particle size distribution measurements beyond 10 µm: Counting efficiency and unit-to-unit variability of four aerodynamic particle size spectrometers

The aim of this study was to establish traceable number concentration measurements of airborne particles beyond 10 μm in particle size. To this end, the primary standards for particle number concentration at the National Metrology Institutes of Switzerland and Japan were further developed to extend their measurement capabilities. Details on the upgraded setup are provided. An inter-comparison of the two primary standards using an optical particle counter as transfer standard showed that these agree well within the stated uncertainties at polystyrene (PS) equivalent optical diameter of 15 µm. Subsequently, four Model 3321 (TSI Inc., USA) aerodynamic particle size spectrometers (APS) were calibrated against the primary standard of Switzerland using size-certified PS spheres with optical/aerodynamic diameter up to 20 µm as test aerosols. The counting efficiency profile and unit-to-unit variability of the APS units were determined. The results presented here can be useful for the analysis and interpretation of data collected by the different atmospheric aerosol networks worldwide. The outlined methodology can also be applied in the calibration of automated bio-aerosol monitors.

AIE fluorescent probe based on tetraphenylethylene and morpholine-thiourea structures for detection of HClO

As an important signal molecule in the living body, hypochlorous acid (HClO) participates in various physiological processes. However, excessive hypochlorous acid will cause some oxidative damage. The organic aggregation-induced emission luminogens (AIEgens) based on tetraphenylethylene (TPE) structures have recently become research hotspots as fluorescent probe materials. In this paper, a kind of water-soluble fluorescent probe TPE-M based on TPE and morpholine-thiourea structures were designed and synthesized for the detection of HClO. Due to the introduction of morpholine structures, the TPE-M showed excellent water solubility. The fluorescence properties of the TPE-M were strongly affected by the polarity of the solvent. Besides, the cation-anion and reactive oxygen species recognition experiments indicated that the fluorescent probe TPE-M displayed a single recognition characteristic for HClO because of the existence of thiourea structures. The limit of detection for HClO was calculated to be 0.25 μM. The particle size distribution measurement under the water phase revealed that the particle size of the TPE-M was mainly centered at 150 nm. The recognition mechanism of HClO by the probe TPE-M was proposed and explained by mass spectra and Gaussian calculation. Furthermore, a cell imaging experiment proved that the TPE-M probe successfully detected HClO in Hela cells.

Technical features of vaping drug delivery system for bronchodilator delivery

PurposeSeveral technical features influencing bronchodilator delivery were evaluated using different vaping drug delivery systems (VDDS). MethodsTerbutaline in powder form, combined with 1, 3- propanediol used as e-liquid was tested at different concentrations (1 and 2.5 mg/mL), power levels (15 W and 30 W), and set applied resistances (0.15 to 1.5 O) to compare the efficiency of three VDDS (GS AIR2, GS TANK, CUBIS). Samples were collected with a Glass Twin Impinger (GTI). A High Performance Liquid Chromatography (HPLC) was used for drug quantification. The Next Generation Impactor (NGI) measured particle size distribution. Results were also considered with a clinical jet nebulizer (Cirrus TM 2, 2 mL of terbutaline at 2.5 mg/mL). ResultsGS AIR2 with resistance = 1.5 O; power = 15 W, and [Terbutaline] = 2.5 mg/mL represents the optimal VDDS conditions to deliver a respirable dose of 20.05 ± 4.2 µg/puff with a mass median aerodynamic diameter (MMAD) of 1.41 ± 0.03 µm. Thus, 52 puffs were required (lasting approximately 15 min of vaping) to reach similar respirable dose and MMAD compared to nebulization. ConclusionWe proved that several crucial VDDS technical parameters govern the performance of respiratory bronchodilator delivery including the resistance, power level and atomizer design.

Optical sensor for combustion aerosol particle size distribution measurement based on embedded chip with low-complexity Mie scattering algorithm

Particle size distribution (PSD) is an indispensable index in combustion analysis. Combustion aerosol PSD measurement based on Mie scattering theory are recognized as the most efficient non-invasive on-line sensing method. However, the high computational complexity of the scattering algorithm has limited the development of sensors with embedded chips. Hence, this study proposes a low-complexity Mie scattering algorithm (LCMSA) that relates the scattered light intensity and particle size as linear functions of the volume and surface-area response of the particles. The use of the LCMSA, which is a quantitative refinement of Gebhart's law, reduced the computation time of the classical Mie scattering algorithm by approximately 28 times, and was robust under various testing scenarios. The median diameter and standard deviation obtained from combustion experiments demonstrated the efficiency of the LCMSA-based sensor in measuring the PSD. Thus, the LCMSA can facilitate PSD measurements using sensors with embedded chips in distributed systems.

Optical aerosol sizing method without prior refractive index

Existing light-based aerosol size analyzers suffer from measurement errors or even fail to measure particle size distribution (PSD) when the refractive index is unknown. To overcome this limitation, we introduced a new aerosol sizing method without the prior refractive index using the light scattering intensity field (LSIF) and deep learning. The LSIF is the intensity distribution of the light scattered in all directions around aerosol particles, which can be used to simultaneously characterize the PSD and the refractive index. A PSD retrieval approach based on deep learning was developed to efficiently retrieve (about 100 ms) the unconstrained PSD (141 independent channels). Our proof-of-concept prototype was tested on various aerosol samples with different particle sizes and refractive indices, where the relative standard deviation (RSD) of the particle size was 1.94% in the test of monodisperse aerosols and the Kullback-Leibler divergence of PSD was 0.13 in the test of polydisperse aerosols.

Suspended Particulate Matter Investigations by the Optical Method in the Franz-Victoria Trough, the Barents Sea

The article describes results of the suspended particulate matter during 80th cruise of the RV Akademik Mstislav Keldysh in the Franz-Victoria Through, northern Barents Sea. Two perpendicular transections were carried out by means of small-angle laser diffractometer LISST-Deep operating in the red range with a wavelength of 670 nm. Observed data consist 7 thousand volume concentration and particle size distributions (PSD) measurements. Weather conditions during expedition allowed to extend the transection to southern part of Nansen basin. The volume concentration of suspended matter varied up to 7.58 μl/l in the euphotic zone and layer and from 0.2 to 0.5 μl/l in the nepheloid layer. Paper demonstrates construction possibilities of the particle size distributions profiles by depth. Transection comparison with measurement results by the conductometric method on a Coulter Counter of the bathometric samples were carried out.

(Digital Presentation) Investigation on Effects of I/C Ratio on Dispersion Structure of PEFC Catalyst Ink By Scanning Electron Assisted Dielectric Microscopy

To achieve high power density operation of polymer electrolyte fuel cells (PEFCs), it is required to realize higher performance catalyst layer with low oxygen transport resistance, high proton conductivity, and low Platinum loading. Because dispersion structure of catalyst ink strongly affects the catalyst layer structure, it is crucial to understand the dispersion mechanism of PEFC catalyst ink. We have reported that that solvent composition (ethanol concentration) of the catalyst ink strongly affect dispersion of the catalyst ink [1, 2], but effects of other components on the dispersion of the catalyst ink were not fully understood yet. In this study, effect of I/C ratio (amount of ionomer) on the dispersion of the catalyst ink was investigated.The catalyst inks were fabricated by mixing platinum-supported carbon (TEC10V30E, Tanaka Kikinzoku), ionomer (DE1021, Sigma-Aldrich), and water/ethanol solvent. To investigate the effect of ionomer on dispersion of the catalyst ink, solvent compositon (ethanol/water = 20/80 wt%), amount of the platinum-supported carbon and solid content of the catalyst ink were kept constant., and the I/C ratio was changed from 0.25 to 1.25. Viscosity characteristics were measured at each shear rate in the range of 0.01 to 1000 1/s by a rotary rheometer (MCR302, Anton-Paar), and particle size distribution of the catalyst ink was measured by the laser diffraction type particle size distribution meter (LA-960V2, HORIBA) without any dilution. In addition, we have succeeded to directly observe the dispersion structure of the catalyst ink by using a scanning electron assisted dielectric microscopy (SE-ADM) for the first time. SE-ADM enabled observation of the catalyst ink with very little radiation damage and high-contrast imaging without staining or fixation at an 8-nm spatial resolution, and distribution of the platinum-supported carbon, ionomer, and solvent were clearly observed.Figure (a) showed the effects of I/C ratio on aggregation size. The result clearly showed that the catalyst inks with too less (I/C=0.25) or too much (I/C=1.25) amount of ionomer were aggregated. Figure (b) showed the results of SE-ADM imaging. Because the dielectric constant of materials within the catalyst ink were different, the image clearly visualized distribution of the platinum-supported carbon, ionomer, and solvent, and the visualization results of the catalyst ink with different I/C ratio were consistent with the results of the particle size distribution measurement. Though the ionomer works as a surfactant within the catalyst ink, too much ionomer makes the dispersion of the catalyst ink worth, and tuning the amount of ionomer is important to realize the high performance catalyst layer.AcknowledgementThis presentation is based on results obtained from a project commissioned by the New Energy and Industrial Technology Development Organization (NEDO).[1] Kaname Iida et al. 2020 ECS Trans. 98, 497.[2] Takashi Sasabe et al. 2021 ECS Trans. 104, 191. Figure 1

Soot particle size distributions in turbulent opposed jet flames with premixed propene–air reactants

Emissions of soot are strongly dependent on turbulence-chemistry interactions due to the relatively slow formation and oxidation processes. Studies of laminar flames have shown that both flow conditions and the chemistry of the parent fuel have a significant impact on measured particle size distributions (PSDs). The current study determines the impact of flow on the development of PSDs in premixed turbulent flames through a variation in the total rate of strain using an opposed jet configuration with fractal grid generated turbulence. The impact of fuel chemistry is investigated under such conditions through the use of propene–air flames with results compared to the corresponding ethene–air flames quantified in earlier studies. Samples were extracted using a quartz probe featuring aerodynamic quenching and dual port dilution at the probe tip and in the transfer-line. Spatially resolved PSD data is obtained along the stagnation point streamline using a scanning mobility particle sizer equipped with nano- and long-DMA columns to show the evolution through the turbulent flame brush. Results confirm that PSDs of soot in premixed turbulent flames are exceptionally sensitive to both the chemistry of the parent fuel and the flow field. The reduced residence times in the current turbulent flows lead to maximum median and mean mobility diameters below 10 nm with higher rates of strain promoting unimodal PSD shapes. It is further shown that the chemistry of the parent fuel has a strong influence on PSDs with propene causing a two order of magnitude increase in smaller particles compared to the corresponding ethene flame.

Particle size distribution analysis of mudstone based on digital image processing

Mudstone is becoming increasingly important for unconventional oil and gas development. The morphological characteristics of clastic are not only contributions to the 3D framework of mudstone, but they can clearly affect the physical properties of a mudstone reservoir, including surface area, pore-size distribution, and porosity. However, it is very difficult and time-consuming to measure the particle size distribution (PSD) of mudstone because of its small particle size and strong cementation. However, because of the importance of oil and gas extraction, it is urgent to develop a fast, accurate, and objective analysis method to measure the PSD of mudstone. Based on a comparison of various PSD measurement methods commonly used in the energy industry and geology, the best PSD measurement method for mudstone should be digital image processing. Two imaging methods, trainable Weka segmentation (TWS) and black mudstone particle size measurement, were used to analyze sections of the early Silurian Longmaxi mudstone of China’s Sichuan Basin. The PSD data obtained by manual measurement, TWS, and the contribution method are compared. Image analysis finds that the particle sizes of all samples fall in the range of coarse silt to clay, and the average sizes fall in the range of coarse silt to fine silt. The skewness, kurtosis, standard deviation, and other distribution characteristics parameters find minor errors, and the relative error is less than 15%. The Pearson correlation coefficient of the 10th quantile of TWS, black mudstone particle size measure, and manual measurement were calculated, which found R2 values typically ranging between 0.64 and 0.87. Kolmogorov-Smirnov test results find that the data obtained by the three measurement methods are from the same distribution at the level of 0.05. Analytic results find that the method presented is effective, cost-efficient, and could avoid artificial errors.

Analysis of Particulate and Microbiological Filtration Performance of Air Handling Unit Filters in a Low-Energy Office Building over 12 Months

Indoor air quality is an important consideration for the health and well-being of building occupants, and the SARS CoV-2 pandemic highlighted the importance of maintaining proper ventilation in buildings. Air handling units (AHUs) are used to provide fresh air and maintain occupant comfort. The objective of this work was to study the evolution of filtration efficiency in an AHU fitted with bag filters, installed to treat office air in a low-energy building, over a 12-month period. The particulate filtration efficiency (PFE) and the microbial filtration efficiency (MFE) were quantified by measuring particle size distribution and bacterial and fungal concentration in the air circulating in the AHU. The resulting microbial concentration measurements in the fresh air (between 10²–103 CFU/m3 for fungi and around 103 CFU/m3 for bacteria) were higher than those in the extracted air from the offices (between 101 and 102 CFU/m3 for fungi and around 102 CFU/m3 for bacteria). The PFE and MFE measured were almost constant throughout the 12 months, with an increase of the filter pressure drop from 70 to 90 Pa. The PFE and MFE were quite comparable for a particle diameter. Therefore, the measurement of PFE is a reliable indicator of the MFE.

Prediction of Gas Emissions in the Working Face Based on the Desorption Effects of Granular Coal: A Case Study

The aim of the study in this paper is to establish a prediction model of gas emission in the working face. The gas desorption variation characteristics of coal with different particle sizes were assessed using physical tests and based on the coal body of No. 2 coal seam in Wangjialing Coal Mine, Shanxi, China, to reveal the influence law of coal particle size on coal gas desorption. The gas desorption characteristics in the working face, the law of gas emission of coal cutting, coal caving, coal wall, and remnant coal in the goaf of the production process were then analyzed after establishing a gas emission prediction model based on the particle size of the coal. The accuracy of the gas emission prediction model was finally validated through actual measurement of the coal particle size distribution and gas emission in the test working face. The results of the current study show that the coal particle size is negatively correlated with the gas desorption capacity within a certain range. The initial desorption intensity of the coal gas decreased with an increase in the coal particle size. However, the initial gas desorption intensity and attenuation coefficient of gas emission were constant after a certain level of increase in the coal particle size. It was found that the average error between the gas emission prediction model and the actual gas emission data in the mining process was 5.29% based on the desorption characteristics of granular coal. Therefore, the established gas emission prediction model can characterize the law of gas emission in the actual production process more effectively. Furthermore, it provides reliable support for the prediction and control of gas emissions from the goaf under the condition of fully mechanized mining with top coal caving.

A miniaturized aerosol sizing sensor using light-scattering angular spectrum

In the study of aerosols, great concern has been focused on the particle size distribution (PSD) as a crucial factor of the physical and chemical properties of the aerosols. There are strong and growing demands for on-line and in-situ aerosol analysis technologies, but existing portable aerosol sensors can hardly provide high-resolution and accurate PSD measurement with limited volume and cost. To address this challenge, we introduce the concept of a new optical aerosol sensing method using light-scattering angular spectrum (LSAS), which describes the angular dependence of the scattering light intensity. The key novelty is a compacted LSAS sampling module for collecting the scattering light up to the observing angles. According to the wide-range LSAS sampled by our sensor, high-resolution PSD is predicted by non-negative regularization inversion algorithm. To validate the performance of our sensor, monodisperse di-ethyl-hexyl-sebacate aerosols (DEHS) samples of different sizes and smokes of smoldering cotton rope were tested. The maximum relative error (RE) of LSAS was smaller than 12.02%, while the Kullback-Leibler Divergence (DKL) between inversed and reference PSDs were smaller than 0.05. Without using any particulate pre-separation module and optical lens, we build a novel low-cost and miniaturized sensor only composed of a mirror, a linear charge coupled device (CCD) and a semiconductor laser, which has significant potential for high-resolution aerosol sizing in routine field measurements outside a laboratory.

Towards a Multi-Instrumental Approach to Closing Aerosol Optical Extinction Profiles

A novel methodology is formulated and investigated on test cases for the reconstruction of complete vertical aerosol extinction profiles in which a synergy of remote, in-situ, and airborne measurements is utilized. The GRASP Open aerosol retrieval algorithm is supplied with remote LIDAR and sunphotometer data to obtain aerosol extinction profiles within the LIDAR’s operation range for coarse and fine aerosol modes separately. These are supplemented with ground-based in-situ measurements of particle size distribution that are translated to coarse and fine aerosol extinction coefficients with the use of Mie theory. UAV-based observations with optical particle counters are included to add information on vertical aerosol variability in the near-surface region. The profiles are closed with an analytical interpolation that is fine-tuned to produce continuous and smooth extinction profiles throughout the whole troposphere that are in agreement with columnar aerosol optical depth measurements. We present the possibility of reconstructing a complete and calibrated aerosol extinction profile, based on the case studies at a Central European background station. We include data-denial experiments to show that the inclusion of UAV-based measurements improves such reconstructions by providing crucial information on aerosol profiles near the ground. The proposed methodology can prove to be a potent tool for studies of aerosol concentration and evolution, especially when the majority of the pollution resides near the surface. Such conditions are prevalent in many highly industrialized regions, including central and southern Poland.

Measurement of sediment particle size distribution and shape using dynamic imaging analysis

Hydropower plants operating in fragile mountainous regions face severe sediment erosion of hydraulic turbines, resulting in decreased efficiency, frequent power interruptions, and downtime for maintenance. The sediment size and shape are detrimental to the hydraulic turbines and influence sediment erosion. Sediment management is a crucial aspect of tackling sediment erosion in hydraulic turbines. The traditional method of measuring particle size and shape is time-consuming, labour-intensive, and usually requires statistical analysis. The present study applies the recent technique of dynamic imaging analysis to determine the particle size distribution and shape of sediment. Five different silt-sand mixtures have been used to check the ability of dynamic imaging analysis. Further, the repeatability and reliability of the results were checked by carrying out five repeated measurements of each sample under the same condition in a short period of time. This study will help the researchers and sedimentologists to adopt the dynamic imaging analysis technique for measuring particle size and shape and help the instrument developer in designing a better future version of the instrument.

A hybrid GBPSO algorithm for permeability estimation using particle size distribution and porosity

Particle size distribution measurements can be used for permeability estimation, and it is widely accepted that there exhibits a certain degree of correlation between permeability and porosity. In this paper, an efficient, low-cost, and reliable approach is used to develop an empirical correlation for estimating permeability based on particle size distribution characteristics and porosity in two modes: mode #1 includes 5% (D5), 10% (D10) and 60% (D60) of the cumulative passing particle size distribution curve and porosity for situations where porosity is known, and mode #2 where porosity is unknown. To optimize the coefficient of the proposed relationships, genetic-binary particle swarm optimization algorithm is used. A database consisting of 50 samples collected from four wells drilled in two neighboring pads in Western Canada were used, and their permeability values were predicted successfully. A validation based on a reference study and an application of sand completion design based on the finding of this study are also discussed. The novelties of the proposed approach are examining the effect of fines content, investigating the full range of particle size distribution curve, and using a hybrid intelligent method to optimize the coefficients of the correlations. In addition to sand completion deigns purposes, the proposed method can be used in enhanced oil recovery studies, reservoir management, and reservoir simulation applications.

Synthetic Data for Machine Learning and Novel Edge Detection to Measure Particle Size Distributions in TEM

Synthetic Data for Machine Learning and Novel Edge Detection to Measure Particle Size Distributions in TEM

Particle number size distributions and formation and growth rates of different new particle formation types of a megacity in China

To understand the contribution of new particle formation (NPF) events to ambient fine particle pollution, measurements of particle size distributions, trace gases and meteorological conditions, were conducted at a suburban site (NJU) from October to December 2016 and at an industrial site (NUIST) from September to November 2015 in Nanjing. According to the temporal evolution of the particle size distributions, three types NPF events were observed: typical NPF (Type A), moderate NPF events (Type B) and strong NPF (Type C) events. The favorable conditions for Type A events included low relative humidity, low concentration of pre-existing particles, and high solar radiation. The favorable conditions of Type B events were similar to Type A, except for a higher concentration of pre-existing particles. Type C events were more likely to happen with the higher relative humidity, lower solar radiation and continuous growth of pre-existing particle concentration. The formation rate of 3 nm (J3) was the lowest for Type A events and highest for Type C events. In contrast, the growth rates of 10 nm and 40 nm particles were the highest for Type A, and lowest for Type C. Results show that NPF events with only higher J3 would lead to the accumulation of nucleation mode particles. Sulfuric acid was important for the formation of particles but had little effect on the growth of particle size.

Particle size distribution and particulate matter concentrations during synoptic and convective dust events in West Texas

Abstract. Dust events are an important and complex constituent of the atmospheric system that can impact Earth's climate, the environment, and human health. The frequency of dust events in the Southern High Plains of West Texas has increased over the past 2 decades, yet their impact on air quality in this region is still unclear. This is due to the fact that there is only one air quality monitoring station that measures only PM2.5 concentrations (particulate matter with an aerodynamic diameter < 2.5 µm), and there is no information on other PM sizes or the particle size distribution. The Aerosol Research Observation Station (AEROS) unit provides insight into the local variation in particle concentration during different dust events and allows for a better understanding of the impact of dust events on air quality. As this area is prone to dust events, we were wondering if dust events generated by different meteorological causes (synoptic vs. convective) would present similar particle concentrations or particle size distributions. Thus, in this project, three different dust events were measured by AEROS and compared. Each dust event originated from a different direction and lasted a different duration. One of the dust events was synoptic (10 April 2019) and two were convective (5 and 21 June 2019). Measurements of particle mass and number concentration, size distribution, and meteorological conditions for each dust event were compared. The synoptic dust event (on 10 April) was longer (12 h) and had stronger wind speed conditions (up to 22.1 m s−1), whereas the two respective convective dust events on 5 and 21 June lasted only 20 and 30 min and had lower wind speeds (up to 16.5 and 13.4 m s−1). Observation of PM based on daily and hourly values showed an impact on air quality, yet measurements based on daily and hourly values underestimate the impact of the convective dust events. Observations based on a shorter timescale (10 min) reveal the true impact of the two convective dust events. A comparison of the particle size distribution showed that all three dust events presented an increase in particles in the 0.3–10 µm size range. Comparisons of the particle concentration for particles > 5 and > 10 µm show very high values during the dust events. Some particle sizes even increase in concentration by ∼ 2 orders of magnitude compared with the time before the dust event. This leads us to speculate that the impact of convective dust events on air quality in this region is underestimated with the current (hourly basis) method.

Application Of The Phase Doppler Measurement Technique For The Characterization Of Supersonic Gas Atomization

A dual-mode phase Doppler measurement system has been set up for the characterization of the complex spray produced through supersonic gas atomization. The atomizer design has been based on a generic close-coupled configuration operated with water and air, which leads to high local Mach numbers and complex patterns of compression and expansion waves within the gas flow field. As a result, the dense spray is characterized by high particle velocities and a wide range of particle sizes, which proves challenging for experimental investigations. Measurements of local particle size and velocity distributions have been performed in various radial positions within the spray downstream of the atomizer, where the spray is fully developed. The set point of operation, which is defined by the gas stagnation pressure and the liquid mass flow rate, has been varied systematically, covering a wide range. By decoupling both operational parameters, their influence on the atomization result has been investigated independently. Furthermore, the atomizer geometry has been varied in terms of liquid nozzle diameter and liquid nozzle protrusion length. In accordance with data from the literature, the gas stagnation pressure has been observed to lead to decreasing median particle size and dispersion of the particle size, when increased. However, as a novel finding, the atomization result has been shown to be more sensitive to changes in the liquid mass flow rate. Thus, increasing the liquid mass flow rate results in an increase in both the median particle size and the dispersion of the particle size. The relationship between the atomization result and the gas-to-liquid ratio has been clearly shown to be ambiguous, that is, a function of the gas stagnation pressure and the liquid mass flow rate. Neither the liquid nozzle diameter nor the liquid nozzle protrusion length have been found to have an influence on the median particle size. However, the latter clearly influences the dispersion of the particle size in a complicated way, while the effect of the liquid nozzle diameter is more subtle. It has been concluded that the complex coupling between operational parameters and the specific atomizer design evident in supersonic gas atomization requires a deeper understanding of the local gas flow field and its interaction with the liquid flow.