Individual Droplets Research Articles

DropTrack—Automatic droplet tracking with YOLOv5 and DeepSORT for microfluidic applications

Deep neural networks are rapidly emerging as data analysis tools, often outperforming the conventional techniques used in complex microfluidic systems. One fundamental analysis frequently desired in microfluidic experiments is counting and tracking the droplets. Specifically, droplet tracking in dense emulsions is challenging due to inherently small droplets moving in tightly packed configurations. Sometimes, the individual droplets in these dense clusters are hard to resolve, even for a human observer. Here, two deep learning-based cutting-edge algorithms for object detection [you only look once (YOLO)] and object tracking (DeepSORT) are combined into a single image analysis tool, DropTrack, to track droplets in the microfluidic experiments. DropTrack analyzes input microfluidic experimental videos, extracts droplets' trajectories, and infers other observables of interest, such as droplet numbers. Training an object detector network for droplet recognition with manually annotated images is a labor-intensive task and a persistent bottleneck. In this work, this problem is partly resolved by training many object detector networks (YOLOv5) with several hybrid datasets containing real and synthetic images. We present an analysis of a double emulsion experiment as a case study to measure DropTrack's performance. For our test case, the YOLO network trained by combining 40% real images and 60% synthetic images yields the best accuracy in droplet detection and droplet counting in real experimental videos. Also, this strategy reduces labor-intensive image annotation work by 60%. DropTrack's performance is measured in terms of mean average precision of droplet detection, mean squared error in counting the droplets, and image analysis speed for inferring droplets' trajectories. The fastest configuration of DropTrack can detect and track the droplets at approximately 30 frames per second, well within the standards for a real-time image analysis.

Droplet Microfluidic Device for Chemoenzymatic Sensing.

The rapid detection of pollutants in water can be performed with enzymatic probes, the catalytic light-emitting activity of which decreases in the presence of many types of pollutants. Herein, we present a microfluidic system for continuous chemoenzymatic biosensing that generates emulsion droplets containing two enzymes of the bacterial bioluminescent system (luciferase and NAD(P)H:FMN–oxidoreductase) with substrates required for the reaction. The developed chip generates “water-in-oil” emulsion droplets with a volume of 0.1 L and a frequency of up to 12 drops per minute as well as provides the efficient mixing of reagents in droplets and their distancing. The bioluminescent signal from each individual droplet was measured by a photomultiplier tube with a signal-to-noise ratio of up to 3000/1. The intensity of the luminescence depended on the concentration of the copper sulfate with the limit of its detection of 5 M. It was shown that bioluminescent enzymatic reactions could be carried out in droplet reactors in dispersed streams. The parameters and limitations required for the bioluminescent reaction to proceed were also studied. Hereby, chemoenzymatic sensing capabilities powered by a droplet microfluidics manipulation technique may serve as the basis for early-warning online water pollution systems.

Field‐Induced Structural Transitions in Liquid Crystal Microemulsions

AbstractLiquid crystal (LC) droplets have fascinating properties, such as anisotropic properties, in response to external stimuli. As LC droplet size may determine the proper application of soft composites, various results from numerical simulations and experimental observations of LC droplets are reported. Here, detailed topological responses of individual bipolar droplets to electric fields, are shown. The integration of each response influences the entire electro‐optic behavior. Monodispersed LC bipolar droplets are fabricated in a polyvinyl alcohol‐dissolved aqueous solution via a membrane‐emulsification method. The planar anchoring, provided by the polyvinyl alcohol surface, and surface elasticity, guide the entire LC director configuration, associated with topological defects, in the droplets. By simply blade‐coating the solution, bipolar axes of the droplets can be randomly placed on a flat substrate. Two different subsequential stages are found when applying voltages: 1) director reorientation, which is threshold‐less and 2) topological defect movement, which exhibits a threshold‐like behavior. Various initial directions of the bipolar axes with respect to the field direction provide the transition voltage between these two stages. It is believed that this study can provide important clues to handle several fundamental issues in electro‐optics of encapsulated LCs, such as the determination of response times, threshold, and operating voltages.

Gradient Droplet Arrays by Acceleration‐Mode Dip‐Coating

AbstractDroplet microarray technology is of great interest in biology and chemistry as it allows for significant reactant savings and massive parallelization of experiments. Upon scaling down the footprint of each droplet in an array, it becomes increasingly challenging to produce the array drop‐by‐drop. Therefore, techniques for parallelized droplet production are developed, e.g., dip‐coating of biphilic substrates. However, it is in general difficult to tailor the characteristics of individual droplets, such as size and content, without updating the substrate. Here, the method of dip‐coating of uniformly patterned biphilic substrates in so‐called “acceleration‐mode” to produce droplet arrays featuring gradients in droplet height for fixed droplet footprint is developed. The results herein present this method applied to produce drops with base diameters varying over orders of magnitude, from as high as 6 mm to as small as 50 µm; importantly, the experimentally measured power‐law‐dependency of volume on capillary‐number matches analytical theory for droplet formation on heterogenous substrates though the precise quantitative values likely differ due to 2D substrate patterning. Gradient characteristics, including average droplet volume, steepness of the gradient, and its monotonicity, can all be tuned by changing the dip‐coating parameters, thus providing a robust method for high‐throughput screening applications and experiments.

From impact to solidification in drop-on-demand metal additive manufacturing using MetalJet

Drop-on-demand metal jetting is a promising additive manufacturing (AM) technology that is gaining interest due to its capability to directly print complex single and multi-material components at high resolutions. It also has key advantages over other metal AM techniques, such as avoiding powder handling and extensive post-processing. In this method, parts are built via spatially controlled deposition of individual molten droplets onto a substrate. Therefore, the success of the process entirely depends on the behaviour of these single droplets from deposition to solidification including their interactions with the substrate, which is scarcely investigated to date. To fill this research gap, the in-house MetalJet platform was used to investigate the spreading and solidification of metallic micro-droplets at low Weber numbers. This was undertaken onto various substrates using a range of jetting and substrate temperatures through an integrated experimental, analytical, and computational approach. This study reports that increasing the substrate temperature enhanced the diffusion between the droplet and substrate, hence improving the bonding. Moreover, ripples forming on a droplet’s periphery during solidification disappeared at elevated substrate temperatures, resulting in improved inter-droplet bonding. Furthermore, the significant role of the substrate wettability and thermal properties, which control the droplet’s dynamics and solidification behaviour, respectively, is elucidated. This highlights the importance of substrate material selection using this technology. The results presented in this article underpin the optimal process conditions under which the 3D structures produced with this technology can exhibit reliable integrity and consistency. This represents a step forward in the direct metal printing of high resolution functional multi-material components.

Turbulent droplet breakage in a von Kármán flow cell

Droplet dispersion in liquid–liquid systems is a crucial step in many unit operations throughout the chemical, food, and pharmaceutic industries, where improper operation causes billions of dollars of loss annually. A theoretical background for the description of droplet breakup has been established, but many assumptions are still unconfirmed by experimental observations. In this investigation, a von Kármán swirling flow device was used to produce homogeneous, low-intensity turbulence suitable for carrying out droplet breakage experiments using optical image analysis. Individual droplets of known, adjustable, and repeatable sizes were introduced into an isotropic turbulent flow field providing novel control over two of the most important factors impacting droplet breakage: turbulence dissipation rate and parent droplet size. Introducing droplets one at a time, large data sets were gathered using canola, safflower, and sesame oils for the droplet phase and water as the continuous phase. Automated image analysis was used to determine breakage time, breakage probability, and child droplet size distribution for various turbulence intensities. Breakage time and breakage probability were observed to increase with increasing parent droplet size, consistent with the classic and widely used Coulaloglou–Tavlarides breakage model (C–T model). The shape of the child drop size distribution function was found to depend upon the size of the parent droplet.

Recovery and isolation of individual microfluidic picoliter droplets by triggered deposition

Microfluidic emulsion-based droplet systems have a great potential for inexpensive ultrahigh-throughput experimentation. Yet, picking and upscaling single unique picoliter-sized droplets of interest out of million others for deeper analysis is still a fundamental limitation. In order to overcome this missing gap, we present a system in which droplets of interest are collected into a collection chamber (DropLot) in high throughput and then slowly redirected to an agar surface or microtiter plate via a capillary tube passing through an optical sensor before exiting. The signal of each droplet triggers a positioning algorithm that ultimately places the flowing droplet at a defined position on a Petri dish or microtiter plate. Results indicate effective isolation of single droplets giving rise to colonies on agar surface with a recovery rate of over 93%. The possibility to isolate individual droplets provides a critical feature for interfacing droplet microfluidics with standard laboratory analysis and processing.

Fabrication of stainless-steel microfibers with amorphous-nanosized microstructure with enhanced mechanical properties

Metallic glasses (MG) have attracted much attention due to their superior hardness and good corrosion resistance. However, designing new MG compositions is still a big challenge, and their integration into different systems is limited when they are in the shape of bulk materials. Here, we present a new method for the fabrication of MG in the form of microfibers which could greatly help them to be integrated within different systems. The newly proposed technique has the ability to form MG structure from commercially available alloy compositions thanks to its significantly improved quenching rate(~ 108 K.s−1). In this technique, individual melt droplets are ejected on a rotating wheel forming a thin film which are ruptured upon solidification leading to the formation of MG microfibers. In this regard, we have fabricated microfibers from a commercial DIN 1.4401 stainless-steel which could form a completely amorphous structure confirmed by DSC, XRD, and HRTEM. The fabricated MG microfibers show an increased hardness for more than two-fold from 3.5 ± 0.17 GPa for the as-received stainless-steel to 7.77 ± 0.60 GPa for the amorphous microfibers. Subsequent heat-treatment of the microfibers resulted in a nanocrystalline structure with the presence of amorphous regions when the hardness increases even further to 13.5 ± 2.0 GPa. We propose that confinement of both shear transformation zones and dislocations in the heat-treated MG microfibers plays a major role in enhancing strength.

Evolution and Single‐Droplet Analysis of Fuel‐Driven Compartments by Droplet‐Based Microfluidics

Active droplets are a great model for membraneless organelles. However, the analysis of these systems remains challenging and is often limited due to the short timescales of their kinetics. We used droplet‐based microfluidics to encapsulate a fuel‐driven cycle that drives phase separation into coacervate‐based droplets to overcome this challenge. This approach enables the analysis of every coacervate‐based droplet in the reaction container throughout its lifetime. We discovered that the fuel concentration dictates the formation of the coacervate‐based droplets and their properties. We observed that coacervate‐based droplets grow through fusion, decay simultaneously independent of their volume, and shrinkage rate scales with their initial volume. This method helps to further understand the regulation of membraneless organelles, and we believe the analysis of individual coacervate‐based droplets enables future selection‐ or evolution‐based studies.

Investigation of Vortex Structure Modulation by Spume Droplets in the Marine Atmospheric Boundary Layer by Numerical Simulation

Direct numerical simulation (DNS) of a droplet-laden, turbulent Couette airflow over a waved water surface is performed modeling the marine atmospheric boundary (MABL) layer carrying idealized spume droplets. Both the instantaneous and mean flow properties, the characteristics of the vortex structures and the momentum exchange between air turbulence and waved water surface and droplet-mediated momentum transfer are investigated. A Eulerian–Lagrangian approach is employed in DNS where full, 3D Navier–Stokes equations for the carrier air are solved in a Eulerian frame, and the trajectories of individual droplets are simultaneously tracked in a Lagrangian frame. The impact of the droplets on the carrier air flow is modeled via a point force approximation. The droplets size is considered in the range of spume droplet sizes observed in MABL. Various water surface roughness and droplet injection scenarios are considered, and both instantaneous and phase-averaged flow fields, the Reynolds stresses and the eigenvalues of the local air velocity gradient tensor are evaluated in DNS. Numerical results show a strong dependence of the droplet-mediated airflow modification on-the-droplet injection mechanism. Droplets injected with the surrounding air velocity effectively mitigate the vortex structures by reducing their swirling strength and suppress the momentum flux from air turbulence to water surface by weakening both ejections and sweeping events, and thus accelerating the mean flow as compared to the droplet-free flow. On the other hand, droplets injected with the velocities of the Lagrangian particles of the water surface enhance both the swirling strength of the vortex structures and air-flow turbulent stresses and decelerate the mean wind. The results also show that these effects of droplet-mediated flow modification become less pronounced as the water surface wave steepness increases.

Living polymerization in nano-scale volumes. Impact of process conditions on polymerization kinetics and product characteristics

Living polymerization processes, irreversible and reversible, proceeding in a large number of isolated (no mass exchange) nano-scale reactors (droplets) were modeled using stochastic (Monte Carlo) and deterministic simulations and analytical solutions of derived mathematical equations. Monomer and living unimer used as initiator were redistributed in droplets uniformly or accordingly to the Poisson distribution, resulting in nanoreactors containing a small number of growing chains. Stochasticity of reactions involving low number of molecules affects the concentration of monomer and chain length distributions in individual droplets, both differing from ones accounted in macroscopic system. The developed mathematical description, based on values of rate constants of propagation (kp) and depropagation (kd) reactions and on initial monomer and living unimer concentrations, as well as numerical simulations, allow predicting kinetics of the process and of several characteristics of the products resulting therefrom, e.g. chain length distribution. Moreover, they allow also following evolution of droplet subpopulations that differ in composition. Moreover, for the reversible process the equilibrium monomer concentration in a droplets system [M]eq can be calculated. As living ionic and coordination polymerization and the controlled radical polymerization in nano-scale dispersions are rather little explored the theoretical predictions shown in this work could facilitate their further development.

Hydrogels for Single-Cell Microgel Production: Recent Advances and Applications.

Single-cell techniques have become more and more incorporated in cell biological research over the past decades. Various approaches have been proposed to isolate, culture, sort, and analyze individual cells to understand cellular heterogeneity, which is at the foundation of every systematic cellular response in the human body. Microfluidics is undoubtedly the most suitable method of manipulating cells, due to its small scale, high degree of control, and gentle nature toward vulnerable cells. More specifically, the technique of microfluidic droplet production has proven to provide reproducible single-cell encapsulation with high throughput. Various in-droplet applications have been explored, ranging from immunoassays, cytotoxicity assays, and single-cell sequencing. All rely on the theoretically unlimited throughput that can be achieved and the monodispersity of each individual droplet. To make these platforms more suitable for adherent cells or to maintain spatial control after de-emulsification, hydrogels can be included during droplet production to obtain “microgels.” Over the past years, a multitude of research has focused on the possibilities these can provide. Also, as the technique matures, it is becoming clear that it will result in advantages over conventional droplet approaches. In this review, we provide a comprehensive overview on how various types of hydrogels can be incorporated into different droplet-based approaches and provide novel and more robust analytic and screening applications. We will further focus on a wide range of recently published applications for microgels and how these can be applied in cell biological research at the single- to multicell scale.

One-Step Digital Droplet Auto-Catalytic Nucleic Acid Amplification with High-Throughput Fluorescence Imaging and Droplet Tracking Computation.

Digital droplet technology has emerged as a powerful new tool for biomarker analysis. Temperature cycling, enzymes, and off-chip processes are, nevertheless, always required. Herein, we constructed a digital droplet auto-catalytic hairpin assembly (ddaCHA) microfluidic system to achieve digital quantification of single-molecule microRNA (miRNA). The designed continuous chip integrates droplet generation, incubation, and fluorescence imaging on the chip, avoiding the requirement for extra droplet re-collection and heating operations. Clearly, the digital readout was obtained by partitioning miRNA into many individual pL-sized small droplets in which the target molecule is either present ("positive") or absent ("negative"). Importantly, the suggested enzyme-free auto-catalytic hairpin assembly (aCHA) in droplets successfully mitigated the effects of the external environment and thermal cycling on droplets, and its reaction rate is significantly superior to that of traditional CHA. We got excellent sensitivity with a linear correlation from 1 pM to 10 nM and a detection limit of 0.34 pM in the fluorescence spectrum section, as well as high selectivity to other miRNAs. Furthermore, the minimum target concentration could be reduced to 10 fM based on the high-throughput tracking computation of fluorescent droplets with a self-developed Python script, and the fluorescence intensity distribution agreed well with the theoretical value, demonstrating that it is feasible to detect miRNA efficiently and accurately, which has great potential applications in clinical diagnostics and biochemical research.

Abstract 3992: Modular ddPCR assay design for highly sensitive single nucleotide variant detection

Abstract Introduction: Single-nucleotide variants (SNVs) are key drivers of both oncogenesis and emergent resistance to targeted therapies. Although high-throughput Identification of SNVs can be achieved with Next Generation Sequencing (NGS) technologies, the cost is significant, and proportional to the desired sensitivity of variant detection. Conversely, while only small numbers of SNVs can be queried in an individual quantitative PCR (qPCR) or droplet digital PCR (ddPCR) reaction, a fully optimized qPCR or ddPCR assay can detect SNVs at very low frequencies for a fraction of the cost of sequencing. Herein, we present a generalizable approach to PCR assay design, using a combination of mutation-sensitive induced mismatch primers, wild-type suppressors, and TaqMan probes, that permits detection of SNVs below 0.1%. Method: Known oncogenic hotspot regions were selected for development of mutation-detecting PCR assays. For each hotspot, a mutation-specific-mismatch primer, suppressor, and probe (MSMPSP) cassette was designed consisting of 1) a mutation-bearing forward primer with engineered mismatches, 2) a wild-type, extension-locked blocker oligo, 3) a fluorescent TaqMan probe, and 4) a downstream reverse primer. Designed mutation assays were evaluated using plasmid control sequences, remnant clinical specimens, and healthy donor peripheral blood samples spiked with known quantities of mutation-bearing plasmid or cell lines and processed on the BioRad AutoDG/QX200 droplet digital PCR system. Results: Variant detection below 0.1% was achieved for all tested mutations, including those residing in homopolymeric and GC-rich regions, from as low as 100 ng DNA input, in a single day. At higher variant frequencies accessible to multiple platforms, results with MSMPSP-based ddPCR assays exhibited excellent concordance with NGS and qPCR results and yielded linear signal decline down to 0.01% variant allele frequency. Overall assay sensitivity was proportional to DNA input, and improved detection limits were achieved by increased DNA input and combined well analysis. Conclusion: Utilizing the MSMPSP approach, coupled with ddPCR, variant detection for targeted mutations below 0.1% is achievable in diverse genomic contexts. Furthermore, simple design principles and flexible probe-binding sites permit rapid development of new assays, allowing critical mutations to be tracked as they are discovered. While multiplexing capabilities are reduced compared with NGS, short time-to-results, coupled with low cost-per-sample for MSMPSP ddPCR, permits faster treatment decisions at reduced cost to the healthcare system. Citation Format: Sarah Heine, Ashley Beams, Nathan Riccitelli, Shabnam Tangri. Modular ddPCR assay design for highly sensitive single nucleotide variant detection [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 3992.

Quantification of Biocatalytic Transformations by Single Microbial Cells Enabled by Tailored Integration of Droplet Microfluidics and Mass Spectrometry.

Improving the performance of chemical transformations catalysed by microbial biocatalysts requires a deep understanding of cellular processes. While the cellular heterogeneity of cellular characteristics, such as the concentration of high abundant cellular content, is well studied, little is known about the reactivity of individual cells and its impact on the chemical identity, quantity, and purity of excreted products. Biocatalytic transformations were monitored chemically specific and quantifiable at the single‐cell level by integrating droplet microfluidics, cell imaging, and mass spectrometry. Product formation rates for individual Saccharomyces cerevisiae cells were obtained by i) incubating nanolitre‐sized droplets for product accumulation in microfluidic devices, ii) an imaging setup to determine the number of cells in the droplets, and iii) electrospray ionisation mass spectrometry for reading the chemical contents of individual droplets. These findings now enable the study of whole‐cell biocatalysis at single‐cell resolution.

Numerical Modeling of the Blend Morphology Evolution in Twin‐Screw Extruders

Front Cover: The disperse polymer blend morphology evolution is described using a macroscopic model, which clusters individual droplets in droplet populations. The blend model is used to perform a particle tracking simulation of the morphology evolution inside a twin-screw extruder. The figure shows the size distribution of 1300 droplet populations along the cross-section of a twin-screw extruder. This is reported by Patrick D. Anderson and co-workers in article number 2100087.

Identification of slurry fuel components in a spray flow

The paper presents the experimental research findings for the spraying characteristics of promising composite fuels. Slurries were produced from typical coal processing waste (filter cake), a liquid bio-additive (rapeseed oil), biomass (sawdust) and a liquid noncombustible binder (water). The most important spraying characteristic is the distribution of fuel components in a jet. Optical recording techniques (Laser Induced Fluorescence, Interferometric Particle Imaging and Shadow Photography) were used to study it. A fluorophore (Rhodamine B) was used in the experiments. A group of light filters was also employed for wavelengths 580–680 nm. The research made it possible to identify zones, containing individual components and/or their mixtures, in a sprayed fuel jet. The average concentrations of coal processing waste in individual droplets and in an overall aerosol flow were recorded. The proportion of droplets containing wood biomass in a spray flow was determined. A method was proposed to reliably determine the structure of fuel jets with different component compositions. The method involves combining three optical techniques. The experimental data obtained make it possible to predict the conditions for efficient ignition and combustion of slurry fuel components in combustion chambers, taking into account their separation and atomization when they are sprayed by nozzles.

Non-simultaneous droplet impingement cooling of a solid heated surface

High generation of heat in the electronics industry presents a roadblock for further innovations in higher processing power due to complications associated with overheating. Commonly used air-based systems cannot cool high-performance electronics, mainly due to the relatively poor thermo-physical properties of air. Spray cooling is a technique capable of cooling or quenching objects at very high temperatures and heat fluxes. While there has been considerable research on single droplet impact to study the fundamentals of spray cooling, multiple droplet impingement offers more realistic realisations of the dynamics of spray phenomena. In this paper, we examined the fluid dynamics and heat transfer of multiple droplet impingement using high-speed imaging and fast heat flux measurements to capture droplet-droplet and droplet-surface interactions at constant droplet Weber number. We investigated an individual droplet and two non-simultaneous droplets of water at a constant horizontal droplet spacing and different time separations to analyse the heat transfer at different initial surface temperatures. Although not affected significantly by the surface temperature, the maximum diameter of the combined droplets decreased for increasing time separation due to the kinematic discontinuity from the interaction between droplets moving in opposite direction. For small time separation, the spreading droplet contact line of the first droplet collided with the moving contact line of the second droplet. The receding and the quasi-static contact lines of the first droplet was strongly and mildly impacted by the second spreading droplet diameter, respectively. However, all quasi-static droplet diameters increased for non-simultaneous droplet scenario, following by a small reduction in the droplet diameter when the surface temperature increased due to evaporation. Depending on the surface temperature and time separation between droplets, it was found that the peak heat transfer rates for non-simultaneous droplet impingement scenarios can be increased by 68% to 100% when compared to a single droplet case due to higher combined droplet diameter and fluid volume in contact with the heated solid surface. However, the overall droplet cooling efficiency was higher for the single droplet case, showing that the droplet-droplet interaction can decrease the potential cooling performance of droplets. The present study provides knowledge combining droplet-droplet interaction and heat transfer performance for future spray cooling system design and optimisation.

Colloidal dynamics of emulsion droplets in mouth

The interaction of emulsions with the tongue is key to the sensory appeal of food and can potentially be exploited for oral/buccal pharmaceutical delivery. Whilst there is good understanding of the different mucoadhesive forces governing emulsion interaction with the tongue, their relative importance is not well understood. In addition, the physical location of emulsions within the saliva papillae on the tongue is not understood at all. A combination of ex vivo salivary film, and in vivo oral coating experiments were used to determine the importance of different mucoadhesive forces. Mucoadhesion of cationic emulsions was largely driven by electrostatic complexation. SDS-PAGE of the in vivo saliva coating highlighted that mucins were largely responsible for cationic emulsion mucoadhesion. Anionic emulsions were bound via hydrophobic/steric interactions to small salivary proteins typically located away from the mucin anchor points. The physical location and clustering of emulsions relative to the salivary film/papillae was probed via the invention of a fluorescent oral microscope. Cationic emulsions were densely clustered close to the papillae whilst anionic emulsions were suspended in the salivary film above the papillae. Interestingly, non-ionic emulsions were also trapped within the salivary film above the papillae as individual droplets. These findings highlight that whilst electrostatic complexation with saliva is a powerful mucoadhesive force, hydrophobic and steric interactions also act to induce oral retention of emulsions. The differences in physical location and clustering of emulsions within the salivary film hint at the 3D locations of the different salivary proteins driving each mucoadhesive interaction. This novel understanding of emulsion saliva/papillae interactions has potential to aid efficacy of buccal pharmaceutical delivery and the reduction of astringency in plant-based foods.

Ratio of water/fuel concentration in a group of composite droplets on high-temperature heating

The paper presents the experimental research findings on the water/Diesel fuel concentration ratio in a group of composite droplets after passing through a heated gaseous medium. The research was carried out using the optical methods of Planar Laser Induced Fluorescence and Shadow Photography. The experimental method involved measurements carried out while a group of composite droplets (water/Diesel fuel) was free-falling through a tubular muffle furnace. The findings have shown combined effects of droplets on the water and Diesel fuel concentration ratio at the furnace outlet. We have also shown how droplet collisions with each other and with a heated chamber wall affected the number and size of droplets of water and combustible liquid as they left the high-temperature zone. The limiting temperatures of the gaseous medium have been determined that are sufficient for the breakup of a group of composite droplets free-falling through a fixed-length operating section with heated gases. We have also calculated the required heating time and the length of the channel with a heated gas, so that parent composite drops break up into individual droplets of water and a combustible liquid. The numbers and sizes of fragments with different component compositions after passing through a heated gaseous medium have been determined as well. The relative proportion of composite droplets containing vapor bubbles at the furnace exit.