Droplet Diameter Research Articles

New Supersonic Nozzle Test Rig Used to Generate Condensing Flow Test Data According to Barschdorff

Considerable progress has been achieved in recent decades in understanding the phenomena related to the onset of condensation in steam flows, both experimentally and especially numerically. Nevertheless, there is still a certain disagreement between the different numerical models used. Unfortunately, the available experimental validation data are not sufficiently detailed to allow for proper validation of computational fluid dynamics (CFD) simulations. Therefore, this paper presents new experimental data for condensing steam flows, acquired in a supersonic nozzle according to Barschdorff, at the Institute of Thermal Turbomachinery Laboratory (ITSM) at the University of Stuttgart. A steady inlet pressure of approximately 784 mbar was set for three inlet temperatures down to 100.2 ∘C. Condensation onset is accurately captured across the nozzle, using down to 1 mm spatial resolution for both pneumatic and light spectra measurements. CFD simulations were performed using the commercial solver ANSYS CFX. The droplet diameters are numerically overestimated by approximately a factor of 1.5. Disagreement has been found between original Barschdorff’s experiments and measurements at ITSM. However, there is a good agreement in terms of the pressure distribution along the nozzle axis between experimental and numerical results. The reproducibility of the results is excellent.

Performance of extended surfactant and its mixture with betaine surfactant for enhanced oil recovery in sandstone reservoirs with low permeability

Carboxy betaines CnZC (where n represents the carbon number of the alkyl chain, n = 12,14 and 16) and extended surfactant C16P3E6S were combined to assess their potential application for enhanced oil recovery (EOR) by investigating the surface properties, interfacial properties and emulsifications of the single and compounded surfactants. The results demonstrated that four surfactants with favorable water solubility exhibited better surface properties. Among them, the mixture of betaine surfactant C14ZC and sulfonate surfactant C16P3E6S displayed a synergistic effect in reducing interfacial tension (IFT). The solution with C14ZC mole fractions of 60 % and 50 % possessed an ultra-low IFT (10-3 mN/m order of magnitude) at 10 % NaCl whose emulsification rates of oil in brine for mixtures exceeded 90 % at 4 % NaCl. Notably, the emulsion droplet diameter was smaller compared to other salinity conditions, indicating that the combination of C16P3E6S and C14ZC enhanced emulsion stability, correspondingly ultra-low IFTs at both the oil-emulsion and emulsion-water interfaces. Coreflooding experiments revealed that the depressurization rate for the optimized surfactant system (with a molar fraction of C16P3E6S/C14ZC = 2:3) with superior emulsification properties, effectively abilities of reduced IFT, increased capillary number and lower adsorption loss was 26.7 % and its EOR was 20.4 %, confirming its favorable displacement performance and potential application in medium to high salinity reservoirs.

Influence of fuel characteristics on the alternative jet fuel atomization at non-reacting conditions

Synthetic paraffinic kerosene jet fuel derived from natural gas (NG-SPK) is gaining importance as a low-emission alternative fuel for aviation combustors. In this context, the influence of fuel properties on the atomization of NG-SPK jet fuel at non-reacting, evaporating conditions is investigated. The spray results of NG-SPK jet fuel are compared with the reference, Jet A-1 fuel. This study considers a simplex atomizer, commonly deployed as a pilot injector in aviation gas turbine combustors for ignition at sea level and in high-altitude relight conditions. The local atomization characteristics like droplet concentration, mean diameters, and mean axial droplet velocity is obtained experimentally using phase Doppler anemometry technique at different ambient gas pressures of 100, 500, and 900 kPa while maintaining the ambient temperature at 400 K. The fuel dispersion parameters are measured at two nozzle pressure differentials of 300 and 900 kPa. The NG-SPK jet fuel exhibited higher droplet concentrations for the conditions studied than conventional fuel. Furthermore, the droplet size distribution of NG-SPK jet fuel revealed a higher percentage of smaller droplet diameters than Jet A-1 fuel. This difference in droplet characteristics can positively influence the heat release patterns under reacting conditions.

Droplet dispersion characteristics during human walking in a queue

The dispersion of respiratory droplets is strongly influenced by the complex airflow induced by human activities, such as walking in a queue. Understanding the relationship between local airflow disturbances during queue walking and droplet dispersion is crucial. This study investigates the effects of following distance (1.0, 1.5, 2.0, and 2.5 m), walking speed (0.8, 1.0, 1.2, and 1.4 m/s), and droplet diameter (1, 10, 50, 80, and 120 μm) on droplet dispersion. The findings reveal that the interaction between wake vortex and forward airflow provides a foundation for cross-infection among individuals. An increased following distance leads to an initial rise and subsequent decrease in the concentration in the breathing zone of the susceptible individual. The social distances of 1.0 and 1.5 m are insufficient to mitigate the risk of cross-infection, warranting a recommended following distance of at least two meters. The effect of walking speed on droplet dispersion varies depending on the scenario. In cases involving standing and walking cycles, the infection risk of the susceptible individual gradually increases with higher walking speeds. Conversely, when individuals walk continuously in a queue, the infection risk of the susceptible individual decreases with increased walking speed. Moreover, intermediate-sized droplets play a critical role in the transmission of respiratory infectious diseases and demand heightened attention. This study expounds the intricate airflow dynamics during queue walking and emphasizes the significance of following distance, walking speed, and droplet diameter in minimizing the risk of cross-infection.

MODELLING AND TESTING OF SYNCHRONOUS MOTORS WITH PERMANENT MAGNETS

Applying a layer of polymer material to the fabric gives new characteristics to the base fabric. The resulting coated material may have functional properties such as resistance to dirt, liquid penetration, etc., or the finished leather products may have a completely different aesthetic appeal. The choice of the coating method depends on several factors: the type of substrate, the polymer formula and its viscosity for coating, the desired final product and the accuracy of the coating, the economy of the process. In the conditions of modern enterprises, it is advisable to use the spray application method for the application of polymer coatings due to the fact that the roller and brush methods do not provide the opportunity to operate with different forms of parts, and volumetric application is not always economically feasible. Jet application of the material is similar to spraying, but for polymer coatings, the temperature value is important, which in this case is difficult to control. Therefore, it is advisable to use the spraying method for applying polymer coatings The paper presents the results of preliminary research on the breakdown of polymers into droplets. The shape of the flow coming out of the nozzle was determined, and based on this, a model describing this process was developed. It is shown that for a sheet of polymer flow, its thickness is inversely proportional to the distance from the nozzle and K=2sx, calculated knowing the thickness of the sheet at some distance x from the nozzle. For a “hollow cone” spray nozzle with taper angle, θ and orifice diameter, δ and sheet thickness h, at the nozzle exit, an equation for the flow length break was derived. The obtained results of the calculations of the dependence of the droplet diameter on the flow rate. A spray test was carried out in different modes. The ratio of the length of the jet to the length of the gap L serves as the beginning of the decay mode. It was determined that the ratio of the length of the jet to the length of the gap of the canvas when reaching 1 can be a reasonable criterion for evaluating the determination of the limits of the spraying mode. For a good spraying (for example, tearing of the web), small values of the ratio of the length of the jet to the length of the tearing of the web are necessary. This is achieved due to low surface tension, high gas density, high injection pressure (velocity) and large nozzle exit angles. The obtained results can be used for the design of sprayers and their modes of operation.

On the interaction of Taylor length-scale size droplets and homogeneous shear turbulence

The main objective of the present work is to explain the physical mechanisms occurring in droplet-laden homogeneous shear turbulence (HST) with a focus on the modulation of turbulence kinetic energy (TKE) caused by the droplets. To achieve such an objective, first, we performed direct numerical simulations (DNS) of HST laden with droplets of initial diameter approximately equal to twice the Taylor length scale of turbulence, droplet-to-fluid density and viscosity ratios equal to ten and a 5 % droplet volume fraction. We investigated the effects of shear number and Weber number on the modulation of TKE for $Sh \approx 2$ and $4$ , and $0.02 \le {{We_{rms}}} \le 0.5$ . Then, we derived the TKE equations for the two-fluid, carrier-fluid and droplet-fluid flow in HST and the relationship between the power of surface tension and the rate of change of total droplet surface area, providing the pathways of TKE for two-fluid incompressible HST. Our DNS results show that, for ${{We_{rms}}} = 0.02$ , the rate of change of TKE is increased with respect to the single-phase cases, for ${{We_{rms}}} = 0.1$ , the rate of change of TKE oscillates near the value for the single-phase cases and, for ${{We_{rms}}} = 0.5$ , the rate of change of TKE is decreased with respect to the single-phase cases. Such modulation is explained from the analysis of production, dissipation and power of surface tension in the carrier-fluid and droplet-fluid flows. Finally, we explain the effects of droplets on the production and dissipation rate of TKE through the droplet ‘catching-up’ mechanism, and on the power of the surface tension through the droplet ‘shearing’ mechanism.

Research on the characteristics of flue gas purification reaction in spouted bed

Semi-dry flue gas desulfurization and purification technology is a promising flue gas treatment technique. This study numerically investigated the influence of factors such as nozzle expansion angle, and fluidized particles diameter on the purification of SO2 and HF in the spouted bed. The study showed that in nozzle expansion angles of 5-25°, the 10° expansion angle is optimal for SO2 and HF purification efficiency. The fluidized particles' diameter affects purification efficiency. Desulfurization and defluorination efficiency are optimal when the ratio of fluidized particle diameter to slurry droplet diameter is 15. When Ca(OH)2 accounts for 0.005–0.01 of the slurry, desulfurization and defluorination efficiency are most cost-effective. According to the principle of chemical equilibrium, a higher Ca/S ratio facilitates a complete reaction with SO2 and HF, ensuring effective purification of the flue gas. The optimal Ca/S ratio is 2.5, with a desulfurization efficiency of 93.55% and a defluorination efficiency of 99.79%.

Development of structured W/O emulsions with the use of only candelilla wax

AbstractWe investigated the development of water‐in‐oil (W/O) emulsions using only candelilla wax (CW), evaluating the effects of different water to CW oleogel ratios (40:60, 50:50, 60:40) and the CW concentration (0.75% to 3%). The emulsions were developed by shearing the systems with an ultra‐turrax type homogenizer (60 s at 25°C) at the different water to CW oleogel ratios. After 0 and 20 days of storage (25°C) the emulsions were evaluated through microscopy, rheology, water droplet diameter, emulsion stability, and x‐ray diffraction measurements. The results showed that at all water to CW oleogel ratios the surface‐active components of the CW (i.e., triterpenic alcohols, aliphatic alcohols, and fatty acids) stabilized the oil–water interface, while the n‐alkanes and long chain esters formed an oleogel in the oil phase. Independent of the storage time, all the CW emulsions showed frequency independent rheological behavior. However, after applying a strain within the plastic region the 40:60 and 50:50 emulsions formulated with 1.5% to 3% CW provided the higher elasticity and emulsion stability, even after two freeze‐thaw cycles. In particular, the 40:60 and 50:50 emulsions with 1.5% CW had a recovery profile similar to commercial mayonnaise. In contrast, independent of the CW concentration, the 60:40 emulsions showed the lowest recovery profile and highest emulsion instability. These results showed the CW as a multifunctional material capable to develop structured W/O emulsions at room temperature without adding surfactants. The structured W/O emulsions developed by CW could be useful in the formulation of trans‐free, stable low‐fat edible spreads.

Modeling Multivariate Spray Characteristics with Gaussian Mixture Models

With the increasing demand for efficient and accurate numerical simulations of spray combustion in jet engines, the necessity for robust models to enhance the capabilities of spray models has become imperative. Existing approaches often rely on ad hoc determinations or simplifications, resulting in information loss and potentially inaccurate predictions for critical spray characteristics, such as droplet diameters, velocities, and positions, especially under extreme operating conditions or temporal fluctuations. In this study, we introduce a novel approach to modeling multivariate spray characteristics using Gaussian mixture models (GMM). By applying this approach to spray data obtained from numerical simulations of the primary atomization in air-blast atomizers, we demonstrate that GMMs effectively capture the spray characteristics across a wide range of operating conditions. Importantly, our investigation reveals that GMMs can handle complex non-linear dependencies by increasing the number of components, thereby enabling the modeling of more complex spray statistics. This adaptability makes GMMs a versatile tool for accurately representing spray characteristics even under extreme operating conditions. The presented approach holds promise for enhancing the accuracy of spray combustion modeling, offering an improved injection model that accurately captures the underlying droplet distribution. Additionally, GMMs can serve as a foundation for constructing meta models, striking a balance between the efficiency of low-order approaches and the accuracy of high-fidelity simulations.

Characterization of Sprays Generated by the Expansion of Emulsions with Liquid Carbon Dioxide

AbstractExpanding emulsions with liquid CO2 facilitates the creation of aerosols with an average droplet diameter in the low micrometer size range, which is challenging with conventional atomizers. The droplet formation process of the expansion of high‐pressure emulsions was investigated using a plain‐orifice atomizer and different swirl nozzles. The local droplet size and droplet velocities were measured and used to estimate the local Weber number and thus infer the droplet size reduction. Measurements of the local mass concentration in the aerosol showed that, for the swirl nozzle, the highest concentration was found outside of the central axis, indicating radial momentum generated by the swirl nozzle. Furthermore, it was shown that the type of expansion nozzle used has an influence on the resulting median droplet size in the aerosol. For a water mass load of 0.01, the median droplet diameter was reduced from 8 to 3 μm by increasing the swirl number from 0.01 to 0.1.

Effects of clove essential oil (Caryophyllus aromaticus L.) nanoemulsion incorporated edible coating on shelf-life of fresh cut apple pieces

Fresh cut fruit is ready to eat and can be taken on the go. Freshly cut apple pieces are perishable and prone to contamination that can damage its quality. In the current investigation, clove essential oil was used to formulate nanoemulsion (NE) in three distinct concentrations, NE-1 (0.1%), NE-2 (0.5%), and NE-3 (1%), which were then incorporated with Sodium Alginate (SA) based coating solution to impart their qualities to the outer surface of apple pieces. Sodium alginate layer helps to extend the shelf life of fruits by reducing moisture loss, inhibiting microbial growth, and protecting against physical damage. Physico-chemical properties of this solution were investigated using Box–Behnken design after it was employed to coat the freshly cut apple pieces and stored at 4 °C for 14 days. The clove essential oil nanoemulsion's average droplet size and Zeta Potential were in the nanometric range. The addition of increasing concentrations of clove nanoemulsion to the alginate coating solution decreased the zeta potential of the colloidal dispersion from −51.0 to −3.02 mV. The average droplet diameter of the edible coatings containing different clove nanoemulsion concentrations (81.04–3342 nm), whereas sodium alginate edible coating solution (SA) was in micrometric range. The Total phenol content and Antioxidant content of CEO based samples were found to be high as 38.9 mg/ml and 79.1% respectively because of bioactive chemicals and essential oil properties. NE-3 coated apple samples were found to more affective compared with the control and SA coated samples in terms of sensory and shelf-life metrics among all the treatments.

Functionalized zinc oxide nanorods – polypropylene nonwoven composite with high biological and photocatalytic activity

This work presents a comprehensive approach to elaborating new active polypropylene-zinc oxide composite material with a well-developed specific surface area. Fibrous polypropylene material, made via the melt-blown technique, plays a role of a high-porosity substrate for modification. The hydrothermal chemical bath deposition (CBD) method adjustment is suited to cover its surface with various ZnO nanorods (NRs). Due to the CBD method, it is possible to control the structures of obtained ZnO via the concentration of reagents used in the synthesis. The material analysis allows for determining the crystal form of ZnO, the fiber coverage degree, and the effectiveness of the surface activation process. The investigation also confirmed the bactericidal (differences in microorganism survivability exposed on PP-ZnO material ranged from approx. 50–0%) and photocatalytic (increase in MB decomposition rate constant value from 0.0374 to 0.173 h-1) properties of the developed PP-ZnO composite materials. Aerosol and bioaerosol particles in indoor air may be dangerous, especially for human health, since ventilation and air-conditioning systems create excellent conditions for growing microorganisms. For this reason, an exemplary application of the proposed material is the separation processes. Investigations into the filtration process for solid KCl particles and DEHS droplets (diameters from 20 nm to 2 µm) showed that modified nonwovens maintain their original (before modification) airflow resistance and exhibit increased effectiveness for particles larger than 200 nm (differences in the QF value in the range of 0.001–0.004).

Development of a spray-ejector condenser for the use in a negative CO2 emission gas power plant

One promising solution for developing low-emission power technologies is using gaseous fuel combustion in pure oxygen when the exhaust gas mixture is composed of H2O and CO2, and where CO2 is separated after steam condensation. The paper presents the results of computational analyses providing to the Spray-Ejector Condenser (SEC) development, which is one of the crucial components of the negative CO2 gas power plant (nCO2PP) cycle development. The proposed design of the ejector-condenser to ensure the high effectivity of vapor condensation and CO2 compression with preparation to separation, ready for application in gas power cycle, is a novelty of this research. Different computational techniques leading to the development and better understating of ejector operation were applied. The main operating conditions in the characteristic connected with the developed nCO2pp cycle points were investigated to evaluate the impact of the operating conditions on SEC performances. The amount of motive water needed for the cooling purpose is susceptible to the inlet water pressure and temperature and strongly affects the generated pressure of the suction stream. The preliminary results confirm that the SEC's basic design and geometrical dimensions can be applied in the negative CO2 power plant cycle. Results from CFD modeling give the possibility to investigate the turbulent flow of water/steam/CO2 mixture together with the condensation process occurring at this same time. It is found that the average droplet diameter and motive water supplying method significantly effects the condensation intensity. The further direction of the presented computational research activities and results is to test various designs of Spray-Ejector Condensers that will enable the evaluation of the direct contact condensation process and develop the final geometrical design.

Effect of droplet diameter on oblique detonations with partially pre-vaporized n–heptane sprays

Liquid fuels have been widely used in propulsion systems for their higher energy density and easier storage, but there are few studies on oblique detonation engines (ODEs) using the liquid fuels. In this study, oblique detonation waves (ODWs) in partially pre-vaporized n–heptane sprays are simulated, using a hybrid Eulerian–Lagrangian algorithm with a skeletal chemical mechanism, to facilitate liquid fuels applications in ODE. A novel phenomenon has been observed, illustrating that the ODW initiation lengths in pre-vaporized n–heptane sprays firstly increase and then decrease with increasing fuel droplet diameters. It is found out that an increase of droplet diameter can increase the transferred heat amount caused by droplets evaporation and lower the inflow temperature, so leading to the increase of ODW initiation length firstly. However, extremely large droplet diameter can markedly reduce the heat transfer rate of the droplet and its surrounding mixture, and the compressed gas-stream behind oblique shock wave has a higher temperature that accelerate the induction chemical reaction and results in a decrease in the ODW initiation length. Furthermore, the unsteady oscillations of ODW initiation structures are also observed even for a steady inflow, which involves the periodic hot spots, normal detonation waves and their evolutions. Some factors causing the unsteady behavior of ODWs are tested through a sensitivity analysis method of the initiation lengths. Through the analyzation, the fluctuation of the post-shock temperatures is the main factor causing the fluctuation of initiation lengths, revealing that inhomogeneous heat loss by evaporation of dispersed liquid droplets is the main reason causing the unsteady behaviors of ODWs and the competition between heat release by chemical reactions and heat loss by evaporation determines the steadiness of ODWs.

Are Most Micrometer Droplets (>10 μm) Wasted in Electrospray Ionization? An Insight from Real-Time High-Speed Imaging.

Electrospray ionization (ESI) is one of the main techniques used in mass spectrometry (MS) of nonvolatile compounds. ESI is a disordered process, in which a large number of polydisperse droplets are projected from a fluctuating Taylor cone and jet protruding ESI emitter. Here, we disclose a system for sectioning electrospray plumes to discrete packets with millisecond and submillisecond lifetime, which are introduced to the MS orifice, one at a time. A high-speed camera was triggered at 10,000 frames per second to capture consecutive images of the electrospray packets transmitted to the mass spectrometer. We further correlated the high-speed images of electrospray packets with MS signals of a test analyte (acetaminophen). Following computational treatment of the images, we determined the number of droplet observations (<300), average diameter of droplets (∼10-20 μm), and average volume of droplets (few tens of picoliters) in the individual electrospray packets. The result shows that most micrometer droplets (>10 μm) do not have any significant contribution to the MS signals. This finding is in agreement with the prior conjecture that most of the MS signals are mainly attributed to nanodroplets. Based on this finding, one can deduce that only a small number of the initial microdroplets effectively carry analyte molecules that undergo ionization. We discuss that, in future, one may propose a way to "recharge" the emitted initial micrometer droplets to increase the efficiency of conventional ESI setups.

Study of binary mixtures of Tribulus terrestris extract and Quillaja bark saponin as oil‐in‐water nanoemulsion emulsifiers

AbstractSeveral industrial fields use emulsifiers in their products, with the ones of natural origin gaining increasing relevance. Identifying and using diversified sources for their extraction is a pertinent topic regarding sustainability principles, biodiversity preservation, or cost rationalization. This is the case of Quillaja bark saponin (QS), for which saponin‐rich extracts, for example, Tribulus terrestris (TT), are being highlighted as viable alternatives, even though constraints like performance are still on the table. In this context, an experimental design using binary emulsifier mixtures of TT with pure QS was carried out by changing their composition (50–90%wt. TT), content (1.5–4.5%wt.), and high‐pressure homogenization conditions (5–15 cycles). The emulsions were characterized by zeta potential, morphology, droplet size, and stability (expressed as the number of days without creaming formation). Moreover, the cream index for 30 days was determined to indicate the destabilization extent. The zeta potential showed stable emulsions (values below −41 mV); even still, creaming formed for samples using a low emulsifier and high TT contents. The emulsions' mean droplet diameter (D [3, 2]) was between 78 and 921 nm, with smaller sizes agreeing with higher stability. The statistical analysis indicated an optimum composition range comprising an emulsifier content between 3.9 and 4.5%wt. and TT content between 50 and 56%wt. to reach stable products. Overall, TT can provide an effective solution when combined with QS, decreasing the dependence on Quillaja bark.

Hypergolic ignition response to oxidizer droplet properties

The hypergolic ignition response to oxidizer droplet properties is an important consideration for oxidizer injector design in hybrid rocket motors. Hence, the present work focused on hypergolic ignition characterization as a function of droplet properties and impact dynamics for a promising propellant. The propellant for the present work consisted of rocket grade hydrogen peroxide (RGHP) as oxidizer, high-density polyethylene (HDPE) as fuel and sodium borohydride (NaBH4) as the hypergolic additive embedded in the HDPE matrix. This propellant was chosen for this detailed study since it showed promising results in prior studies, exhibiting low (<10 ms) ignition delays. For this work, in a drop-test setup, RGHP droplet diameters between 1.90±0.11 mm and 4.35±0.26 mm were dropped on the HDPE + NaBH4 fuel samples at velocities between 0.3 m/s to 1.93 m/s. The ensuing ignition event was studied using both visible and infrared high-speed imaging. Post-impact droplet parameters were determined to enable a deeper analysis of observed phenomena. While ignition delay was the focus of this work, flame spread areas and heat release were also studied. Higher impact velocities generally led to lower ignition delays while splashing oxidizer drops increased probability of larger flame areas and higher heat release. Additionally, the initial ignition/heat release event was found to originate in a small region at the thinnest area of the post-impact droplet. Surface temperature measurements were also performed using infrared imaging. The data suggested that the initial heat release was found to be likely due to RGHP-NaBH4 reaction with no contribution from RGHP decomposition. Regression and random forest machine learning analysis found ignition delay depended strongly on the minimum post-impact drop layer thickness. Based on the data analysis, a simple mathematical model was developed whose results matched experimentally observed trends. The study is expected to further understanding of the processes that control hypergolic ignition in addition to aiding rocket engineers design better oxidizer feed systems. Novelty and SignificanceThis work constitutes a novel in-depth study on the influence of drop impact properties on hypergolic ignition. Using innovative techniques, this work is the first to show the overwhelming importance of residual droplet layer thickness on ignition delay. Additionally, a simple mathematical model based on that finding performed well against experimental data which is of substantial significance, given the complex and multi-parametric nature of hypergolic ignition. Finally, the work establishes that operating in the splashing regime enhances heat release and flame spread. The candidate propellant for this work was hydrogen peroxide and high-density polyethylene with embedded NaBH4. However, the findings of this study are likely generalizable over a range of solid-liquid hypergolic propellants involving solid fuels with embedded energetic materials, of which there are many. The findings of this work can enhance understanding of hypergolic ignition in addition to aiding in better rocket injection system design.

Numerical study on spherical flame propagation in dispersed liquid ammonia droplets

Directly using liquid ammonia in combustion devices can simplify the fuel supply system and reduce equipment costs. However, the detailed ignition and propagation mechanisms of liquid ammonia flames have not been fully understood. This study aims to investigate the ignition and propagation of liquid ammonia flames numerically under various conditions. Spherically expanding liquid ammonia flames are studied using detailed chemistry. The effects of initial temperatures, droplet diameters, equivalence ratios, and heat fraction are investigated. The results indicate that the rapid flash boiling of liquid ammonia droplets leads to a strong local heat loss, hindering the ignition and propagation of the flame. Preheating can significantly increase the reaction rate, which compensates for the heat loss caused by phase change, allowing the flame kernel to ignite and propagate outwards. While droplet-flame interaction is present but not significant due to the rapid evaporation of liquid ammonia. The effect of droplet on the flame surface curvature is only distinguishable at conditions of large diameter. Equivalence ratio and ammonia heat fraction ratio change the amount of liquid ammonia. The more liquid ammonia, the more heat is absorbed by the phase change process, making the flame more difficult to be ignited.

Proposal of New Emulsion Systems Containing Hydroxypropylmethylcellulose as a Viscosity Modifier and Diacylglycerols from Mutton Tallow and Hemp Seed Oil

The purpose of this study was to analyze the stability of new emulsions prepared on the basis of modified fats with varying amounts of hydroxypropylmethylcellulose. Selected techniques for evaluating the stability of emulsion systems, such as Turbiscan analysis, and the evaluation of microstructure, texture, particle size and viscosity were used. The evaluation of the above-mentioned studied parameters allowed us to indicate differentiated stability and their properties. The most desired results in terms of stability evaluation were determined for the emulsion prepared on the basis of modified mutton tallow with hemp seed oil in a ratio 3:1 (by weight) containing 0.6% (by weight) of hydroxypropylmethylcellulose. In addition, as the hemp seed oil content in the interesterified fat phase increased, a decrease in the stability of the emulsion systems was noted. Mentioned emulsions were characterized with the lowest value of TSI. Moreover, for those emulsions, the smallest increment in the droplet diameter values of systems after 31 days was recorded. The prepared model formulation can serve as a starting material for new emulsion chemical, cosmetic or food systems.

Experimental modeling of mean drop size and dispersed phase holdup in rotating disc contactors, using RSM

In this study, the behavior of hydrodynamic parameters was investigated in agitated columns including Asymmetric rotating disc contactor (ARDC), Perforated rotating disc contactor (PRDC), Oldshue–Rushton column (ORC), and Kuhni. The effects of various parameters, including rotor speed (rpm), dispersed and continuous phase velocities, interfacial parameters, and type of RDCs on the dispersed phase holdup and Sauter mean drop diameter were studied. The response surface methodology (RSM) based on the central composite design (CCD) approach was applied for the experimental modeling of three standard systems including toluene-water, butyl acetate-water, and butanol-water. Results showed that the enhancement of rotor speed and dispersed and continuous phase velocities would enhance the dispersed phase holdup. PRDC showed the least enhancement of dispersed phase holdup compared to the other three columns. Our investigation demonstrated that Sauter mean droplet diameter decreased with the rotor speed increase, and this declining trend is more appreciable in ORC and Kuhni columns. Additionally, by increasing dispersed phase velocity in the four columns, the droplet size in the ORC column is larger than the columns. However, by increasing continuous phase velocity, subtle changes in droplet size was observed. Based on the experimental data, new correlations have been presented to predict Sauter mean drop diameter and dispersed phase holdup for agitated columns by analysis of variance (ANOVA). The coefficient of determination (R2) was obtained to be 0.9612 and 0.9495 for Sauter mean drop diameter and dispersed phase holdup, respectively, indicating a good correlation between the predicted and observed values of the models.