Spray Dynamics Research Articles

Theoretical analysis of the spray characteristics of ternary blends of diesel, biodiesel, and long-chain alcohols inside a combustion chamber

The diesel and alcohol blends are potential alternatives to biogenic fuels to reduce biodiesel consumption, which might help reduce toxic emissions. Due to the high-quality requirements for engines, the fuel fundaments in the fluid properties and its impact on the macroscopic spray characteristics. Herein, a study proposed the experimental determination of density, viscosity, and surface tension for ternary mixtures of diesel (D) + biodiesel (B) + 1-hexanol (H) and + 1-octanol (O) at 298.15 K. These properties comply with the limits established by the EN 14214 and ASTM D975 standards. Thus, to extend the impact of these results, a theoretical analysis via CFD is carried out in ANSYS FLUENT ® by considering a macroscopic and isothermal system, which involved the independence tests of meshing and turbulence modeling. The numerical results evaluated the spray tip penetration, spray angle, spray morphology, eddy turbulence, and relation of spray volume and surface spray area at the injection pressure of 90 MPa using the Large Eddy Simulation (LES) model. The behavior of the spray tip penetration and spray angle agree with experimental values reported in the literature for diesel fuel. This condition validates our simulations for biodiesel and ternary blends. Therefore, the use of alcohols and biodiesel as new additives to diesel improves the macroscopic spray characteristics, and some ternary mixtures showed similar behavior to conventional diesel: spray tip penetration (70D5B25O, 70D25B5H, and 70D25B5O) and spray angle (70D25B5H, 70D15B15H, 80D5B15O, and 80D15B5). The mixture of 70D25B5H agrees with both spray characteristics; therefore, this mixture could be considered an alternative fuel to conventional diesel. Hence, this analysis presents the essential elements to visualize the macroscopic spray characteristics and the fluid properties. This knowledge serves as a foundation for elucidating the intricate dynamics of spray during combustion processes and the development of complementary studies aimed at optimizing engine performance.

Modelling of fire-suppressant injection into engine nacelle for various flight regimes

In this study, the injection of Halon 1301, an effective fire-suppressing agent, into a helicopter engine nacelle is modelled to provide insights into dispersion behaviour alongside complex flow physics. The injection velocity as well as the mass flow rate were retrieved via a 1-D pipe model to simulate nitrogen-pressurized flow of Halon 1301 in a four-branch pipe system. The Discrete Phase Model in ANSYS Fluent was then used to model the injection of Halon 1301 into an engine nacelle. To simulate engine operation conditions in forward flight and hover regime, external boundary conditions were prescribed to the pressure inlets in the nacelle. When Halon 1301 is injected into the engine bay via the first pair of injection points, the droplets immediately reach their boiling point of 215 K. This resulted in an explosive-dispersion behaviour with a cone angle in the range of 80°–90°. As the agent evaporates, the engine cools and another pair of injection points located at the rear of the engine is subsequently activated, helping to cool the engine further. The two flight regimes considered, namely, hover and forward flight, showed contrast in flow dynamics which affected the cooling of the engine as well as the spray dynamics. In particular, the forward flight case showed more recirculation zones compared to the hover case. The volume concentrations of Halon 1301 were plotted for 11 probe points within the nacelle, and it was observed that two locations showed traces of low concentration levels.

Escape inhibition of unsymmetrical dimethylhydrazine in aqueous solution by carboxyl-rich graphene oxide loaded with Fe3O4

Unsymmetrical dimethylhydrazine (UDMH) is a common liquid propellant. In order to reduce the losses caused by propellant leakage accidents, water spraying devices have been widely applied in UDMH storage sites. However, the UDMH pools are formed in the storage facilities due to this emergency measure, resulting in the generation of toxic UDMH gas. To solve this practical problem, a magnetically recoverable sorbent for UDMH leakage is designed and prepared in this work. The microstructure characteristics of the green recoverable inhibitor which meet the theoretical design requirements are verified, so environmental protection and recyclability can be achieved. The dynamic spray experiments under different leakage conditions show that the treatment of UDMH leakage accidents with this green recoverable agent helps reduce the maximum leakage of UDMH gas, saving valuable time for subsequent emergency rescue. Additionally, the environmental pollution caused by leakage accidents can be greatly reduced.

Autoignition enhancement of ammonia spray under engine-relevant conditions via hydrogen addition: Thermal, chemical, and charge cooling effects

With the growing trend of decarbonization in ground transportation, low and zero-carbon fuels have attracted extensive research interest. Liquid ammonia is a promising alternative fuel due to its relatively high volumetric energy density, mature production and distribution infrastructure, convenience of storage, and zero carbon emissions. However, ammonia combustion also suffers from low flame speed and weak chemical reactivity. In this work, we computationally investigate the suitable engine-relevant thermochemical conditions for auto-ignition of constant volume ammonia spray, as well as its spray dynamics, vaporization, flash boiling effects, and emissions. The simulation is first validated by comparing it against available experimental data from a vaporizing ammonia spray and is then extended to chemically reactive conditions. Results show that ammonia sprays under engine-relevant conditions (60 bar and 1200 K) can only successfully auto-ignite for cases with ambient hydrogen addition, through enhancement of thermal condition and chemical reactivity. A chemical flux analysis is conducted to further understand the important species and reactions that promote ammonia auto-ignition from hydrogen, which potentially can be introduced via H2 solubility, exhaust gas recirculation, and onboard ammonia thermal decomposition. Furthermore, results have indicated that charge cooling effects can further decrease the temperature in the flow field and make auto-ignition more difficult. This study provided useful insights for the application of ammonia as a zero-carbon diesel fuel for ground transportation.

Impact of spray dynamics on combustion instabilities investigated by changing the atomizer recess in a swirl combustor

The present article is aimed at identifying the impact of spray-wall interaction on combustion instabilities. This is achieved by systematically modifying the liquid fuel atomizer location with respect to the injector outlet in experiments carried out on a single-injector swirling combustor. The injector is characterized by a high swirl number and a relatively high pressure drop, and features a pressure atomizer that delivers liquid heptane fuel in the form of a fine spray. In the first set of experiments, longitudinal self-sustained oscillations (SSOs) are examined by varying the atomizer recess distance and using three combustion chamber lengths. Three distinct instability regions characterized by jumps in amplitude and frequency are observed as a function of the atomizer recess. At lower SSO frequencies (obtained for longer chambers), the pressure fluctuation amplitude in the chamber decreases as the atomizer recess distance is reduced, tending towards a stable operation. An opposite behavior is observed at comparatively higher SSO frequencies (obtained with a shorter chamber), where the system becomes less unstable at higher atomizer recess distances. The oscillation frequency is also found to change and increases as the recess distance is reduced. Three recess distances corresponding to each zone of operation are selected to further analyze the flow and flame structures and dynamics. It is found that the mean velocity profiles only reveal moderate differences in the air flow field, but there are significant changes in the fuel spray distribution in the neighborhood of the injector axis. Laser sheet images of the spray reveal two patterns—one where the spray predominantly interacts with the injector end piece when the atomizer is recessed, and the other where this interaction is minimal. In the latter case, corresponding to a small recess, the fuel spray is directly conveyed into the chamber. It is next found that the spray distribution affects the flame pattern defining two distinct configurations. Finally, the flame response to external disturbances is characterized by flame describing functions (FDFs) that allow carrying out a stability analysis. FDF results obtained with two independent methods indicate that the gain and phase at the three recess positions vary substantially and that this can be used in combination with a low-order model to interpret the instability behavior of the system. This study might serve to guide the modeling of combustion dynamics and help design injectors that are less sensitive to instabilities.

Performance of elliptical nozzles on the spray dynamics of convergent and constant section nozzles by means of a [formula omitted] coupled model

In this paper, a computational study on the differences between a convergent and a constant section elliptical nozzle is performed. Coupled internal-external flow simulations were carried out by means of a Σ-Y model experimentally validated. The differences reported in terms of internal flow and spray parameters present the cavitation as an important effect in the elliptical nozzle geometries. The conclusions suggest a mixture improvement potential for the cavitating elliptical nozzles.

Cold Spray Aids Development of Decentralized Energy Harvesters

Abstract Moisture-electric energy transformation (MEET) technology is being developed to further expand the utilization of environmental energy sources like thermal power, wind power, hydropower, and solar energy. The goal of the MEET technology is to extract power from environmental moisture with as few conversion processes as possible to satisfy the ever-growing demand for new and more portable energy sources The use of cold spray to produce MEET devices results in a greener process. While the suitability of polyether ether ketone as a MEET material was proven and the deposition of PEEK using cold gas dynamic spray (CGDS) was achieved, additional work is needed to fully characterize the manufacturing of PEEK-based MEET devices via CGDS.

An Attempt to Understand Stainless 316 Powders for Cold-Spray Deposition

Cold gas dynamic spray (CS) is a unique technique for depositing material using high-strain-rate solid-state deformation. A major challenge for this technique is its dependence on the powder’s properties, and another is the lack of standards for assessing them between lots and manufacturers. The motivation of this research was to understand the variability in powder atomization techniques for stainless steel powders and their subsequent properties for their corresponding impacts on CS. A drastic difference (~30%) was observed in the deposition efficiencies (DEs) of unaltered, spherical and similar sized stainless steel (316) powders produced using centrifugal (C.A) and traditional gas atomization (G.A) techniques. The study highlights more the differences on a precursor level. Using recent advancements in large scale statistical measurements, such as laser diffraction shape analysis and µCT scanning; and traditional methods, such as EBSD and nanoindentation, an attempt was made to understand the powder’s properties. Insights on powder size and shape were documented. Significant differences were observed between C.A and G.A powders in terms of grain size, fraction of high-angle grain boundaries (HAGBs) and nanohardness. The outcomes of this study should be helpful for understanding the commercialization of the cold-spray process for bulk manufacturing of powder precursors.

A novel approach for manufacturing cellular metallic structures using pulsed gas dynamic spraying process

A novel approach for manufacturing cellular metallic structures using pulsed gas dynamic spraying process

Spray dynamics of synthetic dimethyl carbonate and its blends with gasoline

Synthetic dimethyl carbonate (DMC) is a promising alternative or oxygenated additive fuel to reduce not only CO2 but also particle number (PN) emissions from gasoline direct injection (GDI) engines. Despite many investigations on the engine performance of DMC-gasoline blends in the literature, limited reports can be found focusing on their spray characteristics. However, a comprehensive understanding of spray characteristics is crucial to interpret the results of GDI engine tests. Therefore, this study was to examine the near-nozzle spray dynamics of the DMC-gasoline blends by using the X-ray phase contrast imaging technique. First, the fuel properties of the synthetic DMC and regular gasoline blends were quantified. Then, the near-nozzle spray dynamics were examined in both non-evaporating and evaporating conditions, and discussions were made accordingly to link the near-nozzle spray dynamics with fuel properties. It is found that increasing DMC content could enlarge the spray spreading angle and reduce the near-nozzle spray velocity by up to +22 % and –18 %, respectively. The near-nozzle-exit spray velocity depends sharply on the fuel density as the DMC content varies in the blends. However, this dependency gradually becomes insignificant as the spray propagating distance increases. Pure DMC has the largest Sauter mean diameter (SMD) and least droplet number than other blends, but they tend to be consistent as the ambient gas temperature increases. The existing empirical correlation is still feasible to predict the SMD of the DMC-gasoline blends, but certain tuning of the constants is necessary. Within the experimental conditions in this study, the DMC-gasoline blends should undergo the same spray breakup regime, i.e., the atomization regime.

Simulation study of fuel spray dynamics in a constant volume combustion chamber

ABSTRACT The OpenFOAM computational fluid dynamics code was used to investigate the performance characteristics of spray jet in a constant volume combustion bomb. The total duration of fuel spray was approximately 1.25 × 10 − 3 second, and the total mass of fuel sprayed was 6.0 × 10 − 6 kilogram. The results show that there was a positive and somewhat positive qualitative correlation between the profiles of the number of parcels and the mass flow rate of the injected fuel at between 0 ≤ t ≤ 4.4 × 10 − 4 second. Furthermore, at between 9.1 × 10 − 4 ≤ t ≤ 1.3 × 10 − 3 the number of parcels experienced a sharp rise while the injected mass flow rate was decreasing, see Figure 6. The results of the present study show that the spray droplet sizes vary from 0.25 \\mum to 150 \\mum which were found to be reasonably representative of measurement data that are usually observed at the top dead centre position of internal combustion engine test bed experiments. Furthermore, the results of the study show the contour plots of pressure and temperature. The pressure rise varies from the initial value of 50 bar to 75 bar at the end of combustion while the temperature rose from 550 ∘ K to its final value of 2800 ∘ K . The specific details of the results from this study are summarised in the conclusion section.

AXIAL ACOUSTIC VELOCITY INTERACTION WITH HOLLOW CONE LIQUID SHEET IN A SWIRLING FLOW FIELD

This experimental investigation concerns the effect of imposed axial acoustic velocity fluctuations on the primary atomization of a hollow cone liquid sheet in the presence of a strong air swirl. The atomization dynamics are elucidated by positioning the spray at an acoustic velocity node, antinode, and a mixed point in the standing wave field generated due to the imposed axial acoustic excitation. High-speed shadowgraph images acquired in-sync with dynamic pressure measurements are processed to clarify the unstable behavior observed in the spray dynamics; this was achieved by extracting key parameters such as breakup length, spatial growth rates, phase differences, and by employing Proper Orthogonal Decomposition (POD). A novel method to obtain the breakup length of a hollow cone spray from the position of maximum wave amplitude is presented. The breakup length is the smallest for the mixed point. The phase difference between the left and right half-angle fluctuations shows that the flapping motion of the spray is predominantly observed at the mixed point for different air-to-liquid ratios. Another novel approach is adopted to identify the physical mechanisms corresponding to each POD spatial mode by comparing POD spatial modes obtained from experiments to those generated artificially.

Coloristic properties of decorative copper coatings applied by cold gas dynamic spraying

The results of the coloristic properties research of art items with copper coatings applied by cold gas-dynamic spraying (CGDS), as well as the color determination technique, allowing to improve the approach to the decoration and restoration of art items, are presented. This allows us to study the quantitative properties of the color of decorative surfaces, which largely determines the quality and aesthetic properties of coatings and their subsequent decorative treatment.

Coloristic properties of decorative aluminum coatings applied by cold gas dynamic spraying (CGDS)

When making objects of environment design with metal coatings, it is important to consider not only the protective properties of the coatings, but also the decorative ones. The use of aluminum CGDS coatings with subsequent tinting on metal environment design castings will not only increase the corrosion resistance of artistic products, but also give them new aesthetic qualities.

Fabrication and characterization of aluminum-based powders multi-reinforced with nano- and microparticles

Multi-reinforced powders were obtained by high-energy ball milling in a planetary mill. The process of obtaining heterogeneous powders consisted of two stages. At the first stage, a nanocomposite powder of AlMg6 + 0.3 wt.% C60 was obtained. In the second stage, 10, 30, 50, and 70 wt.% Al2O3 were added to the obtained nanocomposite powder and processing continued. Methods such as scanning electron microscopy, X-ray diffraction, and particle size analysis were used to characterize the obtained powders. It is shown that after the first stage of processing, the particles of the composite powder are characterized by an irregular shape. C60 reinforcing particles in the form of nanosized agglomerates were fixed on the surface of aluminum powder particles. After the second stage of processing, the particle size of the powder mixture decreased from 17.8 to 12.3 μm, while the proportion of Al2O3 particles increased from 10% to 70% by weight. It is shown that the synthesized heterogeneous powders were a mechanical mixture consisting of complex composition agglomerates and micro-sized ceramic particles. Complex composition agglomerates were formed from nanocrystalline matrix material particles and C60, and also with Al2O3 microparticles embedded in them, as well as located on the surface. The concentration of Al2O3 particles on the surface and inside the agglomerates increased with increasing weight fraction of ceramic particles in the mixture. It has been found that the introduction of 10-70 wt. % Al2O3 into the powder mixture increases the microhardness of the powder particles by approximately 16-23%. The resulting multi-reinforced powder mixtures can be utilized for coating deposition using the cold gas dynamic spraying method.

INCREASING THE SERVICE LIFE OF THE COVERS OF THE GAS DISTRIBUTION MECHANISM

Micro-arc oxidation is a modern method of hardening aluminum alloy parts. Technological recommendations for the formation of reinforcing coatings by micro-arc oxidation on the working surfaces of the covers of the gas distribution mechanism of engines made of aluminum alloys recovered by the supersonic gas dynamic spraying method are still insufficiently developed. (Research purpose) The research purpose is developing a technology for restoring the covers of the gas distribution mechanism of engines made of aluminum alloys by supersonic gas-dynamic spraying with hardening by micro-arc oxidation, which allows significant increasing their service life. (Materials and methods) Powder materials of grades A-80-13, A-20-11 produced by the Obninsk Powder Spraying Center were used for supersonic gas dynamic spraying. It was noted that the main components of these powder materials are aluminum and zinc, as well as non-metallic ceramic components. A silicate-alkaline electrolyte of the «KOH-Na2SiO3» type was used for microarc oxidation as the most affordable, widely used and easily disposed of. (Results and discussion) We have developed a combined recovery technology with hardening of the working surfaces of the covers of the gas distribution mechanism of engines made of aluminum alloys, which includes the following basic operations: cleaning of the covers; their defecation; preliminary mechanical treatment; supersonic gas-dynamic spraying of worn surfaces; their subsequent hardening by micro-arc oxidation; finishing mechanical treatment of the coating and control. (Conclusions) The developed combined technology will allow an average of 2.4 times to increase the life of the covers in ordinary operation. This technology is universal, and the possibility of restoring the covers of foreign engines is especially relevant due to the need for large-scale import substitution.

Комплексный анализ параметров распыления назальных спреев, содержащих антибиотики, противовоспалительный и сосудосуживающий компоненты

Objective. To compare spraying parameters of two multicomponent nasal sprays, Polydexa with phenylephrine (Polydexa with PE) and its generic, to choose the spary with an optimal quality of spraying. Materials and methods. We used a silicone model of the nasal cavity (Koken Co. Ltd., Tokyo, Japan) to analyze spray distribution in the nasal cavity. A planar simulation model (a plate for thin-layer chromatography “silica gel 60 without fluorescence”) was used to assess spraying parameters and width. Dynamic characteristics of spraying and the dispersed composition of sprays were evaluated using shadow photography. Results. We evaluated the distribution of the spray dose in the nasal cavity using the silicone nose model. We compared dose distribution between the two sprays studied using both full and half-filled bottles. We assessed the breadth and homogeneity of the spray by analyzing the track on a planar simulation model. Shadow photography was used to evaluate the dynamic spraying characteristics, such as total duration, duration of the individual stages of spraying, spray-cone angle, as well as dispersion characteristics, including mean particle sizes and particle size distributions. Conclusion. Experiments with the silicone nose model demonstrated that Polydexa with PE creates a larger area of spray distribution than generic, which indicates its better coverage of the nasal mucosa. Сomparison of the dynamic spraying characteristics showed a significant difference between the two sprays studied caused by differences in the design of their vials. The dispersed compositions of both sprays were similar, although Polydexa with PE produced a more homogeneous and finely dispersed spray than generic. Comparison of the shape and area of the spraying track on a planar simulation model showed a wide but uneven spraying of generic and a narrow, dense and homogenous one of Polydexa with PE. Key words: nasal spray, silicone nose model, shadow photography, spraying characteristics, neomycin, polymyxin B, dexamethasone, phenylephrine

Transient Nozzle-Exit Velocity Profile in Diesel Spray and Its Influencing Parameters

Article Transient Nozzle-Exit Velocity Profile in Diesel Spray and Its Influencing Parameters Ya Gao 1, Weidi Huang 2,*, Raditya Hendra Pratama 2, and Jin Wang 1 1 Advanced Photon Source, Argonne National Laboratory, 9700 S Cass Ave, Lemont, IL 60439, United States 2 Research Institute for Energy Conservation, National Institute of Advanced Industrial Science and Technology, Ibaraki 305-8564, Japan * Correspondence: wd.huang@aist.go.jp Received: 24 September 2022 Accepted: 10 November 2022 Published: 25 December 2022 Abstract: The primary breakup in the diesel spray relies closely on the initial dynamics at the nozzle exit. However, solid experimental results are still missing due to the great difficulties in measuring the near-nozzle spray dynamics. This study proposed an investigation focusing on the transient nozzle-exit spray dynamics by taking advantage of the X-ray phase contrast imaging technique. The in-nozzle needle motion, spray morphology, and dynamics at a commercial diesel nozzle exit were obtained. Experimental results were then examined, linking with the needle motion to understand the transient spray dynamics. The effect of the initial conditions (i.e., the injection pressure and ambient density) on the resulting trends were also considered. It is found that the nozzle-exit spray morphology and velocity profile highly relate to the in-nozzle needle lift. Once the needle sufficiently opens, the spray reaches steady status, and the nozzle-exit velocity becomes almost constant. The spray width slightly increases with the increasing ambient gas density or the decreasing injection pressure. Injection pressure significantly affects the spray velocity amplitude, whereas the ambient gas density alters the spray-velocity profiles mainly in the periphery of the spray. Finally, an analytic analysis was conducted to further examine the transient spray axial velocity with the changing radial locations. It is found the nozzle-exit spray velocity can be predicted in the Gaussian-type formula. This feature likely relates to in-nozzle flow characteristics.

Numerical investigation of AdBlue film formation and NH3 conversion in generic SCR system using Eulerian stochastic fields method

In this paper, the Eulerian stochastic fields (ESF) method in a LES framework is applied to a generic selective catalytic reduction (SCR) configuration in order to retrieve seamlessly the effect of turbulence–chemistry interaction on the NH3-conversion and AdBlue film formation. The ESF method is based on the transport equation of a joint scalar filtered density function. The injection of AdBlue and relevant spray dynamics are modeled by the Lagrange-particle description where a computational parcel represents a cluster of real AdBlue droplets. Owing to the low injection pressure, weak atomization of AdBlue leads to intense droplet wall-impingement and film formation on the SCR duct wall and/or on the mixer elements, if present. A 2-D thin film approach is adopted to model the film formation and dynamics in combination with multi-regimes droplet–wall interaction model. After verification tasks against the reference data for simple gas phase reactive cases, the verified ESF method is coupled with a one-equation based LES turbulence model together with the Lagrange particle-tracking which is combined with the 2-D thin film approach to simulate the AdBlue injection and the film formation in the generic SCR configuration. At first, the assessment of the adopted LES mesh is carried out in terms of the so-called LES quality of index to determine the optimal mesh resolution. Next, to ensure the convergence with respect to the number of required ESF and mesh resolution, SCR simulations are performed by using various (2, 4, 6, 8, 12 and 16) stochastic fields and also with refined mesh. Thereby, the sensitivity of the predictive capability of the numerical tool is evaluated for the production of NH3 and HNCO with and without ESFs. This clearly indicates the importance of an accurate description of the turbulence–chemistry interaction to retrieve reliably the conversion of NH3. Finally, the film dynamics especially the evolution of the film thickness described with six required ESF and without ESF is compared with experimental data from the generic SCR configurations. To further demonstrate the potential of suggested numerical approach, a detailed numerical analysis is provided in terms of spray-impingement dynamics, scalar uniformity index, droplet life time and characteristics of the droplets prone to form solid deposits in the monolith channel.

Investigation on Spray Morphology, Droplet Dynamics, and Thermal Characteristics of Iso-Pentane Flashing Spray Based on OpenFOAM

Leakage of high-pressure hydrocarbon liquid from a vessel or pipe may easily result in a two-phase flashing spray due to the rapid pressure drop, which might produce catastrophic consequences. Understanding the flashing spray process is essential to prevent these consequences and minimize the impact. This paper conducted a numerical study through OpenFOAM to investigate the two-phase behavior of flashing spray using a volatile and flammable substance of iso-pentane. The evolution of spray morphology and the distributions of droplet temperature, diameter, and velocity under various initial injection pressures (Pinj) and temperatures (Tinj) were investigated. The simulation result showed good agreement with the experimental result in spray morphology under various Pinj and Tinj. The simulation results indicate that a higher Pinj causes a larger gas phase diffusion length, while Tinj contributes little to this length. However, increasing the Pinj and Tinj shortens the liquid penetration distance. Near the nozzle exit field of about 10 mm, liquid droplets experience a rapid decrease in diameter and velocity along the spray central axis. Meanwhile, spray presents an obvious expansion via the introduction of a spray angle as the input boundary condition of the simulation and droplet temperature has a large gradient toward the radial direction within this field. Droplets in the spray’s downstream region achieved a more stable state with less change in droplet diameter, velocity, and temperature.