Gas Crossflow Research Articles

Effects of Viscosity and Shear-thinning Characteristics of a Liquid Jet in Air Crossflow

In the present study, we performed numerical simulations of a single liquid jet with varying viscosities and non-Newtonian characteristics in uniform gas crossflows at different velocities, to investigate the effects of liquid properties on jet deformation and breakup behavior. By utilizing air as the gas and examining both Newtonian fluids with different viscosities and a shear-thinning fluid as the liquid, we aimed to uncover the intricate dynamics governing liquid jet deformation and breakup under crossflow conditions. At lower air velocities, the liquid jet bent and elongated without undergoing breakup, regardless of the viscosity and shear-thinning characteristics. Notably, in the case of the shear-thinning fluid, the effect of the viscosity was more pronounced in the outer regions of the liquid jet than at its center. In contrast, at higher air velocities, viscosity and shear-thinning characteristics significantly affected jet breakup; the high-viscosity Newtonian liquid jet resisted breakup, while the low-viscosity jet broke up into threads, with a decrease in apparent viscosity leading to increased penetration height.This study introduces a novel method for quantifying the energy transfer from gas to liquid jet, using pressure differences between a deformable liquid jet and an equivalent rigid cylinder as a reference. This approach allows for the separation of bending and breakup energy components, offering new quantitative insights into the forces driving jet deformation and breakup. These insights advance the current understanding of fluid-structure interactions in crossflow conditions.

Energy Recovery from Natural Gas Hydrate and Shallow Gas Reservoirs: Exploring the Impact of Interlayer Gas Cross-Flow Behaviors

Energy Recovery from Natural Gas Hydrate and Shallow Gas Reservoirs: Exploring the Impact of Interlayer Gas Cross-Flow Behaviors

Effect of elevated crossflow temperature on jet primary atomization

Liquid jet in hot gas crossflow is widely employed in industrial combustion devices, especially in the propulsion systems. In this work, the effect of elevated crossflow temperature on the primary atomization of a liquid jet is experimentally investigated, including breakup regime, surface wavelength, column breakup height, and near-field trajectory. The experiments are conducted at crossflow temperatures of 300 K and 500 K, with gas Weber number ranging from 8.82 to 67.55 and momentum flux ratio from 10 to 50. The gas Weber number and momentum flux ratio are kept constant via increasing the crossflow velocity when crossflow temperature increases. The results show that the elevated crossflow temperature weakens surface breakup, particularly at high momentum flux ratios, which makes the transition of breakup regime from column breakup to surface breakup require higher gas Weber number or momentum flux ratio. Besides, the elevated crossflow temperature leads to a slight increase in surface wavelength, column breakup height and near-field trajectory, with the increase in trajectory being more pronounced at lower gas Weber numbers. Finally, an empirical correlation for the near-field trajectory is obtained, including the effects of crossflow temperature, gas Weber number, and momentum flux ratio.

Adaptation of conical liquid sheet and spray morphologies to cross-flowing gas

A variety of industrial devices use liquid injection into the traverse stream of air. Ambient flow changes the spray characteristics, which can alter a system's function. Two different spill-return pressure-swirl atomizers (SRA) were investigated under cross-flow. One of the tested atomizers generates a conical liquid sheet with shorter breakup lengths due to reduced internal air-core stability. Phase Doppler anemometer (PDA) was used for 2D velocity and droplet size measurements, along with high-speed visualization to record instantaneous spray behaviour. A wide range of operating parameters was tested, e.g., inlet pressure (pl) ranging from 0.25 MPa to 1 MPa, spill-to-feed ratio (SFR) from 0 to 0.9, and cross-flow velocity from 0 to 32 m/s. As the cross-flow velocity increases, the spray starts to tilt and the breakup length (lb) shortens as a result of increased aerodynamic forces. This reduces the differences between atomizers. Moreover, the droplet diameter depends on the lb, yet no semi-empirical model was found to accurately predict the droplet sizes. A map of breakup modes was established, and a transition point from long- to short-wave mode was identified. The Linear Stability Analysis of the liquid sheet breakup was used and compared with a semi-empirical approach for the first time for the SRA and cross-flow conditions. The results imply that considering only quiescent ambient conditions during atomizer development might not lead to the optimal design.

Model of cross-flow interference index and application for multi-layer commingled production in Sulige tight sandstone gas reservoir, Ordos Basin, China

Multi-layer commingled production is the main feature of gas well development in Sulige tight sandstone gas reservoir, Ordos Basin. Identifying potential interference between layers and devising methods for their characterization are crucial considerations for optimizing the development of gas reservoirs. To address these issues, we designed a physical simulation experiment process and interlayer commingled mining schemes, implementing various interlayer combination modes. The results show that a common occurrence in the process of multi-layer commingled production of tight gas and water layers, whether it involves gas layers production alone or simultaneous production of gas and water layers. This phenomenon involves the crossflow of gas and water between layers, resulting in interlayer interference and a subsequent reduction in gas reservoir recovery. Based on these observations, the concept of an interlayer interference index in multi-layer commingled production in tight sandstone gas reservoirs is proposed. The interference index model is obtained by fitting the multiple linear regression method, showcasing its correlation with the physical properties of the reservoir. High water saturation and a significant permeability ratio of the water layer to the gas layer (exceeding the critical value of 1) can result in the early occurrence of interlayer interference and yield a higher interference index. Furthermore, based on the interference index model, a novel method for productivity evaluation of gas wells in tight gas reservoirs is established. The calculations demonstrate that the interference index curve effectively characterizes the interlayer interference performance of gas wells. The productivity and production performance predictions derived from this model align closely with historical production data, affirming the model's effectiveness and accuracy. Therefore, the interference index model emerges as a valuable tool for predicting the productivity and production performance of gas wells in Sulige tight sandstone gas reservoirs. The research results have important theoretical guidance and practical significance for the efficient development of Sulige tight sandstone gas reservoirs.

Combined optical connectivity and optical flow velocimetry measurement of interfacial velocity of a liquid jet in gas crossflow

Liquid jet in crossflow (LJIC) is a process in which a high-speed gas crossflow deforms and shears a continuous liquid flow into tiny droplets. This study quantifies the liquid surface motion of LJIC during the primary breakup process, which has not been quantified due to the optical limitation close to the nozzle exit. The interfacial velocity of a breaking liquid jet indicates the local interaction of the gas and liquid flows and determines the initial velocity of the stripped droplets. The local interfacial liquid velocities of LJIC have only been estimated from theoretical and computational studies, which have not been evaluated from measurements. Optical Connectivity (OC) introduces a laser beam through an atomiser nozzle and relies on total internal reflection at the liquid interface to propagate the laser light inside the continuous liquid to record the instantaneous features of the interface of the continuous liquid during the primary atomisation at the near nozzle region through imaging of the emitted fluorescent intensity from the liquid flow. The current study combines Optical Connectivity with Optical Flow Velocimetry (OFV) to quantify the time-dependent, local interfacial velocity of the liquid interface structures of the LJIC for gas Weber numbers between 14.9 - 112.6 and liquid-to-gas momentum ratios between 2.1 - 36.4. The combined OC-OFV measurements of the spatial distribution of the mean and fluctuating values of the different components of the liquid interfacial velocity of LJIC demonstrate how the gaseous shear and liquid jet geometry interact to influence the atomisation process.

Optimization of the Performance of a Cross-flow Gas Mixer for a Partial Oxidation Reactor Through Numerical Modelling

Efficient mixing of gases has many different applications in science and engineering. Gas mixers are often used in chemical reactors that use pre-mixed gases in their reaction process. In this work, we vary the geometry of a mixer in order to maximize the uniformity of the mixed gases. The mixing happens in several pipes that have small cross-flow inlets on the sides that stimulate turbulent mixing. The mixer geometry is varied by changing the configuration of the small cross-flow inlets on the pipes, and the mixing quality is quantified by the distribution of gases at certain distances from the cross-flow inlets. The flow was modelled by using open-source finite volume code. We show that standard RANS k-ϵ steady state numeric models greatly overestimate the mixing rate between different gasses, as it ignores transient changes in the flow. Transient simulations using a LES turbulence model show that the gas concentrations in the mixing pipe exhibit a pulsating behavior. The amount and the configuration of the cross-flow inlets play a significant role in how the gases mix and how the concentrations vary over time. The resulting mixer geometry will be used as a part of a partial oxidation reactor design in the future.

Experimental Study on Breakup Characteristics of Hollow Cone Spray in Gas Crossflow

Hollow cone spray with a medium spray half-cone angle (in the range of 36°–45°) exposed to a gaseous crossflow is a situation that has been extensively investigated experimentally. In this experiment, flow visualization techniques are employed to examine the initial liquid sheet thickness at the nozzle orifice exit and the sheet breakup process. The dynamics of the primary breakup of the sheet is analyzed based on the observations of the sheet breakup in the near-nozzle region. The experimental results show that the breakup mechanism of the liquid sheet varies greatly depending on liquid centrifugal momentum and aerodynamic force. Four distinct breakup modes are observed, and the breakup regimes are mapped in the parametric space based on the liquid Weber number (84–2175) and the liquid-to-air momentum ratio (22–8455). It is observed that the leeward side of the sheet is dominated by shear oscillation breakup within the range of the liquid-to-air momentum ratio less than 600. The influences of the aerodynamic Weber number on breakup frequency and the number of surface waves observed on the leeward side sheet are discussed by analyzing the spray images. The breakup-regime transition criteria for hollow cone spray in crossflow and the trajectory of spray in crossflow are proposed by employing a multivariable regression method.

A new Sauter mean diameter correlation suited for the gas cross flow in packed bed reactors based on PSO optimization algorithm

ABSTRACT Cross-flow in packed bed reactors (PBRs) was often encountered in industries. However, the effect of inlet and outlet nozzle position on the droplet diameter was little considered. In this study, the effect of inlet and outlet nozzle angles of the gas on the spray disintegration was assessed by changing the angle (i.e., 0°, 30°, 45°, and 60°). A 3D computational fluid dynamic (CFD) model was involved to understand the influence of cross-flow of a single and two-phase gas–liquid flow in PBR. An Eulerian–Lagrangian approach (E-L) was used for solving the flow pattern and the spray disintegration. The RNG k-ε model was employed to simulate the turbulent flow. First, an indirect validation of the cross-flow packed bed was proposed based on a single phase. Second, the variation in parameters such as superficial liquid and gas velocity, mass flow rate, and gas angle orientation were investigated and graphically represented. A new correlation of Sauter mean diameter was developed using particle swarm optimization (PSO) with respect to gas angle orientation. This correlation was done for 64 cases and validated with existing correlations in the literature, giving an MAPE of ±12% and indicating a good agreement with the data.

VALIDATION OF A STOCHASTIC BREAKUP MODEL FOR TURBULENT JETS IN HIGH-SPEED CROSSFLOW: ASSESSMENT OF TURBULENT INTERACTIONS AND SENSITIVITY TO BOUNDARY CONDITIONS

Improving the mixing of fuel and air by injecting a turbulent liquid fuel jet into a high-speed cross-flowing gas can reduce the emissions of gas turbine applications. To facilitate and hasten the development of such low-emissions technologies, accurate predictions of the spray characteristics are needed. The objective of the present study is to validate the predictive capabilities of a stochastic breakup model for turbulent transverse jets over a wide range of representative pressures and atomization characteristics. The effect of turbulence modeling is also assessed to provide accurate and computationally less expensive Eulerian-Lagrangian transient approaches. To do so, the predictions made with the large eddy simulation (LES) approach for different subgrid-scale (SGS) models and with the synthetic eddy method (SEM) are compared to the ones made using the unsteady Reynolds-averaged Navier-Stokes (RANS) approach with and without a turbulent dispersion model. The sensitivity of the numerical methodology to the upstream velocity profile, pressure, and momentum flux ratio were also assessed. Properly accounting for the upstream gas velocity profile was found to be critical to ensure accurate predictions of the spray characteristics. The unsteady RANS (URANS) turbulent approach coupled with the turbulent dispersion model showed good agreement with experimental data, but the LES approach tends to overpredict the spray penetration and underpredict the Sauter mean diameter (SMD). This could be due to the lower turbulent interactions it predicts, which may lead to lower momentum transfer between the phases.

Experimental validation of a coupling concept for drop formation and growth onto porous materials by high-resolution X-ray imaging technique

Droplets formed on the hydrophobic surface of a porous medium exposed to a cross-flowing gas stream have a strong influence on the mass, momentum, and energy exchange across the porous interface, being of importance in several physical systems and engineering applications, like fuel cells. However, the fluid displacement front is highly complex at the pore-scale, since it is characterized by the surface wettability and a contact angle variation along the triple line. Furthermore, the droplet formation is affected by the pore geometry and the surface wettability. These result in a challenging multi-phase scenario with controversial literature, and few studies consider the detailed mechanism of droplet formation on the surface of the porous medium. In this work, two multi-scale simulations for the emerging water droplet from a single hydrophobic capillary pore opening into the gas phase are validated by a benchmark experiment with the help of a high-resolution X-ray imaging technique to characterize the droplet growing. A three-domain approach (gaseous free flow, interface and porous medium, FIP) was compared with a two-domain approach (based on a free-flow and the porous medium, FP). Whereas the three-domain approach introduces two sets of coupling conditions, one for the free flow-interface and one for the interface-porous medium, the two-domain approach introduces only one set of coupling connections for describing the interaction between the domains. In both approaches, droplet formation and growth alter the coupling conditions between the domains. While the FIP approach treats the porous medium as a continuous matter, it is resolved discretely with the help of a pore network in the FP approach. Both approaches show good agreements with the experimental observations and high correspondences for the drop volume, radii and contact angle evolution. The proposed models provide a base for future developments and help to gain a better insight about the impact of the droplet formation on the interface in a coupled free flow-porous medium system.

Combined Optical Connectivity And Optical Flow Velocimetry For Measurement Of The Interfacial Velocity Of A Liquid Jet In Gas Cross-Flow

Liquid jet in crossflow (LJIC) is a process in which a high-speed gas crossflow deforms and shears a continuous liquid flow into tiny droplets. This study quantifies the liquid surface motion of LJIC during the primary breakup process, which has not been fully assessed due to limited optical access close to the nozzle exit. The interfacial velocity of a breaking liquid jet indicates the interaction of the gas and liquid flows and the initial velocity of the stripped droplets. However, the local interfacial liquid velocities have not been measured, since no measurement technique is available, and they have only been estimated from theoretical and computational studies. Optical Connectivity (OC) is a new optical technique, which introduces a laser beam through an atomiser nozzle and relies on total internal reflection at the liquid interface to propagate the laser light inside the continuous liquid. This allows the recording of the instantaneous features of the disintegrating continuous liquid and its interface during the primary atomisation at the near nozzle region through imaging of the emitted fluorescent intensity from the liquid flow. The current research reports time-dependent OC measurements of the temporal evolution of the liquid interface structures along a LJIC. The LJIC breakup behaviour is reported for different atomisation regimes, as determined by non-dimensional parameters. Optical Connectivity is combined with Optical Flow Velocimetry (OFV) to quantify the local interfacial liquid velocities of liquid interface structures of the LJIC for a range of gas Weber numbers between 14.9 - 112.6 and liquid-to-gas momentum ratios between 2.1 - 36.4. The combined OC-OFV measurements report the spatial distribution of interfacial velocities along the surface of LJIC and reveal the physics of the contribution of gaseous shear and liquid jet geometry on the atomisation process.

Heat and Mass Transfer Correlations for Staggered Nanoporous Membrane Tubes in Flue Gas Crossflow

Abstract The use of transport membrane condenser (TMC) technology to recover heat and mass from the flue gas has been increasing recently. The heat and mass transfer from the TMC tube bundle have been studied experimentally and numerically, and several numerical models have been proposed. Although many heat transfer and pressure drop correlations are available for single-phase flows over tube bundles of solid walls, to the best of our knowledge, there is a lack of heat and mass transfer and pressure drop correlations for the porous membrane tubes with condensing flue gas that cover a wide range of parameters. In this study, the heat transfer, mass transfer, and pressure drop imposed by the crossflow ceramic nanoporous tubes in TMC have been studied numerically within wide ranges of tube diameters (4.57–7.62 mm), number of rows (2–24 rows), and Reynolds number (170–8900), under flue gas condensation. The turbulent flow of the flue gas mixture was modeled by the shear stress transport SST k−ω turbulence model. A hybrid/mixed condensation model written in user defined functions was employed to calculate the water vapor condensation rate. Numerical results with condensing flue gas are compared to available correlations for single-phase Nusselt number and pressure drops in the literature. It was found that except for selected conditions, the single-phase correlations noticeably differed from the TMC numerical results. Empirical TMC correlations for heat transfer and pressure drops with respect to condensation rate, number of rows, and the nanoporous membrane geometrical properties were derived thereby. The derived correlations for TMC show a good agreement with numerical data for all investigated parameters and can predict the 96% of the convective Nusselt number, overall Nusselt number, and friction factor inside the TMC within ±10%, ±10%, and ±15%, respectively. The effects of key parameters on the heat transfer, mass transfer, and pressure drops are illustrated and discussed in detail.

Practical aspects of induced structurization of rock mass

Ground control is connected with monitoring of deformations of enclosing rock mass in the course of mining for ensuring stability of underground openings. One of the negative consequences of redistribution of rock pressure in an extraction panel during mining operations is swelling of floor rocks. The present article considers mining conditions of coal seams using the features of formation and development of nonlinear structurization of rock mass during longwall advance, earlier revealed at the Institute of Coal. The calculation basis is the developed parametrical model of geomechanical processes in rock mass during mining using the longwall top coal caving method. The rock mass is considered at the first approximation as a uniform isotropic medium without regard to mechanical properties of rocks. The model rock mass is presented as a set of manmade geomechanical layers. Their formation begins from a coal seam being mined and develops with the longwall advance with regard to elastic energy of rock mass. In the manmade change of external conditions, the rock mass rebates its energy potential via arching and movement. The bodies of “arches of movement” tend to paraboloids in shape. Formation of such shapes corresponds to the concept of minimum energy spend for the creation of a new surface under uniaxial unloading. The height of the arches-paraboloids is equal to the thickness of geomechanical layers at different scales of the structural hierarchy of rock mass. The horizontal dimension of the archesparaboloids is divisible by a longwall length. It is possible to detect sites of increased rock pressure applied to the boundaries and roof support of underground openings by means of geometrical overlapping of circles having diameters equal to the basal parts of displacement arches with load-bearing edges. Integration of the displacement arches of the adjacent extraction panels leads to connection of their mined-out areas and to gas cross-flow between them. The cardinally new approach to understanding geomechanical processes in rock mass can allow predicting adverse phenomena of rock pressure and the increased methane emission during high-rate longwalling.

Сapillatry effects manifested in the process of draining a liquid film that evaporated into a gas cross flow

The aim of the work is to determine the regularities of changes in the width of the flowing liquid film evaporating into a gas cross flow resulting from thermocapillary and concentration-capillary effects (Marangoni effect).
 The research was carried out experimentally employing an installation with a heated (working) surface, on which a liquid film (water or aqueous glycerol solution) was flowing. A flow of air was fed into the space between the working surface and the enclosing wall located at a distance from it, evenly in height and perpendicularly to the film movement. The film width was measured along the height of the working surface and the obtained dependencies were presented as graphs for different parameters of the flowing process.
 In all experiments, the graphs have an initial section with a sharp decrease in the film width, below which its change occurs smoothly. The degree of reduction in the film width depending on the parameters of the flowing process can reach 80%. In laminar mode, the reduction of the film width is more uniform than in turbulent mode, when some rise of the curves beyond the initial section is observed and can be explained by intensive mixing of the liquid. As the initial liquid flow increases, the degree of reduction in the film width decreases. Significant influence on the change in the film width is exerted by the temperature of the working surface during the flow of water: with increasing temperature, the film width decreases. At values of this temperature greater than 100℃, the rise of the curves is observed, possibly associated with the transition to volumetric evaporation.
 When the glycerol solution is flowing, the temperature of the working surface less influences the change in film width, although its decrease along the height of the working surface is greater than for water. The process parameters such as initial liquid temperature, initial solution concentration, and velocity and air temperature have relatively little effect on the change in film width. To correct the area of the film evaporation surface, determined by technological calculation, the width of the average evaporation surface is introduced under capillary effects. Its value increases with the initial liquid flow. For water, this dependence is characterized by a jump-like decrease in the film width in the transition from laminar to turbulent flow mode. This effect is absent on the dependence for glycerol solution, which can be explained by its higher viscosity. As the temperature of the working surface increases, the width of the average evaporation surface of the film decreases, some decrease being also observed with an increase in air velocity. Empirical equations for estimation of the correction factor were obtained. Capillary effects in this case are expressed by decrease in the width of the film at the height of its runoff, which leads to the need to correct the area of the film evaporation surface determined by technological calculation.

A treatment protocol for controlling gas oil ratio in heterogeneous carbonate reservoirs by foam injection: Case study simulation

In this study, foam is selected to treat production wells of heterogeneous reservoirs that are suffering from high amounts of gas oil ratio (GOR). To this end, a numerical study is carried out by injecting foam through the perforations that produce high amounts of gas to block the gas path and allow much more oil to be simultaneously produced from the remaining perforations by applying a new technology in well completion. For this purpose, three heterogeneous synthetic base sectors are simulated in which large amounts of injected gas are produced from the upper, middle and lower perforations of the producing well, known as gas overriding, gas channeling-midriding and gas channeling-underriding, respectively. Since Kv/Kh is an important, decisive and effective parameter, different values of it have been considered for each of three base sector models including 0.001, 0.01, 0.1, 0.3, 0.5, 0.7, 0.9 and 1.0. Then, depending on the magnitude of Kv/Kh, the most optimal treatment method is sensitivity analyzed. In the following, foam injection parameters, e.g. surfactant concentration, depth of packer set, foam injection sequence and foam injection rate are sensitivity analyzed. Also, the phenomenon of gas cross-flow during the treatment process is investigated. The simulation results show that if after some time following well treatment, the GOR level increased, it is suggested to take a production test to determine what length of the production well below the packer produces lots of gas to set the packer at the lower depth and inject a larger volume of foam to block that gas path so that the GOR is reduced. The results also conclude that the magnitude of Kv/Kh on one hand and the location of gas entry to the production well on the other hand play a key role in the selection of the best treatment scenario in heterogeneous reservoirs. This has led to presenting a protocol for treatment of high GOR production wells in a wide range of reservoirs based on anisotropy ratios. Finally, in order to validate the protocol, a real specific sector of a heterogeneous carbonate reservoir located in the Middle East, in which the GOR level has increased, is simulated and treated. The results indicate that the protocol is efficient and causes a reduction in GOR by 60%. • A comprehensive treatment protocol for high GOR production wells is presented. • The effect of different anisotropy ratios is investigated. • A new method of foam injection/oil production is used at the simulation scale.

Application of Planar Laser Rayleigh Scattering for Measurement of Gas Temperature Distributions in Effusion Jet Cooled Panels Exposed to High Temperatures

Abstract This experimental study examines the use of planar laser Rayleigh scattering to measure instantaneous gas temperature distributions at different heights above the surface of an effusion cooled plate. An experimental test rig was used to model combustor conditions with a bulk crossflow temperature of 1500 K. Carbon dioxide was used as coolant at multiple blowing ratios ranging from 1.12 to 11.1. A “temperature-pegging” methodology was used to process Rayleigh light scattering images to create high resolution and accurate temperature images at heights of 2, 2.75, and 3.5 mm above the surface of a prototypical effusion plate. Measured temperature distributions were used to calculate root-mean-square (RMS) distributions, and were also converted to film effectiveness maps based on the upstream crossflow gas and effusion coolant temperatures. It is found that the film cooling region spreads upstream with increasing effusion jet blowing ratio parameter. The RMS deviation of gas temperatures over each measurement plane shows that the RMS fluctuations are low inside and outside the effusion film, but are high near the film edge. At a given height above the effusion panel, the RMS fluctuations decrease in the film region with increasing blowing ratio. Film effectiveness follows similar trends with high film effectiveness region expanding with increasing effusion jet blowing ratios.

Evaluation of the Efficiency of Transfer Processes in a Rotary Apparatus

This paper considers the possibility of using vortex devices for interphase interaction while carrying out various physical and chemical processes in the chemical, food, gas production, construction and other industries. In the processes of mass transfer, one or several distributed components perform the transition from one phase to another through the active surface of their interface. To perform the implementation of these processes in absorbers, rectifiers, adsorbers, extractors effectively, the developed surface of the interacting phases acquire s a particular significance. Most of the chemical reactions in reaction devices and heterogeneous media occur when the initial distributed substances are supplied to the reaction zone and when the resulting products are removed from the chemical interaction zone through the phase interface. The processes under consideration are also used in solving environmental problems, viz. for sanitary cleaning of ventilation gases, wet cleaning of emissions. During evaporation, absorption, rectification, wet cleaning of gases and other processes, the problem of preventing the entrainment of liquid droplets with the gas flow is of great importance. One of the designs of a rotary multistage mass transfer apparatus is considered which makes it possible to achieve a finely dispersed liquid spray, uniform in height, with an ascending cross-flow of gas. The diagrams of installations for carrying out the experiment are given. On the basis of experimental studies, the dependence of the average diameter of dispersed liquid droplets on the geometric and hydrodynamic parameters has been obtained. The dispersed composition is described and dependences are given for determining the main characteristics used in physicochemical processes. The theoretical calculation of the movement of particles of the dispersed phase in the working volume of the apparatus at different flow rates of liquid and gas has been carried out. Theoretical and experimental methods were used to estimate the carryover of the liquid phase, an analysis of the process was carried out, and practical recommendations were given.

Numerical and experimental investigation into gas flow field and spattering phenomena in laser powder bed fusion processing of Inconel 718

Accumulated spatters not only deteriorate the quality of the built parts in terms of surface roughness and/or density but also sabotage the whole fabrication process via damaging the powder re-coater. A cross-flow of inert gas inside the processing chamber is by far the only effective mean of removing the spouted spatters from the build platform. Despite the essential role, there are few efforts to investigate the interactions between the cross-flow dynamics and the spouted spatters, and hence, to optimize the design and settings of the cross-flow. Therefore, in this study, a coupled computational fluid dynamics (CFD) – discreate element method (DEM) simulation framework is proposed to study the interactions between the flow field and the spouted spatters during the single scan process. The simulation results for the maximum ejection distance and maximum ejection height of the spatters were shown to deviate from the numerical results reported in the literature by no more than 15%. Moreover, the simulation results for the distribution of the landing sites of the spatters were consistent with the experimental observations, which showed that a large number of large spatters landed near the scan track, while a small number of large spatters landed at a greater distance from the scan track. To the best of the authors’ knowledge, this study represents the first reported attempt to use a coupled CFD-DEM simulation framework to investigate the spatter dynamics within an LPBF chamber and to validate the results with experimental observations and published data. The proposed model is an important tool to optimize and calibrate the cross-flow inside the L-PBF processing chamber.

Dynamic mode decomposition of elliptical liquid jets in crossflow

The dynamics of round and elliptical liquid jets in subsonic crossflow was studied using high-speed imaging technique. The experiments were performed at constant gaseous Weber number and liquid–gas momentum flux ratios of 6.45 and 17.87, respectively, with orifices of different aspect ratios (AR) having an equivalent diameter of 0.43 mm. All of the cases were carried out inside an open-loop subsonic wind tunnel with a test section of 100 mm × 100 mm × 750 mm. For each case, dynamic modes were generated directly from the snapshots using a variant of the Arnoldi method known as the dynamic mode decomposition (DMD). The DMD results indicate that elliptical liquid jets have more small-scaled patterns with higher frequencies compared with the round liquid jets. As the first attempt to investigate the dynamics of elliptical liquid jets in crossflow, this study captures the dominant spatiotemporal structures. We also found that the orifice AR can significantly alter the jet wavelengths. The data from this study contribute to understanding the behavior of elliptical liquid jets exposed to gas crossflow in an enhanced capillary breakup regime.