Atomization Model Research Articles

An improved theoretical formulation for Sauter mean diameter of pressure-swirl atomizers using geometrical parameters of atomization

This study discusses the development of a mathematical model that is capable of predicting the drop size mean diameter of the spray generated by a pressure swirl atomizer, considering the effects of the liquid's viscosity and the geometrical parameters of this type of injector, as well as the angle of incidence of the inlet channels (ψ and β) and atomization parameters (k, ϰ), obtained from hyperbolic relations. Additionally, this model investigates the phenomena of rupture and stability that are observed in the conical liquid film, in which the importance of a new geometrical parameter of atomization, “ϰ”, which immediately influences the drop size diameter of the spray, should be highlighted. The results that are obtained using this model are compared with analytical results of Couto, Wang and Lefebvre, Jasuja, Radcliffe and Lefebvre, experimental results and numerics (Hollow cone atomization model), using the Ansys Fluent software for the validation and consistency of the model proposed in Rivas (2015). This model yields good approximations as compared to that yielded using other alternative mathematical models, demonstrating that the new atomization geometric parameter “ϰ” is an “adjustment” factor that exhibits considerable significance while designing pressure swirl atomizers according to the required SMD. Furthermore, this model is easy to use, with reliable results, and has the advantage of saving computational time.

Multiphase model to predict particle size distributions in close-coupled gas atomization

A novel two-stage multiphase model is developed for close-coupled gas atomization by combining formulations available in the literature. Primary atomization is simulated using an Eulerian atomization model, and the outputs are used as inputs of a Lagrangian particle tracking approach to predict the particle size distribution resulting from secondary atomization. The results given by the primary atomization model are validated with published Direct Numerical Simulations (DNS) values and by comparison with experimental images of the spray, while the particle size distributions obtained are accurately fitted to a log-normal distribution, and with powder mean diameters showing good agreement with experimental data. The variation of powder characteristic diameters d10, d50, and d90 as a function of the gas-to-melt mass flow rate ratio follows correct trends, and the values of powder mean diameters d50 are correctly predicted by the model.

Stochastic Model of Liquid Fuel Spraying at High Pressures and High Reynolds Numbers

The paper describes the main features of the combustion of liquid fuel injections, developed a stochastic model for the atomization of liquid fuels injected into the combustion chamber at high pressures and high Reynolds numbers. A mathematical model for the combustion of liquid injections at high pressures and high Reynolds numbers is presented, which includes: the equations of continuity, motion, internal energy, the K-ε model of turbulence, a system of equations describing the processes of evaporation, mixing, rupture and coalescence of liquid fuel droplets. A stochastic model of atomization of liquid fuels injected into a combustion chamber at high pressures and high Reynolds numbers has been developed. On the basis of the proposed model, computational experiments were carried out to study the combustion of liquid fuel depending on the injected mass in the combustion chamber under given initial conditions in full. When studying the effect of the mass of liquid fuel on the processes of ignition and combustion at high pressures and high Reynolds numbers, the mass values for octane 6 mg and for dodecane 7 mg were taken as the most optimal. A further increase in the injection mass, both for octane and dodecane at optimal pressures, worsens the combustion process. The results obtained are of fundamental and practical importance and can be used to develop the theory of combustion of gaseous and liquid fuels.

An improved numerical model of ski-jump flood discharge atomization

An improved numerical model of ski-jump flood discharge atomization

Model development for flash boiling spray and validations with isooctane, hexane, ethanol and their binary mixtures

The main objective of this study is to develop a comprehensive model for spray atomization under the consideration of flash boiling, which includes nucleation, bubble growth, and droplet breakup. Although flash boiling has been previously studied, there is still no well-established analytical and numerical model of their mechanisms, or general guidelines on the implementation of this atomization strategy. In this study, detailed formulations are elaborated for the unified spray atomization model under both non-flash and flash boiling conditions. Next, the model was implemented into CFD software and 3-D simulations were performed for model validations. Two fuel blends are tested: ethanol-isooctane blends and hexane-isooctane blends. Simulation results were compared with the experimental measurements conducted using two methodologies, DBI (Diffuse Backlight Imaging) system for spray images captured by a high-speed camera, and a PDA (Phase Doppler Anemometry) system for droplet size measurement during the spray injection process. It was found that the current flash boiling model can accurately capture the spray characteristics under different environment conditions, such as the spray plume interactions and liquid penetration. The averaged Sauter mean diameter (SMD) calculations match the measurement sufficiently well. The spray structures for both single- and multi-component fuels during the injection process are well represented by current model.

Johnson Matthey launches HyCOgen, an enabling technology to efficiently convert CO2 and green hydrogen into sustainable aviation fuel

Autothermal reforming is a promising technology to produce syngas from diesel fuel. However, the mixing of liquid diesel fuel with high temperature streams of steam and oxygen presents a challenge: how to avoid formation of ethylene, a likely deposit precursor, in the region upstream of the catalyst bed. This work describes a coupled CFD-kinetics study in the mixing region of a diesel autothermal reformer that considers: (1) an atomizer model to explicitly account for fuel evaporation, (2) n-dodecane as a surrogate diesel fuel, (3) oxygen as the oxidant instead of air. The predictions indicate unacceptable levels of ethylene (>0.1 mol%) will be present at the mixer exit if the mixer gas temperature is greater than ∼350 °C. This temperature is likely to be too low for proper catalyst performance. Thus this analysis suggests that either improved mixer designs or a different choice of catalyst might be required to achieve suitable diesel autothermal reforming performance.

Численное моделирование образования температурного факела неизотермических жидких впрысков

В данной работе представлены результаты вычислительных экспериментов по исследованию образования распыла и температурного факела неизотермических жидких впрысков при высокой турбулентности. Проведено численное моделирование распыла и горения жидких впрысков топлив и влияния начальной температуры газа в камере сгорания на данные процессы. Температура в камере сгорания менялась от 700 до 1500 К для двух видов жидких топлив: октана и додекана. Построены распределения капель жидких топлив по радиусам и по температуре в различные моменты времени. Выявлено оказываемое влияние начальной температуры на концентрационные характеристики топлива различного вида топлив. В результате установлено, что при давлении более 80 бар при высокой турбулентности за оптимальную принимается температура газа равная 900 К. При данной температуре камера прогревается до высоких значений температур и концентрация образующихся продуктов реакции наименьшая. Полученные результаты могут быть применены при построении теории горения жидких топлив и будут способствовать более глубокому пониманию сложных физико-химических явлений, которые происходят в камерах сгорания.

Prediction of the particle size distribution of the aerosol generated by a pressurized metered-dose inhaler

Pressurized metered dose inhalers (pMDIs) are devices widely used for drug delivery in the respiratory tract. In this work, a mathematical model to predict the complete particle size distribution (PSD) of the aerosol generated by a pMDI is developed. The model combines the equations developed by Clark in 1999 that describe the flow within the inhaler, the Linear Instability Sheet Atomization (LISA) model and a method based on the Maximum Entropy Principle (MEP). Mathematically it is found that the PSD can be represented by a lognormal function with geometric standard deviation equal to 1.56. The model does not contain fitting parameters and is validated with experimental information for a formulation containing salbutamol and HFA-134a as drug and propellant, respectively. Simulations are performed to explore how the propellants HFA-134a and HFA-227ea affect the PSD of the aerosol generated by the inhaler.

Atomic Spacetime Model Based on Atomic AString Functions

A novel model of spacetime and fields atomization based on Atomic Series over finite Atomic AString Functions is offered. Formulated Atomization Theorems allow representing polynomials, analytic functions, and solutions of field equations including General Relativity via superposition of solitonic atoms which can be associated with flexible spacetime quantum, metriants, or elementary distortions. Spacetime is conceptualized as a lattice of flexible Atomic Solitons adjusting locations to reproduce different metrics and other physical fields. It may offer the variants of unified field theory based on Atomic Solitons where, like in string theory, fields become interconnected having a common mathematical ancestor.

Spray in cross–flow: comparison of experimental and numerical approach

The spray behaviour and droplet trajectories in realistic conditions are of crucial importance in many industrial, agricultural and chemical applications. Droplet characteristics and spray trajectory in chemical applications (e. g. flue gas scrubbing, CO2 capture in spray column) determine the amount of mass involved in the gas scrubbing process, mass trapped by the flow or attached to the walls. Knowledge of the droplet behaviour can improve a nozzle design and scaling, increase the process efficiency, minimize the process liquid and blow away the fraction. In this study, experiments with pressure swirl nozzle in cross–flow of air were performed at one nozzle injection pressure (0.5 MPa) and several cross–flow velocities (8, 16, 32 m/s). The results on droplet trajectories are compared with numerical results obtained by ANSYS Fluent. Two Lagrange approaches for spray modelling were used. Injection of droplet groups and Linearized Instability Sheet Atomization (LISA) model incorporated within ANSYS Fluent were used to represent the spray. The CFD results of spray penetration and droplet trajectories are compared with experimental data. A simple analytical model is able to well predict trajectories of large droplets, but fails to predict trajectories of small droplets. The LISA model yields a better accuracy for spray in cross-flow prediction.

Modeling of Film Formation in Airless Spray

Aiming at the spraying process of airless atomization spraying, a coating film forming model based on Euler-Lagrangian method is proposed. A Rosin-Rammler atomization model was established. In the spraying model, for the discrete phase, a force balance equation is established. At the same time, a continuity equation and a momentum equation are established to describe the motion of the continuous phase. The momentum equation of the continuous phase is closed by the standard k-ε model. The continuity equation and momentum equation are established in the adhesion deposition model to solve the coating thickness. PC-SIMPLE algorithm was used to solve the model. Finally, the dynamic spraying simulation is verified through experiments, and the numerical simulation results are in good agreement with the experiments as a whole. It is proved that the film forming model can be used to predict the film forming results of airless spraying.

Spin-Mediated Electron Pairing

IJPSR emphasizes on various innovative, experimental and hypothetical studies related to all aspects of physics. The scope of the journal covers a large range from difficult atoms and diatomic interactions to modelling of atoms and molecules using electromagnetic waves.

A Computational Fluid Dynamics-based Correlation to Predict Droplet Sauter Mean Diameter for Σ− Yliq Atomization Model in Pressure Swirl Atomizer

Liquid atomization is crucial to ensure efficient combustion as it is an inherent part of the injector system. The combustion of fuels relies on effective atomization to increase the surface area of the fuel and consequently achieve high rates of mixing and evaporation. Pressure swirl atomizers are inexpensive and reliable type of atomizer for fuel injection owing to its superior atomization characteristics and relatively simple geometry. The Sauter mean diameter (SMD) of atomizer contributes significantly to the combustion chamber performance. This paper presents a two-step strategy to predict droplet SMD for atomisation model in pressure swirl atomizer through the combination of experimentally validated Computation Fluid Dynamics (CFD) and Optimal Latin Hypercubes (OLHC) Design of Experiments (DoE) techniques. A three-dimensional Eulerian two-phase CFD model is developed to account for liquid and gas phases as a single continuum with high-density variation at large Reynolds and Weber numbers and validated against experimental measurements, before being employed to carry out a parametric study involving operating conditions and fluid properties of the pressure swirl atomizer. The atomizer is then represented in terms of four design variables, namely liquid viscosity, liquid velocity, surface tension and atomizer exit diameter. An 87-point OLHC DoE is constructed within the design variables space using a permutation genetic algorithm resulting in an accurate SMD prediction. Results show the newly developed SMD prediction is found to be superior compared with existing correlations and indicate significant improvement in the droplets SMD.

A Computational Fluid Dynamics-based Correlation to Predict Droplet Sauter Mean Diameter for ?? Yliq Atomization Model in Pressure Swirl Atomizer

Liquid atomization is crucial to ensure efficient combustion as it is an inherent part of the injector system. The combustion of fuels relies on effective atomization to increase the surface area of the fuel and consequently achieve high rates of mixing and evaporation. Pressure swirl atomizers are inexpensive and reliable type of atomizer for fuel injection owing to its superior atomization characteristics and relatively simple geometry. The Sauter mean diameter (SMD) of atomizer contributes significantly to the combustion chamber performance. This paper presents a two-step strategy to predict droplet SMD for atomisation model in pressure swirl atomizer through the combination of experimentally validated Computation Fluid Dynamics (CFD) and Optimal Latin Hypercubes (OLHC) Design of Experiments (DoE) techniques. A three-dimensional Eulerian two-phase CFD model is developed to account for liquid and gas phases as a single continuum with high-density variation at large Reynolds and Weber numbers and validated against experimental measurements, before being employed to carry out a parametric study involving operating conditions and fluid properties of the pressure swirl atomizer. The atomizer is then represented in terms of four design variables, namely liquid viscosity, liquid velocity, surface tension and atomizer exit diameter. An 87-point OLHC DoE is constructed within the design variables space using a permutation genetic algorithm resulting in an accurate SMD prediction. Results show the newly developed SMD prediction is found to be superior compared with existing correlations and indicate significant improvement in the droplets SMD.

An Atomization Model of Air Spraying Using the Volume-of-Fluid Method and Large Eddy Simulation

When painting complex surfaces, such as large-curvature surfaces, poor coating quality is often obtained, which may be caused by lack of an appropriate atomization model, insufficient understanding of atomization mechanisms and laws, and improper painting parameters. This paper presents a numerical model of paint atomization of air spraying using the volume-of-fluid method and large eddy simulation. The interface capture and the turbulent flow were mainly considered in the model: the former was tracked by the volume-of-fluid method and the latter was predicted by the large eddy simulation. After the computational domain being meshed by the staggered-grid method, the governing equations were discretized by the finite volume method and were solved by the SIMPLE (Semi-Implicit Method for Pressure-Linked Equations) Consistent algorithm. The results of numerical simulations show that the characteristics of atomization flow field, such as velocity variation, pressure distribution, and paint volume fraction are in agreement with the regularities of atomization. Moreover, the primary and secondary atomization phenomena can be clearly observed: as soon as the paint issues from the nozzle, the paint flow begins to distort and the paint fragments continuously eject from the main paint flow and then these paint fragments distort and disintegrate into smaller elements. A comparison with the experimental data from the literature proves that the model of the whole atomization process of air spray is effective. The model is suitable for simulating the whole atomization process and easy to obtain initial conditions, which can be applied to set the appropriate painting parameters and study paint atomization mechanisms and laws in depth.

Laser Challenge of China

IJPSR emphasizes on various innovative, experimental and hypothetical studies related to all aspects of physics. The scope of the journal covers a large range from difficult atoms and diatomic interactions to modelling of atoms and molecules using electromagnetic waves.

Numerical and experimental analysis on spray characteristics of biodiesel (waste cooking oil) using pressure swirl atomizer

Atomization characteristics and evaporation have major role in air-fuel mixing and the combustion process in diesel engine. The aim of this study is to perform numerical and experimental analysis to investigate the spray pattern of biodiesel (waste cooking oil) generated from pressure swirl atomizer. The computation exhibits Eularian-Lagrangian method to comprise flow of multiphase and also linearized instability sheet atomization (LISA) model to envisage atomization, sheet breakup, and film formation. The model's strength is the identification structure of spray created from pressure swirl atomizer. A three-dimensional computational fluid dynamics work consisting of LISA and Taylor analogy breakup model are certified via experimentation taken from constant volume chamber. Further, spray tip penetration, cone angle, and sauter mean diameter (SMD) are identified for fuel (B100, B25, and D) under injection pressure of 110 and 160 MPa, and 2.8 MPa ambient pressure using swirl atomizer in constant volume chamber. This particular spray is quite important for application in diesel engines but is not extensively explored. The results reveal that as injection pressure increases from 110 MPa to 160 MPa. The spray tip penetration for B100, B25, and D are increased by 19.86%, 14.90%, and 14.50% respectively, further, cone angle at the start of injection decreases by 6%, 5%, and 3.41%, similarly, the average SMD decreases by 25%, 33.33%, and 25.4%, respectively. This is due to the rheological property of fuel, turbulent energy of droplet and air is maximum in primary breakup zone.

Spray characteristics of standard and alternative aviation fuels at high ambient pressure conditions

The spray characteristics of standard and alternative aviation fuels generated by a hybrid pressure-swirl airblast (HPSA) atomizer were investigated at high ambient pressure conditions. The measurements were performed in an optically accessible pressure vessel at pressures of 1, 2, 3, 4, 5, and 9.5 bar with heated gas and fuel temperatures of 394 K and 332 K, respectively. The drop size and drop velocity of sprays from a standard (Jet-A) and an alternative (C-5) aviation fuels were measured using phase Doppler anemometry (PDA), and 2-D visualization of spray was imaged using simultaneous fuel-Planar Laser Induced Fluorescence (PLIF) and Mie scattering. The spatially resolved PDA drop size measurements were obtained at 25.4 mm downstream of the swirler exit plane and up to 30 mm in the radial direction from the spray centerline. The Sauter Mean Diameter (D32) was observed to decrease significantly with increasing ambient pressure, up to 5 bar. However, the change in D32 was observed to be limited with a further increase in the ambient pressure. A higher swirler pressure drop resulted in a significant reduction in the D32 at an ambient pressure of 5 bar. Using simultaneous fuel-PLIF and Mie scattering imaging, the feasibility of the laser sheet drop-sizing (LSD) technique was examined for the spray at high ambient pressure application. In addition, the effect of ambient pressure on the spray cone angle was investigated using both instantaneous and averaged Mie images. The distribution of fuel vapor and droplets in the spray was also imaged and identified by comparing instantaneous fuel-PLIF and Mie images. A phenomenological three-step atomization model was used to predict the drop size and demonstrate the drop size trend with increasing ambient pressure.

Theoretical Atomization Model of Liquid Sheet Generated by Coaxial Swirl Injectors

This paper describes the atomization process of a liquid sheet generated by a coaxial swirl injector and it establishes a theoretical breakup model to predict the Sauter mean diameter (SMD) in the entire spray field. The two stage breakup model, which includes Kelvin-Helmholtz (K-H) and Rayleigh-Taylor (R-T) instability, is established and combined with the dispersion relation obtained by linear stability analysis. The theoretical expression to predict the SMD is then determined by full wavelength integration. The validity of the present model is first verified; the results predicted by the theoretical model showed good agreement with previous experimental data. Subsequently, effects of fluid physical properties and flow parameters on the SMD are also investigated. The related conclusions are compared and concur well with the existing literature.

Effect of outlet temperature and total soluble solid in 2-stage spray dryer on black tea powder extract production

The black tea powder extract produced through the spray drying technique is an alternative to tea steeping or brewing in the industry. The production of black tea powder extract using the 2-stage spray dry method still has problems such as different colour, product swelling or inflate and blocking. To determine the source of the problem, this study used varied outlet temperatures 105°C, 110°C, 115°C, 120°C and total soluble solids (TSS) 31.3, 35.2, 37.2, 43.9, 44.1, 47.4. Spraying through 2-stage spray dryer with combi fluid bed and high nozzle pressure atomizer model SC 40 SDX III by Delavan. The results show a significant difference between the outlet chamber temperatures with the flowrates, the pressures, and the densities. An increase in outlet temperatures by a multiple of 10°C can significantly reduce the pressure and the flow rate, while the temperatures multiple of 20°C can significantly reduce the densities, but not for the moisture contents and the powder colours. Changes in the outlet temperatures did not have a 0.2% effect on the steeping colours but were affected by TSS. The higher TSS’s value gives an increase in flow rate, pressure, moisture content and steeped powder colours of 0.2%