Pressure-swirl Atomizer Research Articles

Breakup of Swirling Films Issued from a Pressure-Swirl Atomizer

Breakup of Swirling Films Issued from a Pressure-Swirl Atomizer

Spray curtains as devices for surface spraying during the SARS-CoV-2 pandemic

Counteracting the spread of the SARS-CoV-2 virus is a current and important problem. A crucial issue in this area is the disinfection of various surfaces, as well as the air itself. For this purpose, devices such as foggers, which have different designs, are used. The appropriate size of droplets and their distribution determines the effectiveness of disinfectants. The paper presents droplet size distributions and characteristic mean droplet diameters, which are obtained with the use of a conical pressure-swirl atomizer. For the purpose of the analysis, the laser diffraction method was used. The influence of gas pressure and the distance from the atomizer's orifice on the spray angle and the distance between the nozzles on the spray curtain was also demonstrated.

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.

Effect of geometric parameters on spray characteristics of air assisted pressure swirl atomizer

In the present work, a modified Pressure Swirl Atomizer (PSA) was introduced to operate as an Assisted Pressure Swirl Atomizer (AAPSA). Different mass flow rates of assisted air were experimentally tested. The studied parameters are the orifice length to diameter ratio (L/Do), swirl chamber length/diameter ratio (Ls/Ds) and swirling passage size (width × depth). The spray characteristics were studied using water as the atomized liquid. The spray was photographed using a high-speed camera to determine the spray shape, the cone angle and the spray breakup length. Moreover, photos taken by the high-speed camera were processed using IMAGE J software to obtain the droplet size diameters. The spray concentrations were measured by the patternator tubes technique. The results indicated that the spray cone angle increased by increasing the value of the L/Do ratio or by decreasing the assisted air mass flow rate. The spray concentration maximum value is shifted inward with the assist air injection. The breakup length decreased by about 65% for the PSA and 77% for the AAPSA when the value of the Ls/Ds ratio is decreased from 1.163 to 0.664. With the injection of assist air at a rate of 2 g/s, the Sauter Mean Diameter (SMD) is reduced by about 64% compared to a PSA having the same geometry.

Effect of Application of Electric Force to Diesel Fuel Droplets Charged Through Millikan Oil-Drop Experiment on Physical and Thermal Characteristics of Flame

Abstract This paper proposes a new feasible method to allow continuous change in the primary injection spray cone angle of liquid fuel droplets, which are injected from nozzles in liquid fuel combustion systems, to control the flame shape and thermal characteristics of the flame. The method is based on electric force applied to fuel droplets charged through frictional effects between the internal surface of the nozzle and the fuel flow as the liquid fuel is sprayed (based on the Millikan oil-drop experiment). A sprint computational fluid dynamics code was developed to investigate the effect of application of electric force to charged diesel fuel droplets, which were injected from a pressure swirl atomizer, on physical and thermal characteristics of a two-dimensional axisymmetric turbulent jet diffusion flame. The results show that an electric field applied to charged fuel droplets (electric force) changes the spatial distribution of the liquid fuel droplets in the flame reaction zone. An applied electric force in (−y) direction diverts the fuel droplets towards the axis centerline of the furnace and, consequently, decreases the primary injection cone angle and increases the concentration of the evaporated droplets around the axis centerline, which enhances the fuel-oxidant mixing rate and raises the flame temperature. Unlike an applied electric force in (−y) direction, an applied electric force in (+y) direction decreases the flame temperature. However, as the primary injection cone angle is decreased, an applied electric force in (+y) direction increases the flame temperature.

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.

Study of pressure-swirl atomizer with spiral path at design point and outside of design point

Studies on pressure-swirl atomizers have mainly focused on pressure-swirl atomizers with tangential input while there are limited studies on pressure-swirl atomizers with a spiral path. This study applies experimental and computational methods to provide a better understanding of flow development in this type of atomizer at the design point and outside the design point. Experimental results showed that as the pressure increases, the spray cone angle increases. This increase initially occurs with a higher slope and then the slope is toned down. While the drainage coefficient remains constant, the droplet diameter decreases as the pressure increases. It is observed that similar to the pressure-swirl atomizer with tangential input, the pressure-swirl atomizer with a spiral path has a conical hollow spray. At the constant mass flow rate, as the spiral path cross-section, the length of the swirl chamber and orifice diameter increase, the fluid film thickness and average diameter of droplets increase while the spray cone angle reduces. Further, increasing the number of spiral paths causes a wider spray cone angle, higher discharge coefficient, larger fluid film thickness, and larger droplet diameter. The results also showed that increasing the length of the orifice marginally affected the properties of the spray while significantly reducing the spray cone angle. It is important to note that the numerical results are in good agreement with the experimental data.

Characteristics of Ammonia Spray Injected by Pressure-Swirl Atomizers

Characteristics of Ammonia Spray Injected by Pressure-Swirl Atomizers

Investigating the performance of an airblast pressure swirl atomizer

Investigating the performance of an airblast pressure swirl atomizer

Available Simplified Semi-empirical Correlation to Predict Hollow Spray Cone Angle for Practical Pressure Swirl Atomizers with Viscous liquid

Available Simplified Semi-empirical Correlation to Predict Hollow Spray Cone Angle for Practical Pressure Swirl Atomizers with Viscous liquid

Assessment of Primary Breakup of Liquid Sheet Emanating from a Pressure Swirl Atomizer for Non-Newtonian Fluids

Assessment of Primary Breakup of Liquid Sheet Emanating from a Pressure Swirl Atomizer for Non-Newtonian Fluids

Comparison of numerical models for prediction of pressure-swirl atomizer internal flow

Comparison of numerical models for prediction of pressure-swirl atomizer internal flow

Characteristics of Spray Angle and Discharge Coefficient of Pressure-Swirl Atomizer

A widely distributed spray is an important feature for an atomizer which is required in various applications such as gas cooling, gas turbine combustion, and fluidized bed granulator. Pressure-swirl atomizer is an example of atomizer which provides a wide spray angle through the swirling effect inside the atomizer. One of the important parameters affecting spray angle is atomizer geometrical constant, K. Another important parameter of pressure-swirl atomizer is discharge coefficient, Cd. Discharge coefficient describes the throughput of the liquid flow. An experimental test-rig was constructed to conduct the performance test of the atomizer. Acquired images were analysed using image-processing software. It was found that K has inverse relation with spray angle and direct relation with Cd. Prediction of spray angle and Cd using existing correlations also yields similar trends with the experimental results, but some parameters still need to be considered to perform an accurate prediction.

Effect of Low Ambient Pressure on Spray Cone Angle of Pressure Swirl Atomizer

Pressure swirl atomizers are widely used in gas turbine combustor; this paper is aimed at researching the effect of low ambient pressure (0.1 MPa to 0.01 MPa, lower than an atmosphere) on the spray cone angle of pressure swirl atomizer. The spray angle is captured by high-speed photography; then, an image post program is used to process the spray angle magnitude. A mathematical model of a single droplet’s movement and trajectory based on force analysis is proposed to validate the spray angle variation. The maximum variation of the spray cone angle, which is observed when fuel supply pressure drop through the atomizer is 1 MPa as the ambient pressure decreases from 0.1 MPa to 0.01 MPa, is found to be 23.9%. The experimental results show that the spray cone angle is expected to increase with the ambient pressure decrease; meanwhile, mathematical results agree well with this trend.

Investigation of Oil Droplet Breakup during Atomization of Emulsions: Comparison of Pressure Swirl and Twin-Fluid Atomizers

The goal of this study was to investigate oil droplet breakup in food emulsions during atomization with pressure swirl (PS), internal mixing (IM), and external mixing (EM) twin-fluid atomizers. By this, new knowledge is provided that facilitates the design of atomization processes, taking into account atomization performance as well as product characteristics (oil droplet size). Atomization experiments were performed in pilot plant scale at liquid volume flow rates of 21.8, 28.0, and 33.3 L/h. Corresponding liquid pressures in the range of 50–200 bar and air-to-liquid ratios in the range of 0.03–0.5 were applied. Two approaches were followed: oil droplet breakup was initially compared for conditions by which the same spray droplet sizes were achieved at constant liquid throughput. For all volume flow rates, the strongest oil droplet breakup was obtained with the PS nozzle, followed by the IM and the EM twin-fluid atomizer. In a second approach, the concept of energy density EV was used to characterize the sizes of resulting spray droplets and of the dispersed oil droplets in the spray. For all nozzles, Sauter mean diameters of spray and oil droplets showed a power-law dependency on EV. PS nozzles achieved the smallest spray droplet sizes and the strongest oil droplet breakup for a constant EV. In twin-fluid atomizers, the nozzle type (IM or EM) has a significant influence on the resulting oil droplet size, even when the resulting spray droplet size is independent of this nozzle type. Overall, it was shown that the proposed concept of EV allows formulating process functions that simplify the design of atomization processes regarding both spray and oil droplet sizes.

Three-dimensional computational fluid dynamics simulation of the hollow-cone spray process: The stability of the conical liquid sheet

The characterization of atomization in small-scale applications, such as those typical of the consumer goods industry, is not widely investigated, despite its enormous interest as in the case of sanitation. In this field, the features of the atomizer are selected to achieve a wide spray pattern. This is the case of the pressure-swirl atomizer, where the swirl flow leads the liquid sheet to exhibit a distinctive hollow-cone shape. The configuration of the atomizer and the properties of the multiphase system (liquid–gas) affect the spray morphology and the droplets/ligaments distribution. The aim of the work is to investigate through computational fluid dynamics the stability of the gas–liquid interface produced by a swirling liquid injection. By implementing the volume-of-fluid method, we show transient simulations, in which the liquid–gas interactions take place within and outside the nozzle simultaneously. Depending on the different liquid properties and geometric features, we examine the hollow-cone spray performance in terms of cone angle and liquid sheet morphology. A stability analysis allows to determine whether spraying or jetting conditions are attained depending on Reynolds and Ohnesorge numbers, as the hollow-cone shape can degenerate into a straight jet under specific operating conditions. Viscosity is known to be a relevant parameter in fluid formulation, which impacts on both relevant dimensionless parameters. Newtonian and non-Newtonian rheologies are here considered for their ubiquitous presence in detergent or sanitation fluids. In both cases, we find a critical condition that marks the switch from the spraying to the jetting regime.

Experimental study of the effect of the spray cone angle on the temperature distribution in a can micro-combustor

In this study, the performance of a can micro-combustor of a micro turbine is studied experimentally. The purpose of this study is to show the coupling effect of air flow rate and fuel injection on temperature distribution and flame blowoff limits in the combustion chamber. In this regard, by changing the spray cone angle, the flame structure and the characteristics of the combustion chamber are investigated. In the present study, the liquid kerosene is injected through a pressure swirl atomizer. Experiments have been done for various conditions of air flow rates and fuel injection angles. The combustion zone at the main part of the chamber is investigated by measuring temperature distribution. The results show the significant effect of fuel injection angle on flame structure. By changing the air flow rate, in fact, the effect of fuel injection angle is studied for different overall equivalence ratios from extreme lean to rich conditions. By increasing the fuel injection angle, flame stabilization is accessible even for extreme lean conditions. The more intense combustion zones occur near the liner which can potentially cause structural problems.

A study on the geometric characteristic influence on the liquid fuel flow in a three-way pressure-swirl atomizer

An important factor that affects the characteristics of combustion processes in the combustion chambers of aircraft engines is the fuel atomization. Semi-empirical methods are usually used to determine the characteristics of liquid fuel atomization by pressure-swirl atomizers. The input data for semi-empirical methods are the geometric parameters of the atomizer, as well as the spray cone angle and the nozzle discharge characteristic. These parameters can be obtained experimentally, which requires the availability of appropriate apparatus and a sample of a pressure-swirl atomizer, which is associated with significant material costs. An alternative way to determine these characteristics is to use numerical methods for modelling two-phase flows. Therefore, it is convenient to use a combination of empirical and numerical methods (hybrid method) to determine the spray parameters of a pressure-swirl atomizer. In this paper, we studied the effect of geometric and operating parameters on spray characteristics using the hybrid method, which includes the volume of fluid (VOF) numerical method and the semi-empirical equation. The calculation results are compared with empirical generalizations and experimental data of such parameters as the discharge coefficient, the air core ratio and the spray cone angle. The results of this work were compared with the values of such parameters as the air core ratio and the spray cone angle obtained using the proposed method and analytical techniques.

Erratum to: Experimental Studies on Fuel Spray Characteristics of Pressure-Swirl Atomizer and Air-Blast Atomizer

Erratum to: Experimental Studies on Fuel Spray Characteristics of Pressure-Swirl Atomizer and Air-Blast Atomizer