Ammonia is an ideal alternative fuel for mitigating carbon emissions. High-pressure direct injection of liquid ammonia (LNH3) offers significant advantages in enhancing energy efficiency and minimizing emissions. Due to the high saturation vapor pressure, the injection of LNH3 is susceptible to flash boiling. This study established a high-pressure common-rail LNH3 jet experimental platform and investigated the flash boiling spray characteristics of round and elliptical hole nozzles, by using the high-speed micro-imaging technology with backlight lighting. The results demonstrate that under non-flash boiling conditions, the residual LNH3 in the SAC chamber and nozzle can rapidly corrode the acrylic material of the nozzle, leading to deformation and failure of the nozzle structure. Under flash boiling conditions, LNH3 ejected from the hole will produce spherical macroscopic spray morphology. Then the spray gradually transitions from an elliptical profile to a conical profile as back pressure increases. Compared with round hole nozzles, elliptical hole nozzles exhibit higher flow velocity which enhances oil-gas mixing and promotes more pronounced flash boiling phenomena. Flash boiling occurs at an earlier stage with increased spray cone angle thereby improving atomization characteristics both during flash and non-flash boiling conditions. The tail jet of elliptical hole nozzles terminates earlier while exhibiting a higher rate decrease in average gray value, which improves the atomization quality in the tail spray stage and meets the requirements of timing, quantification, and precise control of the fuel injection system.
{"title":"Experimental Study on Flash Boiling Spray of High Pressure Liquid Ammonia Jet with Round and Elliptical Hole Nozzles","authors":"Chen Li, Zhixia He, Yizhou Yang, Jiafeng Chen, Wenjun Zhong","doi":"10.1615/atomizspr.2024050358","DOIUrl":"https://doi.org/10.1615/atomizspr.2024050358","url":null,"abstract":"Ammonia is an ideal alternative fuel for mitigating carbon emissions. High-pressure direct injection of liquid ammonia (LNH3) offers significant advantages in enhancing energy efficiency and minimizing emissions. Due to the high saturation vapor pressure, the injection of LNH3 is susceptible to flash boiling. This study established a high-pressure common-rail LNH3 jet experimental platform and investigated the flash boiling spray characteristics of round and elliptical hole nozzles, by using the high-speed micro-imaging technology with backlight lighting. The results demonstrate that under non-flash boiling conditions, the residual LNH3 in the SAC chamber and nozzle can rapidly corrode the acrylic material of the nozzle, leading to deformation and failure of the nozzle structure. Under flash boiling conditions, LNH3 ejected from the hole will produce spherical macroscopic spray morphology. Then the spray gradually transitions from an elliptical profile to a conical profile as back pressure increases. Compared with round hole nozzles, elliptical hole nozzles exhibit higher flow velocity which enhances oil-gas mixing and promotes more pronounced flash boiling phenomena. Flash boiling occurs at an earlier stage with increased spray cone angle thereby improving atomization characteristics both during flash and non-flash boiling conditions. The tail jet of elliptical hole nozzles terminates earlier while exhibiting a higher rate decrease in average gray value, which improves the atomization quality in the tail spray stage and meets the requirements of timing, quantification, and precise control of the fuel injection system.","PeriodicalId":8637,"journal":{"name":"Atomization and Sprays","volume":"27 1","pages":""},"PeriodicalIF":1.2,"publicationDate":"2024-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140202569","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-02-01DOI: 10.1615/atomizspr.2024051425
Dino Zrnić, Günter Brenn
A study of axisymmetric shape oscillations of viscoelastic drops in a vacuum is conducted, using the method of weakly nonlinear analysis. The motivation is the relevance of the shape oscillations for transport processes across the drop surface, as well as fundamental interest. The study is performed for, but not limited to, the two-lobed mode of initial drop deformation. The Oldroyd-B model is used for characterizing the liquid rheological behaviour. The method applied yields a set of governing equations, as well as boundary and initial conditions, for different orders of approximation. In the present paper, the equations and solutions up to second order are presented, together with the characteristic equation for the viscoelastic drop. The characteristic equation has an infinite number of roots, which determine the time dependency of the oscillations. Solutions of the characteristic equation are validated against experiments on acoustically levitated individual viscoelastic aqueous polymer solution drops. Experimental data consist in decay rate and oscillation frequency of free damped drop shape oscillations. With these data, solutions of the characteristic equation dominating the oscillations are identified. The theoretical analysis reveals nonlinear effects, such as the excess time in the prolate shape and frequency change for varying initial deformation amplitude. The influences of elasticity, measured by the stress relaxation and deformation retardation time scales, are quantified, and the effects are compared to the Newtonian case in the moderate-amplitude regime.
{"title":"Nonlinear effects in viscoelastic drop shape oscillations","authors":"Dino Zrnić, Günter Brenn","doi":"10.1615/atomizspr.2024051425","DOIUrl":"https://doi.org/10.1615/atomizspr.2024051425","url":null,"abstract":"A study of axisymmetric shape oscillations of viscoelastic drops in a vacuum is conducted, using the method of weakly nonlinear analysis. The motivation is the relevance of the shape oscillations for transport processes across the drop surface, as well as fundamental interest. The study is performed for, but not limited to, the two-lobed mode of initial drop deformation. The Oldroyd-B model is used for characterizing the liquid rheological behaviour. The method applied yields a set of governing equations, as well as boundary and initial conditions, for different orders of approximation. In the present paper, the equations and solutions up to second order are presented, together with the characteristic equation for the viscoelastic drop. The characteristic equation has an infinite number of roots, which determine the time dependency of the oscillations. Solutions of the characteristic equation are validated against experiments on acoustically levitated individual viscoelastic aqueous polymer solution drops. Experimental data consist in decay rate and oscillation frequency of free damped drop shape oscillations. With these data, solutions of the characteristic equation dominating the oscillations are identified. The theoretical analysis reveals nonlinear effects, such as the excess time in the prolate shape and frequency change for varying initial deformation amplitude. The influences of elasticity, measured by the stress relaxation and deformation retardation time scales, are quantified, and the effects are compared to the Newtonian case in the moderate-amplitude regime.","PeriodicalId":8637,"journal":{"name":"Atomization and Sprays","volume":"176 1","pages":""},"PeriodicalIF":1.2,"publicationDate":"2024-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139658520","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-02-01DOI: 10.1615/atomizspr.2024051301
Jean-Baptiste Le Gac, Carole Planchette
Free drop-particle collisions occurring in air are experimentally produced by combining a stream of drops and a stream of particles, which results from the selective and ultra-fast hardening of another regular drop stream. The set-up offers the possibility to accurately vary the drop and particle diameter, the collision eccentricity and the relative drop-particle velocity. First observations obtained with drop Weber numbers ranging from 30 to 300, drop Reynolds number between 390 and 4600, and with typical equilibrium contact angle of 70° evidence the existence of full deposition, separation and bouncing events. For off-center separation, a liquid ligament forms between the particle and the outlying drop cap that fragments due to excessive stretching, a phenomenon similar to what can be observed for drop-drop collisions. In contrast, for head-on collisions and intermediate inertia, a lamella first forms, whose constrained recoil leads to liquid protuberance(s) that eventually pinch(es)-off. These outcomes can be distinguished using a bi-dimensional regime map built on the impact parameter and the drop Weber number. Despite remarkable similarities with binary drop collisions, important differences are observed especially for low and moderate eccentricities.
{"title":"A novel experimental approach to study drop-particle collisions","authors":"Jean-Baptiste Le Gac, Carole Planchette","doi":"10.1615/atomizspr.2024051301","DOIUrl":"https://doi.org/10.1615/atomizspr.2024051301","url":null,"abstract":"Free drop-particle collisions occurring in air are experimentally produced by combining a stream of drops and a stream of particles, which results from the selective and ultra-fast hardening of another regular drop stream. The set-up offers the possibility to accurately vary the drop and particle diameter, the collision eccentricity and the relative drop-particle velocity. First observations obtained with drop Weber numbers ranging from 30 to 300, drop Reynolds number between 390 and 4600, and with typical equilibrium contact angle of 70° evidence the existence of full deposition, separation and bouncing events. For off-center separation, a liquid ligament forms between the particle and the outlying drop cap that fragments due to excessive stretching, a phenomenon similar to what can be observed for drop-drop collisions. In contrast, for head-on collisions and intermediate inertia, a lamella first forms, whose constrained recoil leads to liquid protuberance(s) that eventually pinch(es)-off. These outcomes can be distinguished using a bi-dimensional regime map built on the impact parameter and the drop Weber number. Despite remarkable similarities with binary drop collisions, important differences are observed especially for low and moderate eccentricities.","PeriodicalId":8637,"journal":{"name":"Atomization and Sprays","volume":"76 1","pages":""},"PeriodicalIF":1.2,"publicationDate":"2024-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139753348","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-02-01DOI: 10.1615/atomizspr.2024050444
J.E. Park, T.-W. Lee, M Maly, O Cejpak, Jan Jedelsky
We have extended the primary atomization analysis to swirl injection in cross flows, impinging and effervescent injectors. Using the integral form of the conservation equations, the drop size can be expressed in terms of injection and fluid parameters, the main variable being the liquid and gas velocities. Using the measured velocities as inputs to this D32-equation, good agreement with experimental data is found for the three spray geometries. This analytical solution can also be used as the drop size-velocity correlation, to generate drop size distributions. In contrast to modeling, current approach uses a universal theoretical framework, and different velocity and viscous dissipation terms are input to find the drop size. Similar to previous work, this method can also be used as the primary atomization module in computational simulations of sprays in these injection geometries.
{"title":"Determination of the Drop Size and Distributions in Swirl Injection in Cross Flows, Impinging, and Effervescent Injectors","authors":"J.E. Park, T.-W. Lee, M Maly, O Cejpak, Jan Jedelsky","doi":"10.1615/atomizspr.2024050444","DOIUrl":"https://doi.org/10.1615/atomizspr.2024050444","url":null,"abstract":"We have extended the primary atomization analysis to swirl injection in cross flows, impinging and effervescent injectors. Using the integral form of the conservation equations, the drop size can be expressed in terms of injection and fluid parameters, the main variable being the liquid and gas velocities. Using the measured velocities as inputs to this D32-equation, good agreement with experimental data is found for the three spray geometries. This analytical solution can also be used as the drop size-velocity correlation, to generate drop size distributions. In contrast to modeling, current approach uses a universal theoretical framework, and different velocity and viscous dissipation terms are input to find the drop size. Similar to previous work, this method can also be used as the primary atomization module in computational simulations of sprays in these injection geometries.","PeriodicalId":8637,"journal":{"name":"Atomization and Sprays","volume":"194 1","pages":""},"PeriodicalIF":1.2,"publicationDate":"2024-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139926251","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-01-01DOI: 10.1615/atomizspr.2024049985
Marija Stipic, Branislav Basara, Steffen Schmidt, Nikolaus A. Adams
For internal combustion engine, the determination of combustion characteristics and subsequent emissions formation relies heavily on the fuel injection process. With the increasing demand for enhanced fuel efficiency and reduced emissions, it becomes vital to develop fundamental understanding of physical process involved in the fuel injection process. In this study, an optimal numerical approach to predict high pressure liquid injection process in the context of industrial computations has been investigated. In particular, this study focuses on the respective performance of the Partially-Averaged Navier-Stokes and Large Eddy Simulation models to predict turbulent igniting sprays. Both approaches are coupled with widely used Lagrangian Discrete Droplet Method for spray modelling. The results are validated against well established ECN Spray A case in reactive and non reactive conditions. For reacting conditions, Flamelet Genrated Manifold (FGM) combustion model is employed in the present work. Comparative study and validation against experimental data showed that PANS turbulence model allows for coarser grids while still maintaining accurate results.
对于内燃机来说，燃烧特性的确定以及随后排放物的形成在很大程度上依赖于燃料喷射过程。随着对提高燃油效率和减少排放的需求不断增加，从根本上了解燃料喷射过程中涉及的物理过程变得至关重要。在本研究中，研究了在工业计算背景下预测高压液体喷射过程的最佳数值方法。本研究特别关注部分平均纳维-斯托克斯模型和大涡流模拟模型在预测湍流点火喷射时各自的性能。这两种方法都与广泛使用的拉格朗日离散液滴法相结合，用于喷雾建模。在反应和非反应条件下，结果与已建立的 ECN Spray A 案例进行了验证。在反应条件下，本研究采用了小火焰生成歧管（FGM）燃烧模型。与实验数据的对比研究和验证表明，PANS 湍流模型允许使用更粗的网格，同时仍能保持精确的结果。
{"title":"Computational study of high-pressure liquid injection process by means of LES and PANS approaches","authors":"Marija Stipic, Branislav Basara, Steffen Schmidt, Nikolaus A. Adams","doi":"10.1615/atomizspr.2024049985","DOIUrl":"https://doi.org/10.1615/atomizspr.2024049985","url":null,"abstract":"For internal combustion engine, the determination of combustion characteristics and subsequent emissions formation relies heavily on the fuel injection process. With the increasing demand for enhanced fuel efficiency and reduced emissions, it becomes vital to develop fundamental understanding of physical process involved in the fuel injection process. In this study, an optimal numerical approach to predict high pressure liquid injection process in the context of industrial computations has been investigated. In particular, this study focuses on the respective performance of the Partially-Averaged Navier-Stokes and Large Eddy Simulation models to predict turbulent igniting sprays. Both approaches are coupled with widely used Lagrangian Discrete Droplet Method for spray modelling. The results are validated against well established ECN Spray A case in reactive and non reactive conditions. For reacting conditions, Flamelet Genrated Manifold (FGM) combustion model is employed in the present work. Comparative study and validation against experimental data showed that PANS turbulence model allows for coarser grids while still maintaining accurate results.","PeriodicalId":8637,"journal":{"name":"Atomization and Sprays","volume":"1 1","pages":""},"PeriodicalIF":1.2,"publicationDate":"2024-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139409948","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-01-01DOI: 10.1615/atomizspr.2024050582
Dmitrii Antonov, Pavel Strizhak, Elena Shchepakina, Vladimir Sobolev, Sergei Sazhin
The previously developed analytical/numerical model for predicting heat transfer and component diffusion in composite multi-component droplets is adjusted for use in practical engineering applications related to the analysis of droplet heating and evaporation, and the onset of puffing and micro-explosions in those droplets. This adjustment allowed us to gain new insights into the previously developed models of these processes. The focus of the analysis is on kerosene/water droplets. It is demonstrated that the number of terms in the series in the analytical solution to the heat transfer equation can be reduced to just one or two to ensure that the maximal error of the model prediction does not exceed 1%, unless we are interested in the processes at the very start of heating. At the same time, the minimal number of terms in the series in the analytical solution to the component diffusion equation should be at least seven to ensure that the errors of the prediction of the numerical code do not exceed 3%. It is shown that, to ensure that the analytical/numerical code predicts physically consistent results, the maximal absolute error of calculation of the eigenvalues based on the bisection method cannot exceed 10^-7. It is shown that using these limiting values for each of these input parameters leads to about 50%-75% reduction in the CPU time required to obtain results close to those which were obtained using the non-optimised version of the numerical code. The overall reduction in CPU time can be as up to about 95%. The predictions of the adjusted analytical/numerical code are validated against in-house experimental data and data available in the literature.
{"title":"A combined analytical/numerical approach to the modelling of the processes leading to puffing and micro-explosion in a composite multi-component fuel/water droplet","authors":"Dmitrii Antonov, Pavel Strizhak, Elena Shchepakina, Vladimir Sobolev, Sergei Sazhin","doi":"10.1615/atomizspr.2024050582","DOIUrl":"https://doi.org/10.1615/atomizspr.2024050582","url":null,"abstract":"The previously developed analytical/numerical model for predicting heat transfer and component diffusion in composite multi-component droplets is adjusted for use in practical engineering applications related to the analysis of droplet heating and evaporation, and the onset of puffing and micro-explosions in those droplets. This adjustment allowed us to gain new insights into the previously developed models of these processes. The focus of the analysis is on kerosene/water droplets. It is demonstrated that the number of terms in the series in the analytical solution to the heat transfer equation can be reduced to just one or two to ensure that the maximal error of the model prediction does not exceed 1%, unless we are interested in the processes at the very start of heating. At the same time, the minimal number of terms in the series in the analytical solution to the component diffusion equation should be at least seven to ensure that the errors of the prediction of the numerical code do not exceed 3%. It is shown that, to ensure that the analytical/numerical code predicts physically consistent results, the maximal absolute error of calculation of the eigenvalues based on the bisection method cannot exceed 10^-7. It is shown that using these limiting values for each of these input parameters leads to about 50%-75% reduction in the CPU time required to obtain results close to those which were obtained using the non-optimised version of the numerical code. The overall reduction in CPU time can be as up to about 95%. The predictions of the adjusted analytical/numerical code are validated against in-house experimental data and data available in the literature.","PeriodicalId":8637,"journal":{"name":"Atomization and Sprays","volume":"112 1","pages":""},"PeriodicalIF":1.2,"publicationDate":"2024-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139459995","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-01-01DOI: 10.1615/atomizspr.2024049993
Andrew Mullis
We explore the extent to which imaging of the melt plume during High Pressure Gas Atomisation using consumer DSLR (Digital Single Lens Reflex) equipment provides useful information about the process. We show that the colour imaging and high spatial resolution can be a useful adjunct to the more widely reported imaging using specialist high frame rate cameras. With knowledge of the camera’s colour response curves, the ratio of the signals in the red, green and blue channels can be used to make spatially resolved temperature estimates of the material within the melt plume. Moreover, by combining these temperature estimates, which depend only upon intensity ratios, with the actual intensity of the optical signal we propose it is possible to obtain estimates of the relative surface area of the melt within the plume. This in turn can be related to the extent of melt break-up with the atomization plume.
{"title":"In situ Melt Temperature and Particle Size Analysis During High Pressure Gas Atomization of Liquid Metals","authors":"Andrew Mullis","doi":"10.1615/atomizspr.2024049993","DOIUrl":"https://doi.org/10.1615/atomizspr.2024049993","url":null,"abstract":"We explore the extent to which imaging of the melt plume during High Pressure Gas Atomisation using consumer DSLR (Digital Single Lens Reflex) equipment provides useful information about the process. We show that the colour imaging and high spatial resolution can be a useful adjunct to the more widely reported imaging using specialist high frame rate cameras. With knowledge of the camera’s colour response curves, the ratio of the signals in the red, green and blue channels can be used to make spatially resolved temperature estimates of the material within the melt plume. Moreover, by combining these temperature estimates, which depend only upon intensity ratios, with the actual intensity of the optical signal we propose it is possible to obtain estimates of the relative surface area of the melt within the plume. This in turn can be related to the extent of melt break-up with the atomization plume.","PeriodicalId":8637,"journal":{"name":"Atomization and Sprays","volume":"17 1","pages":""},"PeriodicalIF":1.2,"publicationDate":"2024-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139497928","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-01-01DOI: 10.1615/atomizspr.2024050888
Raul Payri, Gabriela Bracho, Pedro Martí-Aldaraví, Javier Marco-Gimeno
NOx emission regulations have become more and more restrictive for Internal Combustion Engines vehicles, especially for road transport applications. To minimize emissions and comply with regulations, Selective Catalytic Reduction (SCR) systems are the most efficient deNOx technology thanks to the injection of a Urea-Water Solution (UWS). State-of-the-art Computational Fluid Dynamics (CFD) techniques employ Eulerian-Lagrangian frameworks to deal with the two phases of such problems. Still, the associated low velocities make using standard breakup models to generate initial drop size distributions difficult. Several studies end up needing experimentally characterized drop size distributions to initialize the CFD simulations or using expensive Eulerian-Eulerian simulations to obtain the outcomes of the primary breakup of the liquid jet. The Maximum Entropy Principle (MEP) allows generating a droplet size-velocity Probability Distribution Function (PDF) from initial injection conditions and injector characteristics while satisfying conservation equations. The most probable PDF curve is determined by the distribution that maximizes the entropy of the problem. A critical Weber number has been proposed to select which droplets will break up subsequently after the initial droplet break up. Validation is done against experimental results obtained by High-Resolution Laser Backlight Imaging. Comparable results have been found and realistic tendencies were achieved, decreasing the expected droplet size with increasing injection pressures. The proposed model could help introduce alternative breakup models for low-velocity applications without the need for prior droplet size knowledg
氮氧化物排放法规对内燃机汽车的限制越来越严格，尤其是公路运输应用。为了最大限度地减少排放并符合法规要求，选择性催化还原（SCR）系统通过注入尿素水溶液（UWS）成为最有效的脱硝技术。最先进的计算流体动力学（CFD）技术采用欧拉-拉格朗日框架来处理此类问题的两个阶段。不过，由于相关的速度较低，因此很难使用标准的破裂模型来生成初始液滴粒度分布。有几项研究最终需要用实验表征的液滴大小分布来初始化 CFD 模拟，或使用昂贵的欧拉-欧拉模拟来获得液体射流的初级破裂结果。最大熵原理（MEP）允许根据初始喷射条件和喷射器特征生成液滴大小-速度概率分布函数（PDF），同时满足守恒方程。最可能的 PDF 曲线由问题熵最大化的分布决定。提出了一个临界韦伯数，用于选择初始液滴破裂后哪些液滴会随后破裂。根据高分辨率激光背光成像获得的实验结果进行了验证。得出的结果具有可比性，并呈现出现实的趋势，即随着注入压力的增加，预期液滴尺寸会减小。所提出的模型有助于为低速应用引入替代破裂模型，而无需事先了解液滴尺寸。
{"title":"A MAXIMUM ENTROPY PRINCIPLE MODEL FOR THE INITIALIZATION OF EULERIAN-LAGRANGIAN SPRAYS","authors":"Raul Payri, Gabriela Bracho, Pedro Martí-Aldaraví, Javier Marco-Gimeno","doi":"10.1615/atomizspr.2024050888","DOIUrl":"https://doi.org/10.1615/atomizspr.2024050888","url":null,"abstract":"NOx emission regulations have become more and more restrictive for Internal Combustion Engines vehicles, especially for road transport applications. To minimize emissions and comply with regulations, Selective Catalytic Reduction (SCR) systems are the most efficient deNOx technology thanks to the injection of a Urea-Water Solution (UWS). State-of-the-art Computational Fluid Dynamics (CFD) techniques employ Eulerian-Lagrangian frameworks to deal with the two phases of such problems. Still, the associated low velocities make using standard breakup models to generate initial drop size distributions difficult. Several studies end up needing experimentally characterized drop size distributions to initialize the CFD simulations or using expensive Eulerian-Eulerian simulations to obtain the outcomes of the primary breakup of the liquid jet. The Maximum Entropy Principle (MEP) allows generating a droplet size-velocity Probability Distribution Function (PDF) from initial injection conditions and injector characteristics while satisfying conservation equations. The most probable PDF curve is determined by the distribution that maximizes the entropy of the problem. A critical Weber number has been proposed to select which droplets will break\u0000up subsequently after the initial droplet break up. Validation is done against experimental results obtained by High-Resolution Laser Backlight Imaging. Comparable results have been found and realistic tendencies were achieved, decreasing the expected droplet size with increasing injection pressures. The proposed model could help introduce alternative breakup models for low-velocity\u0000applications without the need for prior droplet size knowledg","PeriodicalId":8637,"journal":{"name":"Atomization and Sprays","volume":"14 1","pages":""},"PeriodicalIF":1.2,"publicationDate":"2024-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139552497","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-01-01DOI: 10.1615/atomizspr.2024051142
Daniel Vasconcelos, Andre R. R. Silva, Jorge M. M. Barata
Evaporation and boiling are processes that occur in many industrial applications involving multiphase flows. For liquid films, however, studies are scarce regarding heat and mass transfer mechanisms, and require further research. The main objective of this work is to evaluate bubble formation and detachment, followed by the impact phenomena. Therefore, an experimental setup was built and adapted for this purpose. A borossilicate glass impact surface is placed over a heat source, which consists of an aluminium block with 4 embedded cartridge heaters which heats the liquid film by conduction. Water and n-heptane are the fluids adopted for the experimental study, as the differences in thermophysical properties allow for a wider range of experiments. Study cases include dimensionless temperatures of $theta>0.6$ for similar impact conditions. In terms of bubble formation, n-heptane displays smaller bubble diameters and higher release rates, whereas water exhibits larger bubbles and lower rates. Qualitatively, liquid film temperatures close to the saturation temperature do not reveal a direct influence on the crown development and posterior secondary atomisation. For later stages of the impact, the central jet height and breakup are influenced by the film temperature, which is associated with the variation of thermophysical properties.
{"title":"Influence of bubble growth and liquid film instabilities on droplet impact phenomena under saturated boiling regimes","authors":"Daniel Vasconcelos, Andre R. R. Silva, Jorge M. M. Barata","doi":"10.1615/atomizspr.2024051142","DOIUrl":"https://doi.org/10.1615/atomizspr.2024051142","url":null,"abstract":"Evaporation and boiling are processes that occur in many industrial applications involving multiphase flows. For liquid films, however, studies are scarce regarding heat and mass transfer mechanisms, and require further research. The main objective of this work is to evaluate bubble formation and detachment, followed by the impact phenomena. Therefore, an experimental setup was built and adapted for this purpose. A borossilicate glass impact surface is placed over a heat source, which consists of an aluminium block with 4 embedded cartridge heaters which heats the liquid film by conduction. Water and n-heptane are the fluids adopted for the experimental study, as the differences in thermophysical properties allow for a wider range of experiments. Study cases include dimensionless temperatures of $theta>0.6$ for similar impact conditions. In terms of bubble formation, n-heptane displays smaller bubble diameters and higher release rates, whereas water exhibits larger bubbles and lower rates. Qualitatively, liquid film temperatures close to the saturation temperature do not reveal a direct influence on the crown development and posterior secondary atomisation. For later stages of the impact, the central jet height and breakup are influenced by the film temperature, which is associated with the variation of thermophysical properties.","PeriodicalId":8637,"journal":{"name":"Atomization and Sprays","volume":"34 1","pages":""},"PeriodicalIF":1.2,"publicationDate":"2024-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139096088","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The internal flow in pressure swirl atomisers (PSAs) is numerically predicted by performing large eddy simulations and using a volume of fluid approach. The output of the numerical model is validated by comparing it with three databases of experimental measurements obtained on large-scale PSAs available in the open literature. A simplified analytical model previously developed by the authors, which relate the swirl intensity to the thickness of the fluid exiting the nozzle, is used to analyse the flow behaviour in three PSAs, with large differences in the injector geometry, the operating conditions and the fluid thermophysical properties. This simple relationship is found to hold for the three PSAs, with small changes of the parameter that accounts for energy losses, while data obtained with relatively small variations of the injector geometry are found to collapse on the same curve. The effects of operating conditions and fluid thermophysical properties on this relation are found to be irrelevant.
{"title":"The effects of shape and liquid properties on pressure swirl atomiser in-nozzle flow","authors":"Simona Tonini, Pierangelo Conti, Gianpietro Elvio Cossali","doi":"10.1615/atomizspr.2024050406","DOIUrl":"https://doi.org/10.1615/atomizspr.2024050406","url":null,"abstract":"The internal flow in pressure swirl atomisers (PSAs) is numerically predicted by performing large eddy simulations and using a volume of fluid approach. The output of the numerical model is validated by comparing it with three databases of experimental measurements obtained on large-scale PSAs available in the open literature. A simplified analytical model previously developed by the authors, which relate the swirl intensity to the thickness of the fluid exiting the nozzle, is used to analyse the flow behaviour in three PSAs, with large differences in the injector geometry, the operating conditions and the fluid thermophysical properties. This simple relationship is found to hold for the three PSAs, with small changes of the parameter that accounts for energy losses, while data obtained with relatively small variations of the injector geometry are found to collapse on the same curve. The effects of operating conditions and fluid thermophysical properties on this relation are found to be irrelevant.","PeriodicalId":8637,"journal":{"name":"Atomization and Sprays","volume":"6 1","pages":""},"PeriodicalIF":1.2,"publicationDate":"2024-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139648445","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
京公网安备 11010802042870号
京ICP备2023020795号-1
扫码关注我们
求助内容：
应助结果提醒方式：