Modelling and Validating the Spray Characteristics of a Co-axial Twin-Fluid Atomizer Using OpenFOAM (original) (raw)
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Progress in Energy and Combustion Science, 2010
This review attempts to summarize the physical models and advanced methods used in computational studies of gasÀliquid two-phase jet flows encountered in atomization and spray processes. In traditional computational fluid dynamics (CFD) based on Reynolds-averaged NavierÀStokes (RANS) approach, physical modelling of atomization and sprays is an essential part of the two-phase flow computation. In more advanced CFD such as direct numerical simulation (DNS) and large-eddy simulation (LES), physical modelling of atomization and sprays is still inevitable. For multiphase flows, there is no model-free DNS since the interactions between different phases need to be modelled. DNS of multiphase flows based on the one-fluid formalism coupled with interface tracking algorithms seems to be a promising way forward, due to the advantageous lower costs compared with a multi-fluid approach. In LES of gasÀliquid two-phase jet flows, subgrid-scale (SGS) models for complex multiphase flows are very immature. There is a lack of well-established SGS models to account for the interactions between the different phases. In this paper, physical modelling of atomization and sprays in the context of CFD is reviewed with modelling assumptions and limitations discussed. In addition, numerical methods used in advanced CFD of atomization and sprays are discussed, including high-order numerical schemes. Other relevant issues of modelling and simulation of atomization and sprays such as nozzle internal flow, dense spray, and multiscale modelling are also briefly reviewed.
Spray Formation in the Multi-Hole Nozzle of Twin-Fluid Atomizers
2019
1 Automotive and Combustion Synergies Technology Group, Faculty of Engineering Technology, Universiti Tun Hussein Onn Malaysia, Pagoh Higher Education Hub, 84600 Pagoh, Muar, Johor, Malaysia 2 Combustion Research Group (CRG), Centre for Energy and Industrial Environment Studies (CEIES), Faculty of Mechanical and Manufacturing Engineering, Universiti Tun Hussein Onn Malaysia, 86400 Parit Raja, Batu Pahat, Johor, Malaysia
An Evaluation of Atomization Models for Dense Sprays
Calculations of a transient atomization process are presented, which simulates fuel injection of sprays in gasoline direct injection engines. Only non-reacting sprays are considered with the focus on the atomization process. The FIRE code, developed by AVL, is used as the platform to test three different atomization models: (i) Taylor Analogy Breakup (TAB) model; (ii) surface wave instability (WAVE) model; and the more recent (iii) FIPA (Fractionnement Induit Par Acceleration) model. Comparisons of calculations with experimental data reveal significant discrepancies regardless of the atomization model used. It is acknowledged that, in this study, only the standard model constants are adopted and that may be further optimised to improve the calculations. However, the fact remains that all the atomization models start with an initial distribution of spherical droplets at the injector tip. An assumption that is not supported by recent measurements which show that fluid elements rather than spherical droplets dominate this early zone.
Tehnicki vjesnik - Technical Gazette, 2022
In this paper, by using a numerical solution and experiment investigation, a non-dimensional number is introduced to estimate the characteristics of a real engine airblast atomizer spray. This type of atomizers is usually used in airplain engines. The test is conducted in ambient atmospheric pressure and at 300 K temperature and the effects of pressure on atomizer flow rate and spray con angle are investigated. We used the discrete phase model and real information of the ALF502 engine for simulations and for boundary conditions respectively. Since the main application of this airblast atomizer is in aircraft engines and in the real working conditions, none of the pressure and flow rate parameters is constant, thus, the main aim of this research is to define a nondimensional number K, which considers the effects of working liquid flow rate, air flow rate and pressure on the droplets average diameter and spray con angle simultaneously. The results showed that, in general, with the increase of non-dimensional K number, the average diameter of droplets in primary and secondary break up increases, but spray con angle decreases. Furthermore, numerical solution results are compared with experiment results and 9.98% error was observed.
SAE Technical Paper Series, 2011
During the last fifteen years Computational Fluid Dynamics (CFD) has become one of the most important tools to both understand and improve the Diesel spray development in Internal Combustion Engine (ICE). Most of the approaches and models used pure Eulerian or Lagrangian descriptions to simulate the spray behavior. However, each one of them has both advantages and disadvantages in different regions of the spray, it can be the dense zone or the downstream dilute zone. One of the most promising techniques, which has been in development since ten years ago, is the Eulerian-Lagrangian Spray Atomization (ELSA) model. This is an integrated model for capturing the whole spray evolution, including primary break-up and secondary atomization. In this paper, the ELSA numerical modeling of Diesel sprays implementation in Star-CD (2010) is studied, and simulated in comparison with the Diesel spray which has been experimentally studied in our institute, CMT-Motores Térmicos. Since many of the most important characteristics of the spray development, as the penetration or the axial velocity, can be captured using 2D simulations, in this preliminary validation of ELSA model only two-dimensional simulations have been performed. Moreover, the main objective of the paper is to: firstly, obtain mesh independency for further analysis and secondly, improve the classic k-ε RANS model for ELSA model. Apart from this, several characteristics of the spray as can be the droplet formation of the liquid penetration are also showed.
Experimental Investigations on Spray Characteristics in Twin-Fluid Atomizer
Procedia Engineering, 2011
A twin-fluid atomizer was designed and developed for fuel atomization. The droplet characteristic in the spray which was produced with the atomizer was investigated experimentally. Air flow induced in the atomizer causes a pressure reduction, hence the fuel is sucked into the atomizer. The mixture flow of air and liquid caused the atomization downstream due to the turbulence. In the twin-fluid atomizer, atomization is attained by injecting an air stream at tip of the liquid inlet port. In this research, the test liquid supply pressure was kept constant and the air flow rate through the atomizer was varied over a range of air supply pressure to obtain the variation in air liquid mass flow ratio (ALR) from 0.2 to 2.7. The results revealed that the air assisted atomizer had a capability to inject the test liquid in the range of the rates of 0.0019-0.00426 kg/s, with the use of air pressure supplied from 68.9 to 689 kPa. The images of the spray were obtained with a shadowgraph technique and analyzed to obtain the particle size and its distribution. Droplet size from twin-fluid atomizer had various sizes in the range of about 17-200 m. The atomizer can be applied for aerosol and combustion purposes.
Evaluation of the Eulerian-Lagrangian spray atomisation (ELSA) in spray simulations
International Journal of Vehicle Systems Modelling and Testing, 2011
The aim of this paper is the evaluation and validation of the Eulerian-Lagrangian Spray Atomization (ELSA) model implemented in a CFD code by Renault. ELSA is an integrated model for capturing the whole spray evolution, in particular including primary break-up and secondary atomization. Two-dimensional simulations have been performed during the study, which is in fact enough to capture some of the main features of the spray, such as the spray penetration and the axial velocity. A mesh independence study has also been carried out in order to characterize the lowest mesh size that can be used to correctly characterize the spray. Furthermore, the two-equation k-ε turbulence model has been adjusted by changing some of the parameters of the dissipation rate transport equation in order to accurately characterize the spray. Finally some analyses of the results obtained, in terms of penetration, liquid mass fraction and droplet number and size, are presented in the last section of the paper.
Evaluation of the Eulerian-Lagrangian Spray Atomization (ELSA) model in spray simulations: 2D cases
Mathematical and Computer Modelling
The aim of this paper is the evaluation and validation of the Eulerian-Lagrangian Spray Atomization (ELSA) model implemented in a CFD code by Renault. ELSA is an integrated model for capturing the whole spray evolution, in particular including primary break-up and secondary atomization. Two-dimensional simulations have been performed during the study, which is in fact enough to capture some of the main features of the spray, such as the spray penetration and the axial velocity. A mesh independence study has also been carried out in order to characterize the lowest mesh size that can be used to correctly characterize the spray. Furthermore, the two-equation k-ε turbulence model has been adjusted by changing some of the parameters of the dissipation rate transport equation in order to accurately characterize the spray. Finally some analyses of the results obtained, in terms of penetration, liquid mass fraction and droplet number and size, are presented in the last section of the paper.
Modeling atomization process in high-pressure vaporizing sprays
1987
A multi-dimensional computer model is used to study atomization and vaporization of a liquid jet injected from a round hole into a compressed gas. Atomization is described using a new method whereby 'blobs' are injected (with sizes equal to the nozzle exit diameter), and breakup of the blobs and the resulting drops is modeled using a stability analysis for liquid jets. This method can also predict various regimes of breakup which result from the action of different combinations of liquid inertia, surface tension and aerodynamic forces on the jet. The product drops are distinguished from the parent drop by having different dropsizes (previous drop breakup models have lumped the parent and product drops together). This has a significant effect on the fuel vapor distribution in a high-pressure spray because the small product drops vaporize rapidly. Like existing models, the model accounts for drop collision and coalescence, and the effect of drops on the gas turbulence. These effects are important in high-pressure sprays where breakup of the liquid yields a core region near the nozzle containing large drops. Fuel vaporization in the core is found to depend strongly on the atomization details near the nozzle. Downstream of the core, fuel-air mixing is found to be determined by a competition between local drop breakup, coalescence and vaporization rates.