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Holistic Approach of Spray Injection through a Generalized Multi-phase Framework

Periodic Reporting for period 2 - HAoS (Holistic Approach of Spray Injection through a Generalized Multi-phase Framework)

Reporting period: 2017-11-01 to 2019-10-31

HAoS-ITN network has developed a new generation of numerical tools that are available to both academic and non-academic sectors which can be utilized to design more advanced and efficient fuel injection systems and as a result, the fuel consumption and CO2 emissions from the transport sector would be reduced

The work has been completed according to the Grant Agreement, fully respecting the overall project aim. The scientific outcomes of HAoS have been published in numerous peer-reviewed and highly esteemed journal papers and conference proceedings. In addition to the conducted research, the HAoS network has trained the ESRs on a range of unique scientific modules, that have broadened their perspectives in both research and classical engineering skills. Equally important, ESRs have been trained on a range of transferable skills. Last but not least, the ESRs have been engaged in numerous outreach activities, disseminating their work to relevant non-specialised communities that made the EU funding and the impact of the performed research visible to the general public.
HAoS-ITN has successfully addressed the following scientific objectives:

(1) Performed quantitative flow measurements characterising the chain of events from in-nozzle flow down to fuel vaporisation.
(2) Performed numerical experiments using DNS aiming to derive closure models suitable for implementation to the Σ-Υ LES-PDF model.
(3) Developed/extended the Σ-Υ LES-PDF approach to include surface area generation/destruction closure models accounting for in-nozzle multi-phase phenomena (cavitation and flash boiling) and turbulence effects on primary and secondary atomisation
(4) Validated and applied the developed models to cases of industrial interest;
(5) Developed a training programme and succesfully trained the recruited fellows.
WP1: EXPERIMENTS AND INITIAL CONDITIONS
1. The combination of selected non-intrusive techniques resulted in an improved vision of the cavitating flows which are used for validation of computational simulations.
2. Combination of the experiments with a modelling effort, enable a deeper analysis and understanding of the bubble and jet dynamics. Data will be valuable in the development of models for cavitation-bubble-induced spray break-up.
3. Offered a better description of the flow in the nozzle. The way the TAP has been analysed and the results this analysis returned are progresses in the field of liquid atomization mechanism.
4. The CFD methodologies developed in this project can bring new insights into the complex multiphase flow phenomenon, produce new physics understandings, generate innovation ideas. The tools can lead towards higher precision products that contribute to the reduction of CO2 and toxic emissions over engine lifetime.

WP2: DNS ON PRIMARY/SECONDARY ATOMISATION

1. The produced data can be used in the derivation of collapse-induced atomization models for problems of larger scales; while also valuable insight gained into the mechanisms that lead to the development of high levels of pressure within the flow and on nearby surfaces.
2. Droplet size statistics and droplet velocity distributions have been determined with unprecedented detail for conditions relevant for upper stage rocket engines and orbital manoeuvring systems using direct numerical simulations and high performance computing capabilities. These DNS data are to be used for LES model development and future LES will aid combustor development and lead to the replacement of the current toxic hypergolic fuels by environmentally more friendly alternatives based on cryogenic liquids.
3. Proposed accurate numerical methods that can be used in the Navier-Stokes equation solver for simulating the physical configurations of aero-engine fuel injection.
4. For the first time, simulations for the breakup of droplets were performed at representative engine conditions (Diesel, scramjet and marine) as well as for cluster formations (tandem, parallel and combined). Correlations and simultions produced can be utilized in macroscopic CFD codes for the simulation of sprays, which can be utilized to design an efficient fuel injection system with a potential reduction in NOx emissions
5. It was observed that, for a range of conditions, breakup of a W/HFO emulsion droplet is faster and more optimized relative to the aerodynamic breakup of the corresponding neat HFO droplet. That information could be utilized as modeling insights for the simulation of W/HFO emulsion sprays.

WP3: HOLISTIC LES MODEL DEVELOPMENT
1. With the help of comparison with experimental data was observed that ELSA formulation using LES has the potential to simulate realistic fuel injection systems; the same formulation can be used to simulate injection systems in aerospace sector.
2. The developed multiscale numerical method has been developed for realistic engineering applications and differentiates from the analytical solutions of theoretical purposes.
3. The develop models use novel probabilistic approaches to determine the evolution of the liquid volume and surface as the liquid breaks into droplets and fragments. The results show that the method not only provides good predictions in air-blast atomizers but can also be applied directly to other types of fuel injectors, such as Diesel sprays for internal combustion engines.
4. Contribution towards predictive LES by developing a physics based LES SGS model for turbulence modulation effects in sprays. The model is based on a stochastic modeling approach called one-dimensional turbulence (ODT) resolving all scales. The model allows predictions of turbulence modulation effects in parameter regimes relevant to engineering problems which are mostly beyond the capabilities of DNS.
5. The new hybrid Euler-Euler and Euler-Lagrange model i.e. VOF-to-DPM
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