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Report

Teaser, summary, work performed and final results

Periodic Reporting for period 1 - HAoS (Holistic Approach of Spray Injection through a Generalized Multi-phase Framework)

Teaser

HAoS, is a unique international, interdisciplinary and intersectoral research consortium that aspires to create the new generation of numerical tools that will be available to both academic and non-academic sectors and will facilitate the cost effective design of novel FIE...

Summary

HAoS, is a unique international, interdisciplinary and intersectoral research consortium that aspires to create the new generation of numerical tools that will be available to both academic and non-academic sectors and will facilitate the cost effective design of novel FIE. HAoS program aims to develop a large eddy simulation (LES) CFD model that will account for the influence of unresolved sub-grid-scale (SGS) processes to engineering scales at affordable computing time scales. The bridging parameter between SGS and macro-scales flow processes is the surface area generation/destruction occurring during fuel atomisation; relevant SGS closure models will be developed through tailored experiments and DNS and will be implemented into the LES model redicting the macroscopic spray development as function of the in-nozzle flow and surrounding air conditions.

The topics to be addressed in the corresponding work packages WP1 to W6 are the following:

(1) To perform quantitative flow measurements characterising the chain of events from in-nozzle flow down to fuel vaporisation.
(2) To perform numerical experiments using DNS aiming to derive closure models suitable for implementation to the Σ-Υ LES-PDF model.
(3) To develop/extend 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) To validate and apply the developed model to cases of industrial interest;
(5) To develop a training programme for the recruited fellows.
(6) To effectively manage the proposed programme in accordance with the guidelines of the Marie-Curie ETN programmes, and to disseminate the knowledge and the tools built at the network level, relevant industries, international level and the general public.

Work performed

The HAoS project up to month 24:

1.HAoS partners have submitted 17 deliverables with due date until month 24.
2.Up to month 24, 4 milestones have been met.
3.The recruited Fellows have been provided with a range of scientific and general skills training.
4.The HAoS partners have started disseminating the outcome of the work performed and have engaged the Fellows to outreach activities.
5.Has recruited 15 Research Fellows (ESRs) that are funded by the programme and 1 Research Fellow that is funded directly by UMELB.

Final results

According to the submitted deliverables up to month 24 the following research highlights should be mentioned:

WP1: EXPERIMENTS AND INITIAL CONDITIONS

D1.1: \'High speed imaging in cavitating orifice\'
The cavitating flow has been visualised in a flow orifice. Two vortices have been found, one in the direction of the flow and one originating from the sharp edge at the inlet of the orifice, having direction normal to the main flow. The dominant frequencies of fluctuation of longitudinal cloud cavity length was found to be identical to the fluctuations of vertical vortex diameter in many cases .

D1.7: \'Flow visualisation during sac volume filling\'
The sac filling process simulation shows evidence laminar turbulent transition and cavitation in the sealing area. The atomisation process in GDi nozzles is shown to start in the spray hole due to cavitation, as well high speed air entrainment is predicted in the counter bore which shows the need of modelling the air compressibility. Finally at needle closing fuel throttling causes low pressure in the sac which promotes sac cavitation and air but also fuel suction as well as low speed liquid fuel ligaments . The fuel suction can be a major contribution to the injector tip diffusion flame and coking.

WP2: DNS ON PRIMARY/SECONDARY ATOMISATION

D2.1: \'DNS validation of bubble collapse atomization\'
The 1D-IIM model that was developed in order to resolve the wave interactions at the liquid-gas interface in a physically accurate manner is a novel method for the definition of the inter-component boundary conditions in multi-dimensions. It is a method that combines high accuracy, low computational cost and is easy to implement compared to other methods in the literature.

D2.7: \'DNS for non-evaporating droplet clusters\'
In the current work the breakup of Diesel and HFO droplets was simulated for the first time in conditions encountered in real engines. Based on the simulations, interesting conclusions were drawn about the effect of Oh number and density ratio on useful quantities for spray systems such as the drag coefficient and the liquid surface area. Moreover, a correlation that predicts the breakup initiation time as function of the non-dimensional parameters (We, Oh, Re and ε), was proposed.

WP3: HOLISTIC LES MODEL DEVELOPMENT

D3.11: \'Internal Nozzle Flow Simulations\'
The VOF method more accurately track the interface between the phases but it is very computationally expensive while scale resolving technique more accurately depicts the turbulence. WMLES subgrid model is relatively computationally affordable as compared to conventional subgrid scale models.


The work under way in the HAoS project addresses these issues. Advanced models are currently under development and will become available to the industrial partners, aiming to assist in the design of efficient fuel system and combustion concepts

Website & more info

More info: http://haos-itn.eu/.