Abstract
Predictive simulation of liquid fuel injection in automotive engines has become a major challenge for science and applications. The key issue in order to properly predict various combustion regimes and pollutant formation is to accurately describe the interaction between the carrier gaseous phase and the polydisperse evaporating spray produced through atomization. For this purpose, we rely on the EMSM (Eulerian Multi-Size Moment) Eulerian polydisperse model. It is based on a high order moment method in size, with a maximization of entropy technique in order to provide a smooth reconstruction of the distribution, derived from a Williams-Boltzmann mesoscopic model under the monokinetic assumption [O. Emre (2014) PhD Thesis , Ecole Centrale Paris; O. Emre, R.O. Fox, M. Massot, S. Chaisemartin, S. Jay, F. Laurent (2014) Flow, Turbulence and Combustion 93 , 689-722; O. Emre, D. Kah, S. Jay, Q.-H. Tran, A. Velghe, S. de Chaisemartin, F. Laurent, M. Massot (2015) Atomization Sprays 25 , 189-254; D. Kah, F. Laurent, M. Massot, S. Jay (2012) J. Comput. Phys. 231 , 394-422; D. Kah, O. Emre, Q.-H. Tran, S. de Chaisemartin, S. Jay, F. Laurent, M. Massot (2015) Int. J. Multiphase Flows 71 , 38-65; A. Vie, F. Laurent, M. Massot (2013) J. Comp. Phys. 237 , 277-310]. The present contribution relies on a major extension of this model [M. Essadki, S. de Chaisemartin, F. Laurent, A. Larat, M. Massot (2016) Submitted to SIAM J. Appl. Math.], with the aim of building a unified approach and coupling with a separated phases model describing the dynamics and atomization of the interface near the injector. The novelty is to be found in terms of modeling, numerical schemes and implementation. A new high order moment approach is introduced using fractional moments in surface, which can be related to geometrical quantities of the gas-liquid interface. We also provide a novel algorithm for an accurate resolution of the evaporation. Adaptive mesh refinement properly scaling on massively parallel architectures yields a precise integration of transport in physical space limiting both numerical dissipation as well as the memory trace of the solver. A series of test-cases is presented and analyzed, thus assessing the proposed approach and its parallel computational efficiency while evaluating its potential for complex applications.
Highlights
In the last decades, automotive industries have been widely concerned by the efficiency of combustion devices and the reduction of pollutant emissions
Once a model has been obtained with a clear relationship with geometrical quantities in separated phases averaged models and once a realizable, and robust, and accurate numerical scheme coupled to a mesh adaptation strategy has been designed, several steps have to be conducted in order to assess the proposed strategy
Beyond providing a verification of the proposed new geometrical moment and related algorithm compared to the EMSM model, we aim at proving that: 1- the Adaptive Mesh Refinement (AMR) solver reaches a very nice level of accuracy once we have chosen a proper refinement criterion; 2- the proposed strategy is valid for complex droplet models, that is for source term with a much higher level of complexity leading to much higher arithmetic intensity; 3- that we have a high level of scalability and efficiency of the parallel implementation of the numerical strategy relying on realizable schemes and splitting
Summary
Automotive industries have been widely concerned by the efficiency of combustion devices and the reduction of pollutant emissions. In automotive engines, the fuel is stored as a liquid phase and injected at high pressure in the combustion chamber. Close after the outlet nozzle, the fuel is still in liquid form and separated from the gaseous phase by an interface; we have to deal in this region with what is called a separated phases two-phase flow. The atomization process is going to produce a complex dynamics of the interface and eventually yields a polydisperse evaporating spray, which will control the combustion regime as well as pollutant formation. It has been shown that the polydisperse character of the spray has a key influence and should be described in any attempt of modeling such flows. The challenge is as much a scientific as an application one
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