Aerodynamics and Sprays during TRansients of Gasoline Direct Injection Engines – ASTRIDE

This work will in particular profit from the innovative development of an analysis method of fast PIV velocity measurements for quantifying transient aerodynamics, and of a LES methodology for engine transients. This will be supported by experimental and modelling work concerning the characterization of sprays generated by last generation multi-hole injectors, their impact on a wall, the formation and evolution of a film, as well as of the evaporation of a film in a simplified configuration representative of the GDI context.
The thus acquired understanding of the specificities of interactions between in-cylinder aerodynamics and the spray in GDI transients, and of their impact on the film formation and evolution, will be capitalised in the form of models for system simulation.
The work proposed by ASTRIDE hereby aims at developing and validating breakthrough design tools that could contribute after the project to the emergence of GDI engines exhibiting soot particle production levels inside the cylinder that would be sufficiently low in order to avoid the negative impact in terms of cost and efficiency generated by the usage of soot particle filters in the exhaust.

Characterization of injection and spray / wall interactions :
Experimental and numerical databases have been constructed to provide detailed information on the spray issued from a gasoline multihole injector. An experimental database on spray/wall interactions has been constructed. These results permit to envisage the fitting of injection on engine computations realised in the engine CFD part (5.2) and to characteriez the dynamics of the spray/wall interaction of the model developed in 3.3.

Development and validation of an evaporating liquid film :
The measurement technique for vapour concentration in the vicinity of the liquid film has been developed. First results are now used to help validate the experimental task of task 3.3.


Exploration and experimental analysis of aerodynamics in engine transients :
First acquisitions of PIV measurements in transient operating conditions have been performed. The EMD2D analysis tool will be exploited on these PIV. Quantitative comparisons of LES simulations can now be envisaged with these results during task 5.2


Development of 1D/3D two way coupling for engine transients :
Prototype coupling tool for 1D/3D coupled simulations has been first tests in stabilised operating conditions.

In the last part of the project, system simulation models will be developed. In particular, in a first part of this work limitations have been identified in the formulation of the turbulence model presently used. It is a crucial point because the combustion velocity is directly related. The modeling effort in this phase will mainly focus on the improvement of the turbulence model as a key input parameter for reactive simulations. It will rely on analysis from 3D CFD, which is perfectly in relation with the context of the project.
Such improvements, will be exploited in coming studies on combustion during transients, in particular in terms of pollutants.

Bivariate EMD behavior for separating coherent structures from interference fluctuations in homogeneous isotropic turbulence, M. Sadeghi, K. Abed-Meraim, F. Foucher, C.Mounaïm-Rousselle, Submitted to Progress in Turbulence.

Measurements of 3-Pentanone Laser Induced Fluorescence with Application for Imaging Concentration of an Evaporate Fuel Film of n-Heptane, Mouret Q., Manuel Q., Vena P., Cédric G., Escudié D., submitted in International Journal of Heat and Mass Transfer.

LES Study on mixing and combustion in a Direct Injection Spark Ignition engine, N. Iafrate, A. Robert, B. Cuenot, J.-B. Michel, International Journal of Engine Research, to be submitted 2015.

Analysis of the EMD behavior for separating coherent structure from interference fluctuations in homogeneous isotropic turbulence, M. Sadeghi, K. Abed-Meraim, F. Foucher, C.Mounaïm-Rousselle, iTi CONFERENCE ON TURBULENCE VI, September 21-24, 2014| Bertinoro, Italy time

Prediction of cyclic combustion variability in internal combustion engines via coupled 1D-3D LES method, J. bohbot, B. Roux, P. Sagaut, Q-H. Tran, 11th World Congress on Computational Mechanics, 20-25 July 2014, WCCM XI, Barcelona, 2014.

Gasoline direct injection (GDI) is among the technologies with a strong potential for improving the efficiency of spark-ignition engines. Considering the evolution of pollutant regulations, transient phases will play an increasingly critical role, and recent research has shown that transient phases are responsible for high particulate emission levels of GDI engines. The exact reasons of this observation are poorly understood, and classical design techniques that have proved their adequacy for optimising stabilized GDI operating points do not allow mastering these issues. In this context the objective of ASTRIDE is to contribute to a better understanding of the mixture preparation and the formation of liquid films during cold transients of internal combustion, gasoline direct injection (GDI) engines. Recent work has indeed shown that transients are responsible for important levels of soot particle emissions in such engines. The reasons for this are poorly understood, and classical design techniques having proven their adequacy for optimising stabilized operation of GDI engines fail to master them.
The highly innovative work proposed by ASTRIDE is based on a combined usage of experimental techniques and Large-Eddy Simulation (LES) for studying transients in a single cylinder GDI engine, in a breakthrough approach as compared to classical techniques. This work will in particular profit from the innovative development of an analysis method of fast PIV velocity measurements for quantifying transient aerodynamics, and of a LES methodology for engine transients. This will be supported by experimental and modelling work concerning the characterization of sprays generated by last generation multi-hole injectors, their impact on a wall, the formation and evolution of a film, as well as of the evaporation of a film in a simplified configuration representative of the GDI context.
The thus acquired understanding of the specificities of interactions between in-cylinder aerodynamics and the spray in GDI transients, and of their impact on the film formation and evolution, will be capitalised in the form of models for system simulation.
The work proposed by ASTRIDE hereby aims at developing and validating breakthrough design tools that could contribute after the project to the emergence of GDI engines exhibiting soot particle production levels inside the cylinder that would be sufficiently low in order to avoid the negative impact in terms of cost and efficiency generated by the usage of soot particle filters in the exhaust.