ASTRIDE

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.