Introduction

Downsizing and Direct Injection (DI) implementation are two main trends in the gasoline engine development for the last decade. Both bring improvements in efficiency but also new challenges for engine optimization. On this way, the gasoline direct injection (GDI) engines are growing fast in the U.S. market place representing more than 50% of vehicles produced in 2017[1]. One of the main challengers is the spray and wall interaction, because it is accepted that the deposition of liquid fuel wall films on the combustion chamber is a significant source of particulate formation in GDI engines [2,3]. In order to know the effect of the distribution of the heavy and light fraction of a multicomponent fuel after the injection, the vaporization process around the impingement region was analyzed, because it can have a huge influence in the soot generates inside the pool fires during the combustion[4,5]. The methodology proposed for Itani et al. [6] and discussed by Bardi et al.[7] was used.

Material and methods

The fluorescence of two tracer was studied: 1-MethylNaphthalene (1-MN) and 2,4 DifluorBenzene (DFB). The first one is used as tracer of the heavy fraction and the second one to light-medium fraction. A transparent fuel was used in order to no interfere in the emission spectrum of the tracers, with a composition of: iso-octane, hexane and dodecane. Additionally, In order to verify the quality of the calibration reference images (Im1, Im2, Im3) were acquired before the injection event (Im4), as it can be observed on the Figure 1. The classical arrangement to produce a light sheet at 266 nm is used and the signal of fluorescence was acquired using an image doubler for the camera ICCD, the image double permit to capture two images in simultaneous. These considerations permitted to study the variation of the composition around the fuel film after the injection. The injection pressure was changed between 30 to 200 bar.

Results and discussion

It was possible to identified the local variation with the time of the two fraction studied: light-medium to heavy fractions. The Figure 2 show some of the result when the plate have a fixed temperature of 120 °C, the injection pressure was of 100 bar. On this way the result when the injection pressure was changed from 30 bar to 200 bar will be discussed.

Note: please check the figures on the PDF file