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This paper describes an experimental bench for a non-intrusive characterization of fuel sprays. The characterization is obtained by computer analysis of the fuel spray images acquired using a high-resolution CCD camera. The bench has been developed by AEA for Siemens Automotive, in collaboration with Siemens' R&D staff and Perugia University researchers. Two different techniques have been implemented to obtain the jet images. The main target of this paper is the comparison of the results obtained using the two different methodologies of analysis.

The control of mixture formation by gasoline direct injection requires the continuous adaptation of the fuel spray characteristics in a broad range of load and speed. This paper presents an experimental analysis of the main spray characteristics for a jet generated by a GDI system with high pressure modulation (Zwickau Ram Tuned). The experimental method is based on spray visualization by a laser sheet technique. The radiation of a Nd-Yag pulsed laser is scattered by the spray droplets laying on the lighted plane and collected by a CCD camera, being fed to a frame grabber. Time and space related structure can be analyzed in any cross section of interest, giving information about jet form and penetration length. In particular, a suitable elaboration (Presence Probability Imaging) of several image series, collected at different delay times after injection start, supplies information about the probability of presence in space of spray liquid fractions.