Application of an Imaging-based Diagnostic Technique to Quantify the Fuel Spray Variations in a Direct-Injection Spark-Ignition Engine

This paper presents an imaging-based diagnostic technique to quantify the pulse-to-pulse variability of macroscopic fuel spray characteristics for Direct-Injection Spark-Ignition (DISI) engine applications. The analysis approach is based on the construction of a spray ensemble image, reflecting the regions of probability of liquid presence for a set of images. Overlaying of an individual spray boundary on the probability-based ensemble image can further enhance the two-dimensional visualization of the pulse-to-pulse spray variations. Spray structures at three experimental conditions were examined: room ambient, and early and late injection conditions inside an optical engine. While the spray structure was observed to be considerably different for the three conditions, the magnitudes of variation of global spray shape and spray tip penetration distance were found to be of similar order.

This methodology is capable of capturing the magnitude of pulse-to-pulse variability in penetration and spray geometry and displaying the variations in a two-dimensional representation. It is a useful diagnostic tool for fuel injector spray evaluation and can be used in support of the fuel injector development and application process for DISI engines.