Experimental Characterization of Ethanol Sprays from a Single Hole Direct Injection Injector

This study concerns the sprays produced by a single hole direct injection injector through a systematic image treatment methodology. The images were obtained by high speed recording associated with shadowgraph technique. The recording frequency was 6504 Hz. Grayscale images were obtained after a process of histogram adjusting and image subtraction. The spray volume and penetration was evaluated through a process of edge detection in the hollow cone of the spray injection. A criterion based on pixel values was taken to localize the spray edges as angles and x and y position data. The high pixel values were associated with liquid phase while the low pixel values were associated to its absence. Computational codes written in Matlab environment were used to analyze the numerical matrices associated to the images. The high frequency image recording allowed studying the sprays in all its development. The tests were conducted with injection pressure variation. The injection pressures in this work were 30, 50, 70, 90, 100 and 110 bar. EXXSOL D60 was the tested fluid. This fluid simulates ethanol fuel properties. Nitrogen was the gas used in a pressurized chamber to give the required injection pressures. The results show little cone angle variation with injection pressure, higher spray penetration for higher pressures for sufficient time after start of injection (ASOI) and spray volume with linear behavior with the time ASOI.