Macroscopic and microscopic characteristics of ethanol and gasoline sprays

This paper reports the macroscopic and microscopic characteristics of ethanol and gasoline direct injection sprays from a multi-hole injector. The spray experiments were conducted in a constant volume chamber in atmospheric condition (1 bar and 300 K ambient condition). Compressed nitrogen was used to pressurize the injection pressure which was 6.0 MPa. The injection pulse width was 2.0 ms. The high speed Shadowgraphy imaging technique with a speed of 20000 fps @ 608×288 pixels was used to capture the macroscopic spray characteristics. Based on that, the high magnification imaging of the ethanol and gasoline sprays close to the nozzle exit was conducted with the same flash and camera but with an AFTVision ZL0911 microscope. In order to capture the first fuel seen from the nozzle exit, the camera speed was increased to 50000 fps @ 240×88 pixels. Results showed that the macroscopic characteristics of ethanol and gasoline sprays were rather similar in terms of spray tip penetration, spray angle and spray projected area in spite of the differences in physical properties. However, the magnified spray images at the nozzle exit showed that ethanol spray had a larger and sheet-like ligaments at the end of injection than gasoline spray did due to ethanol's larger surface tension and viscosity. It may imply that the fuel properties only have significant effect on the spray during the primary breakup process, but not on the secondary breakup process