Effects of Ambient Temperature and Pressure on Direct Injection Fuel Spray for S.I. Engine

High-pressure fuel spray proposed for direct injection gasoline engine was evaluated by means of a phase Doppler anemometer (PDA) and flow visualization. The intermittent fuel spray from a swirl type injector was injected in a constant volume chamber under various conditions of backpressure and ambient temperature. The backpressures were set to 0, 0.5 and 1 MPa in gauge pressure. The ambient temperatures were set to 293, 373, 423 and 473K. Normal-heptane was used as a fuel with injection pressure of 10MPa and injection frequency of 10Hz. Spray characteristics of the temporal and spatial distributions of the mean velocity and the mean diameter were measured by the PDA. Visualizations of spray were also made by a particle image velocimetry (PIV). The experimental results show the effects of backpressure and ambient temperature on the spray shape and characteristics of droplet size and velocity distributions. It is also confirmed that the time-dividing method proposed by the authors was useful for analyzing the intermittent spray.