Ethanol, a renewable fuel, has significant potential for enhancing engine combustion efficiency and reducing emissions. However, studies on the macroscopic spray development characteristics of ethanol in multi-hole injector under engine-relevant conditions remain relatively limited. In this study, a constant-volume chamber combined with shadowgraph imaging and high-speed photography was employed to systematically investigate the effects of injection pressure (10–30 MPa), ambient backpressure (0.1–0.7 MPa), and ambient temperature (20°C–120°C) on the macroscopic spray characteristics of ethanol. The results show that increasing injection pressure significantly enhances spray penetration and spatial dispersion, whereas increasing ambient backpressure suppresses spray development. Under elevated temperature conditions, enhanced evaporation leads to a slight reduction in spray penetration and spray area, while the spray cone angle exhibits an overall decreasing trend. Further dimensionless analysis based on the Reynolds number and Weber number indicates that spray penetration increases with increasing Re, whereas the spray cone angle shows an increasing trend with increasing We. These results suggest that dimensionless parameters can effectively characterize the variation of spray behavior under different operating conditions. This study provides experimental insights into the spray characteristics of ethanol in multi-hole injector and offers useful guidance for the optimization of gasoline direct injection systems and the application of renewable fuels.
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