The maximum liquid penetration length in evaporating spray of hydrated ethanol diesel emulsified fuels was investigated using Mie-scattered light imaging.The measurements for the pure Diesel fuel and the hydrated ethanol diesel emulsified fuels with varied fractions of the water-containing ethanol were carried out in a constantvolume,high-temperature and high-pressure vessel with varied fuel injection pressures,ambient gas temperatures and densities.Fuel injections were conducted with an electronically controlled common-rail high pressure injection system.The results show that the maximum liquid penetration length of the hydrated ethanol diesel emulsified fuels exhibits different behaviors compared to the pure diesel fuel.This is attributed to the two facts: 1)the different properties of distillation temperature; 2)the different latent heat during the evaporating processes for the different fuels.