The effects of surface temperature on the deposit behaviors of gasoline on a hot surface

The formation of the internal deposits inside a gasoline direct injection (GDI) injector is directly related to the oxidation of the remained gasoline in the nozzle after injection. In the present paper, an experimental facility and procedure for gasoline deposits forming on a hot surface were carefully designed to simulate the deposit behavior inside the GDI injector. In the experiments, the evaporation characteristics of gasoline droplets were observed, and the quantities of deposits at different temperatures of the hot surface were measured. Besides, the morphology, elements and components of the deposits obtained at different surface temperatures were examined to identify the variation of the components in gasoline after heating and oxidation. The experimental results showed that surface temperature influenced the evaporation form of droplets significantly, which would be reflected in the morphology of the deposits obtained, leading to the deconcentration and miniaturization trend of deposits with the increase of surface temperature. The variation in the quantities of deposits obtained with the surface temperature presents a two-peak shape, and the main components of the deposits in the two peaks differed completely in terms of morphology and elements. The heavy ends of the gasoline, such as naphthalene and its derivatives, should be responsible for the major deposits forming at low temperature, and the oxidation degree of deposits increased with the temperature. In addition, carbon-oxygen double bond was generated universally at each temperature, and the benzene ring was abundant in the deposits obtained at a lower temperature, while seldom existed in the deposits obtained at a higher temperature.