Multi-component fuel drop-wall interactions at high ambient pressures

摘要

In direct injection engines, multicomponent fuels are injected at high pressures-resulting in a finely atomized spray which impacts on the hot wall of the piston crown and cylinder liner. The variable operating load of typical combustors results in widely varying wall temperature and ambient pressures. For quantitative prediction of the combustion spray physics, detailed data is required for the impact of multicomponent fuel drops on these heated surfaces at combustor-relevant pressures. A series of experiments are presented for blends of n-heptane and n-decane, as well as a commercial gasoline blend impacting heated walls at ambient pressures in the range of 1-20 bar and wall temperatures up to 350 degrees C. Time-resolved image sequences for single drop impacts are used to classify the onset of Leidenfrost phenomena, nucleate boiling, and film spreading. Results are summarized by impact regime diagrams, and bi-component mixtures are found to replicate the systematic behavior observed for a gasoline drop with the higher volatility components controlling behavior at low pressure, and a decreasing effect at high pressure. These experiments establish a baseline for multicomponent drop-wall interactions at combustor-relevant pressure, and will aid in development of simulations incorporating relevant spray-wall physics in combustors.