Rayleigh Scattering Measurements of Transient Fuel Vapor Concentration in a Motored Spark Ignition Engine

Laser Rayleigh scattering was applied for the remote, nonintrusive measurements of the time history of the transient fuel vapor concentration in the combustion chamber which was caused by the timed injection of unleaded regular gasoline, n-Pentane and n-Hexane into the intake port of a motored automotive spark ignition engine. The results denonstrated that the fuel vapor concentration increased with the time elapsed from the start of the fuel injection and reached a peak after which it decreased during the intake stroke. It showed a very slight increase during the compression stroke. It was also revealed that the fuel vapor concentration increased with an increase in the quantity of fuel injected, the engine speed and the fuel injection pressure. It showed a maximum as a function of the fuel injection timing. The strong correlation was observed between the peak vapor concentration during the intake stroke and the vapor concentration at the end of the compression stroke.

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