Quantitative Measurement of Liquid and Vapor Phase Concentration Distributions in a D.I. Gasoline Spray by the Laser Absorption Scattering (LAS) Technique

To get quantitative measurements of liquid and vapor phase concentration distributions in a gasoline spray, a laser-based absorption and scattering (LAS) technique was developed. The LAS technique adopts ultraviolet and visible lasers as light sources and a test fuel, which absorbs the ultraviolet light but does not absorb the visible light, instead of gasoline. The LAS principle is based on the incident light extinction in the ultraviolet band due to both vapor absorption and droplets scattering, whereas in the visible band, the incident light extinction is due only to the droplet scattering. The absorption spectra and molar absorption coefficients of the candidate test fuels including p-xylene, benzene and toluene, all of which have physical properties similar to gasoline, were investigated, and p-xylene was finally selected as a test fuel. Measurement accuracy of the LAS technique was discussed. Finally, experiments were conducted on a spray injected into a constant volume vessel by a swirl injector for a direct injection (DI) gasoline engine. The concentration distributions of both liquid and vapor phases in the spray were quantitatively clarified and their variations with time was elucidated. The effects of ambient temperature on the concentration distribution were also investigated.