Laser-based measurements and analyses on cycle-to-cycle variations of mixture formation in binary-component fuel sprays

The cyclic variations of vapor distributions of a binary-component fuel spray were experimentally investigated. Ultraviolet–visible laser absorption/scattering technique was adopted for quantitative measurement of vapor mass distributions in a binary-component fuel spray. n-Hexane and p-xylene were chosen to form the binary-component test fuel. Intersection-over-union, an important concept in object detection, was firstly introduced to characterize more precisely the spray cyclic variations, in comparison with other traditional methods including presence probability image and coefficient of variation in spray penetration. As a result, a larger fluctuation was observed in vapor distributions of the higher boiling point component (p-xylene) in the binary-component fuel compared to that of the pure p-xylene spray, indicating that evaporation characteristic of multi-component fuel spray is one of the significant factors that affects the cyclic variations. Based on large amount of experimental observations, a concept of spray vapor distribution area with consideration of cyclic variation was proposed to give a more reasonable expression of spray structure, and a new empirical formula of spray vapor distribution area was given for prediction and numerical model validation.