Correlation of spatial heterogeneity of fuel vapor concentration and turbulent vortex in evaporating intermittent spray

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To explore the correlation of the fuel vapor concentration and the turbulent vortex in evaporating spray, we performed the researches on the spatial heterogeneity of fuel concentration in intermittent fuel spray and the measurement technique of flow velocity by 2D image analysis in parallel.In the study of the spatial heterogeneity of fuel concentration, the characteristic movements of fuel particles were captured and analyzed through the high speed photography of 2D sectional image of intermittent non evaporating spray, and the new knowledge for the formation process of spray structure was obtained. Through the visualization of fuel vapor concentraition in evaporating spray by the exciplex fluorescence method, the heterogeneity of vapor concentration was characterized. The structure of fuel vapor distribution in evaporating spray is similar to that of droplets distribution in non evaporating spray though the spatial scale is a little bit larger than that in non evaporating one.In the study of the measurement technique of flow velocity by 2D image analysis, a new course of image analysis technique was examined in particle image velocimetry, PIV.By condensing each particle image information into its gravity center, the calculation of auto-correlation plain was greatly reduced into the comparison of each particle displacing. Analyzing the shape of the second peak of auto-correlation plain obtained in this way, identification of each particle motion can be carried out, and several tens of velocity vectors were extracted within a single interrogation spot. The local turbulent intensity and integral length scale were analyzed from these extracted velocity vectors. By applying this PIV technique to the evaporating spray under the high pressure and high temperature condition, the instantaneous velocity vectors maps were obtained successfully.