Development of High-Speed Laser Absorption Scattering (HS-LAS) System for Measuring Vapor and Liquid Phase Concentration Distributions in Evaporating Diesel Spray

Paper in proceeding, 2022

The fundamental concept of the LAS technique is to understand the fuel concentration by attenuation of both visible and ultraviolet light. The intensity of visible light is only attenuated by the scattering of droplets, while that of ultraviolet light is attenuated by the scattering of droplets and the absorption of vapors. The conventional LAS uses the ND: YAG pulse laser, CCD cameras and one shot for one spray, which takes time and effort. Moreover, temporal variation measurement of a single shot spray is not possible by the conventional LAS. To record the distribution of the whole vapor phase in an injection event and measure the liquid and vapor concentration inside the spray, a high-speed laser absorption scattering (HS-LAS) technique was developed applying continuous diode light source, high-speed video cameras, and image intensifier for UV light, which can provide the temporal variation of a single shot spray. In the experiment, a commercial seven-hole injector with a hole diameter of 0.123 mm allowing high injection pressure up to 100 MPa was used to avoid the potential inconsistencies with single-hole test injector. The diesel surrogate fuel which consists of 97.5 % n-tridecane and 2.5 % of volume-based 1-methylnaphthalene was used. The injection amount 5.0 mg/hole were selected to investigate the structure and mixture formation process of the spray. The findings of the experiments show that this imaging approach is a promising diagnostic technique for concurrently obtaining quantitative information on the quantity of vapor and droplets in a fuel spray. Furthermore, the turbulent/vortex fluid dynamics' temporal development/variation can be investigated.