Development of Quantitative Fuel Film Distribution Measurement by LIEF Technique and Application to Gasoline Spray 2020-01-1159

From the point of global and local environment, internal combustion engine is facing the need for significant improvement of exhaust emission. Especially, important is the reduction of unburned hydrocarbon (HC) from fuel film on liner under cold condition. In this study, at first, quantitative fuel film measurement technique by using Laser Induced Exciplex Fluorescence (LIEF) was developed. For the light source, 4th harmonic pulse yttrium aluminum garnet (YAG) laser (266nm) was used. For the tracer, the combination of N,N-Dimethylaniline (DMA) and naphthalene was used and quantitative concentration was decided by calibration test. With LIEF, the distribution of fuel film can be obtained by measuring the fluorescence only from the liquid phase. In order to evaluate the effect of fuel film on exhaust HC emission from engine, the film distribution was measured using quartz glass liner. For the injector, a prototype 6-hole gasoline injector was used. For the evaluation of total amount of fuel film on liner, the film distribution image was taken from both the exhaust and front side. The effect of fuel pressure (between 20 to 60 MPa) and of temperature was analyzed. Then, the correlation between the measured total amount of fuel film and the unburned HC from the engine was confirmed by the engine test. Additionally, a computer fluid dynamics (CFD) simulation model was validated against the measured results and a design with better flow rate of each hole was proposed. Additionally, the fuel film results were tried to explain from the character of spray. Spray velocity and vaporization rate were decided by direct scattering measurement of spray. And liquid particle diameter was also measured by two methods [phase Doppler particle analyzer (PDPA), combination of Mie scattering and LIEF]. These spray results were compared with theory and confirmed the validity of the results. Finally, the effect of fuel pressure and temperature et al. to fuel film was explained by the measured spray character.