A study on the in-cylinder flow characteristics of GDI high-pressure fuel injector using a transparent engine system

The direct-injection spark-ignition engine is one of the promising gasoline engine designs for achieving higher engine performance and lower fuel consumption while maintaining the excellent driving performance and low emissions. Thus an in-cylinder spray flow motion plays an important role in the adjustment of mixture preparation with fundamental spray characteristics and in- cylinder flow field as well. In this study, the fundamental spray characteristics such as drop size, velocity distribution, spray angle, in- cylinder spray flow motion in order to optimize intake port, piston top land and combustion chamber shapes in the development stage of mass-produced GDI engine. For this purpose, the PDPA measurements and Mie scattering technique were used for detailed spray characteristics. In-cylinder spray motions were captured by ICCD camera through the single-cylinder optical engine. From the experimental results, the test injector shows a good low-end linearity between the dynamic flow and fuel injection pulse width and the fuel spray of 20 μm or less in SMD with good spray symmetry. In addition, the in-cylinder tumble flow has more effect on the homogeneous mixture formation than that of in-cylinder swirl flow at early injection mode and the in-cylinder swirl flow plays a better role of stratified mixture preparation than tumble flow at late injection mode.