(3-11) Techniques for Analyzing Swirl Injectors of Direct-injection Gasoline Engines and Its Application((FS-1)Fuel Sprays 1-Gasoline sprays)

Abstract

This paper describes the numerical and experimental approaches that were applied to study swirl injectors that are widely used in direct-injection gasoline engines. As the numerical approach, the fuel and air flow inside an injector was first analyzed by using a two-phase flow analysis method employing a volume of fluid (VOF) model. The calculated results made clear the process from initial spray formation to liquid film formation. Spray droplet formation was then analyzed with a discrete droplet model (DDM). As the experimental approach, particle image velocimetry (PIV) was used to measure the spray velocity distribution. These approaches were applied to test nozzles having a tapered tip geometry at the nozzle exit (Fig. I). The spray shapes that are come out from the nozzles skewed to tapered side (Side A). And the cone angle of skewed side spray does not change not so much even under high ambient pressure conditions (Fig. II). Because of this reason since the tapered nozzle is able to make fuel mixture reach towards the spark plugs on the stratified engine condition, i.e. compression condition, we consider this nozzle as the effective tool. At first, internal flow analysis of the nozzles by using VOF model was done, and the results show that the cone angle at the skewed side is larger than that of non-skewed side (Fig. III). After that, Velocity distribution during injection were measured by using PIV (Fig. IV). And the results show that as it apart from the nozzle exit, skewed spray velocity decline much slower than non-skewed spray velocity does. This phenomena are caused mainly by the reason that the quantity of the fuel of the skewed side (Side A) is larger than that of the iron-skewed side (Side B). Spray calculation was done setting this circumferential fuel distribution as initial conditions, the results show on Fig. II, The calculated results show good agreement with the experimental results. These results above show that the spray shapes are influenced mainly by spray cone angle and circumferential fuel mass distribution at the nozzle exit.