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Numerical simulation of hollow-cone sprays in gasoline direct-injection engines
Technical Paper
2000-05-0141
Sector:
Language:
English
Abstract
The main purpose of this study is to reveal the mechanism of
stratified- mixture formation in gasoline direct-injection engines.
So far the authors have developed a computer code "GTT"
for numerically simulating the fuel spray behavior in fuel
injection engines, and have proposed the physical models for
droplet breakup, spray impingement and liquid film formation on a
wall, and evaporation of a droplet and liquid film, which have been
applied mainly to the sprays injected from hole nozzles for diesel
engines.
In this study, in order to numerically simulate the hollow-cone
sprays injected from a swirl injector for gasoline direct-injection
engines, a physical model for hollow-cone sprays has been proposed.
The injection boundary condition and the model coefficients for the
droplet breakup model (improved wave breakup model) have been
determined appropriately. By means of this hollow-cone spray model,
the shapes and Sauter mean diameters of hollow-cone sprays in low-
and high-pressure ambient gases at room temperature under the
conditions for testing a swirl injector have been predicted
reasonably well.
Furthermore, in two types of gasoline direct-injection engines
with a piston cavity of bowl-like or cup-like shape, the behavior
of the fuel spray injected from a swirl injector into the cylinder
in the last period of compression stroke has been numerically
simulated using the GTT code. As a result, it has been shown that a
cloud of fuel vapor and air mixture within combustible air- fuel
ratio is formed near the spark plug at the time corresponding to
ignition timing in each engine. The effect of gas flow (tumble
vortex or swirl) on the stratified-mixture formation in each engine
has been made clear. It is expected that the spray model and the
computational results in this study can be utilized for developing
gasoline direct-injection engines.