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The performance of the slit V-gutter flameholders with fuel
injection technique are investigated by experimental method.
The test model is the slit V-gutter flameholder with the
geometrical blockage ratio of 40% and apex angle of 46°. The
tests are ca rried out in a rectangular duct with cross section
of 10cm×10cm The fuel is supplied by a control mechanism. The
fuel supply in cludes: (a)Main Fuel Injections by Single-Fuel
Bar & Twin-Fuel Bar are studied, (b)By-path Fuel Injection
Technique. Most of the fuel is supplied to the Single-Fuel Bar
or the Twin-Fuel Bar located at 40cm and 35cm upstream of the
flameholder, res- pectively. The by-path fuel that is a small
portion of the fuel, typically 1 % - 5 %, is divided from the
main fuel supply and directly injected into the lower slit of
the slit V-gutter flameholder. Results show that the local fuel
concentration in the region of recirculation zone increases,
especially near the by-path fuel injection port, when a small
amount of by-path fuel(1%-5%) is injected. The lean ignition
limit hence extends significantly due to this fuel
redistribution. Mea- surements of concentration of combustion
products also show that the local unburned fuel concentration
in the lower bound shear layer region increases due to this by-
path fuel. Hence, the lean blow-off limit is also significantly
extended. Flow visualization shows that there is a stable
combustion zone at the lower bound shear layer region under the
by-path fuel injection. This, in turn, provides heat source to
stabilize the flame. Consquently, the combustion process turns
from the unstable condition to a stable condi- tion and the
amplitude of pressure oscillation reduces sig- nificantly once
the by-path fuel is injected during the lean blowout operation.
This indicates the by-path fuel injection technique can be used
to stabilize the unstable flame occurs in the flashback
extinction process.
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