Experimental and Numerical Study of Swirling ... - Solid Mechanics

Experi imental and Numerical N Stud dy of Swirling g Flow in Scaveenging
Processs
for 2-Stroke
Marin ne Diesel Engin nes
Fi igure 4.3:
Vis sual presentation n of in-
pla ane velocity
dis stribution on the
cir rcumference line at a
rad dial distance of 200 2
mm m and 75 mm
(Sc chnipper, 2010).
Chapter 4
a radial l distance of 238 2 mm), theere
exists a larrge
wake behiind
each bladde.
Howeve er, at a radial distance of 2000
mm the waake
has considderably
reduceed.
The flow w enters the contraction c seection
at a raddial
distance of
170 mm from
the cylinder
axis and it can thus bee
assumed that
there will bee
no wake effeect
in the flow fl entering the t contractionn
region.
Figure 4.3 4 is a visual representationn
of the distribbution
of in pplane
velocity at
differen nt circumferen ntial positions at radial distaance
of 200 mmm
(outer circcle
with blue
dots) and 75 mm (innerr
circle with bblue
dots). Thhe
length of thhe
2 2
arrows indicate the e magnitude of inplane velocity ( V V Vr ) annd
directio on is based on n the angle bbetween
the raadial
and tanngential
velociity
compon nents. The detailed
results are given in figure 4.4 whhere
the verticcal
axis on the left hand d side represennts
the angle aand
on the rigght
hand side it
represen nts the inplan ne velocity maagnitude.
It ccan
be observeed
that a radiial
distance e of 200 mm m, the magnitude
and diirection
of thhe
flow is not
symmet tric and vary at different ciircumferentiall
positions (Fiigure
4.4a). Thhe
maximu um variation in angle is measured to be approximmately
6°. Thhis
indicate es that the gu uide vanes in the inlet sectiion
are not perfectly
aligneed
thus cau using an asym mmetric flow ddistribution.
HHowever,
afterr
the flow passses
through h the contract tion section, tthe
results at a radial position
of 75 mm
show th hat this variat tion in angle is reduced appproximately
to 1.5° and thhe
flow is comparatively
c
y more symmeetric.
Figure 4.5 4 shows tan ngential velociity
profile acrooss
the cylindder
cross sectioon
at z/D = 0.368 measur red using LDAA.
It can be seeen
that despitte
small relativve
flow asy ymmetry in th he swirl generrator,
an axis symmetric floow
exists in thhe
cylinder
before the cross-sectionaal
positions wwhere
PIV meeasurements
aare
conducted.
The mea asurement verry
close to thhe
cylinder geeometric
centter
52
Swirling Flow in a Pipe