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
Fig gure 2.7:
Illus stration of design n
swir rl parameter.
dc
D tan
Where D is the intern nal diameter
between n cylinder rad dius and direct
the con nditional circ cle (an imagi
directio on makes a tan ngent) and i
2.6).
A
of the cylindrrical
chamber,
is the anggle
tion of nozzlee/
inlet, d c is the diameter of
inary circle tto
which thee
nozzle/ inllet
i is the total aarea
of nozzles/
inlets (Figuure
Estimat tion of swirl in ntensity can aalso
be based oon
streamline angle equatioon
(2.10) evaluated e at some s positionn
in the cross-section.
However,
an axiial
change in the swirl angle a can alsoo
be due to axxial
changes inn
the axial floow
field an nd near the wall w the swirl aangle
is a funnction
of rate of decay rathher
than to swirl intensity y itself (Steenbbergen
et al., 11998).
1 V
tan
n Va
The sw wirl paramete er though immportant
is nnot
the onlyy
parameter to
characte erize the swi irling flows. There can bbe
swirl flowws
having samme
Reynold ds number an nd the swirl intensity but having quitee
different floow
structur res due to dif fferent bounddary
conditionns
(Alekseenkko
et al., 20077).
Parame eters like swir rl distributionn,
distributionn
of stagnatioon
pressure annd
vorticity y are also imp portant to chaaracterize
a givven
swirling fllow
yet none of
the mentioned
param meters can independently
ccharacterize
a given swirlinng
flow (G Greitzer et al., 2004). 2
The dec cay of the swi irl is caused bby
the transpoort
of angular momentum to
the vor rtex chamber wall (wall fr friction) and is a functionn
of streamwiise
position n z . Steenberg gen et al. (19998)
reports thaat
in most obseerved
referencces
with lo ow swirl inten nsities the deccay
in the swiirl
is exponential
and can bbe
Chapter 2
(2. 9)
(2.10)
21
Swirling Flows