Spray angle procedure calcualtion and verification
1. Calculation of Spray location and injection Axis
Background: Spray is injected in the mixing tube before the flapper mixers for
better mixing.
Fig 1
2. 1. Identify the injector location as in fig
and mark the center of the location
as shown in figure 2&3
2. Create a geometry surface. (this will
help you to retain the main geometry
and yet identify injection co-
ordinates.) as in figure 4
Fig 2
Fig 3
Fig 4
3. 4. Offset the surface by a
certain distance (eg:3mm) as
shown in fig 5.
5. Use the offset option in
TOPO mode under Faces
module as shown in fig 6.
6. Find the center of the
surface that was offset as
shown in fig 7.
Fig 5
Fig 6
Fig 7
4. 7. Draw a curve and connect both
the mid points as shown in fig 8.
8. Find a point on the curve at 1mm
from the top plane. This will be your
injection point which is inside the
domain as shown in figure 9.
9. Draw a curve to from the center
of the offset surface to one of its
edge as in fig 10.
Fig 8
Fig 9
Fig 10
5. 11. Get the information on cone angle and included angle. For example, from
above figure 11 & 12, the cone angle is 14 degree. This will be my Teeta.
Fig 11
Fig 12
6. 12. You have your adjacent side and opposite sides.
We know the length of the adjacent side. We know
the angle A. We need to find the length of opposite
side at an angle of 14 degree on the curve of
radius.
Tan 14 = x/2mm
0.2493= x/0.002m
X=0.0005m
Opposite side
Adjacent side
Fig 13
Fig 14
7. 13.This is the new point on the
opposite side as in fig 15.
14.Draw a curve from the injection
point to the new identified point. This
will be your axis for one injection as fig
15. If there are 6 injections, then we
rotate this point about the center by 60
degrees by using the transform
operation in ANSA as in fig 17.
Fig 15
Fig 16 Fig 17
8. 16.Select the point created and select the axis around
which it rotates. This will give 5 new points and
respective axis and shown in fig 18-21.
Fig 18
Fig 19
Fig 20 Fig 21
9. 17.Using the transform operation,
just pick any one curve and pick
the point in the direction of spray.
18.In the transform window, you
will see dx, dy and dz. This will be
your axis of injection at required
cone angle.
19.This data should be entered in
injection window of fluent under
axis section as in fig 26.
Fig 22
10. Fig 23
Fig 24
20. In Fluent, go to Define drop
down and select injections as in
fig 23.
21. This will list all injections. If
none present, you can create
using the create option as shown
in figure 24.
11. 22. Location pointed in
figure 25 should be the
injector tip location which
we have identified in slide2.
23. Figure 26 shows the location to enter
axis of each injection which will be
different for all 4/6 injections. However
the injector focal point calculated in slide
2 remains the same for one injector.
Fig 25
Fig 26
12. Fig 27
24. Make sure all other factors are entered correctly in Physical models tab. This will
complete your spray setup.
