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

Experimental and Numerical Study of Swirling Flow in Scavenging Process for 2-Stroke
Marine Diesel Engines
Table 4.2:
Radial Position of
Measuring points along
X-axis for LDA
measurements.
4.1 LDA Measurements (Inlet Section)
Chapter 4
Two components LDA measurements were conducted at different locations
in the swirl generator as described in Section (3.6). The main reason for
using LDA technique has been the possibility of conducting measurements
at locations where PIV measurement becomes very difficult to be conducted
due to guide vanes blocking the laser light (see section 3.1). The
measurements are conducted at volume flow rate of 0.154 m 3 /s.
Different radial positions from origin see figure 3.18, between inlet to swirl
generator and contraction section, are selected and then measurements are
conducted at same radial positions along each of the axes lines (Table 4.2).
Axis
Radial Positions from origin (mm)
275 230 215 200 185
X
-X
This must be mentioned here that in the real swirl generator the assumed
axes lines, while crossing the blade row, do not lie on similar location
between the two adjacent guide vanes e.g. the measurement at the radial
position of 235 mm for negative Y axis is not possible due to the laser beam
being blocked by a guide vane whereas for other axes measurements can be
conducted at the same radial position.
The measured radial velocity profiles for each half axis are shown in figure
4.1a (flow direction is from radial position at 275 mm to 180 mm). The halflength
of each error bar is one standard deviation. It can be seen that the
radial velocity distribution is not symmetric. Flow accelerates while passing
through the row of guide vanes and further downstream due to the
contraction section. Due to wake behind the guide vanes a decrease in the
magnitude is also observed for radial positions of 200 mm along positive X.
The tangential velocity profiles are shown in figure 4.1b. For both half axes,
at radial position of 275 mm, a non-zero tangential velocity is observed
which demonstrates either the flow feeling the presence of the guide vane
being at downstream position or the blade edge facing the inlet section
outlet is not perfectly aligned with the radius. Moreover, different values of
tangential velocity and angle between radial and tangential velocity
components along the axis lines indicate that there exists a small relative
difference in alignment of guide vanes (Figure 4.1c).
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Swirling Flow in a Pipe