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sampling points are located near the throttling section.
cted as required,
px is the positions of the pressure
The locations of all 7 points are shown in Fig.3 too.
The FLUENT software is used to solve the gove- rning equations for the water phase. As the height of
measuring point in the passage. The CFD simulation boundary conditions for this case are as follows: the water temperature is 15oC, the inlet velocity is 9.5 m/s,
the inlet static pressure is 355.6 kPa and the outlet sta- tic pressure is 118.1 kPa. The Reynolds number is 1.315×105 correspondingly at the inlet section. The results indicate that the difference is very small. For
3.2 The pressure and the velocity in the passage
Figure 5 shows the pressure contours and the velocity vectors of the prototype channel in the follo- wing case: the inlet velocity is 6.33 m/s (Reynolds
example, the maximum difference is at point 6, which is about 4.5%. Therefore, the 2-D CFD simulation
number
1.6 kPa.
Re = 1.051105 ) and outlet pressure is
approach is valid to investigate the characteristics of
the pressure and the velocity in the labyrinth passage.
3. Numerical results of prototype passage
The numerical results of the contours in Fig.5(a) show that the pressure in the “series passage” is dro- pped from 400 kPa to 165 kPa, the difference is 335 kPa. While the pressure difference in the “parallel passage” is only about 163.4 kPa. That is, the former contributes about 83.8% of the total pressure drop.
3.1 The boundary conditions
The pressure loss coefficient
= 16.72 .
The geometrical structure of the prototype pass-
age is shown in Fig.2. The boundary conditions for different cases are listed in Table 2.
Table 2 The boundary conditions for 3 cases
Case Re Inlet
velocity/ Outlet
pressure/ Water
temperature/
ms−1 kPa oC
1 1.051×105 6.33 1.6 15
2 8.304×104 5.00 102 15
3 5.531×104 3.33 243 15
Fig.5 Flow characteristics of labyrinth passage for Case 1
The velocity vector depicted in Fig.5(b) indicates six large vortex areas in the passage where the right angle turns are distributed along the flow direction. It is also shown that from the first vortex to the fifth in the “series passage”, the area of the vortex section is increased gradually, but every vortex density eddy still maintains at a reasonable level without dramatic cha- nges. Judged from the density variations of the stream lines, they vary also gently. It denotes that the pressu- re drops evenly too, thus the energy losses are kept within a certain range through each corner.
Fig.6 Flow characteristics of labyrinth passage for Case 2