4 Computational Fluid Dynamics
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length of the fan blade is 0.586–0.838 m, the chord length of anti-twist guide
vane is 1.838–1.915 m, the chord length of the front cone support plate is
2.0 m, and the chord length of the tail cover support plate is 1.5 m. Under the
design working condition of fan, the wind speed in the experimental section
is 100 m/s, the volume flow is 1200 m 3 /s, the pressure rise is 2450 Pa, the
design rotation speed of fan is 310 rpm, corresponding to the linear speed
of propeller tip 119.7 m/s, which is within the limit of 150 m/s of propeller
tip speed. The efficiency of the fan system is 86.2%, the thrust of the fan
system is 64.3 kN, the torque is 105.1 kN*m, and the power is 3412 kW,
which also determines the power and type selection of the drive motor. In
order to reduce the noise of the coupling and bearing between the motor and
the hub, the direct connection is adopted according to DNW wind tunnel
(the fan hub is directly installed on the motor shaft). As shown in Fig. 4.31,
the three-dimensional mode of fan system is given.
4.6.3 Mesh Generation and Boundary Conditions
As the fan section is a rotating machine, the grid quality should be good;
while there are many corner deflectors in other working sections of the wind
tunnel, especially in the corner section, it is difficult to generate mesh for the
model. Therefore, in the actual simulation, the meshes of the fan segment
and the rest of the working segment of the model are generated separately.
The special software NUMECA is used to generate the structural mesh of
the fan segment. The unstructured mesh of the rest section of the wind
tunnel is generated by employing ICEM. After the meshes of the two sections
are generated, combine them to generate the whole meshes of the model,
and carry out the next numerical simulation (as shown in Figs. 4.32, 4.33,
4.34 and 4.35). The number of fan section structural mesh is 3 million
(Fig. 4.32); the number of the unstructured mesh of the rest section is 20
million (Fig. 4.34).
4.6.4 Results
In the simulation, the wind speed of the test section is 20, 40, 60, 80,
100 m/s, respectively, the corresponding rotation speed of the fan is 62, 124,
186, 248, 310 rpm, the temperature (static temperature) is 288.15 k, and
the air density is 1.225 kg/m 3 . Firstly, the simulation results of the design
conditions are analyzed. The wind speed of the test section is 100 m/s, the
temperature (static temperature) is 288.15 k, the density is 1.225 kg/m 3 , and
325
length of the fan blade is 0.586–0.838 m, the chord length of anti-twist guide
vane is 1.838–1.915 m, the chord length of the front cone support plate is
2.0 m, and the chord length of the tail cover support plate is 1.5 m. Under the
design working condition of fan, the wind speed in the experimental section
is 100 m/s, the volume flow is 1200 m 3 /s, the pressure rise is 2450 Pa, the
design rotation speed of fan is 310 rpm, corresponding to the linear speed
of propeller tip 119.7 m/s, which is within the limit of 150 m/s of propeller
tip speed. The efficiency of the fan system is 86.2%, the thrust of the fan
system is 64.3 kN, the torque is 105.1 kN*m, and the power is 3412 kW,
which also determines the power and type selection of the drive motor. In
order to reduce the noise of the coupling and bearing between the motor and
the hub, the direct connection is adopted according to DNW wind tunnel
(the fan hub is directly installed on the motor shaft). As shown in Fig. 4.31,
the three-dimensional mode of fan system is given.
4.6.3 Mesh Generation and Boundary Conditions
As the fan section is a rotating machine, the grid quality should be good;
while there are many corner deflectors in other working sections of the wind
tunnel, especially in the corner section, it is difficult to generate mesh for the
model. Therefore, in the actual simulation, the meshes of the fan segment
and the rest of the working segment of the model are generated separately.
The special software NUMECA is used to generate the structural mesh of
the fan segment. The unstructured mesh of the rest section of the wind
tunnel is generated by employing ICEM. After the meshes of the two sections
are generated, combine them to generate the whole meshes of the model,
and carry out the next numerical simulation (as shown in Figs. 4.32, 4.33,
4.34 and 4.35). The number of fan section structural mesh is 3 million
(Fig. 4.32); the number of the unstructured mesh of the rest section is 20
million (Fig. 4.34).
4.6.4 Results
In the simulation, the wind speed of the test section is 20, 40, 60, 80,
100 m/s, respectively, the corresponding rotation speed of the fan is 62, 124,
186, 248, 310 rpm, the temperature (static temperature) is 288.15 k, and
the air density is 1.225 kg/m 3 . Firstly, the simulation results of the design
conditions are analyzed. The wind speed of the test section is 100 m/s, the
temperature (static temperature) is 288.15 k, the density is 1.225 kg/m 3 , and