6 Wind and Water Tunnel Equipment
399
tunnel wall; the velocity distribution at the outlet of the contraction
section should be uniform, the direction should be straight and stable.
The length of the contraction section is appropriate. If the length
is too long, the construction cost and the flow energy loss will be
large. Whether the contraction segment can meet these requirements
depends mainly on two aspects: contraction ratio and contraction
curve. The general contraction ratio is between 6 and 12, and there are
many design methods for the contraction curve, such as cubic curve,
double cubic curve, and fifth curve (as shown in Figs. 6.14 and 6.15).
(7) Power section, which is the heart of a low-speed wind tunnel, generally adopts an axial flow fan. The main parts are as follows: power
section shell (round section pipe); Blade; Drive motor; Fairing; Front
guide piece or pre-twist piece; anti-twist vane or anti-twist vane. The
motor can be mounted inside the fairing or outside the hole (driven
by a long shaft fan). The function of the fan is to fuel the airflow in
the wind tunnel to ensure that the airflow maintains a certain speed.
Figures 6.14 to 6.16 show the single-stage axial flow fan system, and
Figs. 6.17 and 6.18 show the two-stage axial flow fan system.
Fig. 6.14 Axial fan system for power segment (7 m in diameter)
399
tunnel wall; the velocity distribution at the outlet of the contraction
section should be uniform, the direction should be straight and stable.
The length of the contraction section is appropriate. If the length
is too long, the construction cost and the flow energy loss will be
large. Whether the contraction segment can meet these requirements
depends mainly on two aspects: contraction ratio and contraction
curve. The general contraction ratio is between 6 and 12, and there are
many design methods for the contraction curve, such as cubic curve,
double cubic curve, and fifth curve (as shown in Figs. 6.14 and 6.15).
(7) Power section, which is the heart of a low-speed wind tunnel, generally adopts an axial flow fan. The main parts are as follows: power
section shell (round section pipe); Blade; Drive motor; Fairing; Front
guide piece or pre-twist piece; anti-twist vane or anti-twist vane. The
motor can be mounted inside the fairing or outside the hole (driven
by a long shaft fan). The function of the fan is to fuel the airflow in
the wind tunnel to ensure that the airflow maintains a certain speed.
Figures 6.14 to 6.16 show the single-stage axial flow fan system, and
Figs. 6.17 and 6.18 show the two-stage axial flow fan system.
Fig. 6.14 Axial fan system for power segment (7 m in diameter)