Fan Section and Low Speed Diffuser
The tunnel airflow is powered by the main fan; the air moves through the fan from left to right:
Drive Shaft
The fan is driven by an 18.6 Megawatt (25000 horsepower) motor connected to the drive shaft. At maximum power, it requires a huge amount of electricity – the equivalent of over three hundred thousand 60 watt light bulbs. The Mach number in the test section is controlled with the fan speed which rises from 160 rpm at Mach 0.2 to 485 rpm at Mach 0.8 and above.
Pre-Rotation Vanes
As it enters the fan, the air passes through the first set of fixed vanes which twist the air flow before it reaches the fan blades to make the fan operate more efficiently.
Servo-Assisted Flaps
The Mach number in the test section is fine-tuned with the flaps which act as a break on the airflow moving through the fan. The flaps are automatically driven by a servo to maintain a target air pressure in the test section.
Fan Blades
The fan blades are what power the tunnel. They suck the air into the fan and compress it to raise the air pressure. The resulting high pressure at the fan exit is what drives the flow around the tunnel circuit – through the test section and past the model being tested. There are two sets of fan blades – each set preceded by a set of Pre-Rotation Vanes.
Straightening Vanes
As the air leaves the fan blades, it has a higher pressure but it is also swirling because of the rotation of the fan blades. The straightening vanes remove some of this swirl and more is removed later at the Flow Smoothing Honeycomb before the air enters the test section.
Low Speed Diffuser
The low speed diffuser keeps the air flow smooth and efficient as it exits the fan at a high pressure but relatively low speed.
For more detailed technical information on the fan section,
please download the following document:
