Low Speed Compressor Cascade Wind Tunnel
The Low Speed Compressor Cascade Wind Tunnel was designed to simulate conditions found near the tips of fan blades in high bypass ratio aircraft engines. Coincidentally it is also a fairly good representation of flow near the blade tips of a marine propulsion pump. It is sited in the basement of Randolph hall. The cascade consists 8 cantilevered GE rotor B section blades mounted with an adjustable tip gap. The blades are fabricated from aluminum and have a total chord of 10" and an effective span of 10". The blades are instrumented with mean surface pressure taps, and a microphone array for unsteady surface pressure measurement. The cascade configuration has a rectangular cross section of 65" by 10". The blade spacing is 9.29" , and the stagger angle of the cascade is 56.93 degrees. The inlet angle of the cascade is 65.1 degrees. The centrifugal fan powering the facility produces a free steam velocity of about 25m/s resulting in a chord Reynolds number of close to 400,000.
This facility includes a unique moving end-wall system, consisting of a belt that moves beneath the blade tips to simulate the relative motion between blades and casing found in a real turbomachine. The layout of the moving endwall system is shown above. The moving wall is a continuous flat belt driven by rollers at speeds of up to 25m/s. The belt is made from 0.01"-thick Mylar film. The width of the belt is 27". The total length of the belt is about 25' . The belt is driven by a 8" diameter high precision flat-surface roller. Another 8" diameter crowned surface roller is used to adjust and keep the position of the belt. The driving rollor is powered by a 15-horse power AC motor. A digital motor controller is used to control the rotating speed of the motor by changing the output frequency. The belt is supported by a flat Teflon coated bed. Several slots cut into the bed provide suction to hold the belt on the bed, restricting its vertical vibration to a few microns.
Instrumentation regularly used with the facility includes a two-axis computerized traverse, single and 3-component hot-wire anemometry, a 3-component fiber-optic LDV system, and instrumentation to sense the instantaneous position and speed of the belt. Work is being conducted on this facility by research groups under the direction of Dr. William Devenport and Dr. Roger Simpson. Recent sponsors include the Office of Naval Research and NASA Langley.
|
|
|
|
AOE Research
|
