Passive and Active Trailing Edge Noise Control
Trailing edge treatment has shown noise reduction in aircraft engines, however, most of this data is preliminary. Therefore, this study concerns itself with analyzing the effects of trailing edge treatments (passive and active) on the fundamental wake characteristics downstream of a cascade row. By analyzing the wakes, it will be possible to assess if trailing edge treatments on fan blades will be able to reduce the tonal noise in an aircraft engine. The experiment will be performed in an 8 blade, 7 passage linear cascade tunnel using GE rotor B profile blades. The wind tunnel has an inlet angle of 65.1°, a stagger angle of 56.9°, a solidity of 1.08 with an exit turning angle of the blade is 11.8°. These blades simulate the tip of fan blades found in aero-engines with a tip gap setting of 1.65%. Four sets of GE rotor blades will have modified trailing edge shapes, while a fifth set will use blowing to fill in the momentum deficit of the wakes. Three-component velocity measurements will be made using 4 sensor hotwires at 4 axial downstream locations of 0.6, 1.2, 1.8 and 2.4 from the trailing edge. From these measurements, the Reynolds' turbulent stresses and the triple-products will be determined. This data will used to predict the overall noise reduction in the flow for blades with modified trailing edge shapes as well as for the case of blown wakes. Prior studies have shown favorable results especially for blades with trailing edge blowing. However, the prediction of fans wakes using this technology is not straight-forward. With the completion of this study a database of experimental data for both passive and active wake control will be created from which the CFD tools can be developed as well as tested for reliability.
Progress
- Passive wake control
As of September 2003, the single-wire baseline measurements have been completed:
Single-wire baseline measurements - Figures
Single-wire baseline measurements - Data
The four-sensor hotwire baseline measurements (single point and two points) are in progress. Blade loading measurements have been realized using two airfoils with pressure ports embedded in the surface of the blades (on the pressure side and suction side respectively):
Blade loading measurements - Data
- Active wake control
The trailing edge blowing system has been designed, and partly built:
Trailing Edge Blowing System - Overall Layout