Benefits of stator sweep and lean for a high tip speed fan

Abstract

A model high-speed fan stage was acoustically tested in the NASA Glenn 9-by 15-Foot Low Speed Wind Tunnel at takeoff/approach flight conditions. The fan was designed for a corrected rotor tip speed of 442 m/s (1450 ft/s), and had a powered core, or booster stage, giving the model a nominal bypass ratio of 5. The model also had a simulated engine pylon and nozzle bifurcation contained within the bypass duct. The fan was tested with three stator sets to evaluate acoustic benefits associated with a swept and leaned stator and with an swept integral vane/frame stator which incorporated some of the swept and leaned features as well as eliminated some of the downstream support structure. The baseline fan with the wide chord rotor and baseline stator approximated a current GEAE CF6 engine. A flyover effective perceived noise level (EPNL) code was used to generate relative EPNL values for the various configurations. Flyover effective perceived noise levels (EPNL) were computed from the model data to help project noise benefits. A tone removal study was also performed. The swept and leaned stator showed a 3 EPNdB reduction at lower fan speeds relative to the baseline stator; while the swept integral vane/frame stator showed lowest noise levels at intermediate fan speeds. Removal of the bypass blade passage frequency rotor tone (BPF) showed a 4 EPNdB reduction for the baseline and swept and leaned stators, and a 6 EPNdB reduction for the swept integral vane/ frame stator. Therefore, selective tone removal techniques such as active noise control and/or tuned liner could be particularly effective in reducing noise levels for certain fan speeds.

Fan Noise for a Concept Commercial Supersonic Transport

“…A number of reports have been published about the fan performance and acoustics results from this test. [15][16][17][18] The GE HSF data set was found to be ideal for evaluating a high-tip speed single-stage fan against the existing fan models. A photograph of the GE HSF in the 9x15 LSWT is shown in Figure 9.…”

Aircraft Fan Noise Reduction Technology Using Leaned Stator Blades

“…Consequently, there is an additional decrease in the sound wave amplitude. The fan model (D=0.559 m or 22 inches) installed in a wind tunnel is used to study the effect of swept-andleaned stators [6,7]. Three stator configurations are the following: the reference version with radial vanes, the second version with swept vanes (by 30°), and the third version with swept (by 30°) and leaned (by 30°) vanes.…”

An analytical investigation of stator lean on rotor–stator interaction noise

“…The tone-noise level of the modified stators was significantly reduced beyond what was achieved by simply relocating the conventional radial stator to the downstream location. According to Woodward et al, 8,9 there were different benefits of noise reduction at different compressor running conditions for different stator-leaned/swept angles. The swept and leaned stator demonstrated a 3EPNdB reduction at lower fan speeds relative to the baseline stator, while the swept integral vane/frame stator showed lowest noise level at intermediate fan speeds.…”