Experimental Investigation of an Aspirated Fan Stage

Abstract

This thesis focuses on the use of aspiration on compressor blade design. The pressure ratio can be significantly increased by controlling the development of the blade and endwall boundary layers. This concept is validated through an aspirated fan stage experiment performed in the MIT Blowdown Compressor Facility. The fan stage was designed to produce a pressure ratio of 1.6 at a throughflow adiabatic efficiency of 89% at a rotor tip speed of 750 ft/s. Aspiration equal to 0.5% of the inlet flow was applied to the blade surface of both the rotor and stator. Aspiration was also used on the endwall boundary layers. Detailed flowfield measurements are made behind the rotor and stator, and the ensemble-averaged data is compared with a 3-D, viscous analysis tool.The time-accurate flow measurements show a large blade to blade variation due to unsteady vortex shedding, which is not captured by conventional 3-D, viscous analysis tools. An incompressible, vortex shedding model calibrated to the experimental data shows that the vortex shedding induces radial flows that redistribute flow properties in the spanwise direction. 'Correction' of the experimental data using the model gives a better comparison with the 3-D, viscous analysis solution.In order to understand the possible benefits of aspiration, a meanline parameter study is performed over a range of rotor inlet Mach numbers, flow coefficients, and work coefficients. Viscous and shock losses are estimated for both conventional and aspirated stages. The results suggest that aspiration can have the largest impact on compressor performance at high stage pressure ratios.

Effects of tip clearance size on the performance and tip leakage vortex in dual-rows counter-rotating compressor

“…Since the beginning of 2000, researchers at the Massachusetts Institute of Technology(MIT) have been investigating the use of aspiration, which removes the low-momentum flow from boundary layers of blades to increase the pressure ratio per stage and extend the diffusion factor design space for a highly loaded compressor. The first attempt 8,9 was a transport engine aspirated transonic conventional fan stage, rotor plus stator, with a pressure ratio of 1.6 at a tip speed of only 228.6 m/s. More ambitious research had been reported by Kerrebrock et al.…”

Study on flow separation and suction control of a compressor tandem cascade

“…Considering the practical engineering application value, although the performance of a compressor can be further improved by suction flow rates of about 2%, it is to be appreciated that the actual suction flow rate required in experiments is less than that designed by numerical calculation. 18,25,26 As a result, the effects of boundary layer suction and suction slot location on the tandem cascade flow field are discussed with suction flow rate of about 1%.…”

Investigation on the aerodynamic performance of high camber turning angle cascade with tubercle leading edge

“…For example, the aspirated blade technology proposed by Massachusetts Institute of Technology is using the boundary layer suction method to suppress the separation of the suction surface boundary layer of a blade with a high camber turning angle. 4–6 Watts and Fish 7 concluded that the tubercle leading edge could increase the lift by 4.8% more than an ordinary model when the attack angle is 10°. Miklosovic et al.…”