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UNSTEADY AERODYNAMICS, AEROACOUSTICS AND AEROELASTICITY OF TURBOMACHINES Episode 8

Tham khảo tài liệu 'unsteady aerodynamics, aeroacoustics and aeroelasticity of turbomachines episode 8', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | Experimental Investigation of Compressor Cascade Wake-Induced Transition 359 Figure 1. Compressor Cascade V103-220 EIZ Erzeuger Instationaerer Zustroemung see Fig. 2 and its constructional principles are explained by Acton and Fottner 1996 in more detail. The cylindrical steel bars create a far wake very similar to the one produced by an actual airfoil Pfeil and Eiter 1976 . Preliminary tests showed that the wakes shed by bars of 2 mm diameter are representative for the wakes of the V103 profile geometry regarding the wake width. The distance ratio between the bars and the cascade inlet plane is about x l 0.35 see Fig. 1 . Two different bar pitches of 40 mm and 120 mm were used. The belt mechanism drives the bars with speeds of up to 40 m s. However the maximum bar speed for the present investigation is 20 m s thus generating Strouhal numbers between 0.22 and 0.66 for the investigated test cases. Figure 2. Wake generator EIZ with installed compressor cascade 360 It should be noted that the maximum bar speed together with the axial velocities is still too slow to produce a Strouhal number and inlet velocity triangle representative for modern compressors. The wakes enters the cascade passage almost parallel to the blades. Therefore the data acquired with this setup cannot be transferred directly to real turbomachines. The measurements should be considered as basic investigations of the unsteady multimode transition process. As the main purpose of the present experimental investigations is to obtain a deeper unterstanding of the fl w phenomena and to provide a sound database for the validation of unsteady numerical fl w solvers and particular transition models the angle of the incoming wake is of minor importance. 2.3 Test facility The experiments were carried out in the High Speed Cascade Wind Tunnel of the University of the Federal Armed Forces Munich which is an open-loop test facility located inside an evacuable pressure tank Fig. 3 . Mach and Reynolds number in .