Influence Of Stagger Angle And Reynolds Number On Aerodynamic Noise Performance Of Compressor Cascade

Aerodynamic parameters of airfoil/cascade have important influence on theaerodynamic performance of compressor. Comprehensive research data foraerodynamic characteristics of cascade are got through the experiments and numericalsimulation. As the social and economic development, people have a very high demandfor surrounding environment comfort and gradually pay more attentions to theaerodynamic noise of turbomachinery. In that case, compressor designers must masterthe relationship between noise induced by the flow of blade/cascade and aerodynamiccharacteristics.Turbulence boundary layer and vortex shedding from trailing edge result from airflows through cascade surface, which cause the pressure fluctuations and form dipolenoise source; when boundary layer increases, either angle of attack is large, the vortexseparation of cascade surface is clear, which change the pressure fluctuationcharacteristics and can also affect aerodynamic noise by the turbulence flow of cascade.In this present paper, three different cascades are got by changing the stagger angle30°,45°,60°with solidity1.0, then turbulent flow field of cascade channel and aerodynamicnoise induced by flow are simulated by the computational fluid dynamics and boundaryelement method, in order to analyze the influence of unsteady flow characteristics andradiation noise in different stagger angle, free stream Reynolds number and attack ofangle. The main work and conclusions are as follows:(1) Firstly, this paper focuses on the mesh scale and influence on flow field andsound field of sample points of sound source; meanwhile, the precision and accuracy ofthe calculation method are verified combining with the previous experimental data.(2) When the Reynolds number is252000, stagger angle is30°, attack angle rangesfrom-5°to20°, the turbulence flow and noise induced by flow field of cascade arecalculated. The vortices, transient streamlines, changes of pressure fluctuation oftrailing point and far-field noise radiation varying with attack angle are analyzed. Theresults are shown that the frequency of vortex shedding from trailing edge decrease asattack angle increases. At larger positive attack angle, low frequency fluctuation isdominant. The frequency of vortex shedding displays obvious discrete characteristics atattack angle5°and broadband characteristics at negative and larger positive attackangles. The amplitudes of pressure fluctuation decrease as attack angle increase. As for the total sound pressure level of monitor point at far-field, the minimum appears atangle of attack0°and the size is6.5dB, the total sound pressure level increases sharplyat attack angle-5°,5°and the trend change gently at5°~20°. The change trend of totalsound pressure level doesn’t coincide with the drag coefficient.(3) When the Reynolds number is252000, stagger angle is45°,60°, from theresults of flow field and noise field, the frequency of monitor vortex shedding fromtrailing has the same change trend with that of stagger angle30°, the frequency ofvortex shedding from trailing decrease as attack angle increases except for the negativeangle. The minimum total sound pressure levels of monitor point of different staggerangle appear at attack angle0°, and the total sound pressure level of stagger angle60°increases by6dB than others; at negative attack angle, the total sound pressure levelincreases varying with the stagger angle; however the total sound pressure lever issmaller than others when stagger is60°and attack angle is5°~20°. Combined with theflow field, we can amuse that at the stagger angle60°and larger positive attack angle,dissipative phenomenon on suction surface of cascade become serious and can consumea part of energy, in that case, the sound pressure level decrease.(4) When the stagger angle is30°, attack angle is0°, and the Reynolds numberincreases, the amplitudes of pressure fluctuation of vertex shedding from trailingbecome strong, the sound pressure level of far-field become large, the cascades surfaceboundary layer thickness becomes thin and the flow loss decrease...