Experimental and Computational Investigation of Radial Impellers with respect to Efficiency and Acoustic Optimization

In the present paper the flow inside radial impellers and the sound radiated from radial impellers with high rotating speed was investigated. For this purpose numerical and experimental techniques were applied. The aim was to get detailed information about the physical process leading to sound generation in the radial impellers. The phenomena responsible for tonal noise and broadband noise were identified. Using this knowledge, design-guidelines were given to optimize the impeller in both aerodynamic and aeroacoustic way in order to obtain a less noisy and more efficient centrifugal turbomachines. Nomenclature = acoustic pressure p′ 0 ρ = density at ambient conditions 0 a = speed of sound at ambient conditions R = distance between surface source and the observer position i u = velocity vector i U = velocity times ratio of density to ambient density r L = compressible and dynamic stress i n ˆ = outward normal vector ij