Measured and calculated unsteady pressure field in a vaneless diffuser of a centrifugal compressor

An unsteady experimental and numerical investigation was conducted to a centrifugal compressor with a vaneless diffuser. The unsteady static pressure was measured at the diffuser inlet and outlet at three different circumferential positions. Also a time-accurate numerical simulation was carried out. The whole compressor was modeled. Turbulence was modeled with the low Reynolds number k - epsilon turbulence model. The measurements were made in operation points near the surge, near the choke and at the design operation point of the compressor. The numerical simulations were conducted at the design operation point and at the operation point near the choke. The gathered numerical and experimental unsteady pressures were compared with each other.