NUMERICAL ANALYSES ON FLOW FIELDS OF A SMALL-SIZE TURBO-COMPRESSOR WITH VARIOUS DIFFUSER TYPES

摘要

In general, impeller, difruser, and casing have an important role in a turbo-compressor, because the dynamic energy of the impeller transformed into the pressure energy in the diffuser and casing. The performance characteristics of the difruser are complicated with different geometric shapes. To improve the performance of the small-size turbo compressor with a high rotating speed, we have studied on the effects of difruser types such as rectangular and conical vane diffusers. A blade of an impeller has backswept two-dimensional shape due to tip clearance. In order to predict the flow pattern inside the entire impeller, diffuser and casing, calculations with multiple frames of reference method between the rotating and stationery parts of the domain are carried out. All domains for analyses are discretized by hexahedral elements. Three-dimensional, unsteady, viscous governing equations are solved using FVM, SIMPLE algorithm, and κ ― ε turbulence model. The pressure recovery coefficient (Cp) and the loss coefficient (K) have been calculated to estimate the performance and loss of the diffuser. Furthermore, the magnitude of velocity and the distributions of static and total pressures are calculated along the flow direction and the cross-section of the diffuser.