Elias Sundström

Assessment of the 3D Flow in a Centrifugal compressor using Steady-State and Unsteady Flow Solvers

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Centrifugal compressor: The sound of surge

When the centrifugal compressor operates at low mass flow rates (close to the unstable operating condition called surge), flow instabilities may develop and severe flow reversal may occur in the wh ...

Generation Mechanisms of Rotating Stall and Surge in Centrifugal Compressors

Flow instabilities such as Rotating Stall and Surge limit the operating range of centrifugal compressors at low mass-flow rates. Employing compressible Large Eddy Simulations (LES), their generation mechanisms are exposed. Toward low mass-flow rate operating conditions, flow reversal over the blade tips (generated by the back pressure) causes an inflection point of the inlet flow profile. There, a shear-layer induces vortical structures circulating at the compressor inlet. Traces of these flow structures are observed until far downstream in the radial diffuser. The tip leakage flow exhibits angular momentum imparted by the impeller, which deteriorates the incidence angles at the blade tips through an over imposed swirling component to the incoming flow. We show that the impeller is incapable to maintain constant efficiency at surge operating conditions due to the extreme alteration of the incidence angle. This induces unsteady flow momentum transfer downstream, which is reflected as compression wave at the compressor outlet traveling toward the impeller. There, the pressure oscillations govern the tip leakage flow and hence, the incidence angles at the impeller. When these individual self-exited processes occurs in-phase, a surge limit-cycle establishes.

Similarities and differences concerning flow characteristics in centrifugal compressors of different size

The aim of the present investigation is to explain the differences in the compressor map by analyzing the compressible flow in two compressor designs, i.e. a small passenger car design and a sportive car design. The two different compressor designs are assessed with steady state Reynolds Averaged Navier-Stokes simulations for several operating conditions. Similar flow features are observed near optimal efficiency operating conditions when the flow field parameters are scaled properly. The present investigation elucidates the reason for the different limiting shapes of the surge line for the two compressor maps at high speed lines.

On the Assessment of Centrifugal Compressor Performance Parameters by Theoretical and Computational Models

1D performance prediction modeling and steady-state CFD are applied to assess a high-performance centrifugal compressor. Computed total pressure ratio is compared with experimental data obtained fr ...

A Comparison of Performance Predictions Between 1D Models and Numerical Data for a Turbocharger Compressor

Compressor performance prediction models, based on integral conservation of mass, momentum and energy with empirical loss terms, are important tools in early design stages. Two such models from lit ...

Evaluation of centrifrugal compressor performance models using large eddy simulation data

Zero-dimensional (OD) compressor performance models, which consist of several sub-models for different loss terms, are useful tools in early design stages. In this paper, one typical model for cent ...