CENTRFUGAL COMPRESSOR ANALYSIS

Traditionally, for centrifugal compressor operation analysis for design and off-design points, the verification analysis problem has been performed in 1D formulations.

In verification analysis of a centrifugal compressor, flow is treated as one-dimensional only [6]. Obviously, there is significant 3D flow in a centrifugal compressor. Considering the importance of quick review of design results, a 3D potential flow solver was developed and embedded into the system.

In contrast to 3D viscous flow calculations in a flow path, simplified 1D methods provide a close approximation for experimental data depending on the quality of empirical methods used to determine losses and deviation angles.

Due to the absence of reliable energy loss and flow deviation angles in cascades, there is a significant challenge in developing radial turbomachinery verification calculation algorithms. In practice, [1] the various known construction losses obtained from experimental data are used.

Centrifugal compressor flow path losses and outlet flow deviation angles are estimated based on existing data in literature [5,6]. Though obtained results can be characterized as satisfactory, loss models require further refinement One way of increasing the reliability of results is the use of custom libraries for proven loss models within the integrated design system environment.

The typical approach to solve this task and boundary condition is presented in [6]. The authors of this paper used the same method, so it is not necessary to explain it. As an example, validation of the 1D solver was performed based on experimental data presented in [7].

Flow path of the compressor shown in Fig.2 was studied with both a vaned and a vaneless diffuser. Performance calculations show a close correlation of the obtained efficiency with experimental data for the vaneless diffuser design in a quantitative sense and a close correlation for vaned diffuser design in a qualitative sense (Fig.3). Efficiency levels at 80% rotation speed coincide closely with experimental data as well. (Fig.4, Fig.6). The literature only cites CFD calculations results (Figs.7a,7b,7c,7d) and experimental data at an 80% rotation speed ([9], [10] etc.). These results correlate closely to experimental data at an 80% speed as well.

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