One of the necessities of a simulation software is to model the behavior of compressor stations. The main device modeled in a compressor station is a compressor.

The article presented concerns mathematical description of centrifugal and axial compressors, the most frequently used equipment in the gas transportation pipelines or pipeline networks.

Traditionally, both in the machinery industry and in the gas industry, these are mainly modelled using complete biquadratic polynomial approximation of the working space. The characteristics parameterized by the rotation speed values are then represented as 2nd-order parabolas in the satisfactorily invariant (relative to inlet gas status) coordinate system Qvol - Had. Exactly the same approach is basically used for the working space in efficiency variables ?- Qvol. and, parameterized by the efficiency values, also projected (and displayed) in the same invariant coordinate system Qvol - Had.

However, there have been new developments in design and production area, and also the community of the user wishes - namely we are talking about axial compressors that contain several compression stages integrated internally. The characteristics of such devices can no longer be described precisely enough in the traditional simple way represented by 2nd-order parabolas, so better methods of modelling needed to be found.

After some testing of various methods, we propose to model these compressors using linear interpolation approach, when the boundaries of a revolution working area are described using cubic splines and the working point parameters are found using linear interpolation within a small enough quadrangle defined by these splines. There are some challenges using this approach, namely a need to harmonize mathematically precise solution and possibilities of computers. Finally, we realized that the new approach is a bit slower to traditional one, but on the other hand, when comparing the precision, the result is significantly better in favor of the new model.

In conclusion, with the advancements of technology, new ways of modelling need to be constantly devised. Our new way of modelling compressors is fast and robust enough to be rolled out to our customers in order to improve the model quality specifically for the compressors that cannot be processed in a traditional way.

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