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The influence of the equivalent sand roughness of compressor impeller on the characteristics of centrifugal compressor low-emission stage a numerical analysis

DOI: 10.17586/1606‑4313‑2020‑19‑4-3-11
UDC 621.515

The influence of the equivalent sand roughness of compressor impeller on the characteristics of centrifugal compressor low-emission stage a numerical analysis

Yablokov Aleksei M. , Kozhukhov Y.V., Sadovsky Nikolay I.

For citation: Yablokov A. M., Kozhukhov Y. V., Sadovsky N. I. The influence of the equivalent sand roughness of compressor impeller on the characteristics of centrifugal compressor low-emission stage a numerical analysis. Journal of International Academy of Refrigeration. No 4. p. DOI: 10.17586/1606‑4313‑2020‑19‑4-3-11

Abstract
The results of numerical analysis for the influence of the equivalent sand roughness of compressor impeller on the characteristics of centrifugal compressor low-emission intermediate type stage are presented. Low-emission stags are widely used in high-pressure compressors as the final stages. Compressors of the type are used for natural gas injection as well as in the production of methanol, ammonia, high pressure polyethylene and other processes. Operating efficiency of low-emission stages is lower than the one of medium- and high-efficiency stages of centrifugal compressor. This is due to the fact that the high pressure and with low gas volume flow rate volumes and, therefore, are characterized by narrow annulus channels, high friction losses on the boundary surfaces, and the leakages in labyrinth packings. A mathematical model of the stage is represented by the sectors of the compressor flowpath elements. In the first part of the article the identification of the mathematical model for the flowpath is made and the results of low-emission stage tests are presented. In the second part of the article a modelling of a viscous gas flow under various values of equivalent sand roughness ks for all internal surfaces of the impeller is carried out. N2 perfect gas is used as a medium for modelling. The operating pressure at the stage inlet is four atmospheres. The characteristics of the stage for four various values of ks are obtained and the losses in the impeller are evaluated. When the values of ks increase a uniform decrease of polytropic pressure head and efficiency coefficient are not observed for all characteristic of the low-emission stage. The characteristics are much lower in the high flow zones and do not differ greatly at minimum flow. The dependence of internal head coefficient on ks is low.

Keywords: mathematical model, centrifugal compressor, compressor impeller, nitrogen.

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