Centrifugal Compressor Configuration, Selection and Arrangement: A User's Perspective

Abstract

The detailed sizing and selection of centrifugal compressors may be somewhat of a mystery to the typical user. Once the suction and discharge process conditions and required flow rates are established, they are submitted to an equipment supplier for sizing and selection. The resulting combination of impeller diameters, casing sizes and operating speed determined by the equipment supplier can be puzzling to the engineer charged with evaluating the selections. This tutorial is intended to introduce the dimensional and dimensionless similarity parameters that can be utilized to perform an independent, equivalent selection for a compression application or provide a more thorough evaluation of the selections provided by an equipment supplier. These performance parameters will allow prediction of design point head and efficiency, approximate impeller diameters, and approximate compressor operating speeds. Furthermore, the inter-relationship between impeller diameter and rotational speed will be investigated to highlight the trade-offs in changing either of these design variables. The tutorial will also investigate useful mechanical parameters and guidelines that allow comparative preliminary assessment of proposed designs. When significant head and/or flow requirements exist for a specific application, it becomes necessary to divide the compression service into multiple sections and in some situations multiple casings. Although a few different ways to configure multiple compressor sections exist, there are benefits and issues associated with each of these configurations. The potential benefits and issues of different arrangement options will also be addressed in this tutorial.