New IMechE Journal Paper - Re

20 May 2011

This paper was presented at the 9th European Turbomachinery Conference (ETC9) in Istanbul, Turrkey, from 21 to 25 March and already appears in the proceedings of that conference. The organising committee of the conference, and the editor of the journal, have now selected the paper for publication in the special issue on Turbomachinery in the IMechE Journal of Power and Energy. Only selected papers of appropriate quality achieve this recommendation.


A unified correction method for Reynolds number, size, and roughness effects on the performance of compressors

MV Casey and CJ Robinson


An equation is derived that relates the changes in turbomachinery efficiency with
Reynolds number to the changes in the friction factor of an equivalent flat plate. This equation takes into account the different Reynolds number and roughness dependencies of the individual components, and can be used for whole stages and multistage machines. The new method is sufficiently general to correct for changes in Reynolds number due to changes in fluid properties or speed, changes in machine size, or changes in the surface roughness of components for all types of turbomachinery, but is calibrated here for use on axial and radial compressors. The
method uses friction factor equations for a flat plate which include fully rough behaviour above an upper critical Reynolds number, a transition region depending on roughness and a region with laminar flow below the lower critical Reynolds number.


The correction equation for efficiency includes a single empirical factor. Based on a simple loss analysis and a calibration with over 30 sets of experimental test data covering a wide range of machine types, a suggestion for the variation of this factor with specific speed has been made.

Additional correction equations are derived for the shift in flow and the change in pressure rise with Reynolds number and these are also calibrated against the same data.


Proc. IMechE Vol. 225 Part A: Journal of Process Mechanical Engineering