Observations of Separated Laminar Flow on Axial Compressor Blading

Abstract

This paper describes some detailed observations of separated laminar flow regions on the rotating and stationary blading of a single-stage axial compressor operating at low speed. The data covers the “critical” Reynolds number range where “bursting” of laminar separation bubbles causes a sharp increase in blade profile losses. The experimental results are compared with various empirical correlations and theoretical models proposed by other workers. Horton’s semi-empirical model of separation bubble bursting is broadly supported by the present investigation. However, it appears that some aspects of Horton’s theory require significant modification in order to give an accurate description of the separation bubble behavior on the blades in an axial compressor. It is stressed that correlations of the critical Reynolds number for axial compressor cascades in terms of overall performance parameters should be applied with caution, as they are only likely to be valid for a narrow range of conditions.