Generation of Vortex Lift Through Reduction of Rotor/Stator Gap in Turbomachinery

Abstract

The axial gap between blade rows in turbomachinery should be minimized in order to reduce size requirements and increase efficiency; although, there is a tradeoff between gap width and flow steadiness. The aerodynamic interaction between rotors and stators influences system performance under both steady and transient conditions. To investigate the basic physical mechanisms associated with the rotor/stator interaction, an efficient numerical scheme for solving unsteady, viscous flows on a quasi-three-dimensional coordinate system is established using an immersed boundary method. The data transfer between moving and stationary grids that slip against each other in traditional numerical methods is avoided. The effects of the axial gap between adjacent blade rows are studied by considering the flow evolution through a rotor and stator stage in different Reynolds number regimes. Results indicate that reduced blade gap leads to high lift on the rotor blade and improved stage loading. At the same time, the rotor/stator interaction increases flow unsteadiness, which may in turn increase noise and vibration. It is found that the reduced blade gap does not always improve performance, in spite of the generation of vortex lift. The present work provides guidelines for optimization of the axial gap between blade rows for turbomachinery design.