Rotor-Stator Interactions in a Four-Stage Low-Speed Axial Compressor—Part I: Unsteady Profile Pressures and the Effect of Clocking

Abstract

This two-part paper presents detailed experimental investigations of unsteady aerodynamic blade row interactions in the four-stage Low-Speed Research Compressor of Dresden. In part I of the paper the unsteady profile pressure distributions for the nominal setup of the compressor are discussed. Furthermore, the effect of blade row clocking on the unsteady profile pressures is investigated. Part II deals with the unsteady aerodynamic blade forces, which are calculated from the measured profile pressure distributions. The unsteady pressure distributions were analyzed in the first, a middle and the last compressor stage both on the rotor and stator blades. The measurements were carried out on pressure side and suction side at midspan. Several operating points were investigated. A complex behavior of the unsteady profile pressures can be observed, resulting from the superimposed influences of the wakes and the potential effects of several up- and downstream blade rows of the four-stage compressor. The profile pressure changes nearly simultaneously along the blade chord if a disturbance arrives at the leading edge or the trailing edge of the blade. Thus the unsteady profile pressure distribution is nearly independent of the convective wake propagation within the blade passage. A phase shift of the reaction of the blade to the disturbance on the pressure and suction side is observed. In addition, clocking investigations were carried out to distinguish between the different periodic influences from the surrounding blade rows. For this reason the unsteady profile pressure distribution on rotor 3 was measured, while stators 1–4 were separately traversed stepwise in the circumferential direction. Thus the wake and potential effects of the up- and downstream blade rows on the unsteady profile pressure could clearly be distinguished and quantified.

Effect of clocking on unsteady rotor blade loading in a low-speed axial compressor at design and off-design operating conditions

“…Because the unsteady pressure fluctuation on the rotor blades changes nearly simultaneously along the whole blade chord [11,22], it can be assumed that the effect of the IGV wake and the potential effect appear nearly at the same point in time along the whole blade chord, respectively. Figures 9 and 10 show the unsteady pressure fluctuation on the PS and SS of the rotor blades along the chord length for the design point and the operating point near the stability limit at clocking position IGV 0.0 and IGV 0.6, respectively.…”

“…Mailach and Vogeler [11] investigated the effect of stator clocking on unsteady pressure fluctuations on the rotor blades. In a 1.5-stage low-speed axial compressor, the effect of stator clocking on the unsteady pressure fluctuation and the blade pressure force of the rotor blades was numerically carried out by Jia and Vogeler [12].…”

Vane Clocking Effects on Stator Loss for Different Compressor Loading Conditions

“…Some authors [10,14] have identified changes in the rotor flowfield character due to vane clocking, but none have drawn conclusions connecting rotor performance differences with vane clocking with the efficiency changes. Results from Key [17] showed that the change in compressor efficiency associated with vane clocking is caused by losses on the downstream vane.…”

“…Vane clocking also has a significant effect on the unsteady rotor blade loading [9,10]. The relative position of the upstream potential and vortical disturbances with respect to the downstream potential fields can have a strong effect on the rotor unsteady pressure amplitude.…”

Investigation of Flow Physics of Vane Clocking Effects on Rotor Resonant Response

“…Mailach and Vogeler [12] performed experiments in a low-speed compressor with four identical stages. Blade surface pressures were measured on the suction surface and pressure surface at midspan on a single rotor in stage 3.…”