Periodical Unsteady Flow Within a Rotor Blade Row of an Axial Compressor—Part II: Wake-Tip Clearance Vortex Interaction

Abstract

In this two-part paper, results of the periodical unsteady flow field within the third rotor blade row of the four-stage Dresden low-speed research compressor are presented. The main part of the experimental investigations was performed using laser Doppler anemometry. Results of the flow field at several spanwise positions between midspan and rotor blade tip will be discussed. In addition, time-resolving pressure sensors at midspan of the rotor blades provide information about the unsteady profile pressure distribution. In Part II of the paper, the flow field in the rotor blade tip region will be discussed. The experimental results reveal a strong periodical interaction of the incoming stator wakes and the rotor blade tip clearance vortices. Consequently, in the rotor frame of reference, the tip clearance vortices are periodical with the stator blade passing frequency. Due to the wakes, the tip clearance vortices are separated into different segments. Along the mean vortex trajectory, these parts can be characterized by alternating patches of higher and lower velocities and flow turning or subsequent counter-rotating vortex pairs. These flow patterns move downstream along the tip clearance vortex path in time. As a result of the wake influence, the orientation and extension of the tip clearance vortices as well as the flow blockage periodically vary in time.

Aerodynamic Design and Numerical Analysis of Supersonic Turbine for Turbo Pump

“…This is probably due to the interaction between the upstream wake and tip leakage vortex. Analogous phenomenon were observed by Sirakov [21], Mailach [22] and Zhang [23], who drawed the same conclusion in the study. Figure 21 shows axial vorticity distribution on the cross section 85% C x downstream of rotor leading edge at time t ¼ T (only 0.5-1 span showed).…”

Unsteady Flows in Turbines

“…It was found that strong interaction between upstream wake and rotor tip leakage vortex could lead to a performance benefit in the rotor tip region during the whole operability range of interest. The experimental result of Mailach et al (2008) revealed a strong periodical interaction of the incoming stator wakes and the compressor rotor blade tip clearance vortices. As a result of the wake influence, the tip clearance vortices are separated into different segments with higher and lower velocities and flow turning or subsequent counter-rotating vortex pairs.…”

Challenges of creating realistic periodical unsteady inflow conditions in a linear compressor cascade

“…To allow for studies of the periodically disturbed TLV seen by Mailach et al (2008) in the LSRC, the linear cascade setup was chosen to match the geometry and particularly reproduce the kinematics found in the rotating rig. Figure 3(a) shows the pitch averaged inlet conditions to the rotor blade row of the LSRC and the values adjusted in the wind tunnel.…”

“…In the case of compressor rotors the main secondary flow phenomenon affected by the incoming wakes is the tip leakage vortex (TLV). As shown by Mailach et al (2008), incoming stator wakes trigger a cyclic segmentation of the TLV structure by interacting with its outer shear layer. Besides continuative experimental studies (e.g.…”