Rotating stall and stall-controlled performance of a single stage subsonic axial compressor

Abstract

Activities by various authors on aerodynamics and control dynamics of rotating stall in axial compressor are first traced. Then, a process of stall cell evolution in a subsonic stage is discussed based on a 2-D CFD. A few numbers of vortices grow ahead of the rotor accumulating vorticity ejected from lightly stalled blades, and eventually organize a cell of circumferentially aligned huge vortices, which merge and recess repeatedly during the rotation. Such stall disturbance is intensified on trailing side of a circumferential inlet distortion and decays on the leading side. Considering these features, a new algorithm for stall warning is developed based on a correlation between pressure waveforms at each passing of a fixed blade. A remarkable change in the correlation level at near-stall provides a warning signal prior to the stall onset with sufficiently large time margin. This scheme is applied to achieve rotating stall prevention by actuating flaps installed on the hub. The last issue is on characteristics of forward swept blade which has much increased throttle margin with decreased tip loss. A 3-D computation shows that a secondary vortex generated in suction surface mid span interacts to reduce the tip leakage vortex that initiates the stall.

Stall Inception, Evolution and Control in a Low Speed Axial Fan With Variable Pitch in Motion

“…6(c)), resulting in a reduction of its rotational speed. The stall cell followed the feature exposed by Outa [33] in the paper cited above and by Bianchi et al [27].…”

“…After a numerical investigation, Outa [33] linked the cause of this phenomenon to a significant change of flow incidence inside the cell and to the presence of a retarded high pressure passage where the cell trailing edge vortices drive the incident flow to merge with the back flow at the blade leading edge region.…”

“…In general, during stall incipience, the leading instabilities at the blade's leading edge (II and I4) recess at their trailing side [33] and then form a vortex at their leading side which grows and merges into the preceding instability. A typical configuration of such a stall cell is the RS6, as Table 4 illustrates.…”

Stall Inception and Development Process Due to Tip Leakage Flow in Axial Compressor Rotor Blades Row

“…For example, Outa et al [5] and He et al [6] first dealt with a 2D model to study rotating stall under the influence of the tip leakage flow. Some researchers such as Ismail and He [7], Hoying et al [8], Hah et al [9] and Vo et al [10], decided to study the tip leakage flow and its effects on rotating stall through the 3D flow simulations.…”

Experimental and Numerical Research in Flow Field of Low Speed Axial Fan with Forward-Skewed Rotor Blades

“…There was poor performance in aerodynamics of the backward-swept blades. Outa [2] studied rotating stall performance of a single stage subsonic axial compressor and found forward swept blade would increase throttle margin with decreased tip loss. Corsini et al [3,4] studied flow fields of two subsonic axial fans with 35° forward swept blades and with unswept blades respectively.…”