Influencing Parameters of a Tip Blowing Interacting With Rotor Tip Flow

Abstract

The design space of axial-flow compressors is restricted by stability issues. Different axial-type casing treatments have shown their ability to enhance compressor stability and to influence efficiency. Casing treatments have proven to be effective, but there still is need for more detailed investigations and gain of understanding for the underlying flow mechanism. Casing treatments are known to have a multitude of effects on the near-casing 3D flow field. For transonic compressor rotors these are more complex, as super- and subsonic flow regions alternate while interacting with the casing treatment. To derive design rules it is important to quantify the influence of the casing treatment on the different tip flow phenomena. Designing a casing treatment in a way that it antagonizes only the deteriorating secondary flow effects can be seen as a method to enhance stability while increasing efficiency. The numerical studies are carried out on a tip-critical rotor of a 1.5 stage transonic axial compressor. The examined recirculating tip blowing casing treatment, which consists of a recirculating channel with an air off-take above the rotor and an injection nozzle in front of the rotor. The design and functioning of the casing treatment is influenced by various parameters. A variation of the geometry of the tip blowing, more specifically the nozzle aspect ratio, the axial position or the tangential orientation of the injection port, was carried out to identify key levers. The tip blowing casing treatment is defined as a parameterized geometric model and is automatically meshed. A sensitivity analysis of the respective design parameters of the tip blowing is carried out on a single rotor row. Their impact on overall efficiency and their ability to improve stall margin is evaluated. The study is carried out using URANS simulations.

Pathways to Improved Aerodynamic Design

“…Resulting from this work, a recirculation passage geometry similar to that described by Guinet et al [14,15] has been designed and simulated. Design features of the passage are currently under URANS investigation by the authors and are providing early evidence of a significant increase in stall margin.…”

Flow Control by Slot Position and Noise Baffle in a Self-Recirculation Casing Treatment on an Axial Fan-Rotor

“…The recent research of Guinet et al [9] employed a 1.5stage transonic test rig and a carefully designed recirculation duct to study the influence of the tip gap on the stall margin improvement and efficiency penalty of the casing treatment. A detailed parametric study of the recirculation duct was then conducted to investigate the interaction between casing flow and rotor tip flow [10].…”