Influencing Parameters of 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 (CTs) 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 (TBCT) 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 are 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 are evaluated. The study is carried out using unsteady Reynolds-averaged Navier–Stokes (URANS) simulations.

Flow Control Methods and Their Applicability in Low-Reynolds-Number Centrifugal Compressors—A Review

“…High-momentum fluid is recirculated from the impeller to the impeller inlet through the recirculation slot. [180] 2017 Recirculating slots CC − + + [180] 2017 Bleed slots CC 40% ±0% +10% + [181] 2017 Axial slots MC −0.7% +26.4% [182] 2017 Recirculating slots AC 0.27-0.38% ±0% + +20% [183] 2017 Injection nozzle CC 0-80% −1% +3% +40% [184] 2017 Injection nozzle AC + [185] 2017 Grooves HPT cascade 220,000 Max 4% reduction in total pressure loss [186] 2017 Injection nozzle HPT cascade 60,000 0.4% 20% reduction in total pressure loss [187] 2016 Grooves AC ±0% ±0% [188] 2016 Grooves Channel flow 2648-30,000 40% reduction in drag [171] 2016 Recirculating slots with vanes CC, Ns = 1.00 up to 20% −0.25%pt +25% +69% [171] 2016 Recirculating slots with vanes CC, Ns = 0.85 up to 20% −0.4%pt +30% +94% [189] 2016 Recirculating slots AC 0.47% ±0% +6.12% [190] 2016 Grooves AC +5.7% [191] 2016 Bleed chamber AC ±0% ±0% +3.5 . .…”