Influence of Inlet Guide Vane Wakes on the Passage Flow in a Transonic Axial Compressor

Abstract

Variable inlet guide vanes enhance the efficiency and stability of modern transonic compressors. The current quest for compact and highly efficient aero-engines requires for higher stage-loading and small axial gaps between adjacent blade rows, increasing interaction between blade rows and introducing further unsteadiness into the flow. Modeling these interactions is relevant to jet engine implementation. Recent advancements in numerical simulation of unsteady flow in multiple blade rows create an additional way to investigate the flow patterns formed by the unsteady interaction. In the case of transonic compressors, the experimental and numerical database is small. The current article will contribute to this database by investigating the flow downstream of an inlet guide vane and the influence this flow has on the passage in a transonic compressor. Unsteady flow phenomena are resolved by piezoresistive wall pressure tappings. Numerical and experimental data show that the interaction of blade rows influences the formation of the tip leakage vortex. Analyzing the vortex structure within the transonic compressor stage it is possible to show how the blade rows interact and how geometric modifications in the VIGV tip gap model influence simulation results.

Unsteady wall pressure measurement in a one-and-a-half stage axial transonic compressor during stall inception

“…The smallest variation is seen for conf-B (which features the highest inlet swirl). This supports the observations by Biela et al 24 and Leichtfuss et al, 16 which had shown that conf-B not only has a lower TLF, but also a slightly larger stall margin.…”

“…In order to capture these processes in an experiment the application of unsteady wall pressure measurements have been widely used. Inoue et al 15 and Leichtfuss et al 16 show a very good agreement between regions of low wall pressure and the lip leakage vortex. A large number of research groups have used this technique to investigate the unsteady flow features close to the wall.…”

“…Utilising the VIGV three different configurations were investigated by means of steady-stage characteristics and unsteady static wall pressure. Following up the authors' work on the steady operation of this compressor, 16,24,25 investigation of the stall inception was carried out. This suggests an influence of the VIGV-loading on the development of stall cells.…”

“…This is achieved by a simultaneous and even rotation of the vanes with a single actuated unison-ring. Previous experimental investigations by Biela et al 24 and numerical simulations by Leichtfuss et al 16 show that the rotor-tip flow field is influenced by a vortex which is generated by the tip gap of the VIGV. This gap is typical for variable vanes and necessary in order to be able to rotate the vanes without clamping.…”

Assessment of the Severity of Unsteady Mach Number Effects in a 3-Stage Transonic Compressor

“…Others compare steady and unsteady results but only for a single stage and at design speed [7][8][9]. Further single stage unsteady simulations have been presented for part speed calculations [10][11][12] and at design speed [13][14][15][16][17], including Large Eddy Simulations (LES) [18], however, none of these compare the unsteady simulations to steady simulations.…”