Active Flow Control in a Single-Stage Axial Compressor Using Tip Injection and Endwall Boundary Layer Removal

Abstract

Different active flow control techniques have been investigated in a 1.5-stage axial-flow compressor. Looking at a low-speed single-stage environment, many researchers have shown that highly loaded compressors are tip critical, showing stall inception caused by short length scale disturbances (spikes). It has been shown by several authors that these disturbances are related to the spillage of endwall flow ahead of the blading (spill forward). For the present work, different tip injection configurations were investigated in order to stabilize the near casing flow, increasing the operating range of the compressor. Stall margin improvement and the impact on stage efficiency are compared and discussed. Oil flow pictures of the casing wall above the rotor and of the stator blades as well as traverse data from pneumatic 5-hole probes show the impact of flow control on rotor and stator performance. Another method of energizing the casing wall boundary layer is the removal of low energy fluid by a circumferential slot above the rotor, which was also studied experimentally. Again, the impact on compressor operating range and efficiency, as well as flow field information collected by oil flow visualization and traverse data are discussed. Comparing the different flow control techniques, it is shown that increasing stall margin is not directly linked to stage efficiency. As described in various publications, discrete tip injection is a very powerful technique as far as range extension is concerned, but it also has substantial drawbacks such as the circumferential inhomogeneity of the rotor exit flow. These inhomogeneities may result in poor stator performance, overall resulting in a drop of stage efficiency. This problem does not occur if circumferential boundary layer removal above the rotor is used. This method however shows much less potential for increasing the operating range.

Effect of casing aspiration on the tip leakage flow in the axial flow compressor cascade

“…It has been also found that casing aspiration can effectively improve the performance and stability by controlling of TLF and the associated loss generation in compressor stages. [56][57][58] In addition, Tuo et al 67 showed that the unsteady excitation frequency due to the slot number of casing treatment is one of the most important factors influencing the compressor performance. Therefore, the unsteady effects between the aspiration slots and rotor are likely to exist when applying casing aspiration in rotor blade rows and the number of aspiration slots should be considered in detail in the process of casing aspiration design.…”

“…[52][53][54][55] There are several investigations of aspiration techniques on the control of TLF to improve the compressor performance and stability. 51,[56][57][58] Additionally, very little study has been conducted on the effectiveness of different aspiration locations on the casing and the control mechanisms of the different aspiration schemes.…”

Technical Diagnostics of Ventilation Units for Energy Efficiency and Safety of Operation

“…In order to avoid the use of guide vanes and thereby to increase the efficiency of the fan rotation direction of impellers they are made opposite [9,10].…”

Control of Tip Leakage Flow in Axial Flow Compressor Cascade by Suction on the Blade Tip

“…So far the studies about suction mainly concentrate on the control of the boundary layer separation on the blade SS (Song et al 2006;Guo et al 2010;Shi et al 2015b) or the three-dimensional (3D) separation in the hub corner (Sachdeva et al 2011;Pönick et al 2013;Guo et al 2008;Marsan et al 2015). Apart from some researches about the effects of bleeding system on the compressor performance (Leishman et al 2007a(Leishman et al , 2007b(Leishman et al , 2007cGrimshaw et al 2015Grimshaw et al , 2016, there are only several investigations of suction technique on the control of TLF to improve the compressor performance and stability (Gümmer et al 2008;Dobrzynski et al 2008;Shi et al 2015a). It is found that the flow fields in the tip region and operating range can be improved by the suction on the casing.…”