The Effects of Tip Leakage Flow on the Performance of Multistage Compressors Used in Small Core Engine Applications

Abstract

Large rotor tip clearances and the associated tip leakage flows are known to have a significant effect on overall compressor performance. However, detailed experimental data reflecting these effects for a multistage compressor are limited in the open literature. As design trends lead to increased overall compressor pressure ratio for thermal efficiency benefits and increased bypass ratios for propulsive benefits, the rear stages of the high-pressure compressor will become physically small. Because rotor tip clearances cannot scale exactly with blade size due to the margin needed for thermal growth considerations, relatively large tip clearances will be a reality for these rear stages. Experimental data have been collected from a three-stage axial compressor to assess performance with three-tip clearance heights representative of current and future small core machines. Trends of overall pressure rise, stall margin, and efficiency are evaluated using clearance derivatives, and the summarized data presented here begin to narrow the margin of tip clearance sensitivities outlined by previous studies in an effort to inform future compressor designs. Furthermore, interstage measurements show stage matching changes and highlight specific differences in the performance of rotor 1 and stator 2 compared to other blade rows in the machine.

Investigation of Performance and Rotor Tip Flow Field in a Low Speed Research Compressor with Circumferential Groove Casing Treatment at Varying Tip Clearance

“…It confirms the findings of Berdanier and Key [20] and add new information for tip clearances larger than / = 4%.…”

“…The last tested tip clearance increase from / = 3.7% to 5.0% (TC3-4) in this paper, however, shows a remarkably different behavior because the stall mass flow is not increased but decreased and hence the derivative is −0.6. This behavior has not been detected by [1,20,21] because their largest tip clearance size is notably lower than the largest tested tip clearance size in this paper. Wisler et al [15] tested two compressors A and B with largest tip clearance sizes of / = 5.5% and / = 4.5%, Groove s/c = 1.2%  = 1.00…”

“…The following is an addition to a comparison of different investigations in open literature that has been presented by Berdanier and Key [20]. They plotted the percentage increase in stall flow coefficient relative to the smallest tested tip clearance size Δ Stall over tip clearance size for results from Wisler [1], McDougall [21], and their own test results.…”

Investigation of endwall treatment and shock control in a five-stage axial compressor

“…5 found that in multistage axial compressors, an increase of the radial tip clearance leads to a dramatic reduction of operability (by 20%), pressure ratio, and efficiency. Berdanier and Key 6,7 conducted a detailed experiment on a multistage axial compressor with different tip clearances and found tip clearance has different influences on different stages through its influence on tip leakage flow trajectories. A detailed investigation concerning the effect of tip clearance and blockage on the matching of multistage axial compressors as well as on the performance and stability was done by Domercq and Escuret, 8 and this was further validated by Yang et al.…”

Effect of tip clearance size on the performance of a low-reaction transonic axial compressor rotor

“…As is well-known, tip clearance size (TCS) has a large impact on compressor performance and stability, and is therefore a crucial factor in turbomachinery aerodynamic design. 1–4 The influence that TCS exerts over the flow field of the blade tip region has been extensively studied for decades. The TCS of an engine may change because of many uncertainty factors such as varying thermal expansion, casing variations and eccentricity of rotor wheel in casing.…”