Interaction Between Inlet Boundary Layer, Tip-Leakage and Secondary Flows in a Low-Speed Turbine Cascade

Chan, Julia; Yaras, M. I.; Sjolander, S. A.

doi:10.1115/94-gt-250

Cited by 9 publications

(5 citation statements)

References 11 publications

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“…Flow between the tip of a rotating blade and a static casing, referred to as Tip Leakage Flow (TLF), has received considerable attention in research due to its impact on efficiency and quiet operation of ducted propulsors and turbo-machinery. Results from experimentation have explored most flow parameters affecting the cavitation performance including Reynolds number scale effects [1], inlet boundary layer thickness [2], and gap/clearance height [3]. However, the influence of cavitation nuclei concentration on the extent of cavitation in these flows, particularly the precise locations of cavitation inception and desinence, are not yet well understood.…”

Section: Introductionmentioning

confidence: 99%

Nucleation Effects on Tip-Gap Cavitation

Russell¹,

Barbaca²,

Venning³

et al. 2020

Australasian Fluid Mechanics Conference (AFMC)

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Cavitation in tip leakage flows have been investigated in a water tunnel for different concentrations of free-stream cavitation nuclei. High-resolution still photography exhibits similar cavitation topology overall. However, hydro-acoustic measurements reveal stark differences in the desinent extinction of cavitation when different levels of active nuclei are present. Results quantify the anticipated challenges in designing enclosed propulsors and turbo-machinery that operate in flows with varying susceptibility to cavitation.

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Section: Introductionmentioning

confidence: 99%

Nucleation Effects on Tip-Gap Cavitation

Russell¹,

Barbaca²,

Venning³

et al. 2020

Australasian Fluid Mechanics Conference (AFMC)

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“…Tallman and Lakshminarayana 10 implemented numerical simulations for discussing the structure and the generation mechanism of the leakage vortex (LV) in axial flow turbines. Booth et al, 11 Chan et al, 12 and Mischo et al 13 provided detailed studies of the flow pattern of leakage flow. Recent investigations 14,15 showed that the importance of tip leakage flow still can't be ignored and more severe challenges need to be faced by researchers.…”

Section: Introductionmentioning

confidence: 99%

Experimental study on axially non-uniform clearances in a linear turbine cascade with a cavity squealer tip

Chen

Meng

et al. 2018

Proceedings of the Institution of Mechanical Engineers, Part G:

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The effects of axially non-uniform clearances on the tip leakage flow and aerodynamic performance in a linear turbine cascade with a cavity squealer tip were investigated in this study with the objective of improving the flow loss and tip flow field structure. A calibrated five-hole probe was used for the measurement of three-dimensional flows downstream of the cascade. The method of oil-flow visualization was used to show the endwall flow field structure. The distribution of endwall static pressure was measured particularly by using the special moveable endwall. The axially non-uniform clearance, as a novel strategy that has a non-negligible influence on tip clearance flow and clearance leakage loss, may become a potential technology for improving aerodynamic performance in turbine cascades. By using the expanding clearance, the flow loss at the outlet is reduced effectively and an apparent improvement of aerodynamic performance in the turbine cascade is gained. Under the tip clearances of 0.75% H and 2% H, the maximum reduction of overall total pressure loss coefficient at the outlet is separately about 2.3% and 3.5% compared with the uniform clearance. The shrinkage of the buffer zone is considered to be able to weaken the interaction of the tip leakage vortex and passage vortex and thus reduce the loss of passage vortex. For the shrinking clearance, a noticeable decline in the aerodynamic performance of turbine cascade with cavity squealer tip is exhibited at both on and off design conditions in contrast to the uniform clearance. In addition, the effects of axially non-uniform clearances on the aerodynamic performance at off-design conditions have been investigated.

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“…The majority of the loss is due to the interaction between tip leakage and passage secondary flows. Furthermore, the interaction has been investigated in detail by means of experiments by Yamamoto [10] and Chan et al [11]. The results have shown that there is a strong interaction between tip leakage and passage vortexes.…”

Section: Introductionmentioning

confidence: 99%

Effect of axially non-uniform rotor tip clearance on aerodynamic performance of an unshrouded axial turbine

Gao

Zheng

et al. 2011

Proceedings of the Institution of Mechanical Engineers, Part A:

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Tip leakage flow is responsible for a significant amount of aerodynamic losses in a turbine stage, and the mixing of leakage flow with the rotor passage secondary flow causes losses and reduces turbine stage efficiency. This article presents a numerical investigation of the effect of axially non-uniform tip clearance on the aerodynamic performance of an unshrouded axial turbine at design and off-design conditions, in an attempt to seek an optimal tip clearance chordwise distribution to control the interaction between tip leakage and passage secondary flows, and then reduce the total losses in turbines. Different types of axially uniform and non-uniform rotor tip clearances were used in this investigation, which include uniform, expanding, shrinking, and back- and front-step tip clearances. Numerical results show that, for the axially uniform tip clearances, the interaction mechanism between tip leakage and passage secondary flows is different in the relatively small and large tip clearance heights. With the tip clearance height gradually increasing, tip passage vortex at the passage exit is first enhanced, and then it becomes weak. Axially non-uniform tip clearance changes the chordwise distribution of over tip leakage mass flow. The front-step and shrink tip clearances are able to efficiently utilize the interaction of tip leakage flow with passage secondary flows, and then reduce the total losses in turbines. For different axially non-uniform tip clearances, loading distribution near the tip has a great impact on the tip leakage flow. It will result in great losses when the maximum tip clearance and loading positions are in the same position along the blade.

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Interaction Between Inlet Boundary Layer, Tip-Leakage and Secondary Flows in a Low-Speed Turbine Cascade

Cited by 9 publications

References 11 publications

Nucleation Effects on Tip-Gap Cavitation

Nucleation Effects on Tip-Gap Cavitation

Experimental study on axially non-uniform clearances in a linear turbine cascade with a cavity squealer tip

Effect of axially non-uniform rotor tip clearance on aerodynamic performance of an unshrouded axial turbine

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