Direct numerical simulation of a tip-leakage flow in a planar duct with a longitudinal slit

The tip leakage flow in an axial ventilation fan with various tip clearances is investigated by experimental measurement and numerical simulation. For a low-rotating-speed ventilation fan with a large tip clearance, both experimental measurement and numerical simulation indicate that the leakage flow originating from the tip clearance along the chord rolls up into a three-dimensional spiral structure to form a leakage flow vortex. The mixing interaction between the tip leakage flow and the main flow produces a low axial velocity region in the tip region, which leads to blockage of the main flow. As the tip clearance increases, the tip leakage flow and the reverse flow become stronger and fully developed. In addition, the position of the first appearance of the tip leakage vortex moves further downstream in a direction parallel to the mid chord line.

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Experimental and Computational Investigation of the Tip Clearance Flow for an Axial Ventilation Fan

Volume 6: Turbo Expo 2003, Parts A and B ◽

10.1115/gt2003-38673 ◽

2003 ◽

Author(s):

Xiaocheng Zhu ◽

Wanlai Lin ◽

Zhaohui Du

Keyword(s):

Numerical Simulation ◽

Experimental Measurement ◽

Reverse Flow ◽

Three Dimensional ◽

Tip Clearance ◽

Leakage Flow ◽

Tip Leakage Flow ◽

Tip Leakage ◽

Blade Tip ◽

Ventilation Fan

The tip leakage flow in an axial ventilation fan with various tip clearances is investigated by experimental measurement and numerical simulation. The characteristic of a ventilation fan is an extreme low-pressure difference, a large tip clearance with a low rotating speed. A three dimensional PDA (Particle Dynamics Analysis) system is used for the measurement of the velocity field in the tip clearance region. The flow field is surveyed across the whole passage at fifteen axial locations (from 100% axial chord in front of the leading edge to 100% axial chord behind the trailing edge), mainly focusing on areas close to the blade tip (from 90% of the blade span to the casing wall). Both experimental measurement and numerical simulation indicate that the leakage flow originating from the tip clearance along the chord rolls up into a three-dimensional spiral structure to form a leakage flow vortex. A low axial velocity zone shows up in the tip region, which leads to blockage of the main flow. There are under-turning zones near and in the blade tip region, and an overturning zone in a lower span region with a critical span-wise position of about 94%. A reverse flow appears at the suction side near the trailing edge. As the tip clearance increases, the tip leakage flow and the reverse flow become stronger and fully developed. In addition, the position of the first appearance of the tip leakage vortex moves further downstream in a direction parallel to the mid chord line.

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A flow model for tip leakage flow in turbomachinery using a square duct with a longitudinal slit

Aerospace Science and Technology ◽

10.1016/j.ast.2019.105460 ◽

2019 ◽

Vol 95 ◽

pp. 105460 ◽

Cited By ~ 1

Author(s):

Yanfei Gao ◽

Yangwei Liu

Keyword(s):

Flow Model ◽

Leakage Flow ◽

Tip Leakage Flow ◽

Square Duct ◽

Tip Leakage ◽

Longitudinal Slit

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Experimental investigation of the influence on compressor cascade characteristics at high subsonic speed with pressure surface tip winglets

Proceedings of the Institution of Mechanical Engineers Part A Journal of Power and Energy ◽

10.1177/0957650921990198 ◽

2021 ◽

pp. 095765092199019

Author(s):

Wanyang Wu ◽

Jingjun Zhong

Keyword(s):

Numerical Simulation ◽

Flow Field ◽

Leakage Flow ◽

Compressor Cascade ◽

Tip Leakage Flow ◽

Tip Leakage ◽

Pressure Surface ◽

Subsonic Speed ◽

Flow Loss ◽

Blade Tip

To investigate the influence of tip winglets on the tip leakage flow in a compressor cascade with different incidences, the experimental measurement combined with numerical simulation are used to study the conventional cascade and cascades with three different pressure surface tip winglets at five incidences of −6°, −3°, 0°, +3° and +6°. The results indicate that three different tip winglets at five incidences all restrain the occurrence of leakage flow, delay the mixing of leakage flow and the mainstream, change the formation path of leakage vortex and weaken its intensity, reduce the flow loss and improve the uniformity of flow field. The sensitivity of the flow field to variable incidences is reduced. The optimization degree of the flow field is proportional to the width of the blade tip winglet. The improvements are more obvious at positive angles. When the incidence reaches +6°, the flow loss is reduced by 12.4%.

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Effects of Tip Leakage Flow on the Aerodynamic Performance and Stability of an Axial-Flow Transonic Compressor Stage

Energies ◽

10.3390/en14144168 ◽

2021 ◽

Vol 14 (14) ◽

pp. 4168

Author(s):

Botao Zhang ◽

Xiaochen Mao ◽

Xiaoxiong Wu ◽

Bo Liu

Keyword(s):

Boundary Layer ◽

Shock Wave ◽

Axial Flow ◽

Leading Edge ◽

Rotating Stall ◽

Tip Clearance ◽

Leakage Flow ◽

Tip Leakage Flow ◽

Tip Leakage ◽

Transonic Compressor

To explain the effect of tip leakage flow on the performance of an axial-flow transonic compressor, the compressors with different rotor tip clearances were studied numerically. The results show that as the rotor tip clearance increases, the leakage flow intensity is increased, the shock wave position is moved backward, and the interaction between the tip leakage vortex and shock wave is intensified, while that between the boundary layer and shock wave is weakened. Most of all, the stall mechanisms of the compressors with varying rotor tip clearances are different. The clearance leakage flow is the main cause of the rotating stall under large rotor tip clearance. However, the stall form for the compressor with half of the designed tip clearance is caused by the joint action of the rotor tip stall caused by the leakage flow spillage at the blade leading edge and the whole blade span stall caused by the separation of the boundary layer of the rotor and the stator passage. Within the investigated varied range, when the rotor tip clearance size is half of the design, the compressor performance is improved best, and the peak efficiency and stall margin are increased by 0.2% and 3.5%, respectively.

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Discussion: “Tip Leakage Flow in Axial Compressors” (Storer, J. A., and Cumpsty, N. A., 1991, ASME J. Turbomach., 113, pp. 252–259)

Journal of Turbomachinery ◽

10.1115/1.2929096 ◽

1991 ◽

Vol 113 (2) ◽

pp. 259-259 ◽

Cited By ~ 2

Author(s):

I. N. Moyle

Keyword(s):

Leakage Flow ◽

Tip Leakage Flow ◽

Axial Compressors ◽

Tip Leakage

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Development of the Tip-Leakage Flow Downstream of a Planar Cascade of Turbine Blades: Vorticity Field

Volume 1: Turbomachinery ◽

10.1115/89-gt-55 ◽

1989 ◽

Cited By ~ 1

Author(s):

M. Yaras ◽

S. A. Sjolander

Keyword(s):

Simple Model ◽

Turbine Blades ◽

Leakage Flow ◽

Tip Leakage Flow ◽

Vorticity Field ◽

Trailing Edge ◽

Tip Leakage ◽

Blade Row ◽

Axisymmetric Structure ◽

Insight Into

The paper presents detailed measurements of the tip-leakage flow emerging from a planar cascade of turbine blades. Four clearances of from 1.5 to 5.5 percent of the blade chord are considered. Measurements were made at the trailing edge plane, and at two main planes 1.0 and 1.56 axial chord lengths downstream of the cascade. The results give insight into several aspects of the leakage flow including: the size and strength of the leakage vortex in relation to the size of the tip gap and the bound circulation of the blade; and the evolution of the components of vorticity as the vortex diffuses laterally downstream of the blade row. The vortex was found to have largely completed its roll-up into a nearly axisymmetric structure even at the trailing edge of the cascade. As a result, it was found that the vortex could be modelled surprisingly well with a simple model based on the diffusion of a line vortex.

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