Tip leakage vortex trajectory and dynamics in a multiphase pump at off-design condition

An experimental investigation concerning tip flow field unsteadiness was performed for a high-performance, state-of-the-art transonic compressor rotor. Casing-mounted high frequency response pressure transducers were used to indicate both the ensemble averaged and time varying flow structure present in the tip region of the rotor at four different operating points at design speed. The ensemble averaged information revealed the shock structure as it evolved from a dual shock system at open throttle to an attached shock at peak efficiency to a detached orientation at near stall. Steady three-dimensional Navier Stokes analysis reveals the dominant flow structures in the tip region in support of the ensemble averaged measurements. A tip leakage vortex is evident at all operating points as regions of low static pressure and appears in the same location as the vortex found in the numerical solution. An unsteadiness parameter was calculated to quantify the unsteadiness in the tip cascade plane. In general, regions of peak unsteadiness appear near shocks and in the area interpreted as the shock-tip leakage vortex interaction. Local peaks of unsteadiness appear in mid-passage downstream of the shock-vortex interaction. Flow field features not evident in the ensemble averaged data are examined via a Navier-Stokes solution obtained at the near stall operating point.

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Unsteady Aperiodic Behavior of a Periodically Disturbed Tip-Leakage Vortex

AIAA Journal ◽

10.2514/1.13539 ◽

2008 ◽

Vol 46 (5) ◽

pp. 1025-1038 ◽

Cited By ~ 1

Author(s):

Ruolong Ma ◽

William J. Devenport

Keyword(s):

Tip Leakage Vortex ◽

Tip Leakage

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Measurements of the Tip Clearance Flow for a High-Reynolds-Number Axial-Flow Rotor

Journal of Turbomachinery ◽

10.1115/1.2836564 ◽

1995 ◽

Vol 117 (4) ◽

pp. 522-532 ◽

Cited By ~ 23

Author(s):

W. C. Zierke ◽

K. J. Farrell ◽

W. A. Straka

Keyword(s):

Reynolds Number ◽

Flow Visualization ◽

Vortex Core ◽

Rotor Blade ◽

High Reynolds Number ◽

Tip Clearance ◽

Tip Leakage Vortex ◽

Tip Leakage ◽

Blade Tip ◽

High Reynolds

A high-Reynolds-number pump (HIREP) facility has been used to acquire flow measurements in the rotor blade tip clearance region, with blade chord Reynolds numbers of 3,900,000 and 5,500,000. The initial experiment involved rotor blades with varying tip clearances, while a second experiment involved a more detailed investigation of a rotor blade row with a single tip clearance. The flow visualization on the blade surface and within the flow field indicate the existence of a trailing-edge separation vortex, a vortex that migrates radially upward along the trailing edge and then turns in the circumferential direction near the casing, moving in the opposite direction of blade rotation. Flow visualization also helps in establishing the trajectory of the tip leakage vortex core and shows the unsteadiness of the vortex. Detailed measurements show the effects of tip clearance size and downstream distance on the structure of the rotor tip leakage vortex. The character of the velocity profile along the vortex core changes from a jetlike profile to a wakelike profile as the tip clearance becomes smaller. Also, for small clearances, the presence and proximity of the casing endwall affects the roll-up, shape, dissipation, and unsteadiness of the tip leakage vortex. Measurements also show how much circulation is retained by the blade tip and how much is shed into the vortex, a vortex associated with high losses.

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The Behavior of the Casing Boundary Layer With the Presence of Tip Leakage Vortex

Volume 2A: Turbomachinery ◽

10.1115/gt2018-75916 ◽

2018 ◽

Cited By ~ 2

Author(s):

Xi Nan ◽

Feng Lin ◽

Takehiro Himeno ◽

Toshinori Watanabe

Keyword(s):

Boundary Layer ◽

Skin Friction ◽

Three Dimensional ◽

Pressure Rise ◽

Rotating Stall ◽

Tip Leakage Vortex ◽

Tip Leakage ◽

Transonic Compressor ◽

Flow Loss ◽

Produce Flow

Casing boundary layer effectively places a limit on the pressure rise capability achievable by the compressor. The separation of the casing boundary layer not only produce flow loss but also closely related to the compressor rotating stall. The motivation of this paper is to present a viewpoint that the casing boundary layer should be paid attention to in parallel with other flow factors on rotating stall trigger. This paper illustrates the casing boundary layer behavior by displaying its separation phenomena with the presence of tip leakage vortex at different flow conditions. Skin friction lines and the corresponding absolute streamlines are used to demonstrate the three-dimensional flow patterns on and near the casing. The results depict a Saddle, a Node and several tufts of skin friction lines dividing the passage into four zones. The tip leakage vortex is enfolded within one of the zones by the separated flows. All the flows in each blade passage are confined within the passage as long as the compressor is stable. The casing boundary layer of a transonic compressor is also examined in the same way, which results in qualitatively similar zonal flows that enfolds the tip leakage vortex. This research develops a new way to study the casing boundary layer in rotating compressors. The results may provide a first-principle based explanation to stalling mechanisms for compressors that are casing sensitive.

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Unsteady Tip Leakage Vortex Cavitation Originating From the Tip Clearance of an Oscillating Hydrofoil

Journal of Fluids Engineering ◽

10.1115/1.2173290 ◽

2005 ◽

Vol 128 (3) ◽

pp. 421-429 ◽

Cited By ~ 22

Author(s):

Masahiro Murayama ◽

Yoshiki Yoshida ◽

Yoshinobu Tsujimoto

Keyword(s):

Steady State ◽

Qualitative Agreement ◽

Cavity Growth ◽

Simple Calculation ◽

Tip Clearance ◽

Cavity Volume ◽

Cavity Size ◽

Tip Leakage Vortex ◽

Tip Leakage ◽

Unsteady Characteristics

Tip leakage vortex cavitations originating from the tip clearance of an oscillating hydrofoil were observed experimentally. It was found that the delay between the unsteady and the steady-state results of the tip leakage vortex cavitation increase, and that the maximum cavity size decreases when the reduced oscillating frequency increases. To simulate the unsteady characteristics of tip leakage vortex cavitation, a simple calculation based on slender body approximation was conducted taking into account the effect of cavity growth. The calculation and experimental results of the cavity volume fluctuation were found to be in qualitative agreement.

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Numerical and Experimental Investigation of Tip Leakage Vortex Trajectory in an Axial Flow Pump

Volume 1B, Symposia: Fluid Machinery; Fluid Power; Fluid-Structure Interaction and Flow-Induced Noise in Industrial Applications; Flow Applications in Aerospace; Flow Manipulation and Active Control: Theory, Experiments and Implementation; Fundamental Issues and Perspectives in Fluid Mechanics ◽

10.1115/fedsm2013-16058 ◽

2013 ◽

Author(s):

Desheng Zhang ◽

Weidong Shi ◽

Suqing Wu ◽

Dazhi Pan ◽

Peipei Shao ◽

...

Keyword(s):

Flow Rate ◽

Axial Flow ◽

Tip Clearance ◽

High Speed Photography ◽

Rate Condition ◽

Tip Leakage Vortex ◽

Tip Leakage ◽

Starting Point ◽

Axial Flow Pump ◽

Flow Pump

In this paper, the tip leakage vortex (TLV) structures in an axial flow pump were investigated by numerical and experimental methods. Based on the comparisons of different blade tip clearance size (i.e., 0.5 mm, 1mm and 1.5mm) and different flow rate conditions, TLV trajectories were obtained by Swirling Strength method, and simulated by modified SST k-ω turbulence model with refined high-quality structured grids. A high-speed photography test was carried out to capture the tip leakage vortex cavitation in an axial flow pump with transparent casing. Numerical results were compared with the experimental leakage vortex trajectories, and a good agreement is presented. The detailed trajectories show that the start point of tip leakage vortex appears near the leading edge at small flow rate, and it moves from trailing edge to about 30% chord span at rated flow rate. At the larger flow rate condition, the starting point of TLV shifts to the middle of chord, and the direction of TLV moves parallel to the blade hydrofoil. As the increasing of the tip size, the start point of TLV trajectories moves to the central of chord and the minimum pressure in vortex core is gradually reduced.

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Education Committee Best Paper of 1995 Award: Methods of Classical Mechanics Applied to Turbulence Stresses in a Tip Leakage Vortex

Journal of Turbomachinery ◽

10.1115/1.2840917 ◽

1996 ◽

Vol 118 (4) ◽

pp. 622-629 ◽

Cited By ~ 11

Author(s):

J. G. Moore ◽

S. A. Schorn ◽

J. Moore

Keyword(s):

Stress Tensor ◽

Reynolds Stress ◽

Classical Mechanics ◽

Three Dimensional ◽

Surface Model ◽

Reynolds Stresses ◽

Tip Leakage Vortex ◽

Tip Leakage ◽

Stress Tensors ◽

Principal Directions

Moore et al. measured the six Reynolds stresses in a tip leakage vortex in a linear turbine cascade. Stress tensor analysis, as used in classical mechanics, has been applied to the measured turbulence stress tensors. Principal directions and principal normal stresses are found. A solid surface model, or three-dimensional glyph, for the Reynolds stress tensor is proposed and used to view the stresses throughout the tip leakage vortex. Modeled Reynolds stresses using the Boussinesq approximation are obtained from the measured mean velocity strain rate tensor. The comparison of the principal directions and the three-dimensional graphic representations of the strain and Reynolds stress tensors aids in the understanding of the turbulence and what is required to model it.

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Aerodynamic Interaction Between Incoming Vortex and Tip Leakage Flow in a Turbine Cascade

Volume 2B: Turbomachinery ◽

10.1115/gt2018-75138 ◽

2018 ◽

Cited By ~ 1

Author(s):

Kai Zhou ◽

Chao Zhou

Keyword(s):

Numerical Study ◽

Aerodynamic Performance ◽

Leakage Flow ◽

Computational Domain ◽

Turbine Cascade ◽

Tip Leakage Flow ◽

Tip Leakage Vortex ◽

Tip Leakage ◽

Swirl Generator ◽

Swirling Vortex

In turbines, secondary vortices and tip leakage vortices develop and interact with each other. In order to understand the flow physics of vortices interaction, the effects of incoming vortex on the downstream tip leakage flow are investigated in terms of the aerodynamic performance in a turbine cascade. Experimental, numerical and analytical methods are used. In the experiment, a swirl generator was used upstream near the casing to generate the incoming vortex, which interacted with the tip leakage vortex in the turbine cascade. The swirl generator was located at ten different pitchwise locations to simulate the quasi-steady effects. In the numerical study, a Rankine-like vortex was defined at the inlet of the computational domain to simulate the incoming swirling vortex. Incoming vortices with opposite directions were investigated. The vorticity of the positive incoming swirling vortex has a large vector in the same direction as that of the tip leakage vortex. In the case of the positive incoming swirling vortex, the vortex mixes with the tip leakage vortex to form one vortex near the tip as it transports downstream. The vortices interaction reduces the vorticity of the flow near the tip, as well as the loss by making up for the streamwise momentum within the tip leakage vortex core. In contrast, the negative incoming swirling vortex has little effects on the tip leakage vortex and the loss. As the negative incoming swirling vortex transports downstream, it is separated from the tip leakage vortex and forms two vortices. A triple-vortices-interaction kinetic analytical model and one-dimensional mixing model are proposed to explain the mechanism of vortex interaction on the aerodynamic performance.

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