scholarly journals Leakage Effects in the Rotor Tip-Clearance Region of a Multistage Axial Compressor: Part 1 — Innovative Experiments

1998 ◽  
Author(s):  
P. C. Ivey ◽  
M. Swoboda
Keyword(s):  
Numerical Solutions ◽  
Stokes Equations ◽  
Numerical Study ◽  
Measurement Techniques ◽  
Axial Compressor ◽  
Tip Clearance ◽  
Navier Stokes ◽  
Navier Stokes Equations ◽  
Tip Clearance Flow ◽  
Clearance Flow

This paper describes work conducted as part of an experimental and numerical study of leakage effects by numerous Research and Industrial partners. For clarity it is presented in two parts. Part 1 presents measurements of tip-clearance flow for a 3rd stage rotor embedded in a four stage low-speed research compressor. The measurements are innovative and comprise measurements in the rotor relative frame of reference and 3D Laser time-of-flight Anemometry. Both techniques are relevant for improved understanding of multistage compressor flow dynamics and consequently, validated multistage CFD simulations. In part 2 of this paper (see Politis et al 1997b) it is shown that downstream of the rotor passage the location and size of a tip-clearance vortex, identified from both independent measurement techniques in Part 1, is in good agreement with 3D solutions of the Navier-Stokes equations modelling this compressor. These 3D numerical solutions reveal the tip-clearance flow structure using a multiblock grid technique.

Numerical Study of the Tip Clearance Flow Development in a Propulsion Pump Stage

1996 ◽  
Author(s):  
Yu-Tai Lee ◽  
Chunill Hah ◽  
James Loellbach
Keyword(s):  
Vortex Structure ◽  
Stokes Equations ◽  
Numerical Study ◽  
Three Dimensional ◽  
Tip Clearance ◽  
Tip Vortex ◽  
Navier Stokes ◽  
Tip Clearance Flow ◽  
Clearance Flow ◽  
High Reynolds

This paper summarizes a numerical investigation of the fundamental structure of the rotor tip-clearance vortex and its interaction with a passage trailing-edge vortex in a single-stage stator-rotor pump. The flow field of a highly-loaded rotor measured in a high Reynolds number pump facility (HIREP) is used for comparison. The numerical solution was obtained by solving the three-dimensional Reynolds averaged Navier-Stokes equations. The calculated results are visualized in order to understand the details of the tip-vortex structure. The study shows that the tip geometry should be accurately represented to predict the tip-vortex structure correctly.

A numerical study of the interaction between unsteay free-stream disturbances and localized variations in surface geometry

1989 ◽  
Vol 209 ◽  
pp. 285-308 ◽  
Author(s):  
R. J. Bodonyi ◽  
W. J. C. Welch ◽  
P. W. Duck ◽  
M. Tadjfar
Keyword(s):  
Numerical Solutions ◽  
Free Stream ◽  
Stokes Equations ◽  
Numerical Study ◽  
Navier Stokes ◽  
Surface Geometry ◽  
Navier Stokes Equations ◽  
S Waves ◽  
Tollmien Schlichting

A numerical study of the generation of Tollmien-Schlichting (T–S) waves due to the interaction between a small free-stream disturbance and a small localized variation of the surface geometry has been carried out using both finite–difference and spectral methods. The nonlinear steady flow is of the viscous–inviscid interactive type while the unsteady disturbed flow is assumed to be governed by the Navier–Stokes equations linearized about this flow. Numerical solutions illustrate the growth or decay of the T–S waves generated by the interaction between the free-stream disturbance and the surface distortion, depending on the value of the scaled Strouhal number. An important result of this receptivity problem is the numerical determination of the amplitude of the T–S waves.

A Numerical Study on Performances of Centrifugal Compressor Stages With Different Radial Gaps

2000 ◽  
Author(s):  
K. Sato ◽  
L. He
Keyword(s):  
Centrifugal Compressor ◽  
Stokes Equations ◽  
Numerical Study ◽  
Axial Compressor ◽  
Navier Stokes ◽  
Centrifugal Impeller ◽  
Vaned Diffuser ◽  
Navier Stokes Equations ◽  
Performance Predictions ◽  
Radial Gap

A numerical study of 3D unsteady flows in centrifugal compressor stages solving the Navier-Stokes equations is presented. The emphasis is on the effect of the radial gap between blade rows on the aerodynamic performance. In the numerical tests, Krain’s centrifugal impeller was combined with a DCA (Double Circular Arc) type radial vaned diffuser. The compressor stages with three settings of radial gap ranging from 5 to 15 percent of the impeller trailing edge radius are configured and unsteady flow simulations are carried out to compare the time-averaged efficiencies. The performance predictions show that the efficiency is deteriorated if the radial gap between blade rows is reduced with intensified blade row interaction, which is in contradiction to the general trend for axial compressor stages. In the centrifugal compressors tested, wake chopping by diffuser vanes, which usually benefits efficiency in axial compressor stages, causes unfavourable wake compression through the diffuser passages to deteriorate the efficiency.

Leakage Effects in the Rotor Tip-Clearance Region of a Multistage Axial Compressor: Part 2 — Numerical Modelling

1998 ◽  
Author(s):  
E. S. Politis ◽  
K. C. Giannakoglou ◽  
K. D. Papailiou
Keyword(s):  
Axial Compressor ◽  
Tip Clearance ◽  
Navier Stokes ◽  
Computational Domain ◽  
Loose Coupling ◽  
Tip Clearance Flow ◽  
Clearance Flow ◽  
Flow Effects ◽  
Multistage Axial Compressor ◽  
Asme Paper

Innovative measurements of tip-clearance flow for the 3rd stage rotor embedded in a four stage Low-Speed Research Compressor are presented in the companion ASME paper. Here, in Part 2, the rotor flow is numerically simulated through a Navier-Stokes solver implementing the k-ε turbulence model. The 3rd stage rows are considered as discrete parts of the same computational domain and the flow in each one of them is treated as steady in the corresponding system of reference. An iterative, though loose, coupling between the rotor exit and the stator inlet is established by artificially increasing the inter-row distance. To model tip-clearance flow effects with sufficient accuracy, a two-block grid system per row is used. Comparisons with measurements published in Part 1 for the average flow quantities at the exit of both rows are presented. Row patterns close to the rotor tip-clearance region are illustrated.

Axisymmetric Inertial Oscillations in Transient Rotating Flows in a Cylinder

1997 ◽  
Vol 119 (2) ◽  
pp. 390-396
Author(s):  
Jae Won Kim ◽  
Jae Min Hyun
Keyword(s):  
Large Time ◽  
Numerical Solutions ◽  
Stokes Equations ◽  
Numerical Study ◽  
Experimental Studies ◽  
Numerical Results ◽  
Navier Stokes ◽  
Inertial Oscillations ◽  
Time Duration ◽  
Navier Stokes Equations

A numerical study is made of axisymmetric inertial oscillations in a fluid-filled cylinder. The entire cylinder undergoes a spin-up process from rest with an impulsively started rotation rate Ω(t) = Ω0 + εω cos(ωt). Numerical solutions are obtained to the axisymmetric, time-dependent Navier-Stokes equations. Identification of the inertial oscillations is made by inspecting the evolution of the pressure difference between two pre-set points on the central axis, Cp. In the limit of large time, the inertial frequency thus determined is in close agreement with the results of the classical inviscid theory for solid-body rotation. As in previous experimental studies, the t* − (Ω0/ω) plots are constructed for inertial oscillations, where t* indicates the time duration until the maximum Cp is detected. These detailed numerical results are in broad agreement with the prior experimental data. Flow intensifications under the resonance conditions are illustrated based on the numerical results. Depictions are made of the increase in the amplitude of oscillating part of the total angular momentum under the resonance conditions. Also, the patterns of t* − (Ω0/ω) curves are displayed for different inertial frequency modes.

scholarly journals Experimental investigation of unsteady flow phenomena in a three-stage axial compressor

2003 ◽  
Vol 217 (4) ◽  
pp. 341-348 ◽  
Author(s):  
R Niehuis ◽  
A Bohne ◽  
A Hoynacki
Keyword(s):  
Measurement Techniques ◽  
Axial Compressor ◽  
Global Scale ◽  
Rotor Blades ◽  
Tip Clearance ◽  
Tip Clearance Flow ◽  
Clearance Flow ◽  
Flow Phenomena ◽  
Rotor Stator Interaction ◽  
Interaction Phenomena

In the past years, a three-stage axial compressor equipped with a modern controlled diffusion airfoil (CDA) blading has been investigated in much detail, applying state-of-the-art steady and unsteady measurement techniques, at RWTH Aachen University. The compressor under investigation exhibits design features of real industrial compressors. By performing high-resolution measurements both in space and time, a thorough insight into various flow phenomena in the compressor has been achieved, leading to a better understanding of various flow phenomena such as rotor—stator interaction, tip clearance flow and viscous flow effects in a multistage compressor environment. After a short summary of some performance characteristics at design and off-design, this paper focuses on the analysis of interaction phenomena present in the three-stage axial compressor. The interaction phenomena are described on a more global scale. In order to quantify the upstream and downstream influence of the three rotor blades, a suitable parameter is presented.

A Numerical Study of the Influence of Disc Geometry on the Flow and Heat Transfer in a Rotating Cavity

1990 ◽  
Author(s):  
B. L. Lapworth ◽  
J. W. Chew
Keyword(s):  
Heat Transfer ◽  
Numerical Solutions ◽  
Stokes Equations ◽  
Numerical Study ◽  
Navier Stokes ◽  
Navier Stokes Equations ◽  
Model Calculations ◽  
Flow And Heat Transfer ◽  
Rotating Cavity ◽  
Radial Outflow

Numerical solutions of the Reynolds-averaged Navier-Stokes equations have been used to model the influence of cobs and a bolt cover on the flow and heat transfer in a rotating cavity with an imposed radial outflow of air. Axisymmetric turbulent flow is assumed using a mixing length turbulence model. Calculations for the non-plane discs are compared with plane disc calculations and also with the available experimental data. The calculated flow structures show good agreement with the experimentally observed trends. For the cobbed and plane discs, Nusselt numbers are calculated for a combination of flow rates and rotational speeds; these show some discrepancies with the experiments, although the calculations exhibit the more consistent trend. Further calculations indicate that differences in thermal boundary conditions have a greater influence on Nusselt number than differences in disc geometry. The influence of the bolt cover on the heat transfer has also been modelled, although comparative measurements are not available.

Oscillatory flow states in an enclosed cylinder with a rotating endwall

1999 ◽  
Vol 389 ◽  
pp. 101-118 ◽  
Author(s):  
J. L. STEVENS ◽  
J. M. LOPEZ ◽  
B. J. CANTWELL
Keyword(s):  
Oscillatory Flow ◽  
Numerical Solutions ◽  
Stokes Equations ◽  
Numerical Study ◽  
Modulation Frequency ◽  
Reynolds Numbers ◽  
Navier Stokes ◽  
Multiple Time ◽  
Navier Stokes Equations ◽  
Flow States

A combined experimental and numerical investigation is presented of the multiple oscillatory states that exist in the flows produced in a completely filled, enclosed, circular cylinder driven by the constant rotation of one of its endwalls. The flow in a cylinder of height to radius ratio 2.5 is interrogated experimentally using flow visualization and digitized images to extract quantitative temporal information. Numerical solutions of the axisymmetric Navier–Stokes equations are used to study the same flow over a range of Reynolds numbers where the flow is observed to remain axisymmetric. Three oscillatory states have been identified, two of them are periodic and the third is quasi-periodic with a modulation frequency much smaller than the base frequency. The range of Reynolds numbers for which the quasi-periodic flow exists brackets the switch between the two periodic states. The results from the combined experimental and numerical study agree both qualitatively and quantitatively, providing unambiguous evidence of the existence and robustness of these multiple time-dependent states.

Effects of Rotor Tip Clearance on Tip Clearance Flow Potentially Leading to NSV in an Axial Compressor

2012 ◽  
Author(s):  
Hong-Sik Im ◽  
Ge-Cheng Zha
Keyword(s):  
High Speed ◽  
Axial Compressor ◽  
Maximum Amplitude ◽  
Leading Edge ◽  
Tip Clearance ◽  
Tip Vortex ◽  
Navier Stokes ◽  
Tip Leakage Flow ◽  
Tip Clearance Flow ◽  
Clearance Flow

This paper investigates non-synchronous vibration (NSV) mechanism of a high-speed axial compressor with three different rotor tip clearances. Numerical simulations for 1/7th annulus periodic sector are performed using an unsteady Reynolds-averaged Navier-Stokes(URANS) solver with a fully conservative sliding boundary condition to capture wake unsteadiness between the rotor and stator blades. The simulated NSV shows that the frequency and amplitude are strongly influenced by the tip clearance size and shape. The predicted NSV frequency is in good agreement with the experiment. The maximum amplitude of the NSV occurs at about 78% span of the rotor suction leading edge regardless of tip clearance due to a strong interaction of incoming flow, tip leakage flow and tip vortex. The instability of tornado like tip vortex oscillating in streamwise direction appears to be the main cause of the NSV observed in this study.

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