Nonuniform Flow in a Compressor Due to Asymmetric Tip Clearance

2000 ◽  
Vol 122 (4) ◽  
pp. 751-760 ◽  
Author(s):  
Seung Jin Song ◽  
Seung Ho Cho
Keyword(s):  
Analytical Study ◽  
Flow Model ◽  
Axisymmetric Flow ◽  
Tip Clearance ◽  
Linear Perturbation ◽  
Flow Variable ◽  
Nonuniform Flow ◽  
Downstream Flow ◽  
Perturbation Approximation ◽  
Flow Nonuniformity

This paper presents an analytical study of flow redistribution in a compressor stage due to asymmetric tip clearance distribution. The entire stage is modeled as an actuator disk and it is assumed that upstream and downstream flow fields are determined by the local tip clearance. The flow is assumed to be inviscid and incompressible. First, an axisymmetric flow model is used to connect upstream and downstream flows. Second, a linear perturbation approximation is used for nonaxisymmetric analysis in which each flow variable is assumed to consist of a mean (axisymmetric value) plus a small perturbation (asymmetric value). Thus, the perturbations in velocity and pressure induced by the tip clearance asymmetry are predicted. Furthermore, rotordynamic effects of such flow nonuniformity are examined as well. [S0889-504X(00)01404-5]

Non-Uniform Flow in a Compressor due to Asymmetric Tip Clearance

2000 ◽  
Author(s):  
Seung Jin Song ◽  
Seung Ho Cho
Keyword(s):  
Analytical Study ◽  
Flow Model ◽  
Axisymmetric Flow ◽  
Tip Clearance ◽  
Linear Perturbation ◽  
Flow Variable ◽  
Compressor Stage ◽  
Actuator Disc ◽  
Downstream Flow ◽  
Perturbation Approximation

This paper presents an analytical study of flow redistribution in a compressor stage due to asymmetric tip clearance distribution. The entire stage is modeled as an actuator disc, and it is assumed that upstream and downstream flow fields are determined by the local tip clearance. The flow is assumed to be inviscid and incompressible. First, an axisymmetric flow model is used to connect upstream and downstream flows. Second, a linear perturbation approximation is used for non-axisymmetric analysis in which each flow variable is assumed to consist of a mean (axisymmetric value) plus a small perturbation (asymmetric value). Thus, the perturbations in velocity and pressure induced by the tip clearance asymmetry are predicted. Furthermore, rotordynamic effects of such flow non-uniformity are examined as well.

Effects of Circumferential Nonuniform Tip Clearance on Flow Field and Performance of a Transonic Turbine

2020 ◽  
Author(s):  
Yun Zheng ◽  
Xiubo Jin ◽  
Hui Yang ◽  
Qingzhe Gao ◽  
Kang Xu
Keyword(s):  
Flow Field ◽  
Numerical Study ◽  
Circumferential Direction ◽  
Tip Clearance ◽  
Computational Domain ◽  
Aerodynamic Efficiency ◽  
Aerodynamic Loss ◽  
The Difference ◽  
And Performance ◽  
Downstream Flow

Abstract The numerical study is performed by means of an in-house CFD code to investigate the effect of circumferential nonuniform tip clearance due to the casing ovalization on flow field and performance of a turbine stage. A method called fast-moving mesh is used to synchronize the non-circular computational domain with the rotation of the rotor row. Four different layouts of the circumferential nonuniform clearance are calculated and evaluated in this paper. The results show that, the circumferential nonuniform clearance could reduce the aerodynamic performance of the turbine. When the circumferential nonuniformity δ reaches 0.4, the aerodynamic efficiency decreases by 0.58 percentage points. Through the analysis of the flow field, it is found that the casing ovalization leads to the difference of the size of the tip clearance in the circumferential direction, and the aerodynamic loss of the position of large tip clearance is greater than that of small tip clearance, which is related to the scale of leakage vortex. In addition, the flow field will become nonuniform in the circumferential direction, especially at the rotor exit, which will adversely affect the downstream flow field.

scholarly journals The acoustic impedance of a laminar viscous jet through a thin circular aperture

2019 ◽  
Vol 864 ◽  
pp. 5-44 ◽  
Author(s):  
David Fabre ◽  
Raffaele Longobardi ◽  
Paul Bonnefis ◽  
Paolo Luchini
Keyword(s):  
Reynolds Number ◽  
Stokes Equations ◽  
Axisymmetric Flow ◽  
Classical Problem ◽  
Base Flow ◽  
Large Reynolds Number ◽  
Linear Perturbation ◽  
Circular Aperture ◽  
Vena Contracta ◽  
Numerical Resolution

The unsteady axisymmetric flow through a circular aperture in a thin plate subjected to harmonic forcing (for instance under the effect of an incident acoustic wave) is a classical problem first considered by Howe (Proc. R. Soc. Lond. A, vol. 366, 1979, pp. 205–223), using an inviscid model. The purpose of this work is to reconsider this problem through a numerical resolution of the incompressible linearized Navier–Stokes equations (LNSE) in the laminar regime, corresponding to $Re=[500,5000]$. We first compute a steady base flow which allows us to describe the vena contracta phenomenon in agreement with experiments. We then solve a linear problem allowing us to characterize both the spatial amplification of the perturbations and the impedance (or equivalently the Rayleigh conductivity), which is a key quantity to investigate the response of the jet to acoustic forcing. Since the linear perturbation is characterized by a strong spatial amplification, the numerical resolution requires the use of a complex mapping of the axial coordinate in order to enlarge the range of Reynolds number investigated. The results show that the impedances computed with $Re\gtrsim 1500$ collapse onto a single curve, indicating that a large Reynolds number asymptotic regime is effectively reached. However, expressing the results in terms of conductivity leads to substantial deviation with respect to Howe’s model. Finally, we investigate the case of finite-amplitude perturbations through direct numerical simulations (DNS). We show that the impedance predicted by the linear approach remains valid for amplitudes up to order $10^{-1}$, despite the fact that the spatial evolution of the perturbations in the jet is strongly nonlinear.

Analysis of winter heat flow in an ice-covered Arctic stream

1984 ◽  
Vol 11 (3) ◽  
pp. 430-443 ◽  
Author(s):  
A. Wankiewicz
Keyword(s):  
Heat Transfer ◽  
Air Temperature ◽  
Flow Model ◽  
Ice Formation ◽  
Temperature Threshold ◽  
Nonuniform Flow ◽  
Stream Flows ◽  
Transfer Rates ◽  
Arctic Regions ◽  
Thermal Measurements

The growth of river ice during the winter of 1977–1978 is modelled for Caribou Creek, an Arctic stream near Inuvik, Northwest Territories. In midwinter, a period of extensive river icing activity, the stream flows over shallow sections of channel via narrow conduits beneath the ice cover. These relatively high-velocity sections are shown to be concentrations of locally generated friction and convected streambed heat. A nonuniform flow model is used to represent friction generation and heat transfer to ice in both shallow and deep sections of the channel. Bed heat flux is simulated from thermal measurements in the unfrozen ground beneath the channel. A relationship between flow width at shallow sections and recorded air temperature, inferred from streambed temperature recordings, is reproduced by simulating the effect of warm and cold spells on flow conduit dimensions. The low air-temperature threshold for increase in conduit cross section, −20 °C, is shown to result from heat transfer rates which offset the reduced heat loss from an insulating snow cover. Key words: ice formation, streamflow, Arctic regions, thermal analysis.

scholarly journals Interaction of Upstream Flow Distortions With High-Mach-Number Cascades

1984 ◽  
Vol 106 (2) ◽  
pp. 260-270
Author(s):  
G. W. Englert
Keyword(s):  
Analytical Study ◽  
Double Fourier Series ◽  
Pressure Distributions ◽  
Before And After ◽  
Spatial Coordinates ◽  
Vortical Motion ◽  
High Mach ◽  
Downstream Flow ◽  
Upstream Flow

This analytical study models features of the interaction of flow distortions, such as gusts and wakes, with blade rows of advance-type fans and compressors having high-tip Mach numbers. A typical distortion is assumed to have harmonic time dependence and is described, at a far upstream location, in three orthogonal spatial coordinates by a double Fourier series. It is convected at supersonic velocity relative to a linear cascade described as an unrolled annulus. Conditions are selected so that the component of this velocity parallel to the axis of the turbomachine is subsonic, permitting interaction between blades through the upstream as well as downstream flow media. A strong, nearly normal shock is considered in the blade passages which is allowed curvature and displacement. The flows before and after the shock are linearized relative to uniform mean velocities in their respective regions. Solution of the descriptive equations is by adaptation of the Wiener-Hopf technique. This enables a determination of distortion patterns through and downstream of the cascade, and of pressure distributions on the blade surfaces. Details of interaction of the distortion with the in-passage shock are discussed. Influences of amplitude, wavelength, and phase of the distortion on lifts and moments of cascade configurations are presented. Numerical results are clarified by reference to an especially orderly pattern of upstream vortical motion in relation to the cascade parameters.

Magnetohydrodynamic Vortex Containment, Part 3: 1-D Axisymmetric Flow Model

2007 ◽  
Vol 23 (2) ◽  
pp. 404-413
Author(s):  
Raymond J. Sedwick ◽  
Daniel A. Zayas
Keyword(s):  
Flow Model ◽  
Axisymmetric Flow

Experimental and Analytical Study of Flow Diversion Beyond an Underexpanded Nozzle

1991 ◽  
Vol 113 (3) ◽  
pp. 475-478
Author(s):  
E. C. Hansen
Keyword(s):  
Gas Flow ◽  
Analytical Study ◽  
Flow Model ◽  
Ambient Pressure ◽  
Experimental Studies ◽  
Analytic Model ◽  
Steady State Flow ◽  
One Dimensional ◽  
Nozzle Pressure ◽  
Flow Apparatus

A steady-state flow apparatus was used to investigate the process of gun gas diversion through a single hole perforated disk diverter. The amount of diverted flow was found to depend on the distance between the nozzle and the diverter disk and the ratio of nozzle pressure to diverter exit pressure. Experimental studies used nitrogen and carbon dioxide as the working fluids to show the effect of specific heat ratio. At ratios of nozzle pressure to ambient pressure ranging from 4 to 60 diversion efficiencies of 50 to 99 percent were produced. A one-dimensional analytic gas flow model was developed. Results of the analytic model paralleled the experimental data for pressure ratios over 10.

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