Topology and vortex structures of a curving turbine cascade with tip clearance (II)—Topological flow pattern and vortex structure in the transverse section of a blade cascade

2002 ◽  
Vol 23 (8) ◽  
pp. 958-962 ◽  
Author(s):  
Yang Qing-hai ◽  
Huang Hong-yan ◽  
Han Wan-jin
Keyword(s):  
Flow Pattern ◽  
Vortex Structure ◽  
Transverse Section ◽  
Vortex Structures ◽  
Tip Clearance ◽  
Turbine Cascade ◽  
Blade Cascade

scholarly journals Three-Dimensional Navier–Stokes Analysis and Redesign of an Imbedded Bellmouth Nozzle in a Turbine Cascade Inlet Section

1996 ◽  
Vol 118 (3) ◽  
pp. 529-535 ◽  
Author(s):  
P. W. Giel ◽  
J. R. Sirbaugh ◽  
I. Lopez ◽  
G. J. Van Fossen
Keyword(s):  
Three Dimensional ◽  
Navier Stokes ◽  
Experimental Measurements ◽  
Inlet Section ◽  
Turbine Cascade ◽  
Blade Cascade ◽  
Inlet Geometry ◽  
Computational Fluid Dynamics Cfd ◽  
Transonic Turbine ◽  
Flow Nonuniformity

Experimental measurements in the inlet of a transonic turbine blade cascade showed unacceptable pitchwise flow nonuniformity. A three-dimensional, Navier–Stokes computational fluid dynamics (CFD) analysis of the imbedded bellmouth inlet in the facility was performed to identify and eliminate the source of the flow nonuniformity. The blockage and acceleration effects of the blades were accounted for by specifying a periodic static pressure exit condition interpolated from a separate three-dimensional Navier–Stokes CFD solution of flow around a single blade in an infinite cascade. Calculations of the original inlet geometry showed total pressure loss regions consistent in strength and location to experimental measurements. The results indicate that the distortions were caused by a pair of streamwise vortices that originated as a result of the interaction of the flow with the imbedded bellmouth. Computations were performed for an inlet geometry that eliminated the imbedded bellmouth by bridging the region between it and the upstream wall. This analysis indicated that eliminating the imbedded bellmouth nozzle also eliminates the pair of vortices, resulting in a flow with much greater pitchwise uniformity. Measurements taken with an installed redesigned inlet verify that the flow nonuniformity has indeed been eliminated.

scholarly journals Numerical Calculation of Flow for Cascade With Tip Clearance

1994 ◽  
Author(s):  
Shimpei Mizuki ◽  
Hoshio Tsujita
Keyword(s):  
Three Dimensional ◽  
Tip Clearance ◽  
Turbine Cascade ◽  
Governing Equations ◽  
Tensor Form ◽  
Pressure Surface ◽  
Rear Part ◽  
Blade Tip ◽  
Flow Through ◽  
Blade Tip Geometry

Three-dimensional incompressible turbulent flow within a linear turbine cascade with tip clearance is analyzed numerically. The governing equations involving the standard k-ε model are solved in the physical component tensor form with a boundary-fitted coordinate system. In the analysis, the blade tip geometry is treated accurately in order to predict the flow through the tip clearance in detail when the blades have large thicknesses. Although the number of grids employed in the present study is not enough because of the limitation of computer storage memory, the computed results show good agreements with the experimental results. Moreover, the results clearly exhibit the locus of minimum pressure on the rear part of the pressure surface at the blade tip.

Effects of Tip Clearance on Aerodynamic Damping in a Linear Turbine Cascade

2008 ◽  
Vol 24 (1) ◽  
pp. 26-33 ◽  
Author(s):  
Xiuquan Huang ◽  
Li He ◽  
David L. Bell
Keyword(s):  
Tip Clearance ◽  
Turbine Cascade ◽  
Aerodynamic Damping

The Measurement and Formation of Tip Clearance Loss

1989 ◽  
Vol 111 (3) ◽  
pp. 257-263 ◽  
Author(s):  
J. P. Bindon
Keyword(s):  
Pressure Gradient ◽  
Secondary Flow ◽  
Separation Bubble ◽  
Tip Clearance ◽  
Turbine Cascade ◽  
High Loss ◽  
Performance Improvements ◽  
Internal Loss ◽  
Internal Gap ◽  
First Time

The detailed development of tip clearance loss from the leading to trailing edge of a linear turbine cascade was measured and the contributions made by mixing, internal gap shear flow, and endwall/ secondary flow were identified, separated, and quantified for the first time. Only 13 percent of the overall loss arises from endwall/secondary flow and of the remaining 87 percent, 48 percent is due to mixing and 39 percent is due to internal gap shear. All loss formation appears to be dominated by phenomena connected with the gap separation bubble. Flow established within the bubble by the pressure gradient separates as the gradient disappears and most of the internal loss is created by the entrainment of this separated fluid. When this high-loss leakage wake enters the mainstream, it separates due to the suction corner pressure gradient to create virtually all the measured mixing loss. It is suggested that the control of tip clearance loss by discharge coefficient reduction actually introduces loss. Performance improvements may result from streamlined tip geometries that optimize the tradeoff between entropy production and flow deflection.

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

2018 ◽  
Vol 233 (5) ◽  
pp. 1645-1655
Author(s):  
Shaowen Chen ◽  
Qinghe Meng ◽  
Weihang Li ◽  
Zhihua Zhou ◽  
Songtao Wang
Keyword(s):  
Flow Field ◽  
Buffer Zone ◽  
Aerodynamic Performance ◽  
Field Structure ◽  
Tip Clearance ◽  
Turbine Cascade ◽  
Tip Leakage Flow ◽  
Tip Leakage ◽  
Passage Vortex ◽  
Flow Loss

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.

scholarly journals Flow Visualization of Spinning and Nonspinning Soccer Balls Using Computational Fluid Dynamics

2020 ◽  
Vol 10 (13) ◽  
pp. 4543 ◽  
Author(s):  
Takeshi Asai ◽  
Yasumi Nakanishi ◽  
Nakaba Akiyama ◽  
Sungchan Hong
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Lattice Boltzmann Method ◽  
Vortex Structure ◽  
Lattice Boltzmann ◽  
Large Scale ◽  
Vortex Pair ◽  
Vortex Structures ◽  
Soccer Ball ◽  
Boltzmann Method

Various studies have been conducted on the aerodynamic characteristics of nonspinning and spinning soccer balls. However, the vortex structures in the wake of the balls are almost unknown. One of the main computational fluid dynamics methods used for the analysis of vortex structures is the lattice Boltzmann method as it facilitates high-precision analysis. Studies to elucidate the dominant vortex structure are important because curled shots and passes involving spinning balls are frequently used in actual soccer games. In this study, we identify the large-scale dominant vortex structure of a soccer ball and investigate the stability of the structure using the lattice Boltzmann method, wind tunnel tests, and free-flight experiments. One of the dominant vortex structures in the wake of both nonspinning and spinning balls is a large-scale counter-rotating vortex pair. The side force acting on a spinning ball stabilizes when the fluctuation of the separation points of the ball is suppressed by the rotation of the ball. Thus, although a spinning soccer ball is deflected by the Magnus effect, its trajectory is regular and stable, suggesting that a spinning ball can be aimed accurately at the outset of its course.

Numerical Investigations of Centrifugal Compressor Flows With Tip Leakage Using a Pressure Correction Method

1993 ◽  
Author(s):  
A. Tourlidakis ◽  
R. L. Elder
Keyword(s):  
Flow Pattern ◽  
High Speed ◽  
Stokes Equations ◽  
Correction Method ◽  
Secondary Flows ◽  
Tip Clearance ◽  
Physical Models ◽  
Wake Flow ◽  
Operating Characteristics ◽  
Pressure Correction

In this paper, a three-dimensional computational model for the solution of the time-averaged Navier-Stokes equations, based on a pressure correction method and the k-ε turbulence model, is presented and implemented for the viscous flow modelling through a series of centrifugal compressors. Theoretical calculations with the current fully elliptic method are carried out and the results are compared critically with available experimental data and with results from other computational models. A radial and two backswept high-speed subsonic compressors with different geometrical and operating characteristics are analysed at design and off-design conditions. In all cases, a wake flow pattern is evident and strong secondary flows are discerned. The tip clearance effects on the relative flow pattern are found to be important and are appropriately simulated. The predictive capability of the current flow model is judged to be encouraging taking into consideration the limitations of the physical models and the numerical schemes involved in the computations.

Effects of Reynolds Number and Freestream Turbulence on Turbine Tip Clearance Flow

2005 ◽  
Vol 128 (1) ◽  
pp. 166-177 ◽  
Author(s):  
Takayuki Matsunuma
Keyword(s):  
Reynolds Number ◽  
Turbulence Intensity ◽  
Three Dimensional ◽  
Tip Clearance ◽  
Pressure Probe ◽  
Turbine Cascade ◽  
Freestream Turbulence ◽  
Tip Leakage Flow ◽  
Three Dimensional Flow ◽  
Dimensional Flow

Tip clearance losses represent a major efficiency penalty of turbine blades. This paper describes the effect of tip clearance on the aerodynamic characteristics of an unshrouded axial-flow turbine cascade under very low Reynolds number conditions. The Reynolds number based on the true chord length and exit velocity of the turbine cascade was varied from 4.4×104 to 26.6×104 by changing the velocity of fluid flow. The freestream turbulence intensity was varied between 0.5% and 4.1% by modifying turbulence generation sheet settings. Three-dimensional flow fields at the exit of the turbine cascade were measured both with and without tip clearance using a five-hole pressure probe. Tip leakage flow generated a large high total pressure loss region. Variations in the Reynolds number and freestream turbulence intensity changed the distributions of three-dimensional flow, but had no effect on the mass-averaged tip clearance loss of the turbine cascade.

scholarly journals Influences of Tip Cooling Injection on Tip Clearance Control at Design and Off-Design Incidences

2009 ◽  
Vol 2009 ◽  
pp. 1-12 ◽  
Author(s):  
Maosheng Niu ◽  
Shusheng Zang
Keyword(s):  
Heat Transfer ◽  
Tip Clearance ◽  
Air Injection ◽  
Turbine Cascade ◽  
Tip Clearance Flow ◽  
Clearance Flow ◽  
Blade Tip ◽  
Design Value ◽  
Tip Injection ◽  
Clearance Control

A numerical investigation has been performed to study the influences of cooling injection from the blade tip surface on controlling tip clearance flow in an unshrouded, high-turning axial turbine cascade. Emphasis is put on the analysis of the effectiveness of tip injection when the approaching flow is at design and off-design incidences. A total of three incidence angles are investigated, 7.4°, 0°, 0°, 0°, and 7.6°, 0° relative to the design value. The results indicate that even at the off-design incidences, tip injection can also act as an obstruction to the tip clearance flow and weaken the interaction between the passage flow and the tip clearance flow. It is also found that tip injection causes the tip clearance loss to be less sensitive to the incidences. Moreover, with injection, at all these incidences the heat transfer conditions are improved significantly on the blade tip surface in the middle and aft parts of blade. Thus, tip injection is proved to be an effective method of controlling tip clearance flow, even at off-design conditions. Beside that, an indirect empirical correlation is observed to be able to perform well in predicting the losses induced by tip clearance flow at design and off-design conditions, no matter whether air injection is active or not.

Sign in / Sign up

Export Citation Format

Share Document