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.

Effects of Reynolds Number and Free-Stream Turbulence on Turbine Tip Clearance Flow

2005 ◽  
Author(s):  
Takayuki Matsunuma
Keyword(s):  
Reynolds Number ◽  
Turbulence Intensity ◽  
Free Stream ◽  
Three Dimensional ◽  
Tip Clearance ◽  
Turbine Cascade ◽  
Tip Leakage Flow ◽  
Three Dimensional Flow ◽  
Free Stream Turbulence ◽  
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 free-stream 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 free-stream 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 Modification of three-dimensional transition in the wake of a rotationally oscillating cylinder

2009 ◽  
Vol 643 ◽  
pp. 349-362 ◽  
Author(s):  
DAVID LO JACONO ◽  
JUSTIN S. LEONTINI ◽  
MARK C. THOMPSON ◽  
JOHN SHERIDAN
Keyword(s):  
Reynolds Number ◽  
Three Dimensional ◽  
Oscillation Mode ◽  
Critical Amplitude ◽  
Near Wake ◽  
Three Dimensional Flow ◽  
Double Row ◽  
Dimensional Flow ◽  
Spatio Temporal ◽  
Mode A

A study of the flow past an oscillatory rotating cylinder has been conducted, where the frequency of oscillation has been matched to the natural frequency of the vortex street generated in the wake of a stationary cylinder, at Reynolds number 300. The focus is on the wake transition to three-dimensional flow and, in particular, the changes induced in this transition by the addition of the oscillatory rotation. Using Floquet stability analysis, it is found that the fine-scale three-dimensional mode that typically dominates the wake at a Reynolds number beyond that at the second transition to three-dimensional flow (referred to as mode B) is suppressed for amplitudes of rotation beyond a critical amplitude, in agreement with past studies. However, the rotation does not suppress the development of three-dimensionality completely, as other modes are discovered that would lead to three-dimensional flow. In particular, the longer-wavelength mode that leads the three-dimensional transition in the wake of a stationary cylinder (referred to as mode A) is left essentially unaffected at low amplitudes of rotation. At higher amplitudes of oscillation, mode A is also suppressed as the two-dimensional near wake changes in character from a single- to a double-row wake; however, another mode is predicted to render the flow three-dimensional, dubbed mode D (for double row). This mode has the same spatio-temporal symmetries as mode A.

Three-Dimensional Flow and Mixing in an Axial Flow Compressor With Different Rotor Tip Clearances

1992 ◽  
Vol 114 (3) ◽  
pp. 675-685 ◽  
Author(s):  
A. Goto
Keyword(s):  
Velocity Fluctuation ◽  
Three Dimensional ◽  
Axial Flow ◽  
Flow Fields ◽  
Tip Clearance ◽  
Small Scale ◽  
Three Dimensional Flow ◽  
Axial Flow Compressor ◽  
Dimensional Flow ◽  
Flow Compressor

The effect of difference in rotor tip clearance on the mean flow fields and unsteadiness and mixing across a stator blade row were investigated using hot-wire anemometry, pressure probes, flow visualization, and the ethylene tracer-gas technique on a single-stage axial flow compressor. The structure of the three-dimensional flow fields was discussed based on results of experiments using the 12-orientation single slanted hotwire technique and spectrum analysis of velocity fluctuation. High-pass filtered measurements of turbulence were also carried out in order to confirm small-scale velocity fluctuation, which is more realistically referred to as turbulence. The span-wise distribution of ethylene gas spreading, estimated by the measured small-scale velocity fluctuation at the rotor exit, agreed quite well with that which was experimentally measured. This fact suggests the significant role of turbulence, generated within the rotor, in the mixing process across the downstream stator. The value of the maximum mixing coefficient in the tip region was found to increase linearly as the tip clearance became enlarged, starting from the value at midspan.

Wavelet-based adaptive simulations of three-dimensional flow past a square cylinder

2014 ◽  
Vol 748 ◽  
pp. 433-456 ◽  
Author(s):  
Giuliano De Stefano ◽  
Oleg V. Vasilyev
Keyword(s):  
Reynolds Number ◽  
Bluff Body ◽  
Numerical Solutions ◽  
Three Dimensional ◽  
Adaptive Methods ◽  
Three Dimensional Flow ◽  
Dimensional Flow ◽  
Eddy Simulation ◽  
Experimental Findings ◽  
Bluff Body Flows

AbstractThe wavelet-based eddy capturing approach is extended to three-dimensional bluff body flows, where the flow geometry is enforced through Brinkman volume penalization. The wavelet-collocation/volume-penalization combined method is applied to the simulation of vortex shedding flow behind an isolated stationary prism with square cross-section. Wavelet-based direct numerical simulation is conducted at low supercritical Reynolds number, where the wake develops fundamental three-dimensional flow structures, while wavelet-based adaptive large-eddy simulation supplied with the one-equation localized dynamic kinetic-energy-based model is performed at moderately high Reynolds number. The present results are in general agreement with experimental findings and numerical solutions provided by classical non-adaptive methods. This study demonstrates that the proposed hybrid methodology for modelling bluff body flows is feasible, accurate and efficient.

Three-Dimensional-Flow Theories for Axial Compressors and Turbines

1948 ◽  
Vol 159 (1) ◽  
pp. 255-268 ◽  
Author(s):  
A. D. S. Carter
Keyword(s):  
Three Dimensional ◽  
Axial Compressor ◽  
Physical Nature ◽  
Secondary Flows ◽  
Operating Conditions ◽  
Tip Clearance ◽  
Three Dimensional Flow ◽  
Axial Compressors ◽  
Dimensional Flow ◽  
Blade Row

It has long been known that the energy losses occurring in an axial compressor or turbine cannot be fully accounted for by the skin-friction losses on the blades and annulus walls. The difference, usually termed secondary loss, is attributed to miscellaneous secondary flows which take place in the blade row. These flows both cause losses in themselves and modify the operating conditions of the individual blade sections, to the detriment of the overall performance. This lecture analyses the three-dimensional flow in axial compressors and turbines, so that, by appreciation of the factors involved, possible methods of improving the performance can readily be investigated. The origin of secondary flow is first examined for the simple case of a straight cascade. The physical nature of the flow, and theories which enable quantitative estimates to be made, are discussed at some length. Following this, the three-dimensional flow in an annulus with a stationary blade row is examined, and, among other things, the influence of radial equilibrium on the flow pattern is noted. All physical restrictions are then removed, and the major factors governing the three-dimensional flow in an actual machine are investigated as far as is possible with existing information, particular attention being paid to the influence of a non-uniform velocity profile, tip clearance, shrouding, and boundary layer displacement. Finally the various empirical factors used in design are discussed, and the relationships between them established.

Heat Transfer and Turbulent Flow Characteristics of Isolated Three-Dimensional Protrusions in Channels

1991 ◽  
Vol 113 (3) ◽  
pp. 597-603 ◽  
Author(s):  
P. T. Roeller ◽  
J. Stevens ◽  
B. W. Webb
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Nusselt Number ◽  
Channel Wall ◽  
Three Dimensional ◽  
Three Dimensional Flow ◽  
Average Heat ◽  
Flow Acceleration ◽  
Dimensional Flow ◽  
Wall Spacing

The flow structure and average heat transfer characteristics of single, isolated three-dimensional protrusions in a flow channel have been investigated experimentally. This configuration has relevance in the electronics industry. The study was designed to identify the influence of the three-dimensional flow around a heated protrusion on its average heat transfer. Heated protrusions varying in width between 0.12 and 1.0 channel widths for a fixed protrusion height and streamwise length were studied in the channel Reynolds number range 500≤Re≤10,000. The channel wall spacing was also varied parametrically between 1.25 and 2.5 streamwise protrusion lengths. The study included both average heat transfer measurements, and detailed local velocity and turbulent flow structure measurements made using laser-Doppler velocimetry. The experimental results show that the Nusselt number increases with both decreasing channel wall spacing and decreasing protrusion width. The increase in heat transfer with decreasing wall spacing is explained by the accelerated flow due to the protrusion-obstructed channel. Increasing Nusselt number with decreasing protrusion width is a result of increased three-dimensional flow and associated turbulent mixing. Both of these flow-related phenomena are illustrated with local mean velocity and turbulence intensity measurements. The presence of recirculation zones both upstream and downstream of the module is revealed. The flow acceleration around the heated protrusions, and three dimensionality of the flow and heat transfer are competing mechanisms; the higher heat transfer due to flow acceleration around the protrusions for larger protrusions goes counter to the trend for higher heat transfer due to increased three-dimensional flow and transport for smaller protrusions. A Nusselt number correlation is developed as a function of channel Reynolds number and protrusion and channel geometric parameters, which describes the tradeoffs discussed.

Experimental Study on the Three-Dimensional Flow Within a Compressor Cascade With Tip Clearance: Part I—Velocity and Pressure Fields

1993 ◽  
Vol 115 (3) ◽  
pp. 435-443 ◽  
Author(s):  
S. Kang ◽  
C. Hirsch
Keyword(s):  
Three Dimensional ◽  
Leading Edge ◽  
Surface Flow ◽  
Tip Clearance ◽  
Tip Vortex ◽  
Compressor Cascade ◽  
Three Dimensional Flow ◽  
Tip Leakage Vortex ◽  
Tip Leakage ◽  
Dimensional Flow

Experimental results from a study of the three-dimensional flow in a linear compressor cascade with stationary endwall at design conditions are presented for tip clearance levels of 1.0, 2.0, and 3.3 percent of chord, compared with the no-clearance case. In addition to five-hole probe measurements, extensive surface flow visualizations are conducted. It is observed that for the smaller clearance cases a weak horseshoe vortex forms in the front of the blade leading edge. At all the tip gap cases, a multiple tip vortex structure with three discrete vortices around the midchord is found. The tip leakage vortex core is well defined after the midchord but does not cover a significant area in traverse planes. The presence of the tip leakage vortex results in the passage vortex moving close to the endwall and the suction side.

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