Effect of Free-Stream Turbulence on Heat Transfer and Fluid Flow in a Transonic Turbine Stage

2006 ◽  
Author(s):  
F. Mumic ◽  
B. Sunden
Keyword(s):  
Heat Transfer ◽  
Fluid Flow ◽  
Turbulence Intensity ◽  
Rotational Speed ◽  
Free Stream ◽  
Length Scale ◽  
Turbine Stage ◽  
Free Stream Turbulence ◽  
Turbulence Length ◽  
Turbulence Length Scale

In the present work, a numerical study has been performed to simulate the effect of free-stream turbulence, length scale and variations in rotational speed of the rotor on heat transfer and fluid flow for a transonic high-pressure turbine stage with tip clearance. The stator and rotor rows interact via a mixing plane, which allows the stage to be computed in a steady manner. The focus is on turbine aerodynamics and heat transfer behavior at the mid-span location, and at the rotor tip and casing region. The results of the fully 3D CFD simulations are compared with experimental results available for the so-called MT1 turbine stage. The predicted heat transfer and static pressure distributions show reasonable agreement with the experimental data. In general, the local Nusselt number increases, at the same turbulence length scale, as the turbulence intensity increases, and the location of the suction side boundary layer transition moves upstream towards the blade leading edge. Comparison of the different length scales at the same turbulence intensity shows that the stagnation heat transfer was significantly increased as the length scale increased. However, the length scale evidenced no significant effects on blade tip or rotor casing heat transfer. Also, the results presented in this paper show that the rotational speed in addition to the turbulence intensity and length scale has an important contribution to the turbine blade aerodynamics and heat transfer.

Darryl E. Metzger Memorial Session Paper: An Account of Free-Stream-Turbulence Length Scale on Laminar Heat Transfer

1995 ◽  
Vol 117 (3) ◽  
pp. 401-406 ◽  
Author(s):  
K. Dullenkopf ◽  
R. E. Mayle
Keyword(s):  
Heat Transfer ◽  
Free Stream ◽  
Dominant Frequency ◽  
Length Scale ◽  
Free Stream Turbulence ◽  
Laminar Boundary Layers ◽  
Session Paper ◽  
Turbulence Length ◽  
Effective Intensity ◽  
Turbulence Length Scale

The effect of length scale in free-stream turbulence is considered for heat transfer in laminar boundary layers. A model is proposed that accounts for an “effective” intensity of turbulence based on a dominant frequency for a laminar boundary layer. Assuming a standard turbulence spectral distribution, a new turbulence parameter that accounts for both turbulence level and length scale is obtained and used to correlate heat transfer data for laminar stagnation flows. The result indicates that the heat transfer for these flows is linearly dependent on the “effective” free-stream turbulence intensity.

scholarly journals An Account of Free-Stream-Turbulence Length Scale on Laminar Heat Transfer

1994 ◽  
Author(s):  
K. Dullenkopf ◽  
R. E. Mayle
Keyword(s):  
Heat Transfer ◽  
Free Stream ◽  
Dominant Frequency ◽  
Length Scale ◽  
Turbulence Parameter ◽  
Free Stream Turbulence ◽  
Laminar Boundary Layers ◽  
Turbulence Length ◽  
Effective Intensity ◽  
Turbulence Length Scale

The effect of length scale in free-stream turbulence is considered for heat transfer in laminar boundary layers. A model is proposed which accounts for an “effective” intensity of turbulence based on a dominant frequency for a laminar boundary layer. Assuming a standard turbulence spectral distribution, a new turbulence parameter which accounts for both turbulence level and length scale is obtained and used to correlate heat transfer data for laminar stagnation flows. The result indicates that the heat transfer for these flows is linearly dependent on the “effective” free-stream turbulence intensity.

scholarly journals Measurements of the Effect of Free-Stream Turbulence Length Scale on Heat Transfer

1992 ◽  
Author(s):  
R. W. Moss ◽  
M. L. G. Oldfield
Keyword(s):  
Heat Transfer ◽  
Free Stream ◽  
Plate Boundary ◽  
Length Scale ◽  
Turbulence Scale ◽  
Free Stream Turbulence ◽  
High Turbulence ◽  
Gas Turbine Heat Transfer ◽  
Turbulence Length ◽  
Turbulence Length Scale

The effects of free-stream turbulence scale on heat transfer through a turbulent flat plate boundary layer have been measured. A variety of turbulence spectra were produced by parallel bar grids. The design of these was guided by previous measurements of combustion chamber turbulence. Heat transfer was measured transiently using thin film gauges. The heat transfer to the plate was found to be a function of turbulence integral length scale as well as intensity, and is of relevance to gas turbine heat transfer where aerofoils are subject to high turbulence levels from the combustor. Enhancement factors of up to 40% were experienced and the results extend conclusions drawn by other workers to higher turbulence levels and scales.

Free-Stream Turbulence From a Circular Wall Jet on a Flat Plate Heat Transfer and Boundary Layer Flow

1989 ◽  
Vol 111 (1) ◽  
pp. 78-86 ◽  
Author(s):  
R. MacMullin ◽  
W. Elrod ◽  
R. Rivir
Keyword(s):  
Heat Transfer ◽  
Turbulence Intensity ◽  
Free Stream ◽  
Flow Characteristics ◽  
Surface Profile ◽  
Constant Heat Flux ◽  
Length Scale ◽  
Wall Jet ◽  
Reynolds Analogy ◽  
Free Stream Turbulence

The effects of the longitudinal turbulence intensity parameter of free-stream turbulence (FST) on heat transfer were studied using the aggressive flow characteristics of a circular tangential wall jet over a constant heat flux surface. Profile measurements of velocity, temperature, integral length scale, and spectra were obtained at downstream locations (2 to 20 x/D) and turbulence intensities (7 to 18 percent). The results indicated that the Stanton number (St) and friction factor (Cf) increased with increasing turbulence intensity. The Reynolds analogy factor (2St/Cf) increased up to turbulence intensities of 12 percent, then became constant, and decreased after 15 percent. This factor was also found to be dependent on the Reynolds number (Rex) and plate configuration. The influence of length scale, as found by previous researchers, was inconclusive at the conditions tested.

scholarly journals Turbulence Intensity, Length Scale, and Heat Transfer Around Stagnation Line of Cylinder and Model Blade

1999 ◽  
Author(s):  
V. P. Maslov ◽  
B. I. Mineev ◽  
K. N. Pichkov ◽  
A. N. Secundov ◽  
A. N. Vorobiev ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Turbulence Intensity ◽  
Free Stream ◽  
Turbulence Models ◽  
Leading Edge ◽  
Circular Cylinders ◽  
Length Scale ◽  
Stagnation Line ◽  
Free Stream Turbulence ◽  
Wide Range

A hot-wire technique was used to measure turbulence characteristics in the vicinity of the stagnation line of circular cylinders and a turbine blade model (a chord length of 1 metre). Heat transfer intensity at the stagnation line of the cylinders was also measured by on-surface probes. The experiments were carried out in a wide range of the Reynolds number based on the blade leading edge/cylinder diameter, D (Re = 2.103–2.106) and integral length scale of free-stream turbulence, Le (Le = 0.1–10D) at two values of free stream turbulence intensity, Tu (Tu = 0.02 and 0.10). Along with the experimental data results of the 2D RANS computations are presented of the flow and heat transfer at the circular cylinder with the use of two turbulence models: a two-equation, k-ω SST, model of Menter, and a new two-equation, ν1-L, model developed in the course of the present study.

Effects of Freestream Turbulence Intensity, Turbulence Length Scale, and Exit Reynolds Number on Vane Endwall Secondary Flow and Heat Transfer in a Transonic Turbine Cascade

2020 ◽  
Author(s):  
Zhigang Li ◽  
Bo Bai ◽  
Luxuan Liu ◽  
Jun Li ◽  
Shuo Mao ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Secondary Flow ◽  
Turbulence Intensity ◽  
Thermal Load ◽  
Secondary Flows ◽  
Length Scale ◽  
Freestream Turbulence ◽  
Turbulence Length ◽  
Turbulence Length Scale

Abstract In gas turbine engines, the first-stage vanes usually suffer harsh incoming flow conditions from the combustor with high pressure, high temperature and high turbulence. The combustor-generated high freestream turbulence and strong secondary flows in a gas turbine vane passage have been reported to augment the endwall thermal load significantly. This paper presents a detailed numerical study on the effects of high freestream turbulence intensity, turbulence length scale, and exit Reynolds number on the endwall secondary flow pattern and heat transfer distribution of a transonic linear turbine vane passage at realistic engine Mach numbers, with a flat endwall no cooling. Numerical simulations were conducted at a range of different operation conditions: six freestream turbulence intensities (Tu = 1%, 5%, 10%, 13%, 16% and 20%), six turbulence length scales (normalized by the vane pitch of Λ/P = 0.01, 0.04, 0.07, 0.12, 0.24, 0.36), and three exit isentropic Mach number (Maex = 0.6, 0.85 and 1.02 corresponding exit Reynolds number Reex = 1.1 × 106, 1.7 × 106 and 2.2 × 106, respectively, based on the vane chord). Detailed comparisons were presented for endwall heat transfer coefficient distribution, endwall secondary flow field at different operation conditions, while paying special attention to the link between endwall thermal load patterns and the secondary flow structures. Results show that the freestream turbulence intensity and length scale have a significant influence on the endwall secondary flow field, but the influence of the exit Reynolds number is very weak. The Nusselt number patterns for the higher turbulence intensities (Tu = 16%, 20%) appear to be less affected by the endwall secondary flows than the lower turbulence cases. The thermal load distribution in the arc region around the vane leading edge and the banded region along the vane pressure side are influenced most strongly by the freestream turbulence intensity. In general, the higher freestream turbulence intensities make the vane endwall thermal load more uniform. The Nusselt number distribution is only weakly affected by the turbulence length scale when Λ/P is larger than 0.04. The heat transfer level appears to have a significant uniform augmentation over the whole endwall region with the increasing Maex. The endwall thermal load distribution is classified into four typical regions, and the effects of freestream turbulence, exit Reynolds number in each region were discussed in detail.

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