Heat transfer measurements of a turbine endwall with engine-representative freestream turbulence and inlet swirl

2021 ◽  
pp. 1-21
Author(s):  
Xing Yang ◽  
Qiang Zhao ◽  
Hang Wu ◽  
Zihan Hao ◽  
Zhenping Feng
Keyword(s):  
Heat Transfer ◽  
Freestream Turbulence ◽  
Inlet Swirl

scholarly journals Heat Transfer From a Rotating Disc

1990 ◽  
Author(s):  
G. H. Dibelius ◽  
M. Heinen
Keyword(s):  
Heat Transfer ◽  
Free Convection ◽  
Local Heat Transfer ◽  
Local Heat ◽  
Rotating Disc ◽  
Reynolds Analogy ◽  
Inlet Swirl ◽  
Additional Influence ◽  
Run Up ◽  
Cooling Air

The local heat transfer from a plane rotating disc enclosed in a casing has been studied experimentally. The disc of 800 mm diameter can be run up to 2000 min−1 at axial distances between disc and casing varied between 5 and 55 mm. Centrifugal or alternatively centripetal flow of cooling air at rates up to ṁ = 1 kg/s can be applied, both with or without an inlet swirl. With the disc rotating in a closed casing (ṁ = 0 kg/s) the influence of the characteristic dimensionless groups on the local heat transfer has been investigated. At a fixed radius, a variation of the local Reynolds Number by either speed or density results in corresponding changes of the heat transfer. However, with a variation of the radius different heat transfer-Re relations are found. In fact, the temperature distribution in the gas caused by the heat flux results in an additional influence of free convection, to be expressed by a Grashof Number. This is confirmed by a comparison of the experimental results with calculations based on Reynolds Analogy and measured friction coefficients. The discrepancies found can be explained only, if in addition to the limitations of the analogy, the influence of free convection is taken into account. Additional results of ongoing experiments concerning the influence of the geometry of the cavity between disc and casing, of the coolant flow rate and of the swirl are presented.

Prediction of Heat Transfer in Turbulent Decaying Swirling Flow

1999 ◽  
Author(s):  
Yusuf A. Uskaner
Keyword(s):  
Heat Transfer ◽  
Fluid Dynamics ◽  
Experimental Study ◽  
Friction Factor ◽  
Loss Factor ◽  
Swirling Flow ◽  
Swirling Flows ◽  
Heat Transfer Augmentation ◽  
Relative Roughness ◽  
Inlet Swirl

Abstract This paper presents an aproach for the prediction of heat transfer augmentation in decaying swirling flow in a pipe by making an analogy between the increase in friction factor due to swirl and increase in heat transfer due to swirl. The proposed method can be used to predict heat transfer for decaying swirling flow in smooth and rough pipes which can be applied to different swirl generators based on the known inlet swirl conditions. An experimental study is performed regarding the swirling flow of air in smooth and rough pipes. The experimental study covered only the fluid dynamics of swirling flow. No heat transfer experiments were done. It is determined experimentally that in swirling flows degree of swirl decays continuously along the smooth and rough pipes and the total loss factor is the sum of friction factor for non-swirling flow and the swirl loss factor. Swirl loss factor is found to be a function of the degree of swirl and pipe relative roughness. Using the relations obtained experimentally for the variation of swirl strength and loss factor along the pipe, an equation is proposed to be used for the prediction of heat transfer in turbulent decaying swirling flows.

The Effects of Freestream Turbulence, Turbulence Length Scale, and Exit Reynolds Number on Turbine Blade Heat Transfer in a Transonic Cascade

2010 ◽  
Vol 133 (1) ◽  
Author(s):  
J. S. Carullo ◽  
S. Nasir ◽  
R. D. Cress ◽  
W. F. Ng ◽  
K. A. Thole ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Turbine Blade ◽  
Surface Heat ◽  
Length Scale ◽  
Freestream Turbulence ◽  
Surface Heat Transfer ◽  
Mach Numbers ◽  
Turbulence Length ◽  
Turbulence Length Scale

This paper experimentally investigates the effect of high freestream turbulence intensity, turbulence length scale, and exit Reynolds number on the surface heat transfer distribution of a turbine blade at realistic engine Mach numbers. Passive turbulence grids were used to generate freestream turbulence levels of 2%, 12%, and 14% at the cascade inlet. The turbulence grids produced length scales normalized by the blade pitches of 0.02, 0.26, and 0.41, respectively. Surface heat transfer measurements were made at the midspan of the blade using thin film gauges. Experiments were performed at the exit Mach numbers of 0.55, 0.78, and 1.03, which represent flow conditions below, near, and above nominal conditions. The exit Mach numbers tested correspond to exit Reynolds numbers of 6×105, 8×105, and 11×105, based on true chord. The experimental results showed that the high freestream turbulence augmented the heat transfer on both the pressure and suction sides of the blade as compared with the low freestream turbulence case. At nominal conditions, exit Mach 0.78, average heat transfer augmentations of 23% and 35% were observed on the pressure side and suction side of the blade, respectively.

scholarly journals Effect of Discrete Surface Disturbances on Vane External Heat Transfer

1997 ◽  
Author(s):  
R. S. Bunker
Keyword(s):  
Heat Transfer ◽  
Turbulence Intensity ◽  
Pressure Ratio ◽  
Leading Edge ◽  
Suction Side ◽  
External Heat ◽  
Freestream Turbulence ◽  
External Heat Transfer ◽  
Enhancement Factors ◽  
Surface Disturbances

A transonic linear vane cascade has been utilized to assess the effects of localized surface disturbances on airfoil external heat transfer coefficient distributions, such as those which may be created by the spallation of thermal barrier coatings. The cascade operates at an overall pressure ratio of 1.86, with an inlet total pressure of about 5 atm. Cascade Reynolds numbers based on axial chord length and exit velocity range from 2.2 to 4.8 · 106. Surface disturbances are modeled with the use of narrow trip strips glued onto the surface at selected locations, such that sharp forward facing steps are presented to the boundary layer. Surface locations investigated include the near leading edge region on either side of the stagnation point, the midchord region of the pressure side, and the high curvature region of the suction side. Heat transfer enhancement factors are obtained for disturbances with engine representative height-to-momentum thickness ratios, as a function of Reynolds number. Enhancement factors are compared for both smooth and rough airfoil surfaces with added disturbances, as well as low and high freestream turbulence intensity. Results show that leading edge heat transfer is dominated by freestream turbulence intensity effects, such that enhancements of nearly 50% at low turbulence levels are reduced to about 10% at elevated turbulence levels. Both pressure and suction side enhancement factors are dominated by surface roughness caused effects, with large enhancements for smooth surfaces being drastically reduced for roughened surfaces.

Large Eddy Simulation of the Laminar Heat Transfer Augmentation on the Pressure Side of a Turbine Vane Under Freestream Turbulence

2019 ◽  
Vol 141 (4) ◽  
Author(s):  
Yousef Kanani ◽  
Sumanta Acharya ◽  
Forrest Ames
Keyword(s):  
Heat Transfer ◽  
Boundary Layer ◽  
Leading Edge ◽  
Transition To Turbulence ◽  
Experimental Measurements ◽  
Pressure Side ◽  
Freestream Turbulence ◽  
Heat Transfer Augmentation ◽  
Eddy Simulation ◽  
Large Eddy

Vane pressure side heat transfer is studied numerically using large eddy simulation (LES) on an aft-loaded vane with a large leading edge over a range of turbulence conditions. Numerical simulations are performed in a linear cascade at exit chord Reynolds number of Re = 5.1 × 105 at low (Tu ≈ 0.7%), moderate (Tu ≈ 7.9%), and high (Tu ≈ 12.4%) freestream turbulence with varying length scales as prescribed by the experimental measurements of Varty and Ames (2016, “Experimental Heat Transfer Distributions Over an Aft Loaded Vane With a Large Leading Edge at Very High Turbulence Levels,” ASME Paper No. IMECE2016-67029). Heat transfer predictions on the vane pressure side are in a very good agreement with the experimental measurements and the heat transfer augmentation due to the freestream turbulence is well captured. At Tu ≈ 12.4%, freestream turbulence enhances the Stanton number on the pressure surface without boundary layer transition to turbulence by a maximum of about 50% relative to the low freestream turbulence case. Higher freestream turbulence generates elongated structures and high-velocity streaks wrapped around the leading edge that contain significant energy. Amplification of the velocity streaks is observed further downstream with max rms of 0.3 near the trailing edge but no transition to turbulence or formation of turbulence spots is observed on the pressure side. The heat transfer augmentation at the higher freestream turbulence is primarily due to the initial amplification of the low-frequency velocity perturbations inside the boundary layer that persist along the entire chord of the airfoil. Stanton numbers appear to scale with the streamwise velocity fluctuations inside the boundary layer.

Large Eddy Simulation of Bypass Transition in Vane Passage With Freestream Turbulence

2020 ◽  
Vol 142 (6) ◽  
Author(s):  
Yousef Kanani ◽  
Sumanta Acharya ◽  
Forrest Ames
Keyword(s):  
Heat Transfer ◽  
Boundary Layer ◽  
Large Eddy Simulation ◽  
Bypass Transition ◽  
Freestream Turbulence ◽  
Turbulent Spot ◽  
Suction Surface ◽  
Eddy Simulation ◽  
Large Eddy ◽  
Inflow Turbulence

Abstract High Reynolds flow over a nozzle guide-vane with elevated inflow turbulence was simulated using wall-resolved large eddy simulation (LES). The simulations were undertaken at an exit Reynolds number of 0.5 × 106 and inflow turbulence levels of 0.7% and 7.9% and for uniform heat-flux boundary conditions corresponding to the measurements of Varty and Ames (2016, “Experimental Heat Transfer Distributions Over an Aft Loaded Vane With a Large Leading Edge at Very High Turbulence Levels,” ASME Paper No. IMECE2016-67029). The predicted heat transfer distribution over the vane is in excellent agreement with measurements. At higher freestream turbulence, the simulations accurately capture the laminar heat transfer augmentation on the pressure surface and the transition to turbulence on the suction surface. The bypass transition on the suction surface is preceded by boundary layer streaks formed under the external forcing of freestream disturbances which breakdown to turbulence through inner-mode secondary instabilities. Underneath the locally formed turbulent spot, heat transfer coefficient spikes and generally follows the same pattern as the turbulent spot. The details of the flow and temperature fields on the suction side are characterized, and first- and second-order statistics are documented. The turbulent Prandtl number in the boundary layer is generally in the range of 0.7–1, but decays rapidly near the wall.

Rotor Cavity Flow and Heat Transfer With Inlet Swirl and Radial Outflow of Cooling Air

1992 ◽  
Author(s):  
F. W. Staub
Keyword(s):  
Heat Transfer ◽  
Gas Flow ◽  
Crystal Surface ◽  
Ambient Pressure ◽  
Swirl Flow ◽  
Scale Model ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients ◽  
Inlet Swirl ◽  
Radial Outflow

To improve the reliability of turbine disc life prediction, experimental verification is required of analytical tools that calculate the flow field and heat transfer coefficients in turbine-stator cavities. As a first step, a full-scale model of the forward cavity of a typical aircraft gas turbine was employed using a high-molecular-weight gas (Refrigerant-12) at ambient pressure and temperature conditions to match the dimensionless parameters at engine conditions. The cavity temperature and selected cavity velocity profiles were measured using electrical heat addition with liquid crystal surface temperature measurement to obtain local disc heat transfer coefficients. A part of the cooling gas flow was added through a rotating inner seal with the remainder added at high angular swirl in the direction of rotation at a larger radius. Rotational Reynolds numbers were varied up to 9×106 with the radial Reynolds number variation up to 9000. A first-order comparison is given of the velocity distribution and disc heat transfer coefficients calculated by a CFD code and the measured values. The disc heat transfer coefficients can be dominated by the inlet swirl flow or by the rotor speed, depending on whether the coolant flow is greater or smaller than that generated by the rotor alone acting as a free disc.

Momentum and Thermal Boundary Layer Development on an Internally Cooled Turbine Vane

2012 ◽  
Vol 134 (6) ◽  
Author(s):  
Jason E. Dees ◽  
David G. Bogard ◽  
Gustavo A. Ledezma ◽  
Gregory M. Laskowski ◽  
Anil K. Tolpadi
Keyword(s):  
Heat Transfer ◽  
Boundary Layer ◽  
Thermal Boundary Layer ◽  
Conjugate Heat Transfer ◽  
Freestream Turbulence ◽  
Boundary Layer Development ◽  
Turbine Vane ◽  
Internally Cooled ◽  
Momentum Boundary Layer ◽  
Computational Predictions

Recent advances in computing power have made conjugate heat transfer simulations of turbine components increasingly popular; however, limited experimental data exist with which to evaluate these simulations. The primary parameter used to evaluate simulations is often the external surface temperature distribution, or overall effectiveness. In this paper, the overlying momentum and thermal boundary layers at various streamwise positions around a conducting, internally cooled simulated turbine vane were measured under low (Tu = 0.5%) and high (Tu = 20%) freestream turbulence conditions. Furthermore, experimental results were compared to computational predictions. In regions where a favorable pressure gradient existed, the thermal boundary layer was found to be significantly thicker than the accompanying momentum boundary layer. Elevated freestream turbulence had the effect of thickening the thermal boundary layer much more effectively than the momentum boundary layer over the entire vane. These data are valuable in understanding the conjugate heat transfer effects on the vane as well as serving as a tool for computational code evaluation.

Numerical Investigation of Inlet Swirl in a Turbine Cascade

2012 ◽  
Author(s):  
Gregor Schmid ◽  
Heinz-Peter Schiffer
Keyword(s):  
Heat Transfer ◽  
Numerical Investigation ◽  
Leading Edge ◽  
Turbine Cascade ◽  
Lean Burn ◽  
Image Velocimetry ◽  
Turbine Vane ◽  
Inlet Swirl ◽  
Inflow Conditions ◽  
Probe Measurements

New combustion concepts towards lean burn aim at reducing peak temperatures and therefore emissions, especially nitrogen oxides. High swirl is required in order to enhance the mixing of fuel and air and thus, improve combustion and flame stability. In a numerical investigation of a turbine vane cascade the effect of such inlet swirl on aerodynamic losses, secondary flow pattern and heat transfer is investigated. The computations are conducted prior to particle image velocimetry and five-hole-probe measurements in a cascade of six vane passages and swirl generators upstream of each passage. The analysis covers three constituent parts: First, different swirl intensities are simulated which resemble the situation in a real combustion chamber. Second, different clocking positions are investigated — the swirl cores are either aligned with the vane leading edge or with midpassage — and finally, swirl orientation as clockwise, anticlockwise and counter rotating swirl is analysed. Two-dimensional inlet boundary conditions are applied to model the discrete swirl cores. Furthermore, a comparison with circumferentially averaged as well as with axial inflow conditions is made. Increasing the swirl number at the inlet boundary results in reduced heat transfer coefficient within the vane passage and higher pressure loss. Heat transfer through vanes and endwalls is maximal if the swirl generators are aligned with the vane leading edge and counter rotating swirl.

The Effects of Freestream Turbulence, Turbulence Length Scale and Exit Reynolds Number on Turbine Blade Heat Transfer in a Transonic Cascade

2007 ◽  
Author(s):  
J. S. Carullo ◽  
S. Nasir ◽  
R. D. Cress ◽  
W. F. Ng ◽  
K. A. Thole ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Turbine Blade ◽  
Surface Heat ◽  
Length Scale ◽  
Freestream Turbulence ◽  
Surface Heat Transfer ◽  
Mach Numbers ◽  
Turbulence Length ◽  
Turbulence Length Scale

This paper experimentally investigates the effect of high freestream turbulence intensity, turbulence length scale, and exit Reynolds number on the surface heat transfer distribution of a turbine blade at realistic engine Mach numbers. Passive turbulence grids were used to generate freestream turbulence levels of 2%, 12%, and 14% at the cascade inlet. The turbulence grids produced length scales normalized by the blade pitch of 0.02, 0.26, and 0.41, respectively. Surface heat transfer measurements were made at the midspan of the blade using thin film gauges. Experiments were performed at exit Mach numbers of 0.55, 0.78 and 1.03 which represent flow conditions below, near, and above nominal conditions. The exit Mach numbers tested correspond to exit Reynolds numbers of 6 × 105, 8 × 105, and 11 × 105, based on true chord. The experimental results showed that the high freestream turbulence augmented the heat transfer on both the pressure and suction sides of the blade as compared to the low freestream turbulence case. At nominal conditions, exit Mach 0.78, average heat transfer augmentations of 23% and 35% were observed on the pressure side and suction side of the blade, respectively.

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