Evaluation of Alternatives for Two-Dimensional Linear Cascade Facilities

2009 ◽  
Vol 131 (3) ◽  
Author(s):  
Paul M. Kodzwa ◽  
Amanda Vicharelli ◽  
Gorazd Medic ◽  
Christopher J. Elkins ◽  
John K. Eaton ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Turbine Blade ◽  
Low Cost ◽  
Two Dimensional ◽  
Current Standard ◽  
Flow Measurements ◽  
Linear Cascade ◽  
Simulation Tools ◽  
Wide Range ◽  
History Of

This paper presents two low-cost alternatives for turbine blade surface heat transfer and fluid dynamics measurements. These models embody careful compromises between typical academic and full-scale turbomachinery experiments and represent a comprehensive strategy to develop experiments that can directly test shortcomings in current turbomachinery simulation tools. A full contextual history of the wide range of approaches to simulate turbine flow conditions is presented, along with a discussion of their deficiencies. Both models are simplifications of a linear cascade: the current standard for simulating two-dimensional turbine blade geometries. A single passage model is presented as a curved duct consisting of two half-blade geometries, carefully designed inlet and exit walls and inlet suction. This facility was determined to be best suited for heat transfer measurements where minimal surface conduction losses are necessary to allow accurate numerical model replication. A double passage model is defined as a single blade with two precisely designed outer walls, which is most appropriate for flow measurements. The design procedures necessary to achieve a desired flow condition are discussed.

Heat and Mass Transfer in an Incompressible Turbulent Boundary Layer

1972 ◽  
Vol 94 (1) ◽  
pp. 23-28 ◽  
Author(s):  
E. Brundrett ◽  
W. B. Nicoll ◽  
A. B. Strong
Keyword(s):  
Heat Transfer ◽  
Boundary Layer ◽  
Mass Transfer ◽  
Porous Plate ◽  
Mixing Length ◽  
Two Dimensional ◽  
Transfer Data ◽  
Incompressible Turbulent Boundary Layer ◽  
Wide Range ◽  
Incompressible Boundary

The van Driest damped mixing length has been extended to account for the effects of mass transfer through a porous plate into a turbulent, two-dimensional incompressible boundary layer. The present mixing length is continuous from the wall through to the inner-law region of the flow, and although empirical, has been shown to predict wall shear stress and heat transfer data for a wide range of blowing rates.

Heat Transfer and Aerodynamics of Turbine Blade Tips in a Linear Cascade

2004 ◽  
Vol 128 (2) ◽  
pp. 300-309 ◽  
Author(s):  
P. J. Newton ◽  
G. D. Lock ◽  
S. K. Krishnababu ◽  
H. P. Hodson ◽  
W. N. Dawes ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Flow Visualization ◽  
Turbine Blade ◽  
Pressure Coefficient ◽  
Suction Side ◽  
Tip Clearance ◽  
Pressure Side ◽  
Linear Cascade ◽  
Side Edge ◽  
High Heat Transfer

Local measurements of the heat transfer coefficient and pressure coefficient were conducted on the tip and near tip region of a generic turbine blade in a five-blade linear cascade. Two tip clearance gaps were used: 1.6% and 2.8% chord. Data was obtained at a Reynolds number of 2.3×105 based on exit velocity and chord. Three different tip geometries were investigated: A flat (plain) tip, a suction-side squealer, and a cavity squealer. The experiments reveal that the flow through the plain gap is dominated by flow separation at the pressure-side edge and that the highest levels of heat transfer are located where the flow reattaches on the tip surface. High heat transfer is also measured at locations where the tip-leakage vortex has impinged onto the suction surface of the aerofoil. The experiments are supported by flow visualization computed using the CFX CFD code which has provided insight into the fluid dynamics within the gap. The suction-side and cavity squealers are shown to reduce the heat transfer in the gap but high levels of heat transfer are associated with locations of impingement, identified using the flow visualization and aerodynamic data. Film cooling is introduced on the plain tip at locations near the pressure-side edge within the separated region and a net heat flux reduction analysis is used to quantify the performance of the successful cooling design.

Heat Transfer and Aerodynamics of Turbine Blade Tips in a Linear Cascade

2005 ◽  
Author(s):  
P. J. Newton ◽  
S. K. Krishnababu ◽  
G. D. Lock ◽  
H. P. Hodson ◽  
W. N. Dawes ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Turbine Blade ◽  
Pressure Coefficient ◽  
Suction Side ◽  
Tip Clearance ◽  
Flow Visualisation ◽  
Pressure Side ◽  
Linear Cascade ◽  
Side Edge ◽  
High Heat Transfer

Local measurements of the heat transfer coefficient and pressure coefficient were conducted on the tip and near tip region of a generic turbine blade in a five-blade linear cascade. Two tip clearance gaps were used: 1.6% and 2.8% chord. Data was obtained at a Reynolds number of 2.3 × 105 based on exit velocity and chord. Three different tip geometries were investigated: a flat (plain) tip, a suction-side squealer, and a cavity squealer. The experiments reveal that the flow through the plain gap is dominated by flow separation at the pressure-side edge and that the highest levels of heat transfer are located where the flow reattaches on the tip surface. High heat transfer is also measured at locations where the tip-leakage vortex has impinged onto the suction surface of the aerofoil. The experiments are supported by flow visualisation computed using the CFX CFD code which has provided insight into the fluid dynamics within the gap. The suction-side and cavity squealers are shown to reduce the heat transfer in the gap but high levels of heat transfer are associated with locations of impingement, identified using the flow visualisation and aerodynamic data. Film cooling is introduced on the plain tip at locations near the pressure-side edge within the separated region and a net heat flux reduction analysis is used to quantify the performance of the successful cooling design.

Doppler Angle Estimation of Pulsatile Flows Using AR Modeling

2002 ◽  
Vol 24 (2) ◽  
pp. 65-80 ◽  
Author(s):  
Chih-Kuang Yeh ◽  
Pai-Chi Li
Keyword(s):  
Real Time ◽  
Doppler Spectrum ◽  
Acquisition Time ◽  
Two Dimensional ◽  
Flow Measurements ◽  
Angle Estimation ◽  
Flow Angle ◽  
Doppler Angle ◽  
Wide Range ◽  
Pulsatile Flows

In quantitative ultrasonic flow measurements, the beam-to-flow angle (i.e., Doppler angle) is an important parameter. An autoregressive (AR) spectral analysis technique in combination with the Doppler spectrum broadening effect was previously proposed to estimate the Doppler angle. Since only a limited number of flow samples are used, real-time two-dimensional Doppler angle estimation is possible. The method was validated for laminar flows with constant velocities. In clinical applications, the flow pulsation needs to be considered. For pulsatile flows, the flow velocity is time-varying and the accuracy of Doppler angle estimation may be affected. In this paper, the AR method using only a limited number of flow samples was applied to Doppler angle estimation of pulsatile flows. The flow samples were properly selected to derive the AR coefficients and then more samples were extrapolated based on the AR model. The proposed method was verified by both simulations and in vitro experiments. A wide range of Doppler angles (from 30° to 78°) and different flow rates were considered. The experimental data for the Doppler angle showed that the AR method using eight flow samples had an average estimation error of 3.50° compared to an average error of 7.08° for the Fast Fourier Transform (FFT) method using 64 flow samples. Results indicated that the AR method not only provided accurate Doppler angle estimates, but also outperformed the conventional FFT method in pulsatile flows. This is because the short data acquisition time is less affected by the temporal velocity changes. It is concluded that real-time two-dimensional estimation of the Doppler angle is possible using the AR method in the presence of pulsatile flows. In addition, Doppler angle estimation with turbulent flows is also discussed. Results show that both the AR and FFT methods are not adequate due to the spectral broadening effects from the turbulence.

Measurements and Predictions of Surface Roughness Effects on the Turbine Vane Aerodynamics

2003 ◽  
Author(s):  
R. J. Boyle ◽  
R. G. Senyitko
Keyword(s):  
Surface Roughness ◽  
Turbulence Models ◽  
Reynolds Numbers ◽  
Aerodynamic Performance ◽  
Navier Stokes ◽  
Two Dimensional ◽  
Roughness Effects ◽  
Linear Cascade ◽  
Wide Range ◽  
Turbine Vane

The aerodynamic performance of a turbine vane was measured in a linear cascade. These measurements were conducted for exit-true chord Reynolds numbers between 150,000 and 1,800,000. The vane surface rms roughness-to-true chord ratio was approximately 2 × 10−4. Measurements were made for exit Mach numbers between 0.3 and 0.9 to achieve different loading distributions. Measurements were made at three different inlet turbulence levels. High and intermediate turbulence levels were generated using two different blown grids. The turbulence was low when no grid was present. The wide range of Reynolds numbers was chosen so that, at the lower Reynolds numbers the rough surfaces would be hydraulically smooth. The primary purpose of the tests was to provide data to verify CFD predictions of surface roughness effects on aerodynamic performance. Data comparisons are made using a two-dimensional Navier-Stokes analysis. Both two-equation and algebraic roughness turbulence models were used. A model is proposed to account for the increase in loss due to roughness as the Reynolds number increases.

Two-Dimensional Low Mach Number Heat Transfer Simulation of Turbine Blade Leading-Edge Model

2007 ◽  
Author(s):  
Jeff Litzler ◽  
Suman Mishra ◽  
Urmila Ghia ◽  
Karman Ghia ◽  
Shichuan Ou
Keyword(s):  
Heat Transfer ◽  
Turbine Blade ◽  
Bluff Body ◽  
Cross Flow ◽  
Leading Edge ◽  
Experimental Investigations ◽  
Two Dimensional ◽  
Grid Topology ◽  
Hybrid Grid ◽  
Blade Leading Edge

A subsonic, viscous, laminar flow and heat transfer is simulated in the present study over a two-dimensional, isothermal, bluff-body representing a turbine blade leading-edge. The purpose of this simulation is to predict local Frossling number; to determine the accuracy of the predictions as compared to experimental results, and to compare the results from two flow solvers, Fluent and Cobalt. The geometry consists of a half-cylinder of diameter 8.89 cm and a flat after-body, and represents to the model used in the corresponding experimental investigations. The simulations are performed on a multi-block, hybrid grid topology developed using GridGen as the grid generation software. Researchers have earlier investigated heat transfer over a similar model. Utilizing computational modeling techniques, a representative simulation of the physical flow mechanism enables further investigation into the characteristics of the flow. The boundary conditions for the problem are identified as no-slip and isothermal on the bluff body, and uniform velocity is assumed at the inlet. Results are presented in the form of the Frossling number, defined as the Nusselt number divided by the square root of Reynolds number. The results are compared with published experimental data for the experimental geometry described earlier, and the cross-flow-cylinder, to assess the validity of the numerical approaches.

scholarly journals Use of a Two-Dimensional Simulation Model in the Thermal Analysis of a Multi-Board Electronic Module

1994 ◽  
Vol 116 (2) ◽  
pp. 126-133 ◽  
Author(s):  
C. Beckermann ◽  
T. F. Smith ◽  
B. Pospichal
Keyword(s):  
Heat Transfer ◽  
Simulation Model ◽  
Three Dimensional ◽  
Two Dimensional ◽  
Circuit Boards ◽  
Depth Direction ◽  
Wide Range ◽  
Local Board ◽  
Dimensional Simulation ◽  
Effective Component

A study is reported of heat transfer and air flow in an electronic module consisting of an array of narrowly spaced vertical circuit boards with highly-protruding components contained in a naturally vented chassis. A two-dimensional simulation model is developed that accounts for heat transfer by conduction, convection, and radiation, and sensitivity studies are performed. Experiments are conducted using a specially constructed test module. Comparisons with the experiments reveal the need to calibrate the model by selecting an effective component height that represents the drag properties of the actual three-dimensional component geometry. The need to account in the model for heat losses in the depth direction is also discussed. The importance of accurate thermophysical properties and of multi-dimensional radiation is shown. Good agreement with measured velocities and local board temperatures is obtained over a wide range of power levels, and it is concluded that the calibrated model is capable of representing the thermal behavior of the present module.

Heat Transfer Resulting From the Interaction of a Vortex Pair With a Heated Wall

2008 ◽  
Vol 130 (5) ◽  
Author(s):  
Roland Martin ◽  
Roberto Zenit
Keyword(s):  
Heat Transfer ◽  
Nusselt Number ◽  
Vortex Pair ◽  
Reynolds Numbers ◽  
Heated Wall ◽  
Finite Volume Scheme ◽  
Two Dimensional ◽  
Wide Range ◽  
Heated Fluid ◽  
Effective Heat Transfer Coefficient

The motion of a two-dimensional vortex pair moving toward a wall is studied numerically. The case for which the wall is heated is analyzed. The equations of momentum and energy conservation are solved using a finite volume scheme. In this manner, the instantaneous heat transfer from the wall is obtained and is related to the dynamics of the fluid vortex interacting with the wall. It was found that, as expected, when the fluid vortex approaches the wall, the heat transfer increases significantly. The heat transfer changes in a nonmonotonic manner as a function of time: When the vortex first reaches the wall, a volume of heated fluid is convected from the wall; this fluid volume circulates in the vicinity of the wall, causing the rate of heat transfer to decrease slightly, to then increase again. A wide range of Prandtl and Reynolds numbers were tested. A measure of the effective heat transfer coefficient, or Nusselt number, is proposed.

Experimental Investigation on Swirl and Heat Transfer Within a Rotor-Stator Cavity

2016 ◽  
Author(s):  
Daniele Massini ◽  
Bruno Facchini ◽  
Mirko Micio ◽  
Riccardo Da Soghe
Keyword(s):  
Heat Transfer ◽  
Experimental Investigation ◽  
Mass Flow Rate ◽  
Working Conditions ◽  
Mass Flow ◽  
Flow Rate ◽  
System Effect ◽  
Flow Measurements ◽  
Wide Range ◽  
Admission System

A rotating test rig, reproducing a rotor-stator cavity with an axial admission system, has been exploited for an experimental investigation on the internal flow field and its effect on heat transfer on the stator side. Working conditions were varied in a wide range of rotating velocities and superposed mass flow rates. 2D PIV flow measurements were performed in order to obtain a radial distribution of the tangential velocity, results were used to validate numerical simulations aimed at understanding the admission system effect on the swirl distribution. Heat transfer coefficient distribution along the stator disk has been evaluated performing a steady state technique exploiting Thermo-chromic Liquid Crystals (TLC). Tests have been performed varying the superposed mass flow rate up to reaching the condition of cavity completely sealed, further increase of the mass flow rate showed to reduce the effect of the rotation. Working conditions were set in order to investigate cases missing in open literature, however few tests performed in similarity with other researches provided comparable results.

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