Fluid Flow in a 180 deg Sharp Turning Duct With Different Divider Thicknesses

1999 ◽  
Vol 121 (3) ◽  
pp. 569-576 ◽  
Author(s):  
Tong-Miin Liou ◽  
Yaw-Yng Tzeng ◽  
Chung-Chu Chen
Keyword(s):  
Heat Transfer ◽  
Laser Doppler Velocimetry ◽  
Fluid Flows ◽  
Internal Cooling ◽  
Mean Velocity ◽  
Cross Sectional ◽  
Square Duct ◽  
Measured Velocity ◽  
The Past ◽  
Flow Features

The effect of divider thickness on fluid flows in a two-pass smooth square duct with a 180 deg straight-corner turn is an important issue to the turbine blade internal cooling but has not been explored in the past. Laser-Doppler velocimetry measurements are thus presented for such a study at a Reynolds number of 1.2 × 104 and dimensionless divider thicknesses (Wd*) of 0.10, 0.25, 0.50. Results are presented in terms of various mean velocity components in two orthogonal streamwise planes and three cross-sectional planes, the local and regional averaged turbulent kinetic energy and resultant mean velocity distributions, and complemented by the liquid crystal measured heat transfer coefficient contours. The measured velocity data are able reasonably to explain published and present measured heat transfer results. Wd* is found to have profound effects on the flow features inside and immediately after the turn. The turbulence level and uniformity in the region immediately after the turn respectively decrease and increase with increasing Wd*.

scholarly journals Fluid Flow in a 180 Deg Sharp Turning Duct With Different Divider Thicknesses

1998 ◽  
Author(s):  
Tong-Miin Liou ◽  
Yaw-Yng Tzeng ◽  
Chung-Chu Chen
Keyword(s):  
Heat Transfer ◽  
Laser Doppler Velocimetry ◽  
Fluid Flows ◽  
Internal Cooling ◽  
Mean Velocity ◽  
Cross Sectional ◽  
Square Duct ◽  
Measured Velocity ◽  
The Past ◽  
Flow Features

The effect of divider thickness on fluid flows in a two-pass smooth square duct with a 180 deg straight-corner turn is an important issue to the turbine blade internal cooling but has not been explored in the past. Laser-Doppler velocimetry measurements are thus presented for such a study at a Reynolds number of 1.2 × 104 and dimensionless divider thicknesses (Wd*) of 0.10, 0.25, 0.50. Results are presented in terms of various mean velocity components in two orthogonal streamwise planes and three cross-sectional planes, the local and regional averaged turbulent kinetic energy and resultant mean velocity distributions, and complemented by the liquid crystal measured heat transfer coefficient contours. The measured velocity data are able to reasonably explain published and present measured heat transfer results. Wd* is found to have profound effects on the flow features inside and immediately after the turn. The turbulence level and uniformity in the region immediately after the turn respectively decrease and increase with increasing Wd*.

Detached Eddy Simulation of Flow and Heat Transfer in a Stationary Internal Cooling Duct With Skewed Ribs

2005 ◽  
Author(s):  
Aroon K. Viswanathan ◽  
Danesh K. Tafti
Keyword(s):  
Heat Transfer ◽  
Secondary Flow ◽  
Navier Stokes ◽  
Internal Cooling ◽  
Detached Eddy Simulation ◽  
Square Duct ◽  
Eddy Simulation ◽  
Flow And Heat Transfer ◽  
Numerical Predictions ◽  
Flow Features

Numerical predictions of a hydrodynamic and thermally developed turbulent flow for a unit period of a stationary duct using Detached Eddy Simulation (DES) and Unsteady Reynolds Averaged Navier-Stokes (URANS) are presented. The domain under consideration is a square duct with 45° ribs on the top and bottom walls arranged in a staggered fashion. Computations are carried out for a bulk Re of 47,000. The rib height to channel hydraulic diameter (e/Dh) is 0.1 and the rib pitch to rib height (P/e) is 10. DES is applied on two grids 80 × 80 × 80 and 128 × 80 × 80 and the initial results are compared with the experimental results and LES computations. Based on this the 128 × 80 × 80 grid is chosen for the comprehensive study. DES and URANS computations are carried out on the grid. The rib geometry introduces a strong secondary flow along the rib. The presence of the secondary flow introduces a spanwise variation in the heat transfer. DES predicts flow features and heat transfer distribution which is consistent with the experimental observations and LES computations. The average friction and the augmentation ratios predicted by DES also concur with the earlier observations.

scholarly journals Row Resolved Heat Transfer Variations in Pin-Fin Arrays Including Effects of Non-Uniform Arrays and Flow Convergence

1986 ◽  
Author(s):  
D. E. Metzger ◽  
W. B. Shepard ◽  
S. W. Haley
Keyword(s):  
Heat Transfer ◽  
Cross Sectional Area ◽  
Experimental Program ◽  
Internal Cooling ◽  
Sectional Area ◽  
Order Unity ◽  
Cross Sectional ◽  
Turbine Engine ◽  
Pin Fin ◽  
Pin Fin Arrays

Measured streamwise (longitudinal) heat transfer variations, spanwise (transverse) averaged and resolved to single row spacings, are presented for large aspect ratio ducts containing staggered arrays of circular pin fins which span the entire duct height. A number of different array geometries have been investigated in an experimental program, including uniformly spaced arrays in constant cross sectional area ducts with streamwise row spacings over the range 1.5 to 5.0 pin diameters. Such arrays, with pin length-to-diameter ratio of order unity, are often used to enhance heat transfer in internal cooling passages of gas turbine engine airfoils. The effects of various length interruptions in the pin pattern and of abrapt changes in pin diameter are presented for constant cross sectional area ducts. In addition, results are presented for the effect of duct convergence, a common situation in the cooled turbine airfoil application. A concise summary of all the observed behavior is given, useful for predicting the performance of arbitrarily spaced pin fin arrays that may be specified to produce a particular cooling distribution. Predictions are compared with two final test, configurations which combine aspects of all of the effects investigated in the experimental program.

Thermal Results for Forced Heat Convection Through Elliptical Ducts

1962 ◽  
Vol 29 (1) ◽  
pp. 165-170 ◽  
Author(s):  
N. T. Dunwoody
Keyword(s):  
Heat Transfer ◽  
Viscous Fluid ◽  
Cross Section ◽  
Constant Temperature ◽  
Fluid Flows ◽  
Numerical Results ◽  
Heat Convection ◽  
Elliptic Cross Section ◽  
Cross Sectional ◽  
Elliptic Cross

The purpose of the present investigation is to determine numerical results in respect of the heat transfer to the wall of a duct which has an elliptic cross section and through which a hot viscous fluid flows with a steady established laminar motion. The wall of the channel is at a constant temperature which is less than that of the entering fluid. Results for several cross-sectional eccentricities are presented and correlated.

Isolated and Coupled Effects of Rotating and Buoyancy Number on Heat Transfer and Pressure Drop in a Rotating Two-Pass Parallelogram Channel With Transverse Ribs

2017 ◽  
Vol 140 (3) ◽  
Author(s):  
Tong-Miin Liou ◽  
Shyy Woei Chang ◽  
Yi-An Lan ◽  
Shu-Po Chan
Keyword(s):  
Heat Transfer ◽  
Experimental Data ◽  
Pressure Drop ◽  
Turbine Blades ◽  
Internal Cooling ◽  
Cross Sectional ◽  
Gas Turbine Blades ◽  
Performance Factors ◽  
Heat Transfer Efficiency ◽  
Rotating Channel

Detailed Nusselt number (Nu) distributions over the leading (LE) and trailing (TE) endwalls and the pressure drop coefficients (f) of a rotating transverse-ribbed two-pass parallelogram channel were measured. The impacts of Reynolds (Re), rotation (Ro), and buoyancy (Bu) numbers upon local and regionally averaged Nu over the endwall of two ribbed legs and the turn are explored for Re = 5000–20,000, Ro = 0–0.3, and Bu = 0.0015–0.122. The present work aims to study the combined buoyancy and Coriolis effects on thermal performances as the first attempt. A set of selected experimental data illustrates the isolated and interdependent Ro and Bu influences upon Nu with the impacts of Re and Ro on f disclosed. Moreover, thermal performance factors (TPF) for the tested channel are evaluated and compared with those collected from the channels with different cross-sectional shapes and endwall configurations to enlighten the relative heat transfer efficiency under rotating condition. Empirical Nu and f correlations are acquired to govern the entire Nu and f data generated. These correlations allow one to evaluate both isolated and combined Re, Ro and/or Bu impacts upon the thermal performances of the present rotating channel for internal cooling of gas turbine blades.

Three Dimensional Measurements of Instantaneous Flow Field in Corners With Smooth Surfaces Under a Zero Pressure Gradient

2004 ◽  
Author(s):  
Michael Phillips ◽  
Steve Deutsch ◽  
Arnie Fontaine ◽  
Savas Yavuzkurt
Keyword(s):  
Heat Transfer ◽  
Pressure Gradient ◽  
Turbine Blades ◽  
Three Dimensional ◽  
Instantaneous Velocity ◽  
Stream Velocity ◽  
Internal Cooling ◽  
Mean Velocity ◽  
Data Set ◽  
Corner Flow

Three dimensional instantaneous velocity data were taken in a turbulent corner flow with smooth walls under a zero pressure gradient. Experiments were carried out in air with a free stream velocity of 13 m/s and an axial Reynolds number of about 10,000,000. The data were collected using a three-component LDV system that was configured in a nearly orthogonal setup. Measurements were made down to a y+ of approximately 5, and should provide a valuable data set in developing models and predictive codes. Data were collected at two axial locations, 0.93 and 1.26 m measured from the virtual origin. The boundary layer thickness was 20.90 mm and 24.91 mm respectively at these locations. At each position, instantaneous velocity profiles were measured at 6.35, 12.7, 20.6, 41.2, 82.3, 121.9, 164.5, 184.8, and 205.1 mm from the corner. The centerline profiles agree well with classical flat plate data. Three mean velocity and six Reynolds stress components have been calculated. The instantaneous velocity field data set is sufficient to compute higher order correlations. The data will be valuable for development of computer codes and models for heat transfer studies in the internal cooling channels of gas turbine blades and turbine end wall flow and heat transfer studies. An analysis of the data is presented. Future studies will concentrate on one smooth and one rough wall corner flow with favorable and adverse pressure gradients to provide a detailed database for corner flows in complex three dimensional flow fields.

Optimization of Rib Shape and Inclination in a Square Duct with Response Surface Methodology

2021 ◽  
pp. 1-34
Author(s):  
Yigang Luan ◽  
Lanyi Yan ◽  
Yue Yin ◽  
Hao Fu
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Response Surface ◽  
Navier Stokes ◽  
Internal Cooling ◽  
Square Duct ◽  
Flow And Heat Transfer ◽  
Surface Method ◽  
Geometric Factors ◽  
Parameter Ranges

Abstract The paper conducts numerical investigation coupled with Reynolds-averaged Navier Stokes method on detailed flow field and heat transfer characteristics of ribbed channel with symmetric ribs mounted on two walls. The physical domain is modeled by reference to a practical turbine blade internal cooling channel. The effects of three selected geometric factors of ribs, i.e. rib inclination angle, dimensionless rib height and dimensionless rib pitch, on the flow and heat transfer are investigated by variable-controlled simulations with the Reynolds number ranges from 5,000 to 90,000. The parameter ranges are 30°≤a≤90°, 0.5≤e/w≤1.5 and 5≤P/w≤15 with the rib width w fixed at 1mm. It is newly found that the friction factor does not follow a monotonical trend with respect to the Reynolds number under certain rib configurations. In addition, three-level numerical calculations about three geometric factors as well as the Reynolds number are conducted with the response surface method (RSM). Quadratic regression model for the targeted response, TPF, is obtained. The optimal rib shape for the goal of maximizing the channel overall thermal performance turns out to be e/w=0.5, P/w=15, a=30° as Re is fixed at 30,000.

Buoyant miscible displacement flows in rectangular channels

2017 ◽  
Vol 826 ◽  
pp. 676-713 ◽  
Author(s):  
S. M. Taghavi ◽  
R. Mollaabbasi ◽  
Y. St-Hilaire
Keyword(s):  
Flow Regimes ◽  
Channel Cross Section ◽  
Inertial Effects ◽  
Cross Sectional ◽  
Square Duct ◽  
Rectangular Channels ◽  
Flow Motion ◽  
Flow Features ◽  
Displacement Experiments ◽  
Stationary Interface

Buoyant displacement flows of two miscible fluids in rectangular channels are studied, theoretically and experimentally. The scenario considered involves the displacement of a fluid by a slightly heavier one at nearly horizontal channel inclinations, where inertial effects are weak and laminar stratified flows may be expected. In the theoretical part, a lubrication approximation model is developed to simplify the displacement flow governing equations and furnish a semi-analytical solution for the heavy and light fluid flux functions. Three key dimensionless parameters govern the fluid flow motion, i.e. a buoyancy number, the viscosity ratio and the channel cross-section aspect ratio. When these parameters are specified, the reduced model can deliver the interface propagation in time, leading and trailing front heights, shapes and speeds, cross-sectional velocity fields, etc. In addition, the model can be exploited to provide various classifications such as single or multiple fronts as well as main displacement flow regimes at long times such as no sustained backflows, stationary interface flows and sustained backflows. Focusing on the variation of the buoyancy number, a large number of iso-viscous displacement experiments are performed in a square duct and the results are compared with those of the lubrication model. Qualitative displacement flow features observed in the theory and experiments are in good agreement, in particular, in terms of the main displacement flow regimes. The quantitative comparisons are also reasonable for small and moderate imposed displacement flow velocities. However, at large flow rates, a deviation of the experimental results from the model results is observed, which may be due to the presence of non-negligible inertial effects.

Transport of Particulates in a Rotating Internal Cooling Ribbed Duct

2006 ◽  
Author(s):  
Anant Shah ◽  
Danesh K. Tafti
Keyword(s):  
Response Times ◽  
Front Surface ◽  
Hydraulic Diameter ◽  
Internal Cooling ◽  
Particle Sizes ◽  
Mean Velocity ◽  
Square Duct ◽  
Preferential Concentration ◽  
Lagrangian Framework ◽  
Order Of Magnitude

A ribbed square duct (P/e = 10, e/Dh = 0.10, and rotating with an angular velocity ωz) subjected to sand ingestion is studied using an Eulerian-Lagrangian framework. Particle sizes of 10μm and 50μm with response times (normalized by friction velocity and hydraulic diameter) of 0.06875 and 1.71875 respectively are considered. The calculations are performed for a nominal bulk Reynolds number of 20,000 and a Rotation number of 0.35 (based on hydraulic diameter and mean velocity) under fully-developed conditions. It is found that at any given instant in time about 67% of the total number of 10 micron particles are concentrated in the vicinity (within 0.05 Dh) of the duct surfaces, compared to 99% of the 50 micron particles. Both the particle sizes show preferential concentration near the smooth walls. The 10 micron particles, which are more sensitive to changes in flow, exhibit selective concentration on the trailing wall as compared to negligible concentration of the 50 micron particles. Both the particle sizes show negligible accumulation on the leading wall due to the action of Coriolis forces which push the particles towards the trailing wall. At the side walls of the duct, the 10 micron particles exhibit a high potential to erode the region in the vicinity of the rib due to secondary flow impingement. At the ribbed walls, while the 10 micron particles exhibit a fairly uniform but low propensity for erosion, the 50 micron particles show a much higher tendency to erode the surface. The trailing wall rib face facing the flow is by far the most susceptible to erosion and deposition for all particle sizes. In comparison to the front surface, the top and back surfaces of the rib do not exhibit a large propensity to be eroded. The potential for erosion in the rotating duct at the trailing wall and rib is at least an order of magnitude larger than in a stationary duct, whereas the leading wall has little or no erosion.

Influence of Channel Geometry and Flow Variables on Cyclone Cooling of Turbine Blades

2016 ◽  
Vol 138 (6) ◽  
Author(s):  
Martin Bruschewski ◽  
Christian Scherhag ◽  
Heinz-Peter Schiffer ◽  
Sven Grundmann
Keyword(s):  
Heat Transfer ◽  
Swirling Flow ◽  
Turbine Blades ◽  
Transfer Characteristic ◽  
Internal Cooling ◽  
Eddy Simulation ◽  
Magnetic Resonance Velocimetry ◽  
Swirl Generator ◽  
Flow Features ◽  
Flow Variables

A study examining the internal cooling of turbine blades by swirling flow is presented. The sensitivity of swirling flow is investigated with regard to Reynolds number, swirl intensity, and the common geometric features of blade-cooling ducts. The flow system consists of a straight and round channel that is attached to a swirl generator with tangential inlets. Different orifices and 180-deg bends are employed as channel outlets. The experiments were carried out with magnetic resonance velocimetry (MRV) for which water was used as flow medium. As the main outcome, it was found that the investigated flows are highly sensitive to the conditions at the channel outlet. However, it was also discovered that for some outlet geometries the flow field remains the same. The associated flow features a favorable topology for heat transfer; the majority of mass is transported in the annular region close to the channel walls. Together with its high robustness, it is regarded as an applicable flow type for the internal cooling of turbine blades. A large eddy simulation (LES) was conducted to analyze the heat transfer characteristic of the associated flow for S0=3 and Re=20,000. The simulation showed an averaged Nusselt number increase of factor 4.7 compared to fully developed flow. However, a pressure loss increase of factor 43 must be considered as well.

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