Heat Transfer Study in a Linear Turbine Cascade Using a Thermal Boundary Layer Measurement Technique

2007 ◽  
Vol 129 (10) ◽  
pp. 1384-1394 ◽  
Author(s):  
S. Han ◽  
R. J. Goldstein
Keyword(s):  
Heat Transfer ◽  
Mass Transfer ◽  
Turbine Blades ◽  
Local Heat Transfer ◽  
Experimental System ◽  
Local Heat ◽  
Turbine Cascade ◽  
Local Measurements ◽  
End Wall ◽  
Five Axis

An experimental system is designed, constructed, and operated to make local measurements of heat transfer from constant-temperature surfaces in a linear turbine cascade. The system includes a number of embedded heaters and a control system to maintain the turbine blades and end walls in the cascade at a uniform temperature. A five-axis measurement system is used to determine temperature profiles normal to the pressure and suction sides of the blades and to the end wall. Extrapolating these measurements close to the surface, the local heat transfer is calculated using Fourier’s law. The system has been tested in the laboratory, and results are shown for the temperature distributions above the surfaces and for the local variations in the Nusselt number on the different surfaces in the cascade. The system can also be used to study the heat and mass transfer analogy as considerable data are available for mass transfer results with similar geometries.

scholarly journals Effect of Discrete Ribs on Heat Transfer and Friction Inside Narrow Rectangular Cross Section Cooling Passage of Gas Turbine Blade

2021 ◽  
Vol 10 (6) ◽  
pp. 192-209
Author(s):  
Karthik Krishnaswamy ◽  
◽  
Srikanth Salyan ◽  
Keyword(s):  
Heat Transfer ◽  
Gas Turbine ◽  
Turbine Blade ◽  
Turbine Blades ◽  
Local Heat Transfer ◽  
Local Heat ◽  
Hydraulic Diameter ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients ◽  
Cooling Passage

The performance of a gas turbine during the service life can be enhanced by cooling the turbine blades efficiently. The objective of this study is to achieve high thermohydraulic performance (THP) inside a cooling passage of a turbine blade having aspect ratio (AR) 1:5 by using discrete W and V-shaped ribs. Hydraulic diameter (Dh) of the cooling passage is 50 mm. Ribs are positioned facing downstream with angle-of-attack (α) of 30° and 45° for discrete W-ribs and discerte V-ribs respectively. The rib profiles with rib height to hydraulic diameter ratio (e/Dh) or blockage ratio 0.06 and pitch (P) 36 mm are tested for Reynolds number (Re) range 30000-75000. Analysis reveals that, area averaged Nusselt numbers of the rib profiles are comparable, with maximum difference of 6% at Re 30000, which is within the limits of uncertainty. Variation of local heat transfer coefficients along the stream exhibited a saw tooth profile, with discrete W-ribs exhibiting higher variations. Along spanwise direction, discrete V-ribs showed larger variations. Maximum variation in local heat transfer coefficients is estimated to be 25%. For experimented Re range, friction loss for discrete W-ribs is higher than discrete-V ribs. Rib profiles exhibited superior heat transfer capabilities. The best Nu/Nuo achieved for discrete Vribs is 3.4 and discrete W-ribs is 3.6. In view of superior heat transfer capabilities, ribs can be deployed in cooling passages near the leading edge, where the temperatures are very high. The best THPo achieved is 3.2 for discrete V-ribs and 3 for discrete W-ribs at Re 30000. The ribs can also enhance the power-toweight ratio as they can produce high thermohydraulic performances for low blockage ratios.

Local Heat Transfer Characteristics in Simulated Electronic Modules

2003 ◽  
Vol 125 (3) ◽  
pp. 362-368 ◽  
Author(s):  
Seong-Yeon Yoo ◽  
Jong-Hark Park ◽  
Min-Ho Chung
Keyword(s):  
Heat Transfer ◽  
Mass Transfer ◽  
Three Dimensional ◽  
Vortex Generator ◽  
Local Heat Transfer ◽  
Local Heat ◽  
Two Dimensional ◽  
Heat Transfer Characteristics ◽  
Dimensional Array ◽  
Transfer Characteristics

When heat is released by forced convection from electronic modules in a narrow printed circuit board channel, complex flow phenomena—such as stagnation and acceleration on the front surface, separation and reattachment on the top surface, wake or cavity flow near the rear surface—affect the heat transfer characteristics. The purpose of this study is to investigate how these flow conditions influence the local heat transfer from electronic modules. Experiments are performed on a three-dimensional array of hexahedral elements as well as on a two-dimensional array of rectangular elements. Naphthalene sublimation technique is employed to measure three-dimensional local mass transfer, and the mass transfer data are converted to their counterparts of the heat transfer process using the analogy equation between heat and mass transfer. Module location and streamwise module spacing are varied, and the effect of vortex generators on heat transfer enhancement is also examined. Dramatic change of local heat transfer coefficients is found on each surface of the module, and three-dimensional modules have a little higher heat transfer value than two-dimensional modules because of bypass flow. Longitudinal vortices formed by vortex generator enhance the mixing of fluids and thereby heat transfer, and the rectangular wing type vortex generator is found to be more effective than the delta wing type vortex generator.

Darryl E. Metzger Memorial Session Paper: Surface Heat Transfer From a Three-Pass Blade Cooling Passage Simulator

1995 ◽  
Vol 117 (4) ◽  
pp. 650-656 ◽  
Author(s):  
M. K. Chyu ◽  
V. Natarajan
Keyword(s):  
Heat Transfer ◽  
Mass Transfer ◽  
Cross Sections ◽  
Local Heat Transfer ◽  
Local Heat ◽  
Test Model ◽  
Flow Area ◽  
Blade Cooling ◽  
Sharp Turn ◽  
Cooling Passage

Using an analogous mass transfer system based on naphthalene sublimation, the present research focuses on investigating the local heat transfer characteristics from three-pass smooth and turbulated blade cooling passages. To simulate the actual passage geometry, the test model is incorporated with trapezoidal cross sections including variable passage sizes. Measured local mass transfer results reveal strong evidence of velocity redistribution over the trapezoidal flow area. Elevated mass transfer always exists in the vicinity of a sharp turn. However, in the present study, one of the most notable mass transfer increases is perceived in the third pass, downstream to the second turn, where the flow area is reduced severely. Overall, the combined effects of the three-pass and two sharp turns virtually double the mass transfer as compared to its straight counterpart with fully developed, turbulent flow. With a pitch-to-height ratio equal to 10 and 90 deg orientation, the rib turbulators produce approximately an additional 30 percent of overall mass transfer enhancement in comparison to the smooth case. Locally, rib-induced enhancement varies with different surfaces and passes. The greatest enhancement lies on the first pass, about 40 percent; the other two passes are comparable, less than 20 percent.

The Effects of an Excited Impinging Jet on the Local Heat Transfer Coefficient of Aircraft Turbine Blades

1988 ◽  
Author(s):  
P. J. Disimile ◽  
D. M. Paule
Keyword(s):  
Heat Transfer ◽  
Flow Field ◽  
Turbine Blade ◽  
Turbine Blades ◽  
Leading Edge ◽  
Local Heat Transfer ◽  
Impinging Jet ◽  
Local Heat ◽  
Primary Objective ◽  
Inlet Temperature

The primary objective of this paper is to present the results of research into the effects of periodic excitation upon the local heat transfer characteristics of a turbine blade cooled by an impinging jet of air. A curved plate (used to simulate the inner leading edge of a turbine blade) was subjected to a two-dimensional jet flow field (Re = 10,000) with a superimposed periodic acoustic disturbance. When compared to the naturally disturbed flow, the excited flow field was found to reduce the local Nusselt number and cool the blade less efficiently (by as much as ten percent in the extreme cases). The results of the study appear to indicate that harmonic disturbances present a serious controlling factor in the quest for optimization of turbine blade cooling techniques. By isolating dominant frequencies in gas turbine engines and working to suppress them, the authors believe it possible to make significant contributions towards the desired increase in turbine inlet temperature.

Numerical Simulations of Flow Fields and Heat Transfer Characteristics in Tenon Joint Gap Between Turbine Blade and Disk Under Rotating Conditions

2017 ◽  
Author(s):  
Da-wei Chen ◽  
Hui-ren Zhu ◽  
Yang Xu ◽  
Xiao-meng Jia ◽  
Cong Liu ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Turbine Blades ◽  
Local Heat Transfer ◽  
Local Heat ◽  
Local Heat Transfer Coefficient ◽  
Flow And Heat Transfer ◽  
Joint Gap ◽  
The Right

Turbine blades and the disks are connected by tenons. There is a pair of jagged assembly clearance between each tenon and corresponding mortise. In practical engineering applications, flow and heat transfer characteristics in assembly clearance used to be simplified. In order to obtain more accurate temperature fields of the turbine blades and disks, detailed study of the flow and heat transfer mechanism in tenon joint gap is necessary. In this paper, two typical assembly clearances under the stationary and rotating conditions were investigated numerically, including double S-shaped and double Crescent-shaped. The inlet Reynolds numbers range from 5,500 to 50,000 and the Rotation numbers range from 0 to 0.005. The results show that the fluids in the two branches of the double S-shaped channel have different flow characteristics under rotating conditions. A vortex is formed at the corner of the left branch and the vortex scale can be influenced by Re and Ro. The large vortex decreases the local heat transfer coefficient. In the right branch, the three-dimensional flow from the flat wall to the concave wall increases the local heat transfer coefficient of different regions. For the double Crescent-shaped channel, the region with higher velocity is offset to the right of the channel which leads to higher local heat transfer coefficient under rotating conditions. The simulation results have great significance to the heat transfer analysis of turbine blades and disks.

Impairment of Local Heat Transfer of the Turbulent Mixed Convection in a Vertical Flat Plate

2018 ◽  
Author(s):  
Myeong-Seon Chae ◽  
Bum-Jin Chung
Keyword(s):  
Heat Transfer ◽  
Mass Transfer ◽  
Mixed Convection ◽  
Flat Plate ◽  
Forced Convection ◽  
Convection Heat Transfer ◽  
Local Heat Transfer ◽  
Local Heat ◽  
Convection Heat ◽  
Vertical Flat Plate

The heat transfer of the buoyancy-aided turbulent mixed convective flow in a vertical flat plate was investigated experimentally. Mass transfer experiments were carried out based on the heat and mass transfer analogy. The Rayleigh numbers ranged from 1.69 × 108 to 2.11 × 1013, depending on the height of the vertical flat plate. The Reynolds numbers varied from 4,585 to 17,320 for turbulent regimes. The test results for turbulent forced convections agreed well with the forced convection correlations established by Petukhov et al. The local heat transfer rates of the turbulent mixed flow exhibited the impairment of heat transfer compared to the forced convection and non-monotonous behavior along the axial position due to buoyancy effect. The local minimum heat transfer was 38.6% lower than the forced convection heat transfer. The turbulent mixed convection heat transfer is affected by the height of vertical plate.

Local Heat and Mass Transfer Characteristics for Multi-Layered Impingement/Effusion Cooling

2015 ◽  
Author(s):  
Seon Ho Kim ◽  
Kyeong Hwan Ahn ◽  
Jun Su Park ◽  
Eui Yeop Jung ◽  
Ki-Young Hwang ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Mass Transfer ◽  
Local Heat Transfer ◽  
Local Heat ◽  
Narrow Channel ◽  
Design Factor ◽  
Jet Cooling ◽  
Internal Surfaces ◽  
Naphthalene Sublimation ◽  
Sublimation Method

Multi-layered impingement/effusion cooling is an advanced cooling configuration that combines impingement jet cooling, pin cooling, and effusion cooling. The arrangement of the pins is a critical design factor because of the complex heat transfer in the internal structure. Therefore, it is important to measure the local heat transfer at all internal surfaces as a function of the pin spacing. In this study, a naphthalene sublimation method was employed to measure the details of the heat/mass transfer at the internal surfaces, including the injection plate, effusion plates, and the pins. An staggered array of holes was formed at the injection plate and effusion plates where the ratio of the height to the diameter of the pins, h/d, was fixed at 0.25. The ratio of the pin spacing to the diameter, sp/d, was varied in the range 1.5≤sp/d≤6, and the Reynolds number based on the hole diameter was 3000. As a result, a vortex ring formed near the pin, leading to re-impingement flows in the narrow channel. The jet flow impinged strongly on the pin, resulting in a large heat transfer region at each surface. The total average Sherwood number with sp/d=1.5 was larger than that with sp/d=6 by a factor of 1.5.

Turbulent Transport on the Endwall in the Region Between Adjacent Turbine Blades

1988 ◽  
Vol 110 (4a) ◽  
pp. 862-869 ◽  
Author(s):  
R. J. Goldstein ◽  
R. A. Spores
Keyword(s):  
Heat Transfer ◽  
Mass Transfer ◽  
Turbine Blade ◽  
Transport Coefficients ◽  
Accurate Determination ◽  
Three Dimensional ◽  
Local Heat Transfer ◽  
Local Heat ◽  
Three Dimensional Flow ◽  
Dimensional Flow

The complex three-dimensional flow in the endwall region near the base of a turbine blade has an important impact on the local heat transfer. The initial horseshoe vortex, the passage vortex, and resulting corner vortices cause large variations in heat transfer over the entire endwall region. Due to these large surface gradients in heat transfer, conventional measurement techniques generally do not provide an accurate determination of the local heat transfer coefficients. In the present study, the heat/mass transfer analogy is used to examine the local transport coefficients for two different endwall boundary layer thicknesses and two free-stream Reynolds numbers. A linear turbine blade cascade is used in conjunction with a removable endwall plate. Naphthalene (C10H8) is cast into a mold on the plate and the rate of naphthalene sublimation is determined at 6000 + locations on the simulated endwall by employing a computer-aided data acquisition system. This technique allows one to obtain detailed contour plots of the local convection coefficient over the entire endwall. By examining the mass transfer contours, it is possible to infer information on the three-dimensional flow in the passage between the blades. Extremely high transport coefficients on the endwall indicate locations of potential overheating and failure in an actual turbine.

Experimental Study on Local Heat Transfer in a Rotating, Two-Pass Cooling Channel With Dense Array of Turbulence Promoters With Naphthalene Sublimation Method

2014 ◽  
Author(s):  
Tomoko Hagari ◽  
Katsuhiko Ishida ◽  
Kenichiro Takeishi ◽  
Masaharu Komiyama ◽  
Yutaka Oda
Keyword(s):  
Heat Transfer ◽  
Mass Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Surface Area ◽  
Local Heat Transfer ◽  
Local Heat ◽  
Cooling Channel ◽  
Overall Heat Transfer Coefficient ◽  
Rib Turbulators

Detailed heat transfer coefficient distributions in a rotating, two-pass, square channel with densely arranged rib turbulators on the leading and trailing walls are investigated. Rib turbulators have been used in a cooling channel of turbine airfoils. The dense arrangement of the ribs is one of the potential candidates to improve heat transfer performance because of its surface area enlargement effect. The ribs are arranged with a rib height to channel hydraulic diameter ratio (e/Dh) of 0.13, angles of attack to the mainstream of 60 and 90deg, and rib pitch-to-height ratios (P/e) of 3, 6 and 10. Both rib and floor surfaces are coated with naphthalene to measure their local mass transfer rate, which is correlated with heat transfer coefficient through heat/mass transfer analogy. Combination of a laser displacement sensor and a precision auto-traverse system enables detailed measurement of local heat transfer distribution on the floor surface between the ribs. Overall heat transfer coefficient including the effect of the rib is obtained by measuring the decrease in weight of the naphthalene test piece. Reynolds number is set at 50,000 and rotation numbers are up to 0.05. The results show that the effect of rotation on local heat transfer behavior depends on the rib spacing and orientation. Compared the overall heat transfer coefficients with the local ones on the floor surface, they showed different trend in some cases. This suggests that variation of rib heat transfer characteristics due to rotation might determine the overall heat transfer coefficient. Such tendency would be stronger for smaller rib spacing because surface area of the rib has large portion of the total heat transfer area. Further investigation on this effect is expected by measuring heat transfer of rib itself under rotating condition.

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