The Heat/Mass Transfer Analogy for a Simulated Turbine Endwall With Fillets

2008 ◽  
Vol 131 (1) ◽  
Author(s):  
S. Han ◽  
R. J. Goldstein
Keyword(s):  
Heat Transfer ◽  
Mass Transfer ◽  
Heat Mass Transfer ◽  
Measurement Data ◽  
Leading Edge ◽  
Secondary Flows ◽  
Alternative Methods ◽  
Experimental Conditions ◽  
Transfer Data ◽  
Naphthalene Sublimation Technique

Mass transfer measurements are employed as alternative methods for heat transfer measurement because of the difficulty of heat transfer measurements in thin boundary layers, complicated secondary flows, and large thermal gradients. Even though mass transfer experiments are fast and show detailed local measurement data, the conversion of mass transfer results to heat transfer data requires the heat/mass transfer analogy factors in detail. Therefore, the usefulness of mass transfer data depends on finding a simple analogy factor. The heat/mass transfer analogy on a simulated turbine endwall with fillets is evaluated in the present paper. Since the heat/mass transfer analogy factor may not be always the same, the heat/mass transfer analogy should be verified for other different geometries and experimental conditions. To utilize the heat/mass transfer analogy fully, it is necessary to check that the presence of different aerodynamic conditions caused by the fillets affects the heat/mass transfer analogy on a simulated turbine endwall with fillets. To compare heat transfer data and mass transfer data, heat transfer measurements on the endwall with fillets are conducted with a thermal boundary layer measurement technique and mass transfer measurements employing naphthalene sublimation technique on the endwall with the fillets are extracted from literature with equivalent experimental conditions and a similar geometry. As expected by heat transfer and mass transfer equations, the heat/mass transfer analogy factor is applied and shows a good agreement between heat transfer and mass transfer results on the endwall with the fillets from the leading edge to the trailing edge.

scholarly journals Highly Resolved Distribution of Heat Transfer for Turbine Leading Edge Film Cooling Including Reynolds Number and Blowing Rate Effects

1998 ◽  
Author(s):  
K. Jung ◽  
D. K. Hennecke
Keyword(s):  
Heat Transfer ◽  
Mass Transfer ◽  
Reynolds Number ◽  
Film Cooling ◽  
Heat Mass Transfer ◽  
Leading Edge ◽  
Transfer Coefficients ◽  
Complex Flow ◽  
Long Distance ◽  
Naphthalene Sublimation Technique

The effect of leading edge film cooling on heat transfer was experimentally investigated using the naphthalene sublimation technique. The experiments were performed on a symmetrical model of the leading edge suction side region of a high pressure turbine blade with one row of film cooling holes on each side. Two different lateral inclinations of the injection holes were studied: 0° and 45°. In order to build a data base for the validation and improvement of numerical computations, highly resolved distributions of the heat/mass transfer coefficients were measured. Reynolds numbers (based on hole diameter) were varied from 4000 to 8000 and blowing rate from 0.0 to 1.5. For better interpretation, the results were compared with injection-flow visualizations. Increasing the blowing rate causes more interaction between the jets and the mainstream, which creates higher jet turbulence at the exit of the holes resulting in a higher relative heat transfer. This increase remains constant over quite a long distance dependent on the Reynolds number. Increasing the Reynolds number keeps the jets closer to the wall resulting in higher relative heat transfer. The highly resolved heat/mass transfer distribution shows the influence of the complex flow field in the near hole region on the heat transfer values along the surface.

Influence of Blade Leading Edge Geometry on Turbine Endwall Heat(Mass) Transfer

2005 ◽  
Author(s):  
S. Han ◽  
R. J. Goldstein
Keyword(s):  
Mass Transfer ◽  
Heat Mass Transfer ◽  
Leading Edge ◽  
Local Heat ◽  
Secondary Flows ◽  
Transfer Performance ◽  
Turbine Cascade ◽  
Suction Surface ◽  
Naphthalene Sublimation Technique ◽  
Passage Vortex

The secondary flows, including passage and other vortices in a turbine cascade cause significant aerodynamic losses and thermal gradients. Leading-edge modification of the blade has drawn considerable attention as it has been shown to reduce the secondary flows. However, the heat transfer performance of a leading-edge modified blade has not been investigated thoroughly. Since a fillet at the leading edge blade is reported to reduce the aerodynamic loss significantly, the naphthalene sublimation technique with a fillet geometry is used to study local heat (mass) transfer performance in a simulated turbine cascade. The present paper compares Sherwood number distributions on an endwall with a simple blade and a similar blade having modified leading-edge by adding a fillet. With the modified blades, a horseshoe vortex is not observed and the passage vortex is delayed or not observed for different turbulence intensities. However, near the blade trailing edge the passage vortex has gained as much strength as with the simple blade for low turbulence intensity. Near the leading edge on the pressure and the suction surface, higher mass transfer regions are observed with the fillets. Apparently the corner vortices are intensified with the leading-edge modified blade.

Influence of Blade Leading Edge Geometry on Turbine Endwall Heat (Mass) Transfer

2005 ◽  
Vol 128 (4) ◽  
pp. 798-813 ◽  
Author(s):  
S. Han ◽  
R. J. Goldstein
Keyword(s):  
Mass Transfer ◽  
Heat Mass Transfer ◽  
Leading Edge ◽  
Local Heat ◽  
Secondary Flows ◽  
Transfer Performance ◽  
Turbine Cascade ◽  
Suction Surface ◽  
Naphthalene Sublimation Technique ◽  
Passage Vortex

The secondary flows, including passage and other vortices in a turbine cascade, cause significant aerodynamic losses and thermal gradients. Leading edge modification of the blade has drawn considerable attention as it has been shown to reduce the secondary flows. However, the heat transfer performance of a leading edge modified blade has not been investigated thoroughly. Since a fillet at the leading edge blade is reported to reduce the aerodynamic loss significantly, the naphthalene sublimation technique with a fillet geometry is used to study local heat (mass) transfer performance in a simulated turbine cascade. The present paper compares Sherwood number distributions on an endwall with a simple blade and a similar blade having a modified leading edge by adding a fillet. With the modified blades, a horseshoe vortex is not observed and the passage vortex is delayed or not observed for different turbulence intensities. However, near the blade trailing edge the passage vortex has gained as much strength as with the simple blade for low turbulence intensity. Near the leading edge on the pressure and the suction surface, higher mass transfer regions are observed with the fillets. Apparently the corner vortices are intensified with the leading edge modified blade.

scholarly journals An Investigation of Heat Transfer by Leading Edge Film Cooling Applying the Naphthalene Sublimation Technique

1996 ◽  
Author(s):  
J. Richter ◽  
K. Jung ◽  
D. K. Hennecke
Keyword(s):  
Heat Transfer ◽  
Mass Transfer ◽  
Transfer Coefficient ◽  
Mass Transfer Coefficient ◽  
Film Cooling ◽  
Incidence Angle ◽  
Leading Edge ◽  
Naphthalene Sublimation Technique ◽  
Naphthalene Sublimation ◽  
Sublimation Technique

The dependence of heat transfer on film cooling near the leading edge of a blade was investigated using the naphthalene sublimation technique and applying the analogy between heat and mass transfer. Therefore, the local sublimation rate with and without film cooling was measured. The symmetric leading edge was cooled by an air mass flow out of two staggered rows of holes. The measurements were carried out with a constant Reynolds number Re = 80000, different incidence angles φ = 0° to 10° and a blowing rate varying from M = 0.3 to 2.5. The flow without film cooling was visualized around the leading edge with smoke to indicate the existence of separation bubbles. To determine the dependence of incidence angle and blowing rate on jet trajectories, smoke was mixed to the cooling air. The mass transfer coefficient was determined with the naphthalene sublimation technique. Due to the high resolution of the sublimation technique the local mass transfer distribution around the cooling holes could also be measured. Furthermore, the location of stagnation points and separation bubbles were investigated. The results of the tests without film cooling were also compared with those obtained by observing stagnation point mass transfer on a cylinder and with those by laminar flow across a flat plate. The mass transfer coefficient of film cooling experiments was related to the mass transfer coefficient without film cooling to describe the local dependence of heat transfer coefficient on film cooling. An increase on relativ heat transfer near the film cooling holes is obtained by increasing the blowing rate. No further influence on heat transfer along the pressure side is detected for an incidence angle larger than 10° as the cooling films were shifted around the leading edge from the pressure to the suction side.

Heat/Mass Transfer in 1:4 Rectangular Passages With Rotation

2003 ◽  
Author(s):  
Peeyush Agarwal ◽  
Sumanta Acharya ◽  
D. E. Nikitopoulos
Keyword(s):  
Mass Transfer ◽  
Cross Section ◽  
Heat Mass Transfer ◽  
Rectangular Channel ◽  
Transfer Data ◽  
Naphthalene Sublimation Technique ◽  
Rotation Numbers ◽  
Local Mass Transfer ◽  
Naphthalene Sublimation ◽  
Sublimation Technique

The paper presents an experimental study of heat/mass transfer coefficient in 1:4 rectangular channel with smooth or ribbed walls for Reynolds number in the range of 5000 to 40000 and Rotation numbers in the range of 0–0.12. Such passages are encountered close to the mid-chord sections of the turbine blade. Normal ribs (e/Dh = 0.3125, and P/e = 8) are placed on the leading and the trailing sides only. The experiments are conducted in a rotating two-pass coolant channel facility using the naphthalene sublimation technique. For purposes of comparison, selected measurements are also performed in a 1:1 cross-section. The local mass-transfer data in the fully developed region is averaged to study the effect of the Reynolds and the Rotation numbers. The span-wise mass transfer distributions in the smooth and the ribbed cases are also examined.

Heat Transfer on Rotating Channel With Various Heights of Pin-Fin

2008 ◽  
Author(s):  
Jun Su Park ◽  
Kyung Min Kim ◽  
Dong Hyun Lee ◽  
Hyung Hee Cho ◽  
Minking K. Chyu
Keyword(s):  
Heat Transfer ◽  
Mass Transfer ◽  
Heat Mass Transfer ◽  
Transfer Coefficients ◽  
Pin Fin ◽  
Heat Transfer Coefficients ◽  
Naphthalene Sublimation Technique ◽  
Pin Fins ◽  
Naphthalene Sublimation ◽  
Pin Fin Array

Pin-fins have been used to enhance the heat transfer near the trailing edge of a turbine airfoil. Previous pin-fin heat transfer studies focused mainly on the array geometry of pin height-to-diameter equal to unity in a stationary frame. This study experimentally examines the effects of pin height-to-diameter ratio (Hp/Dp) from 2 to 4 and rotation number (Ro) from 0 to 0.2. The tested model used a staggered pin-fin array with an inter-pin spacing of 2.5 times the pin-diameter (S/D = 2.5) in both longitudinal and transverse directions. Detailed heat/mass transfer coefficients were measured using the naphthalene sublimation technique with a heat-mass transfer analogy. The data measured suggest that an increase in Hp/Dp increases the level of array heat/mass transfer. Array averaged Sherwood numbers for Hp/Dp = 3 and Hp/Dp = 4 are approximately 10% and 35% higher than that of Hp/Dp = 2. The effect of rotation induces notable difference in heat/mass transfer between the leading surface and the trailing surface. The heat transfer coefficients change a little although the rotating number increases in the tested range because the pin-fins break the rotation-induced vortices.

Heat Transfer in 1:4 Rectangular Passages With Rotation

2003 ◽  
Vol 125 (4) ◽  
pp. 726-733 ◽  
Author(s):  
Peeyush Agarwal ◽  
Sumanta Acharya ◽  
D. E. Nikitopoulos
Keyword(s):  
Heat Transfer ◽  
Mass Transfer ◽  
Cross Section ◽  
Rectangular Channel ◽  
Transfer Data ◽  
Naphthalene Sublimation Technique ◽  
Rotation Numbers ◽  
Local Mass Transfer ◽  
Naphthalene Sublimation ◽  
Sublimation Technique

The paper presents an experimental study of heat/mass transfer coefficient in 1:4 rectangular channel with smooth or ribbed walls for Reynolds number in the range of 5000–40,000 and rotation numbers in the range of 0–0.12. Such passages are encountered close to the mid-chord sections of the turbine blade. Normal ribs (e/Dh=0.3125 and P/e=8) are placed on the leading and the trailing sides only. The experiments are conducted in a rotating two-pass coolant channel facility using the naphthalene sublimation technique. For purposes of comparison, selected measurements are also performed in a 1:1 cross section. The local mass-transfer data in the fully developed region is averaged to study the effect of the Reynolds and the rotation numbers. The spanwise mass transfer distributions in the smooth and the ribbed cases are also examined.

Mass∕Heat Transfer in Rotating, Smooth, High-Aspect Ratio (4:1) Coolant Channels With Curved Walls

2009 ◽  
Vol 131 (2) ◽  
Author(s):  
Eashwar Sethuraman ◽  
Sumanta Acharya ◽  
Dimitris E. Nikitopoulos
Keyword(s):  
Heat Transfer ◽  
Mass Transfer ◽  
Aspect Ratio ◽  
Cross Sections ◽  
Positive Curvature ◽  
Transfer Data ◽  
Naphthalene Sublimation Technique ◽  
Smooth Channel ◽  
Naphthalene Sublimation ◽  
Curved Walls

The paper presents an experimental study of heat∕mass transfer coefficient in 4:1 aspect ratio smooth channels with nonuniform cross sections. Curved leading and trailing edges are studied for two curvatures of 9.06 m−1 (0.23 in.−1) and 15.11 m−1 (0.384 in.−1) and for two different curvature configurations. One configuration has curved walls with curvature corresponding to the blade profile (positive curvature on both leading and trailing walls) and the other configuration has leading and trailing walls that curve inward into the coolant passage (negative curvature on the leading surface and positive curvature on the trailing surface). A detailed study at Re=10,000 with rotation numbers in the range of 0–0.07 is undertaken for the two different curvature configurations. All experiments are done for a 90 deg passage orientation with respect to the plane of rotation. The experiments are conducted in a rotating two-pass coolant channel facility using the naphthalene sublimation technique. Only the radially outward flow is considered for the present study. The spanwise mass transfer distributions of fully developed regions of the channel walls are also presented. The mass transfer data from the curved wall channels are compared to those from a smooth 4:1 rectangular duct with similar flow parameters. The local mass transfer data are analyzed mainly for the fully developed region, and area-averaged results are presented to delineate the effect of the rotation number. Heat transfer enhancement especially in the leading wall is seen for the lower curvature channels, and there is a subsequent reduction in the higher curvature channel when compared to the 4:1 rectangular smooth channel. This indicates that an optimal channel wall curvature exists for which heat transfer is the highest.

scholarly journals Mass Transfer over a Film-Cooled Turbine Blade

1996 ◽  
Vol 2 (4) ◽  
pp. 221-236
Author(s):  
Ping-Hei Chen ◽  
Jr-Ming Miao
Keyword(s):  
Mass Transfer ◽  
Turbine Blade ◽  
Leading Edge ◽  
Secondary Flows ◽  
Spanwise Direction ◽  
Edge Region ◽  
Blade Surface ◽  
Naphthalene Sublimation Technique ◽  
Naphthalene Sublimation ◽  
Sublimation Technique

A naphthalene sublimation technique was employed to study the mass transfer distributions over a turbine blade surface with secondary flows ejected in the spanwise direction through three rows of equally-spaced injection holes located in the leading edge region. The mass transfer measurements were conducted in a range of blowing ratios from 0.6 to 1.2 at two different mainstream turbulence levels (0.4% and 6.0%) while keeping the exit Reynolds number,Re⁡2, at a constant value of 397,000.

Heat Transfer in Rotating Two-Pass Channel With Bleed Holes on Tip Surface

2014 ◽  
Author(s):  
Ho-Seong Sohn ◽  
Namgeon Yun ◽  
Jun Su Park ◽  
Hyung Hee Cho ◽  
Kyung Min Kim ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Mass Transfer ◽  
Mass Flow ◽  
Heat Mass Transfer ◽  
Local Heat ◽  
Hydraulic Diameter ◽  
Secondary Flows ◽  
Internal Cooling ◽  
Blade Tip ◽  
Cooling Passage

Effusion flow from a blade tip region, not only protect the blade tip directly against hot gas but also influence the cooling performance of the internal cooling passage. The present study investigated the heat/mass transfer of a rotating two-passage rectangular duct using three different types of effusion hole arrays on the internal tip surface. The duct inlet was 80 mm × 16 mm, and the hydraulic diameter was 26.67 mm. The Reynolds number, which is based on the hydraulic diameter, was 10,000. The mass flow rate of the effusion flow was 10% of the total inlet mass flow. The naphthalene sublimation method was used to determine the local heat/mass transfer coefficient. The results indicated that effusion flow enhanced the heat transfer on the tip surface: they decreased the recirculation flow and counter-rotating flow in the turning region of the internal passage. The effusion holes enhanced the local heat transfer around holes due to local secondary flows such as tripping flows. The rotating channel had a different heat transfer distribution compared to the stationary channel due to Coriolis and centrifugal forces.

Sign in / Sign up

Export Citation Format

Share Document