Effect of Trench Width and Depth on Film Cooling From Cylindrical Holes Embedded in Trenches

2008 ◽  
Vol 131 (1) ◽  
Author(s):  
Yiping Lu ◽  
Alok Dhungel ◽  
Srinath V. Ekkad ◽  
Ronald S. Bunker
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Film Cooling ◽  
Lateral Spreading ◽  
Dynamics Simulation ◽  
Clear Understanding ◽  
Freestream Velocity ◽  
Cylindrical Holes ◽  
Trench Width

The present study is an experimental investigation of film cooling from cylindrical holes embedded in transverse trenches. Different trench depths are considered with two trench widths. Trench holes can occur when blades are coated with thermal barrier coating (TBC) layers. The film-hole performance and behavior will be different for the trench holes compared to standard cylindrical holes that are flush with the surface. The trench width and depth depend on the mask region and the thickness of the TBC layer. Detailed heat transfer coefficient and film effectiveness measurements are obtained simultaneously using a single test transient IR thermography technique. The study is performed at a single mainstream Reynolds number based on freestream velocity and film-hole diameter of 11,000 at four different coolant-to-mainstream blowing ratios of 0.5, 1.0, 1.5, and 2.0. The results show that film effectiveness is greatly enhanced by the trenching due to the improved two-dimensional nature of the film and lateral spreading. The detailed heat transfer coefficient and film effectiveness contours provide a clear understanding of the jet-mainstream interactions for different hole orientations. Computational fluid dynamics simulation using FLUENT was also performed to determine the jet-mainstream interactions to better understand the surface heat transfer coefficient and film effectiveness distributions.

Effect of Trench Width and Depth on Film Cooling From Cylindrical Holes Embedded in Trenches

2007 ◽  
Author(s):  
Yiping Lu ◽  
Alok Dhungel ◽  
Srinath V. Ekkad ◽  
Ronald S. Bunker
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Film Cooling ◽  
Cfd Simulation ◽  
Lateral Spreading ◽  
Stream Velocity ◽  
Clear Understanding ◽  
Cylindrical Holes ◽  
Trench Width

The present study is an experimental investigation of film cooling from cylindrical holes embedded in transverse trenches. Different trench depths are considered with two trench widths. Trench holes can occur when blades are coated with thermal barrier coating (TBC) layers. The film hole performance and behavior will be different for the trench holes compared to standard cylindrical holes that are flush with the surface. The trench width and depth depends on the mask region and the thickness of the TBC layer. Detailed heat transfer coefficient and film effectiveness measurements are obtained simultaneously using a single test transient IR thermography technique. The study is performed at a single mainstream Reynolds number based on free-stream velocity and film hole diameter of 11000 at four different coolant-to-mainstream blowing ratios of 0.5, 1.0, 1.5 and 2.0. The results show that film effectiveness is greatly enhanced by the trenching due to improved two dimensional nature of the film and lateral spreading. The detailed heat transfer coefficient and film effectiveness contours provide a clear understanding of the jet-mainstream interactions for different hole orientations. CFD simulation using Fluent was also performed to determine the jet mainstream interactions to better understand the surface heat transfer coefficient and film effectiveness distributions.

Trench Film Cooling: Effect of Trench Downstream Edge and Hole Spacing

2008 ◽  
Author(s):  
Yiping Lu ◽  
Srinath V. Ekkad ◽  
Ronald S. Bunker
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Film Cooling ◽  
Free Stream ◽  
Lateral Spreading ◽  
Stream Velocity ◽  
Clear Understanding ◽  
Cooling Effectiveness ◽  
Cylindrical Holes

The present study is a continuation of an experimental investigation of film cooling from cylindrical holes embedded in transverse trenches. In this study, focus is on varying the downstream edge of the trench by angling it along the flow. Different edge angles are studied for the same trench depth. Also, the effect of hole spacing is considered for one of the standard trenches from previous studies to understand the effect of trenching on overall coolant usage. Detailed heat transfer coefficient and film effectiveness measurements are obtained simultaneously using a single test transient IR thermography technique. The study is performed at a single mainstream Reynolds number based on free-stream velocity and film hole diameter of 11000 at four different coolant-to-mainstream blowing ratios of 0.5, 1.0, 1.5 and 2.0. The results show that film effectiveness is greatly enhanced by the trenching due to improved two dimensional nature of the film and lateral spreading. The detailed heat transfer coefficient and film effectiveness contours provide a clear understanding of the jet-mainstream interactions for different hole orientations. The effect of edge angling is minimal on the overall cooling effectiveness but may have an impact on jet-mainstream interaction aerodynamic losses.

Film Cooling Effectiveness and Heat Transfer of Rectangular-Shaped Film Cooling Holes

2002 ◽  
Author(s):  
Dong Ho Rhee ◽  
Youn Seok Lee ◽  
Hyung Hee Cho
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Film Cooling ◽  
Lateral Spreading ◽  
Two Dimensional ◽  
Rectangular Hole ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Cylindrical Holes

An experimental study has been conducted to measure the local film-cooling effectiveness and the heat transfer coefficient for a single row of rectangular-shaped holes. The holes have a 35° inclination angle with 3 hole diameter spacing of rectangular cross-sections. Four different cooling hole shapes such as a straight rectangular hole, a rectangular hole with laterally expanded exit, a circular hole and a two-dimensional slot are tested. The rectangular cross-section has the aspect ratio of 2 at the hole inlet with the hydraulic diameter of 10 mm. The area ratio of the exit to the hole inlet is 1.8 for the rectangular hole with expanded exit, which is similar to a two-dimensional slot. A thermochromic liquid crystals technique is applied to determine adiabatic film cooling effectiveness values and heat transfer coefficients on the test surface. Both film cooling effectiveness and heat transfer coefficient are measured for various blowing rates and compared with the results of the cylindrical holes and the two-dimensional slot. The flow patterns inside and downstream of holes are calculated numerically by a commercial package. The results show that the rectangular holes provide better performance than the cylindrical holes. For the rectangular holes with laterally expanded exit, the penetration of jet is reduced significantly, and the higher and more uniform cooling performance is obtained even at relatively high blowing rates. The reason is that the rectangular hole with expanded exit reduces momentum of coolant and promotes the lateral spreading like a two-dimensional slot.

Numerical Study on the Influence of Trench Width on Film Cooling Characteristics of Double-Wave Trench

2017 ◽  
Author(s):  
Bo-lun Zhang ◽  
Li Zhang ◽  
Hui-ren Zhu ◽  
Jian-sheng Wei ◽  
Zhong-yi Fu
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Film Cooling ◽  
Numerical Study ◽  
Leading Edge ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Blowing Ratio ◽  
Trench Width

Film cooling performance of the double-wave trench was numerically studied to improve the film cooling characteristics. Double-wave trench was formed by changing the leading edge and trailing edge of transverse trench into cosine wave. The film cooling characteristics of transverse trench and double-wave trench were numerically studied using Reynolds Averaged Navier Stokes (RANS) simulations with realizable k-ε turbulence model and enhanced wall treatment. The film cooling effectiveness and heat transfer coefficient of double-wave trench at different trench width (W = 0.8D, 1.4D, 2.1D) conditions are investigated, and the distribution of temperature field and flow field were analyzed. The results show that double-wave trench effectively improves the film cooling effectiveness and the uniformity of jet at the downstream wall of the trench. The span-wise averaged film cooling effectiveness of the double-wave trench model increases 20–63% comparing with that of the transverse trench at high blowing ratio. The anti-counter-rotating vortices which can press the film on near-wall are formed at the downstream wall of the double-wave trench. With the double-wave trench width decreasing, the film cooling effectiveness gradually reduces at the hole center-line region of the downstream trench. With the increase of the blowing ratio, the span-wise averaged heat transfer coefficient increases. The span-wise averaged heat transfer coefficient of the double-wave trench with 0.8D and 2.1D trench width is higher than that of the double-wave trench with 1.4D trench width at the high blowing ratio conditions.

Heat Transfer Measurements Downstream of Trenched Film Cooling Holes Using a Novel Optical Two-Layer Measurement Technique

2015 ◽  
Vol 138 (3) ◽  
Author(s):  
Peter Schreivogel ◽  
Michael Pfitzner
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Film Cooling ◽  
Slight Reduction ◽  
Superposition Method ◽  
Cooling Effectiveness ◽  
Cylindrical Holes ◽  
The Heat Transfer Coefficient

A new approach for steady-state heat transfer measurements is proposed. Temperature distributions are measured at the surface and a defined depth inside the wall to provide boundary conditions for a three-dimensional heat flux calculation. The practical application of the technique is demonstrated by employing a superposition method to measure heat transfer and film cooling effectiveness downstream of two different 0.75D deep narrow trench geometries and cylindrical holes. Compared to the cylindrical holes, both trench geometries lead to an augmentation of the heat transfer coefficient supposedly caused by the highly turbulent attached cooling film emanating from the trenches. Areas of high heat transfer are visible, where recirculation bubbles or large amounts of coolant are expected. Increasing the density ratio from 1.33 to 1.60 led to a slight reduction of the heat transfer coefficient and an increased cooling effectiveness. Both trenches provide a net heat flux reduction (NHFR) superior to that of cylindrical holes, especially at the highest momentum flux ratios.

EXPERIMENTAL INVESTIGATION ON COOLING PERFORMANCE OF IMPINGEMENT-EFFUSION FULL COVERAGE FILM ON SUCTION SURFACE OF A VANE

2021 ◽  
pp. 1-28
Author(s):  
Fan Zhang ◽  
Cun Liang Liu ◽  
Lin Ye ◽  
Bingran Li ◽  
Shuaiqi Zhang
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Film Cooling ◽  
Net Benefit ◽  
Suction Surface ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Cylindrical Holes ◽  
The Heat Transfer Coefficient

Abstract This research experimentally investigated the net benefit of film cooling with 6 rows of impingement-effusion structures on the suction surface of a vane. The experiment obtained the film cooling effectiveness of double-walled system on the suction surface via the pressure-sensitive paint (PSP) technique. The film cooling effectiveness obtained by the PSP technique is coupled with the transient liquid crystal (TLC) technique to determine the heat transfer coefficient. This combination of techniques reduces the time required for the experiment and improves the efficiency of the experiment. Through the experimentally measured film cooling effectiveness and dimensionless heat transfer coefficient, the net heat flux reduction (NHFR) is calculated to comprehensively measure the net benefit of film cooling. At the same time, in view of the lower net benefit of film cooling of the film holes in the front of the suction surface under higher mass flux ratio, the study improved the cylindrical holes into fan-shaped holes, and proposed two improvement schemes: Vane A and Vane B. The findings show that using the coupling of PSP and TLC to determine the heat transfer coefficient can yield credible results. The improvement of the fan-shaped holes makes the film cooling effectiveness and heat transfer coefficient ratio improved compared with the baseline vane. Changing cylindrical holes to fan-shaped holes does not necessarily lead to better net benefit of film cooling. The fan-shaped holes should be arranged reasonably to obtain better net benefit of film cooling.

Film Cooling Characteristic of Double-Fan-Shaped Film Cooling Holes

2009 ◽  
Author(s):  
Jiang-Tao Bai ◽  
Hui-ren Zhu ◽  
Cun-liang Liu
Keyword(s):  
Heat Transfer ◽  
Numerical Simulation ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Film Cooling ◽  
Diameter Ratio ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Cylindrical Holes ◽  
Film Cooling Holes

The film cooling performance downstream of a single row of double-fan-shaped film cooling holes in a flat plate have been investigated by experimental measurements and numerical simulation. The entrance and exit of double-fan-shaped holes are comprised of a lateral expansion of 15° from the original simple cylindrical shape with stream-wise inclination of 45°. The width of the exit face to cylinder diameter ratio is 1.5; the length-to-diameter ratio is 4.24 and the pitch-to-diameter ratio is 3. The experimental method used to obtain the adiabatic film cooling effectiveness values and the heat transfer coefficient is a transient narrow band liquid crystal technique. Both film cooling effectiveness and heat transfer coefficient are measured at three momentum ratios (I = 0.5, 1, 2) at constant Reynolds number (Re = 10000) and free stream turbulence (Tu = 2%). The film cooling effectiveness, heat transfer coefficient and Net Heat Flux Reduction (NHFR) are presented for detailed distribution and span-wise averaged values. Discharge coefficients are also measured in the experiment. A commercial package is used to numerically simulate the flow and heat transfer of double-fan-shaped holes; simple cylindrical holes are also simulated for comparison. Numerical simulation use RNG turbulence model with a standard wall function for near wall region. Experimental and Numerical simulation results show that: 1) the double-fan-shaped holes present higher discharge coefficient than simple cylindrical holes at respective momentum ratio; 2) the numerical simulation film cooling effectiveness results of double-fan-shaped holes accord well with the experimental results; 3) at measured three momentum ratios, the double-fan-shaped holes demonstrate better film cooling performance (higher NHFR) than simple cylindrical holes, better film cooling expansion on span-wise; 4) the best momentum ratio of double-fan-shaped holes is 0.5.

Film Cooling Measurements for Cratered Cylindrical Inclined Holes

2008 ◽  
Vol 131 (1) ◽  
Author(s):  
Yiping Lu ◽  
Alok Dhungel ◽  
Srinath V. Ekkad ◽  
Ronald S. Bunker
Keyword(s):  
Heat Transfer ◽  
Thermal Barrier Coating ◽  
Film Cooling ◽  
Dynamics Simulation ◽  
Thermal Barrier ◽  
Base Line ◽  
Freestream Velocity ◽  
Film Cooling Effectiveness ◽  
Barrier Coating ◽  
Cylindrical Holes

Film cooling performance is studied for cylindrical holes embedded in craters. Different crater geometries are considered for a typical crater depth. Cratered holes may occur when blades are coated with thermal barrier coating layers by masking the hole area during thermal barrier coating (TBC) spraying, resulting in a hole surrounded by a TBC layer. The film performance and behavior is expected to be different for the cratered holes compared to standard cylindrical holes. Detailed heat transfer coefficient and film effectiveness measurements are obtained simultaneously using a single test transient IR thermography technique. The study is performed at a single mainstream Reynolds number based on freestream velocity and film-hole diameter of 11,000 at four different coolant-to-mainstream blowing ratios of 0.5, 1.0, 1.5, and 2.0. The results show that film cooling effectiveness is slightly enhanced by cratering of holes, but a substantial increase in heat transfer enhancement negates the benefits of higher film effectiveness. Three different crater geometries are studied and compared to a base line flush cylindrical hole, a trenched hole, and a typical diffuser shaped hole. Computational fluid dynamics simulation using FLUENT was also performed to determine the jet-mainstream interactions associated with the experimental surface measurements.

Film Cooling From a Row of Holes Embedded in Transverse Slots

2005 ◽  
Author(s):  
Yiping Lu ◽  
Hasan Nasir ◽  
Srinath V. Ekkad
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Film Cooling ◽  
Flux Ratio ◽  
Stream Velocity ◽  
Cooling Performance ◽  
Cylindrical Holes ◽  
Film Cooling Holes

Film cooling performance for a row of cylindrical holes can be enhanced by embedding the row in transverse slots. The geometry of the transverse slot greatly affects the cooling performance downstream of injection. The effect of the slot exit area and edge shape is investigated. Detailed heat transfer coefficient and film effectiveness measurements are obtained simultaneously using a single test transient IR thermography technique. The study is performed at a single mainstream Reynolds number based on free-stream velocity and film hole diameter of 7150 at three different coolant-to-mainstream blowing ratios of 0.5, 1.0, and 1.5. The results show that the film cooling holes provide higher film effectiveness when embedded in a slot. However, in some geometries when the slot begins at the upstream edge of the hole, the film effectiveness diminishes. The heat transfer coefficient enhancement due to the embedding is not significantly higher compared to the typical unembedded cylindrical hole. The overall heat flux ratio comparing film cooling with embedded holes to unembedded holes shows that the full slot and downstream slot spacing after the hole exit produce the highest heat flux reduction. The holes-in-slot geometry is certainly very promising.

Turbine Shroud Heat Transfer and Cooling With Blade Rotation: Part I — Forward, Backward and Lateral Injection

2017 ◽  
Author(s):  
Onieluan Tamunobere ◽  
Sumanta Acharya
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Film Cooling ◽  
Lateral Spreading ◽  
Film Cooling Effectiveness ◽  
Blade Rotation ◽  
Cooling Behavior ◽  
Injection Methods ◽  
The Heat Transfer Coefficient

This is the first in a two-part series of an experimental film cooling study on a gas turbine shroud with a blade rotation speed of 1200 RPM. In this part of the study, the effect of forward, backward and lateral injection on the shroud heat transfer and cooling behavior is investigated. The shroud with a staggered hole arrangement and a hole pitch to diameter ratio of 4.0, consists of holes angled at 45° to the surface. Four hole configurations using inline and lateral coolant injection methods are utilized in this study. The first configuration consists of streamwise and forward facing holes inclined at 45 degrees to the surface (ϕ = 0°). The second configuration consists of backward facing holes also inclined at 45 degrees to the surface (ϕ = 180°). The third and fourth configurations consist of lateral injection with a surface angle of 45 degrees in the direction of blade rotation (ϕ = 90°) and opposite the direction of blade rotation (ϕ = 270°), respectively. The heat transfer coefficient is reported for the no-coolant case and measurements of the heat transfer coefficient and film cooling effectiveness are reported for each configuration at nominal blowing ratios of 0.5, 1.0, 1.5 and 2.0 using liquid crystal thermography. The results show that in-line injection performs better than lateral injection at low blowing ratios and the reverse is true at higher blowing ratios. Backward injection does show higher laterally averaged effectiveness with increased spreading in the vicinity of the coolant holes than forward injection. With a compact coolant hole arrangement, this results in higher area averaged effectiveness for backward injection than forward injection. With increased lateral spreading of the coolant in the hole region, lateral injection results in higher peak effectiveness values than inline injection. Nevertheless, lateral injection does not have the axial penetration of inline injection and as such leaves regions of the shroud downstream of the coolant holes vulnerable.

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