Heat Transfer Coefficient Augmentation for a Shaped Film Cooling Hole at a Range of Compound Angles

2020 ◽  
pp. 1-30
Author(s):  
Shane Haydt ◽  
Stephen Lynch
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Film Cooling ◽  
Constant Heat Flux ◽  
Cooling Hole ◽  
Adiabatic Effectiveness ◽  
Compound Angle ◽  
The Heat Transfer Coefficient

Abstract Film cooling holes with shaped diffusers are used to efficiently deliver coolant to the surface of a gas turbine part to keep metal temperatures low. Reducing the heat flux into a component, relative to a case with no coolant injection, is the ultimate goal of film cooling. This reduction in heat flux is primarily achieved via a lower driving temperature at the wall for convection, represented by the adiabatic effectiveness. Another important consideration, however, is how the disturbance to the flowfield and thermal field caused by the injection of coolant augments the heat transfer coefficient. The present study examines the spatially-resolved heat transfer coefficient augmentation, measured using a constant heat flux foil and IR thermography, for a shaped film cooling hole at a range of compound angles. Results show that the heat transfer coefficient increases with compound angle and with blowing ratio. Due to the unique asymmetric flowfield of a compound angle hole, a significant amount of augmentation occurs to the side of the film cooling jet, where very little coolant is present. This causes local regions of increased heat flux, which is counter to the goal of film cooling. Heat transfer results are compared with adiabatic effectiveness and flowfield measurements from a previous study.

Heat Transfer Coefficient Augmentation for a Shaped Film Cooling Hole at a Range of Compound Angles

2019 ◽  
Author(s):  
Shane Haydt ◽  
Stephen Lynch
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Film Cooling ◽  
Constant Heat Flux ◽  
Cooling Hole ◽  
Adiabatic Effectiveness ◽  
Compound Angle ◽  
The Heat Transfer Coefficient

Abstract Shaped film cooling holes are used to efficiently deliver coolant to the surface of a gas turbine part to keep metal temperatures low. The ultimate goal of film cooling is to reduce the heat flux into a component, relative to a case with no coolant injection. This reduction in heat flux is primarily achieved via a lower driving temperature at the wall for convection, represented by the adiabatic effectiveness. Another important consideration, however, is how the disturbance to the flowfield and thermal field caused by the injection of coolant augments the heat transfer coefficient. The present study examines the spatially-resolved heat transfer coefficient augmentation for a shaped film cooling hole at a range of compound angles, using a constant heat flux foil and IR thermography. Results show that the heat transfer coefficient increases with compound angle and with blowing ratio. Due to the unique asymmetric flowfield of a compound angle hole, a significant amount of augmentation occurs to the side of the film cooling jet, where very little coolant is present. This causes local regions of increased heat flux, which is counter to the goal of film cooling. Heat transfer results are compared with adiabatic effectiveness and flowfield measurements from a previous study.

Film Cooling Heat Transfer: Shaped and Compound Angle Hole Injection

1998 ◽  
Author(s):  
David J. Seager ◽  
James A. Liburdy
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Film Cooling ◽  
Density Ratio ◽  
Diameter Ratio ◽  
Hole Shaping ◽  
Adiabatic Effectiveness ◽  
Compound Angle ◽  
The Heat Transfer Coefficient

To further understand the effect of compound angle holes and hole shaping on film cooling, detailed heat transfer measurements were obtained using a hue based thermochromic liquid crystal method. This technique is fully described based on its development for film cooling applications. The data were analyzed to determine both the full surface adiabatic effectiveness and the heat transfer coefficient. The compound angles that are presented consist of holes aligned at 0° (streamwise) and 45° to the main cross flow direction. Hole shaping variations from the traditional cylindrically shaped hole include forward diffused and laterally diffused hole configurations. The length to diameter ratio (L/D) was 4.0, the pitch to diameter ratio (P/D) was 3.0, and the inclination angle (α) was 35°. A density ratio (DR) of 1.55 was obtained for all tests using carbon dioxide as the injection fluid into an air stream. For each set of conditions the blowing ratio (M) was varied to be 0.88, 1.25, and 1.88. Adiabatic effectiveness was obtained using a steady state test, while an active heating surface (constant, uniform heat flux) was used to determine the heat transfer coefficient using a transient method.

Freestream Flow Effects on Film Effectiveness and Heat Transfer Coefficient Augmentation for Compound Angle Shaped Holes

2017 ◽  
Author(s):  
Joshua B. Anderson ◽  
John W. McClintic ◽  
David G. Bogard ◽  
Thomas E. Dyson ◽  
Zachary Webster
Keyword(s):  
Heat Transfer ◽  
Boundary Layer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Layer Thickness ◽  
Film Cooling ◽  
Gas Turbines ◽  
Boundary Layer Thickness ◽  
Adiabatic Effectiveness ◽  
Compound Angle

The use of compound-angled shaped film cooling holes in gas turbines provides a method for cooling regions of extreme curvature on turbine blades or vanes. These configurations have received surprisingly little attention in the film cooling literature. In this study, a row of laid-back fanshaped holes based on an open-literature design, were oriented at a 45-degree compound angle to the approaching freestream flow. In this study, the influence of the approach flow boundary layer thickness and character were experimentally investigated. A trip wire and turbulence generator were used to vary the boundary layer thickness and freestream conditions from a thin laminar boundary layer flow to a fully turbulent boundary layer and freestream at the hole breakout location. Steady-state adiabatic effectiveness and heat transfer coefficient augmentation were measured using high-resolution IR thermography, which allowed the use of an elevated density ratio of DR = 1.20. The results show adiabatic effectiveness was generally lower than for axially-oriented holes of the same geometry, and that boundary layer thickness was an important parameter in predicting effectiveness of the holes. Heat transfer coefficient augmentation was highly dependent on the freestream turbulence levels as well as boundary layer thickness, and significant spatial variations were observed.

A Novel Antivortex Turbine Film-Cooling Hole Concept

2008 ◽  
Vol 130 (3) ◽  
Author(s):  
James D. Heidmann ◽  
Srinath Ekkad
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Film Cooling ◽  
Circular Cross Section ◽  
Round Hole ◽  
Net Heat Flux ◽  
Cooling Hole ◽  
Film Cooling Holes

A novel turbine film-cooling hole shape has been conceived and designed at NASA Glenn Research Center. This “antivortex” design is unique in that it requires only easily machinable round holes, unlike shaped film-cooling holes and other advanced concepts. The hole design is intended to counteract the detrimental vorticity associated with standard circular cross-section film-cooling holes. This vorticity typically entrains hot freestream gas and is associated with jet separation from the turbine blade surface. The antivortex film-cooling hole concept has been modeled computationally for a single row of 30 deg angled holes on a flat surface using the 3D Navier–Stokes solver GLENN-HT. A blowing ratio of 1.0 and density ratios of 1.05 and 2.0 are studied. Both film effectiveness and heat transfer coefficient values are computed and compared to standard round hole cases for the same blowing rates. A net heat flux reduction is also determined using both the film effectiveness and heat transfer coefficient values to ascertain the overall effectiveness of the concept. An improvement in film effectiveness of about 0.2 and in net heat flux reduction of about 0.2 is demonstrated for the antivortex concept compared to the standard round hole for both blowing ratios. Detailed flow visualization shows that as expected, the design counteracts the detrimental vorticity of the round hole flow, allowing it to remain attached to the surface.

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.

Film Cooling With Compound Angle Holes: Heat Transfer

1994 ◽  
Author(s):  
Basav Sen ◽  
Donald L. Schmidt ◽  
David G. Bogard
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Film Cooling ◽  
Momentum Flux ◽  
High Momentum ◽  
Transfer Rates ◽  
Compound Angle ◽  
Large Compound ◽  
The Heat Transfer Coefficient

Heat transfer coefficients have been measured for film cooling injection from a single row of holes laterally directed with a compound angle of 60°. Two hole configurations were tested, round holes and holes with a diffusing expansion at the exit. Streamwise directed round holes were also tested as a basis for comparison. All the holes were inclined at 35° with respect to the surface. The density ratio was 1.0, momentum flux ratios ranged from I = 0.16 to 3.9 and mass flux ratios from M = 0.4 to 2.0. Results are presented in terms of hf/h0, the ratio of film cooling heat transfer coefficient to the heat transfer coefficient for the undisturbed turbulent boundary layer at the same location. Results indicate that for the streamwise directed holes, the heat transfer rates are close to the levels that exist without injection. Similarly, at low momentum flux ratio, holes with a large compound angle had little effect on heat transfer rates. But at high momentum flux ratios, holes with a large compound angle had significantly increased heat transfer levels. The results were combined with adiabatic effectiveness results to evaluate the overall performance of the three geometries. It is shown that for evaluation of film cooling performance with compound angle injection, especially at high momentum flux ratios, it is critical to know the heat transfer coefficient, as the adiabatic effectiveness alone does not determine the performance. Compound angle injection at high momentum flux ratios gives higher effectiveness values than streamwise directed holes, but the higher heat transfer levels result in poorer overall performance.

Heat Flux Reduction From Film Cooling and Correlation of Heat Transfer Coefficients From Thermographic Measurements at Engine Like Conditions

2002 ◽  
Author(s):  
S. Baldauf ◽  
M. Scheurlen ◽  
A. Schulz ◽  
S. Wittig
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Film Cooling ◽  
Transfer Coefficients ◽  
Average Heat ◽  
Heat Transfer Coefficients ◽  
New Correlation ◽  
The Heat Transfer Coefficient

Heat transfer coefficients and the resulting heat flux reduction due to film cooling on a flat plate downstream a row of cylindrical holes are investigated. Highly resolved two dimensional heat transfer coefficient distributions were measured by means of infrared thermography and carefully corrected for local internal testplate conduction and radiation effects [1]. These locally acquired data are processed to lateral average heat transfer coefficients for a quantitative assessment. A wide range variation of the flow parameters blowing rate and density ratio as well as the geometrical parameters streamwise ejection angle and hole spacing is examined. The effects of these dominating parameters on the heat transfer augmentation from film cooling are discussed and interpreted with the help of highly resolved surface results of effectiveness and heat transfer coefficients presented earlier [2]. A new method of evaluating the heat flux reduction from film cooling is presented. From a combination of the lateral average of both the adiabatic effectiveness and the heat transfer coefficient, the lateral average heat flux reduction is processed according to the new method. The discussion of the total effect of film cooling by means of the heat flux reduction reveals important characteristics and constraints of discrete hole ejection. The complete heat transfer data of all measurements are used as basis for a new correlation of lateral average heat transfer coefficients. This correlation combines the effects of all the dominating parameters. It yields a prediction of the heat transfer coefficient from the ejection position to far downstream, including effects of extreme blowing angles and hole spacing. The new correlation has a modular structure to allow for future inclusion of additional parameters. Together with the correlation of the adiabatic effectiveness it provides an immediate determination of the streamwise heat flux reduction distribution of cylindrical hole film cooling configurations.

A Novel Anti-Vortex Turbine Film Cooling Hole Concept

2007 ◽  
Author(s):  
James D. Heidmann ◽  
Srinath Ekkad
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Film Cooling ◽  
Circular Cross Section ◽  
Round Hole ◽  
Net Heat Flux ◽  
Cooling Hole ◽  
Film Cooling Holes

A novel turbine film cooling hole shape has been conceived and designed at NASA Glenn Research Center. This “anti-vortex” design is unique in that it requires only easily machinable round holes, unlike shaped film cooling holes and other advanced concepts. The hole design is intended to counteract the detrimental vorticity associated with standard circular cross-section film cooling holes. This vorticity typically entrains hot freestream gas and is associated with jet separation from the turbine blade surface. The anti-vortex film cooling hole concept has been modeled computationally for a single row of 30 degree angled holes on a flat surface using the 3D Navier-Stokes solver Glenn-HT. A blowing ratio of 1.0 and density ratios of 1.05 and 2.0 are studied. Both film effectiveness and heat transfer coefficient values are computed and compared to standard round hole cases for the same blowing rates. A net heat flux reduction is also determined using both the film effectiveness and heat transfer coefficient values to ascertain the overall effectiveness of the concept. An improvement in film effectiveness of about 0.2 and in net heat flux reduction of about 0.2 is demonstrated for the anti-vortex concept compared to the standard round hole for both blowing ratios. Detailed flow visualization shows that as expected, the design counteracts the detrimental vorticity of the round hole flow, allowing it to remain attached to the surface.

An Empirical Study on Heat Transfer Characteristics of CuO/Base Oil Nanofluid Flow in a Tube With Coiled Wire Inserts

2010 ◽  
Author(s):  
M. A. Akhavan-Behabadi ◽  
M. Saeedinia ◽  
S. M. Hashemi
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Constant Heat Flux ◽  
Wire Diameter ◽  
Heat Transfer Characteristics ◽  
Nanofluid Flow ◽  
Base Oil ◽  
The Heat Transfer Coefficient

In the present study, an experimental investigation has been carried out to study the heat transfer characteristics of CuO/Base oil nanofluid flow inside horizontal oiled wire inserted tubes (roughed tubes) under constant heat flux. The nanofluids with CuO nanoparticles weight fraction ranging from 0 to 2% are prepared. The oiled wires with different wire wire diameteres and different oil pitches are used as inserts inside a horizontal plain copper tube. The nanofluid flowing inside the tube is heated by electrical heating coil wrapped around it. The convective heat transfer characteristis of the prepared nanofluids are measured during laminar fully developed flow inside horizontal plain and roughed tubes under constant heat flux. The effect of different parameters such as mass velocity, wire wire diameter, oil pith, nanofluid particles concentration and heat flux on heat transfer coefficient is studied. The heat transfer coefficient is increased when a roughed tube is used instead of a plain tube. Moreover, at the same flow conditions, by increasing of wire wire diameter and decreasing of oil pitch, the heat transfer performance is improved. Observations also show that by using nanofluid instead of base fluid, the heat transfer coefficient increases and this increase grows at higher nanoparticles concentrations. As a result, it an be concluded that increasing of wire wire diameter, decreasing of oil pitch and increasing the concentration of nanoparticle, contribute to the enhancement of heat transfer coefficient.

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