Optimization of Low Jet-to-Target Spacing Ratio for Double Wall Impingement Cooling Applications

2012 ◽  
Author(s):  
Sridharan Ramesh ◽  
Diganta Narzary ◽  
Srinath Ekkad
Keyword(s):  
Impingement Cooling ◽  
Spacing Ratio ◽  
Wall Impingement ◽  
Double Wall ◽  
Target Spacing

Impingement/Effusion Cooling With Low Coolant Mass Flow

2017 ◽  
Author(s):  
H. I. Oguntade ◽  
G. E. Andrews ◽  
A. D. Burns ◽  
D. B. Ingham ◽  
M. Pourkashanian
Keyword(s):  
Heat Transfer ◽  
Mass Flow ◽  
Wall Heat Transfer ◽  
Internal Wall ◽  
Cooling Effectiveness ◽  
Impingement Cooling ◽  
Impingement Heat Transfer ◽  
Design Changes ◽  
Wall Impingement ◽  
The Individual

A low coolant mass flow impingement/effusion design for a low NOx combustor wall cooling application was predicted, using conjugate heat transfer (CHT) computational fluid dynamics (CFD). The effusion geometry had 4306/m2 effusion holes in a square array with a hole diameter of D and pitch of X and X/D of 1.9. It had previously been shown experimentally and using CHT/CFD to have the highest adiabatic and overall cooling effectiveness for this number of effusion holes. The effect of adding an X/D of 4.7 impingement jet wall with a 6.6 mm impingement gap, Z, and Z/D of 2.0, on the overall cooling effectiveness was predicted for several coolant mass flow rates, G kg/sm2bar. At low G the internal wall heat transfer dominated the overall cooling effectiveness. The addition of impingement cooling to effusion cooling gave only a small increase in the overall cooling effectiveness at all G at 127mm downstream of the start of effusion cooling. An overall cooling effectiveness >0.7 was predicted for a low G of 0.30 kg/sm2bar. This represents about 15% of the combustion air for a typical industrial gas turbine combustor and design changes to reduce this further were suggested based on the predictions of this geometry. The main benefit of the impingement cooling was at the start of the effusion cooling, where the overall cooling effectiveness was dominated by the internal wall impingement and effusion cooling. The separate effusion and impingement cooling were also predicted for comparison with their combination. This showed that the combination of impingement and effusion was not the sum of the individual effusion and impingement heat transfer. The predictions showed that the aerodynamic interactions decreased the effusion and impingement internal wall heat transfer.

Effects of Effusion Cooling Pattern Near the Dilution Hole for a Double-Walled Combustor Liner: Part 2 — Flowfield Measurements

2018 ◽  
Author(s):  
Adam C. Shrager ◽  
Karen A. Thole ◽  
Dominic Mongillo
Keyword(s):  
Leading Edge ◽  
Freestream Turbulence ◽  
Gas Turbine Combustor ◽  
Impingement Cooling ◽  
Cooling Pattern ◽  
Image Velocimetry ◽  
Cooling Hole ◽  
Difficult Challenge ◽  
Combustor Liner ◽  
Double Wall

The complex flowfield inside a gas turbine combustor creates a difficult challenge in cooling the combustor walls. Many modern combustors are designed with a double-wall that contain both impingement cooling on the backside of the wall and effusion cooling on the external side of the wall. Complicating matters is the fact that these double-walls also contain large dilution holes whereby the cooling film from the effusion holes is interrupted by the high-momentum dilution jets. Given the importance of cooling the entire panel, including the metal surrounding the dilution holes, the focus of this paper is understanding the flow in the region near the dilution holes. Near-wall flowfield measurements are presented for three different effusion cooling hole patterns near the dilution hole. The effusion cooling hole patterns were varied in the region near the dilution hole and include: no effusion holes; effusion holes pointed radially outward from the dilution hole; and effusion holes pointed radially inward toward the dilution hole. Particle image velocimetry (PIV) was used to capture the time-averaged flowfield at approaching freestream turbulence intensities of 0.5% and 13%. Results showed evidence of downward motion at the leading edge of the dilution hole for all three effusion hole patterns. In comparing the three geometries, the outward effusion holes showed significantly higher velocities toward the leading edge of the dilution jet relative to the other two geometries. Although the flowfield generated by the dilution jet dominated the flow downstream, each cooling hole pattern interacted with the flowfield uniquely. Approaching freestream turbulence did not have a significant effect on the flowfield.

Conjugate Heat Transfer Characteristics of Double Wall Cooling on a Film Plate With Gradient Thickness

2020 ◽  
Author(s):  
Juan He ◽  
Qinghua Deng ◽  
Weilun Zhou ◽  
Wei He ◽  
Tieyu Gao ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Conjugate Heat Transfer ◽  
Flow Direction ◽  
Plate Thickness ◽  
Heat Transfer Characteristics ◽  
Cooling Effectiveness ◽  
Cooling Performance ◽  
Impingement Cooling ◽  
Blowing Ratio ◽  
Double Wall

Abstract Double wall cooling, consisting of internal impingement cooling and external film cooling, is an advanced cooling method of gas turbines. In this paper, the flow and conjugate heat transfer characteristics of double wall cooling which has a film plate with gradient thickness are analyzed numerically. The detailed overall cooling effectiveness distributions are obtained by solving steady three dimensional Reynolds-averaged Navier-Stokes equations. In the double wall cooling scheme, seven vertical film holes and six impingement holes are staggered with same diameter (D), and the hole pitch of them are both set to 6D in flow direction and lateral direction. The gradient thickness along the flow direction is realized by setting the angle (α) between the lower surface of the film plate and the horizontal plane at −1.5 deg and 1.5 deg respectively. By comparing the results of four broadly used turbulence models with experimental data, SST k-ω is selected as the optimal turbulence model for double wall cooling analysis in this paper. In addition, the number of grids are finally determined to be 5.2 million by grid sensitivity calculation. The influence of the thickness gradient on the overall cooling effectiveness is revealed by comparing with the constant thickness film plate (Baseline 1 and 2), and all the cases are performed under four various coolant mass flow rates, which correspond to blowing ratios ranging from 0.25 to 1.5. The calculated results show that the thickening of the film plate downstream is beneficial to improve overall cooling effectiveness at low blowing ratio, which is benefit from two aspects. One is the thicken film plate weakens the flow separation in film hole and velocity of film hole outlet, another is the thicken film plate makes the impingement channels convergence, and impingement cooling is strengthened to some extent. However, with the increase of blowing ratio, the increasing trend gradually weakens due to the jet-off and limited impinge ability. For thickening film plate, the variations of the double wall cooling configurations are considered at initial film plate thickness tf of 2D and 3D, it is found that the ability to improve the overall cooling effectiveness by thickening the film plate downstream decrease as the initial film plate thickness increases, which is due to the increase of heat transfer resistance, and another finding is the cooling effectiveness of downstream thickening film plate with initial thickness of 2D is higher than that of 3D, which will provide a theoretical foundation both for improving cooling performance and reducing turbine blade weight at the same time. The influence of initial impingement gap H is also observed, and the study come to the fact that the best cooling performance occurred in H = 2D.

Impingement Cooling by Multiple Asymmetric Orifice Jets

2021 ◽  
Author(s):  
Chunyu Zhang ◽  
Yanyan Liu ◽  
Taahir Bhaiyat ◽  
Sjouke Schekman ◽  
Tian Jian Lu ◽  
...  
Keyword(s):  
Reynolds Number ◽  
Flat Plate ◽  
Thermal Characteristics ◽  
Jet Impingement ◽  
Diameter Ratio ◽  
Impingement Cooling ◽  
Blunt Edge ◽  
Surrounding Fluid ◽  
Target Spacing

Abstract This study presents impingement cooling from a flat plate by multiple asymmetric jets. Such jets are discharged through blunt-edge inline orifice holes with a thickness-to-diameter ratio of t/Dj = 0.5 and a jet-to-jet spacing of T/Dj = 4.0, at the Reynolds number of 20,000. Firstly, fluidic features are established both in free exit and with impingement, at varying short target spacing (e.g., H/Dj = 4.0). Secondly, thermal characteristics of the jet impingement are elucidated. Results demonstrate that, due to a skewed incidence of the coolant stream upstream of concave orifice holes, the resulting multiple orifice jets are asymmetric and skewed relative to the orifice axis. These results mimic multiple fluidically inclined jets. However, asymmetric entrainment that takes place causes faster mixing with the surrounding fluid at rest as well as faster decay of momentum. This shows more effective cooling from a flat plate for the relatively short H/Dj range than conventional symmetric orifice and nozzle jets.

Heat Transfer Enhancement for Gas Turbine Blade Leading Edge Cooling Using Curved Double-Wall/Vortex Cooling With Various Disturbing Objects

2019 ◽  
Author(s):  
Xiaojun Fan ◽  
Liang Li ◽  
Jiefeng Wang ◽  
Fan Wu
Keyword(s):  
Heat Transfer ◽  
Nusselt Number ◽  
Pressure Loss ◽  
Total Pressure ◽  
Leading Edge ◽  
Total Pressure Loss ◽  
Wall Impingement ◽  
Pin Fins ◽  
Cooling Passage ◽  
Double Wall

Abstract A new double-wall cooling configuration combined with the vortex cooling is established to study the cooling behavior for the gas turbine blade leading edge. This configuration consists of multiple nozzles, a curved inner cooling passage, a row of bridge holes and a curved outer cooling passage with 4 kinds of disturbing objects (namely smooth wall, pin-fins, dimples and protrusions). Numerical simulations are performed based on the 3D viscous steady Reynolds Averaged Navier-Stokes (RANS) equations and the k-ω turbulence model. The cooling behavior of the Double-wall/vortex cooling configuration is compared with the Double-wall/impingement cooling configuration at the same conditions. Generally, the Double-wall/vortex cooling configuration has a better cooling performance. It is found the Nusselt number of the inner surface for the Double-wall/vortex cooling configuration is 46.7% higher. However, the Double-wall/impingement cooling configuration has a smaller friction coefficient and a total pressure loss. Different disturbing objects have significant influences on the heat transfer performance of the outer surface. The Nusselt number of disturbing objects (pin-fins, dimples and protrusions) is much higher than the smooth wall, and the value is 1.27–2.22 times larger. Configuration with protrusions has the highest globally-averaged Nusselt number. For the heat transfer performance of the inner surface and the total pressure loss coefficient, disturbing objects have no obvious influence. As bridge holes row increases, the overall cooling performance is improved. The globally-averaged Nusselt number of the outer target is enhanced while the total pressure loss is reduced.

Computer-Assisted Manufacturing of a Low Thermal Stress Gasturbine Inner Casing

1991 ◽  
Author(s):  
Jürgen Brinkmann ◽  
Peter Dietrich
Keyword(s):  
Gas Turbine ◽  
Design Principle ◽  
Computer Assisted ◽  
Quality Requirements ◽  
Impingement Cooling ◽  
Hot Gas ◽  
Cad Cam ◽  
Manufacturing Techniques ◽  
Important Design ◽  
Double Wall

This technical paper describes the computer-assisted manufacturing of a newly developed gas turbine inner casing designed by Siemens/KWU for hot gas temperatures up to 1350 °C. After explaining the most important design features, double wall casing with intensive impingement cooling, and details on the special materials involved, the manufacturing sequence and requisite special manufacturing techniques are described. The significant advantages and benefits of a CAD/CAM system tailored to the respective technique employed for this key aerodynamically-optimized item of a stationary gas turbine are elucidated in light of economic concerns and quality requirements and conditions imposed. In conclusion, the transferability of the design principle described in this paper and its implementation in future-oriented developments in fabrication techniques employed in the manufacture of hot-gas-path casings at even higher temperatures are discussed.

Impingement Heat Transfer Innovations and Enhancements: a Discussion on Selected Geometrical Features

2021 ◽  
Author(s):  
Sandip Dutta ◽  
Prashant Singh
Keyword(s):  
Heat Transfer ◽  
Convective Heat Transfer Coefficient ◽  
Jet Impingement ◽  
Target Surface ◽  
High Porosity ◽  
Transfer Enhancement ◽  
Impingement Cooling ◽  
Impingement Heat Transfer ◽  
Geometrical Features ◽  
Target Spacing

Abstract Impingement heat transfer is considered as one of the most effective cooling technologies that yields in high localized convective heat transfer coefficient. This paper studies different configurational parameters involved in jet impingement cooling such as, exit orifice shape, crossflow regulation, target surface modification, spent air reuse, impingement channel modification, jet pulsation, and other techniques to understand what are critical and how these heat transfer enhancement concepts work. These enhancement factors have been explored in detail by many researchers, including standard parameters such as normalized distance between adjacent jets and jet-to-target spacing, and those known benefits are not repeated here. The aim of this paper is to stimulate the current scientific knowledge of this efficient cooling technique and instill some thoughts for future innovations. New orifice shapes are becoming feasible due to 3D printing technologies. However, the orifice studies show that it is hard to beat a sharp-edged round orifice. Any attempt to streamline the hole shape indicated a drop in the Nusselt number. Reduction in crossflow has been attempted with channel modifications. Use of high porosity conductive foam in the impingement space has shown marked improvement in heat transfer performance. A list of possible research topics based on this discussion are provided in conclusion.

Effects of Effusion Cooling Pattern Near the Dilution Hole for a Double-Walled Combustor Liner—Part II: Flowfield Measurements

2018 ◽  
Vol 141 (1) ◽  
Author(s):  
Adam C. Shrager ◽  
Karen A. Thole ◽  
Dominic Mongillo
Keyword(s):  
Leading Edge ◽  
Freestream Turbulence ◽  
Gas Turbine Combustor ◽  
Impingement Cooling ◽  
Cooling Pattern ◽  
Image Velocimetry ◽  
Cooling Hole ◽  
Difficult Challenge ◽  
Combustor Liner ◽  
Double Wall

The complex flowfield inside a gas turbine combustor creates a difficult challenge in cooling the combustor walls. Many modern combustors are designed with a double-wall that contain both impingement cooling on the backside of the wall and effusion cooling on the external side of the wall. Complicating matters is the fact that these double-walls also contain large dilution holes whereby the cooling film from the effusion holes is interrupted by the high-momentum dilution jets. Given the importance of cooling the entire panel, including the metal surrounding the dilution holes, the focus of this paper is understanding the flow in the region near the dilution holes. Near-wall flowfield measurements are presented for three different effusion cooling hole patterns near the dilution hole. The effusion cooling hole patterns were varied in the region near the dilution hole and include: no effusion holes; effusion holes pointed radially outward from the dilution hole; and effusion holes pointed radially inward toward the dilution hole. Particle image velocimetry (PIV) was used to capture the time-averaged flowfield at approaching freestream turbulence intensities of 0.5% and 13%. Results showed evidence of downward motion at the leading edge of the dilution hole for all three effusion hole patterns. In comparing the three geometries, the outward effusion holes showed significantly higher velocities toward the leading edge of the dilution jet relative to the other two geometries. Although the flowfield generated by the dilution jet dominated the flow downstream, each cooling hole pattern interacted with the flowfield uniquely. Approaching freestream turbulence did not have a significant effect on the flowfield.

Considerations of a Double-Wall Cooling Design to Reduce Sand Blockage

2010 ◽  
Vol 132 (3) ◽  
Author(s):  
Camron C. Land ◽  
Chris Joe ◽  
Karen A. Thole
Keyword(s):  
Film Cooling ◽  
Turbine Engines ◽  
Gas Turbine Engines ◽  
Gas Temperature ◽  
Impingement Cooling ◽  
Large Particles ◽  
Cooling Design ◽  
Size Of Particles ◽  
Combustor Liner ◽  
Double Wall

Gas turbine engines use innovative cooling techniques to keep metal temperatures down while pushing the main gas temperature as high as possible. Cooling technologies such as film-cooling and impingement-cooling are generally used to reduce metal temperatures of the various components in the combustor and turbine sections. As cooling passages become more complicated, ingested particles can block these passages and greatly reduce the life of hot section components. This study investigates a double-walled cooling geometry with impingement- and film-cooling. A number of parameters were simulated to investigate the success of using impingement jets to reduce the size of particles in the cooling passages. Pressure ratios typically ranged between those used for combustor liner cooling and for blade outer air seal cooling whereby both these locations typically use double-walled liners. The results obtained in this study are applicable to more intricate geometries where the need to promote particle breakup exists. Results indicated that ingested sand had a large distribution of particle sizes where particles greater than 150 μm are primarily responsible for blocking the cooling passages. Results also showed that the blockage from these large particles was significantly influenced and can be significantly reduced by controlling the spacing between the film-cooling and impingement-cooling plates.

Considerations of a Double-Wall Cooling Design to Reduce Sand Blockage

2008 ◽  
Author(s):  
Camron C. Land ◽  
Karen A. Thole ◽  
Chris Joe
Keyword(s):  
Film Cooling ◽  
Turbine Engines ◽  
Gas Turbine Engines ◽  
Gas Temperature ◽  
Impingement Cooling ◽  
Large Particles ◽  
Cooling Design ◽  
Size Of Particles ◽  
Combustor Liner ◽  
Double Wall

Gas turbine engines use innovative cooling techniques to keep metal temperatures down while pushing the main gas temperature as high as possible. Cooling technologies such as film-cooling and impingement cooling are generally used to reduce metal temperatures of the various components in the combustor and turbine sections. As cooling passages become more complicated, ingested particles can block these passages and greatly reduce the life of hot section components. This study investigates a double-walled cooling geometry with impingement and film-cooling. A number of parameters were simulated to investigate the success of using impingement jets to reduce the size of particles in the cooling passages. Pressure ratios typically ranged between those used for combustor liner cooling and for blade outer air seal cooling whereby both these locations typically use double-walled liners. The results obtained in this study are applicable to more intricate geometries where the need to promote particle breakup exists. Results indicated that ingested sand had a large distribution of particle sizes where particles greater than 150 μm are primarily responsible for blocking the cooling passages. Results also showed that the blockage from these large particles was significantly influenced and can be significantly reduced by controlling the spacing between the film-cooling and impingement cooling plates.

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