Enhancement of Impingement Cooling in a High Cross Flow Channel Using Shaped Impingement Cooling Holes

2006 ◽  
Author(s):  
Andrew C. Chambers ◽  
David R. H. Gillespie ◽  
Peter T. Ireland ◽  
Mark Mitchell
Keyword(s):  
Heat Transfer ◽  
Nusselt Number ◽  
Cross Flow ◽  
Target Surface ◽  
Impingement Cooling ◽  
Turbine Cooling ◽  
Impingement Jet ◽  
Coefficient Distribution ◽  
Cooling Passage ◽  
Experimental Rig

Impingement systems are common place in many turbine cooling applications. Generally these systems consist of a target plate that is cooled by the impingement of multiple orthogonal jets. While it is possible to achieve high target surface heat transfer with this configuration, the associated pressure drop is generally high and the cooling efficiency low. Furthermore, especially in large impingement arrays, the build-up of cross flow from upstream jets can be significant and result in deflection of downstream impingement jets reducing the resultant heat transfer coefficient distribution. This paper presents a computational and experimental investigation into the use of shaped elliptical or elongated circular impingement holes designed to improve the penetration of the impinging jet across the coolant passage. This is of particular interest where there is significant cross flow. Literature review and computational investigations are used to determine the optimum aspect ratio of the impingement jet. The improved heat transfer performance of the modified design is then tested in an experimental rig with varying degrees of cross flow at engine representative conditions. In all cases a 16% increase in the Nusselt number on the impingement target surface in the downstream half of the cooling passage was achieved. Under the first 4 impingement holes Nusselt number enhancement of enhancement of 28–77% was achieved provided no additional cross flow was present in the passage. When appropriately aligned, a significant reduction in the stress concentration factor caused by the addition of a hole can be achieved using this design.

Enhancement of Impingement Cooling in a High Cross Flow Channel Using Shaped Impingement Cooling Holes

2009 ◽  
Vol 132 (2) ◽  
Author(s):  
Andrew C. Chambers ◽  
David R. H. Gillespie ◽  
Peter T. Ireland ◽  
Robert Kingston
Keyword(s):  
Heat Transfer ◽  
Nusselt Number ◽  
Cross Flow ◽  
Target Surface ◽  
Impingement Cooling ◽  
Turbine Cooling ◽  
Impingement Jet ◽  
Coefficient Distribution ◽  
Cooling Passage ◽  
Experimental Rig

Impingement systems are common place in many turbine cooling applications. Generally these systems consist of a target plate that is cooled by the impingement of multiple orthogonal jets. While it is possible to achieve high target surface heat transfer with this configuration, the associated pressure drop is generally high and the cooling efficiency low. Furthermore, especially in large impingement arrays, the buildup of cross flow from upstream jets can be significant and results in deflection of downstream impingement jets reducing the resultant heat transfer coefficient distribution. This paper presents a computational and experimental investigation into the use of shaped elliptical or elongated circular impingement holes designed to improve the penetration of the impinging jet across the coolant passage. This is of particular interest where there is significant cross flow. Literature review and computational investigations are used to determine the optimum aspect ratio of the impingement jet. The improved heat transfer performance of the modified design is then tested in an experimental rig with varying degrees of cross flow at engine representative conditions. In all cases, a 16% increase in the Nusselt number on the impingement target surface in the downstream half of the cooling passage was achieved. Under the first four impingement holes, a Nusselt number enhancement of 28–77% was achieved, provided no additional cross flow was present in the passage. When appropriately aligned, a significant reduction in the stress concentration factor caused by the addition of a hole can be achieved using this design.

Effects of Extended Jet Holes to Heat Transfer and Flow Characteristics of the Jet Impingement Cooling

2019 ◽  
Vol 141 (8) ◽  
Author(s):  
Ahmet Ümit Tepe ◽  
Kamil Arslan ◽  
Yaşar Yetişken ◽  
Ünal Uysal
Keyword(s):  
Heat Transfer ◽  
Nusselt Number ◽  
Average Nusselt Number ◽  
Flat Surface ◽  
Flow Characteristics ◽  
Cross Flow ◽  
Jet Impingement ◽  
Target Surface ◽  
Impingement Cooling ◽  
Compressor Power

In this study, effects of extended jet holes to heat transfer and flow characteristics of jet impingement cooling were numerically investigated. Cross-flow in the impinging jet cooling adversely affects the heat transfer on the target surface. The main purpose of this study is to reduce the negative effect of cross-flow on heat transfer by extending jet holes toward the target surface with nozzles. This study has been conducted under turbulent flow condition (15,000 ≤ Re  ≤  45,000). The surface of the turbine blade, which is the target surface, has been modeled as a flat plate. The effect of the ribs, placed on the target surface, on the heat transfer has been also investigated, and the results were compared with the flat surface. The parameters such as average and local Nusselt numbers on the target surface, flow characteristics, and compressor power have been examined in detail. It was obtained from the numerical results that the average Nusselt number increases with decreasing the gap between the target surface and the nozzle. In addition, the higher average Nusselt number was obtained on the flat surface than the ribbed surface. The lowest compressor power was achieved in the 5Dj nozzle gap for the flat surface and in the 4Dj nozzle gap for the ribbed surface.

Experimental and Numerical Study of Jet Impingement Cooling for Improved Gas Turbine Blade Internal Cooling With In-Line and Staggered Nozzle Arrays

2020 ◽  
Vol 143 (1) ◽  
Author(s):  
Abdel Rahman Salem ◽  
Farah Nazifa Nourin ◽  
Mohammed Abousabae ◽  
Ryoichi S. Amano
Keyword(s):  
Heat Transfer ◽  
Nusselt Number ◽  
Gas Turbine ◽  
Numerical Study ◽  
Turbine Blades ◽  
Jet Impingement ◽  
Target Surface ◽  
Internal Cooling ◽  
Impingement Cooling ◽  
Gas Turbine Blades

Abstract Internal cooling of gas turbine blades is performed with the combination of impingement cooling and serpentine channels. Besides gas turbine blades, the other turbine components such as turbine guide vanes, rotor disks, and combustor wall can be cooled using jet impingement cooling. This study is focused on jet impingement cooling, in order to optimize the coolant flow, and provide the maximum amount of cooling using the minimum amount of coolant. The study compares between different nozzle configurations (in-line and staggered), two different Reynold's numbers (1500 and 2000), and different stand-off distances (Z/D) both experimentally and numerically. The Z/D considered are 3, 5, and 8. In jet impingement cooling, the jet of fluid strikes perpendicular to the target surface to be cooled with high velocity to dissipate the heat. The target surface is heated up by a direct current (DC) power source. The experimental results are obtained by means of thermal image processing of the captured infra-red (IR) thermal images of the target surface. Computational fluid dynamics (CFD) analysis were employed to predict the complex heat transfer and flow phenomena, primarily the line-averaged and area-averaged Nusselt number and the cross-flow effects. In the current investigation, the flow is confined along with the nozzle plate and two parallel surfaces forming a bi-directional channel (bi-directional exit). The results show a comparison between heat transfer enhancement with in-line and staggered nozzle arrays. It is observed that the peaks of the line-averaged Nusselt number (Nu) become less as the stand-off distance (Z/D) increases. It is also observed that the fluctuations in the stagnation heat transfer are caused by the impingement of the primary vortices originating from the jet nozzle exit.

High-Fidelity Simulations of Multi-Jet Impingement Cooling Flows

2020 ◽  
Author(s):  
J. Javier Otero-Pérez ◽  
Richard D. Sandberg ◽  
Satoshi Mizukami ◽  
Koichi Tanimoto
Keyword(s):  
Heat Transfer ◽  
Nusselt Number ◽  
Cross Flow ◽  
Distance Effect ◽  
Jet Impingement ◽  
Impingement Cooling ◽  
Cooling Flows ◽  
Turbulent Inflow ◽  
The Cross ◽  
Flow Effects

Abstract This article shows the first parametric study on turbulent multi-jet impingement cooling flows using large-eddy simulations (LES). We focus on assessing the influence of the inter-jet distance and the cross-flow conditions on the heat transfer at the impingement wall. The LES setup is thoroughly validated with both experimental and direct numerical simulation data, showing an excellent agreement. The inter-jet distance effect on the heat transfer is studied comparing three different distances, where the full Nusselt number profile decreases in amplitude when the jet distance is increased. To evaluate the cross-flow effects, we prescribe both laminar and turbulent inflow conditions at different cross-flow magnitudes ranging between 20% and 40% of the impinging jet speed. Large cross-flow intensities cause a jet deflection which reduces the maxima in the Nusselt number distribution, and it increases the heat transfer in the areas of the wall less affected by the jet impingement. Adding realistic turbulent fluctuations to the inflow enhances the cross-flow effects on the heat transfer at the impingement wall.

Effects of Jet Diameter and Surface Roughness on Internal Cooling With Single Array of Jets

2013 ◽  
Author(s):  
Nicholas Miller ◽  
Sin Chien Siw ◽  
Minking K. Chyu ◽  
Mary Anne Alvin
Keyword(s):  
Heat Transfer ◽  
Surface Roughness ◽  
Cross Flow ◽  
Jet Impingement ◽  
Target Surface ◽  
Internal Cooling ◽  
Target Plate ◽  
Surface Features ◽  
Coefficient Distribution ◽  
Rib Turbulators

The current study focused on the effects of varying jet diameter and surface roughness on the target plate from jet impingement. A single row of five jets, plenum fed, expels air onto the flat target surface and the spent air is constrained to exit in only one direction, causing the jets to encounter maximum cross-flow. Baseline jet plates were equipped with pressure taps, one for each jet, to determine flow. The initial parameters, diameter D, height to diameter H/D, and jet spacing to diameter S/D is 9.53 mm (0.375 in), 2 and 4 respectively. Upon defining the optimum array of jet diameters, three test cases will be conducted using different surface features, 90 degree ribs, chevrons and X-shaped ribs on the target plate to further enhance the heat transfer performance of the jet impingement. The parameters, width W and height H, for the surface features will be set constant at 3.18 mm (0.125 in). The Reynolds number, Re, in this experimental study ranged from 50,000 to 80,000. A transient liquid crystal technique is employed in this study to determine the local and average heat transfer coefficient distribution on the target plate. The baseline tests revealed that the heat transfer is more predominate in the upstream jets impingement zones, however, by varying the diameters the heat transfer is more uniformly distributed downstream. The results also revealed that the rib-turbulators, especially X-shaped ribs, can further enhance heat transfer enhancement in the downstream jets where crossflow can affect impingement.

Influences of Target Surface Roughness on Impingement Jet Array Heat Transfer: Part 2 — Effects of Roughness Shape, and Reynolds Number

2016 ◽  
Author(s):  
W. Buzzard ◽  
Z. Ren ◽  
P. M. Ligrani ◽  
C. Nakamata ◽  
S. Ueguchi
Keyword(s):  
Heat Transfer ◽  
Surface Roughness ◽  
Reynolds Number ◽  
Target Surface ◽  
Impingement Cooling ◽  
Impingement Jet ◽  
Heat Transfer Augmentation ◽  
Small Triangle ◽  
Roughness Elements ◽  
Jet Array

The present investigation considers the effects of special roughness patterns on impingement target surfaces to improve the effectiveness and surface heat transfer augmentation levels of impingement jet array cooling. This investigation utilizes various sizes, distributions, shapes, and patterns of surface roughness elements for impingement cooling augmentation. The surface roughness shapes considered here are rectangle and triangle, in combination with larger rectangular pins. Configurations considered include: (i) arrays of small rectangular roughness, (ii) arrays of small triangle roughness, (iii) combinations of small rectangle roughness and large pins together, and (iv) combinations of small triangle roughness and large pins together. Tests are performed at impingement jet Reynolds numbers of 900, 1500, 5000, and 11000. Local and overall impingement cooling performance depends upon the shape of the roughness elements, as well as upon the jet Reynolds number. Depending upon the magnitude of jet Reynolds number, different behavior and trends are observed for the arrays of small rectangle roughness, compared with arrays of small triangle roughness. These differences are related to the abilities of the two different roughness shapes to generate different distributions of local mixing and vorticity at different length and time scales. Overall, results demonstrate the remarkable ability of target surface roughness to produce increased surface heat transfer augmentation levels of impingement jet array cooling, relative to target surfaces which are smooth.

CHT/CFD Predictions of Impingement Cooling With Four Sided Flow Exit

2015 ◽  
Author(s):  
Abubakar M. El-Jummah ◽  
Gordon E. Andrews ◽  
John E. J. Staggs
Keyword(s):  
Heat Transfer ◽  
Cross Flow ◽  
Hole Density ◽  
Ansys Fluent ◽  
Impingement Cooling ◽  
Impingement Jet ◽  
Recirculating Flow ◽  
Target Wall ◽  
Computational Fluid Dynamics Cfd ◽  
Square Array

Impingement/effusion cooling has no cross-flow in the impingement gap if all the coolant flow through the impingement wall passes through the effusion wall. In this investigation, the impingement part of the impingement/effusion cooling was investigated by minimising the cross-flow using a four sided exit impingement cooling geometry. The impingement geometry investigated was a square array of 10 by 10 impingement holes with a pitch to diameter, X/D, of 11, hole density, n, of 4306m−2, and gap to diameter ratio, Z/D, of 7.25 for coolant mass flux G of 0.2–1.1 kg/sm2bar. The impingement target and jet walls were modelled as Nimonic-75 as used in the experimental work used for validation of the computational methods. Conjugate heat transfer (CHT) computational fluid dynamics (CFD) was used with ANSYS Fluent code. The measured impingement target wall pressure loss ΔP/P% and target wall surface averaged heat transfer coefficient together with the heat transfer to the impingement jet wall were all predicted in agreement with the measurements, within the measured error bars. The predicted surface distributions of Nu and turbulent kinetic energy (TKE) were compared with predictions for impingement single sided exit flow and the impingement/effusion approach (target) walls. This showed that the reduced crossflow with the four sided exit gave higher surface averaged heat transfer. However, comparison with the impingement/effusion wall heat transfer, for the same impingement wall geometry, showed that the removal of coolant through the effusion wall reduced the recirculating flow in the impingement gap and this reduced the heat transfer to the impingement jet wall, but increased it to the target effusion wall.

High-fidelity simulations of multi-jet impingement cooling flows

2021 ◽  
pp. 1-21
Author(s):  
Jose Javier Otero Perez ◽  
Richard Sandberg ◽  
Satoshi Mizukami ◽  
Koichi Tanimoto
Keyword(s):  
Heat Transfer ◽  
Nusselt Number ◽  
Cross Flow ◽  
Distance Effect ◽  
Jet Impingement ◽  
Impingement Cooling ◽  
Cooling Flows ◽  
Turbulent Inflow ◽  
The Cross ◽  
Flow Effects

Abstract This article shows the first parametric study on turbulent multi-jet impingement cooling flows using large-eddy simulations (LES). We focus on assessing the influence of the inter-jet distance and the cross-flow conditions on the heat transfer at the impingement wall. The LES setup is thoroughly validated with both experimental and direct numerical simulation data, showing an excellent agreement. The inter-jet distance effect on the heat transfer is studied comparing three different distances, where the full Nusselt number profile decreases in amplitude when the jet distance is increased. To evaluate the cross-flow effects, we prescribe both laminar and turbulent inflow conditions at different cross-flow magnitudes ranging between 20% and 40% of the impinging jet speed. Large cross-flow intensities cause a jet deflection which reduces the maxima in the Nusselt number distribution, and it increases the heat transfer in the areas of the wall less affected by the jet impingement. Adding realistic turbulent fluctuations to the inflow enhances the cross-flow effects on the heat transfer at the impingement wall.

Numerical Study on Flow and Heat Transfer Characteristics of Jet Impingement

2011 ◽  
Author(s):  
Xinjun Wang ◽  
Rui Liu ◽  
Xiaowei Bai ◽  
Jinling Yao
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Nusselt Number ◽  
Average Nusselt Number ◽  
Jet Impingement ◽  
Target Surface ◽  
Heat Transfer Characteristics ◽  
Impingement Cooling ◽  
Transfer Characteristics ◽  
Flow And Heat Transfer

A mathematical model used for studying jet impingement cooling characteristics is established, and the rationality of the calculation model and method is confirmed by the experimental data. The CFX software is used to numerically simulate the jet impingement cooling characteristics on a gas turbine blade. The effects of various parameters, such as the arrays of impinging nozzles, the jet Reynolds number, the jet-to-jet distance, the ratio of nozzle-to-surface spacing to jet diameter H/d, and the radius of curvature of the target surface, on the flow and heat transfer characteristics of a impingement cooling process are studied. The results indicate that the impingement jets can make complex vortex in the cooling channel, the flow boundary layer is extremely thin and highly turbulent. Underneath each impingement nozzle, there will appear a low temperature area and a peak of Nusselt number on the impingement target surface, the distribution of temperature and Nusselt number on the target surface are associated with arrangement of impingement nozzles. The average Nusselt number of the in-line arrangement nozzles is higher than that of the staggered arrangement ones. With the increasing of jet Reynolds number, the velocity impinging on the target surface and Nusselt number increase. However, heat transfer of impingement cooling on target surface is not sensitive to the jet nozzles distance; the velocity impinging on the target surface and Nusselt number decrease with the increasing of the H/d value. For the curved target surface cases, the average Nusselt number of the target surface and the effect of heat transfer decreased with the increasing of curvature radius R.

Influences of Target Surface Roughness on Impingement Jet Array Heat Transfer: Part 1 — Effects of Roughness Pattern, Roughness Height, and Reynolds Number

2016 ◽  
Author(s):  
W. Buzzard ◽  
Z. Ren ◽  
P. Ligrani ◽  
C. Nakamata ◽  
S. Ueguchi
Keyword(s):  
Heat Transfer ◽  
Surface Roughness ◽  
Reynolds Number ◽  
Target Surface ◽  
Impingement Cooling ◽  
Impingement Jet ◽  
Heat Transfer Augmentation ◽  
Small Rectangle ◽  
Roughness Elements ◽  
Jet Array

The present investigation considers the effects of special roughness patterns on impingement target surfaces to improve the effectiveness and surface heat transfer augmentation levels of impingement jet array cooling. This investigation utilizes various sizes, distributions, shapes, and patterns of surface roughness elements for impingement cooling augmentation. The surface roughness shape considered here is rectangle, in combination with larger rectangular pins. Combinations of small rectangle roughness and large pins are considered together, along with arrays of small rectangular roughness alone. Tests are performed at impingement jet Reynolds numbers of 900, 1500, 5000, and 11000. Local and overall impingement cooling performance depends upon the pattern, distribution, arrangement, and height of the roughness elements, as well as upon the jet Reynolds number. Depending upon the magnitude of jet Reynolds number, different behavior and trends are observed for the small rectangle roughness and large pins together, compared with arrays of small rectangular roughness alone. Overall, results demonstrate the remarkable ability of target surface roughness to produce increased surface heat transfer augmentation levels of impingement jet array cooling, relative to target surfaces which are smooth.

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