A Novel Multi-Stage Impingement Cooling Scheme—Part I: Concept Study

2020 ◽  
Vol 142 (12) ◽  
Author(s):  
Kexin Liu ◽  
Qiang Zhang
Keyword(s):  
Cross Flow ◽  
Target Surface ◽  
Cooling Capacity ◽  
Operating Conditions ◽  
Single Stage ◽  
Impingement Cooling ◽  
Flow Effect ◽  
Multi Stage ◽  
Cooling Design ◽  
The Cross

Abstract The impingement cooling for a modern gas turbine component, either a combustor liner or a high-pressure turbine blade, is often not as efficient as required due to strong cross-flow effect and coolant maldistribution. This paper reports a novel multi-stage impingement cooling scheme to effectively use the coolant and minimize the cross-flow effect. The design concept and general working mechanism are introduced in this Part I paper. The extra design flexibilities and optimization strategies are reported in Part II. Numerical simulations on conjugate heat transfer (CHT) were carried out to assess the flow structure and thermal performance between a typical single-stage cooling design and a three-stage cooling design at typical operating conditions. It has been observed that the novel multi-stage cooling design can reinitiate impingement jets at each stage, which greatly reduces the cross-flow impact and local thermal gradient. The staging of cooling air for the target surface also offers better utilization of the cooling capacity. Even by using 50% of the coolant designed for the single-stage impingement cooling, the multi-stage case can still sufficiently cool the target surface. The additional pressure loss penalty introduced in multi-stage design needs further efforts on design optimization.

A Novel Multi-Stage Impingement Cooling Scheme—Part II: Design Optimization

2020 ◽  
Vol 142 (12) ◽  
Author(s):  
Kexin Liu ◽  
Qiang Zhang
Keyword(s):  
Design Optimization ◽  
Gas Turbine ◽  
Cross Flow ◽  
Target Surface ◽  
Optimization Strategy ◽  
Working Mechanism ◽  
Impingement Cooling ◽  
Multi Stage ◽  
Cooling Air ◽  
Combustor Liner

Abstract Cross flow and coolant maldistribution are the common design challenges for impingement cooling in modern gas turbine. This paper reports a novel multi-stage impingement cooling scheme for combustor liner. The design concept and general working mechanism are introduced in the Part I paper. This Part II paper presents the design flexibilities and optimization strategies. Conjugate heat transfer (CHT) analysis was conducted at a range of Reynolds numbers to assess the thermal performance, loss penalty, and the working mechanism behind. The results show that varying the jet hole diameter in each cooling stage can be an effective design optimization strategy in balancing the cooling requirement and loss penalty. Inter-stage bypass design is also another design flexibility offered by the multi-stage scheme to regulate the cooling air consumption at different stages. With these optimization strategies, the target surface temperature and local gradient can be effectively reduced with reasonable pressure loss with 50% reduction in the cooling air consumption compared to conventional single-stage impingement design. This multi-stage impingement concept can be practically applied to gas turbine combustor liner and turbine blade cooling.

Investigations on the Heat Transfer and Flow Characteristics in a Trapezoid Duct for Turbine Blade Leading Edge

2018 ◽  
Author(s):  
Hai-yong Liu ◽  
Cun-liang Liu ◽  
Lin Ye
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Enhancement ◽  
Cross Flow ◽  
Side Wall ◽  
Swirl Flow ◽  
Transfer Enhancement ◽  
Impingement Cooling ◽  
Exit Side ◽  
Target Wall ◽  
The Cross

To evaluate the application of the impingement cooling in a trapezoidal duct, particularly the influence on internal cooling of the cross flow and swirl flow. Experimental and numerical studies have been performed. The experiment focuses on the heat transfer characteristics in the duct, when the numerical simulation focuses on the flow characteristics. Four Reynolds numbers (10000, 20000, 30000 and 40000), six cross flow mass flow ratios (0, 0.1, 0.2, 0.3, 0.4 and 0.5) and two impingement angle (35° and 45°) are considered in both the experiment and the numerical simulation. The temperature on the target wall and the exit side wall is measured by the thermocouples, when the realizable k-ε turbulence model and enhanced wall treatment are performed using a commercial code Fluent. The results show that only part of the jets contribute in the heat transfer enhancement on the target wall, the other jets improve a large anticlockwise vortex occupied the upper part of the duct and drive strong swirl flow. The heat transfer on the exit side wall is enhanced by the swirl flow. The cross flow is induced in the duct by the outflow of the end exit hole. It deflects the jets and abates the impingement cooling on the target wall in the downstream region but has no evidently effect on the heat transfer on the exit side wall. Higher impingement angle helps to augment the impingement cooling on the target wall and improves the resistance ability of the jets against the effect of the cross flow. The heat transfer enhancement ability on the target wall and exit side wall in the present duct is compared to that of a smooth duct. The Nusselt number of the former is about 3 times higher than that of the latter. It indicates that the impingement and swirl play equally important roles in the heat transfer enhancement in the present duct. Empirical dimensionless correlations based on the present experiment data are presented in the paper.

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 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.

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.

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.

Effective strategy of non-axisymmetric endwall contouring in a linear compressor cascade

2021 ◽  
pp. 095441002110375
Author(s):  
Yuchen Ma ◽  
Jinfang Teng ◽  
Mingmin Zhu ◽  
Xiaoqing Qiang
Keyword(s):  
Pressure Gradient ◽  
Pressure Loss ◽  
Cross Flow ◽  
Operating Conditions ◽  
Control Effect ◽  
Corner Separation ◽  
Aerodynamic Pressure ◽  
Compressor Performance ◽  
The Cross ◽  
Endwall Contouring

The corner separation and the related secondary flow have great impact on the compressor performance, and non-axisymmetric endwall contouring is proved effective in improving compressor efficiency. The aim of the study is to improve the compressor performance by two local endwall contouring strategies at the design and off-design conditions. The endwall is parameterized and the Bezier curve is used to loft the endwall surface. The design of the contoured endwall is based on a multi-point optimization method to minimize the aerodynamic pressure loss. In order to identify the influence of the contoured endwall, a detailed flow analysis is conducted on four effective contoured endwall designs. The selected endwall geometries exhibit great control ability on the corner separation and significantly reduce the pressure loss at the two operating conditions. The directional concave near the leading edge can induce strong streamwise pressure gradient and accelerate the endwall flow, greatly reducing the cross-passage pressure gradient. The convex structures near the concave edge and at the outlet can block the cross-flow and prevent the interaction between the cross-flow and the suction corner flow. The benefit of the contoured endwall is mainly due to the re-distributed endwall static pressure and blocking of the cross-flow movement. In terms of the control effect, the shape of the concave also matters and better control effect is observed on the deep and wide concave. The flow will be guided by the concave, and the best suppression on corner separation is observed on the concave which follows the suction side. The results also indicate that the relief of the hub corner separation slightly increases the shroud pressure loss.

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.

Sign in / Sign up

Export Citation Format

Share Document