AN EXPERIMENTAL AND NUMERICAL INVESTIGATION OF IMPINGEMENT HEAT TRANSFER IN AIRFOILS LEADING-EDGE COOLING CHANNEL

2009 ◽  
Author(s):  
Mohammad E. Taslim ◽  
A. Abdelrasoul
Keyword(s):  
Heat Transfer ◽  
Numerical Investigation ◽  
Leading Edge ◽  
Cooling Channel ◽  
Impingement Heat Transfer

Effects of alternating elliptical chamber on jet impingement heat transfer in vane leading edge under different cross-flow conditions

2021 ◽  
pp. 1-17
Author(s):  
K. Xiao ◽  
J. He ◽  
Z. Feng
Keyword(s):  
Heat Transfer ◽  
Velocity Ratio ◽  
Cross Flow ◽  
Leading Edge ◽  
Longitudinal Vortices ◽  
Impingement Jet ◽  
Flow And Heat Transfer ◽  
Impingement Heat Transfer ◽  
Cross Flow Velocity ◽  
The Cross

ABSTRACT This paper proposes an alternating elliptical impingement chamber in the leading edge of a gas turbine to restrain the cross flow and enhance the heat transfer, and investigates the detailed flow and heat transfer characteristics. The chamber consists of straight sections and transition sections. Numerical simulations are performed by solving the three-dimensional (3D) steady Reynolds-Averaged Navier–Stokes (RANS) equations with the Shear Stress Transport (SST) k– $\omega$ turbulence model. The influences of alternating the cross section on the impingement flow and heat transfer of the chamber are studied by comparison with a smooth semi-elliptical impingement chamber at a cross-flow Velocity Ratio (VR) of 0.2 and Temperature Ratio (TR) of 1.00 in the primary study. Then, the effects of the cross-flow VR and TR are further investigated. The results reveal that, in the semi-elliptical impingement chamber, the impingement jet is deflected by the cross flow and the heat transfer performance is degraded. However, in the alternating elliptical chamber, the cross flow is transformed to a pair of longitudinal vortices, and the flow direction at the centre of the cross section is parallel to the impingement jet, thus improving the jet penetration ability and enhancing the impingement heat transfer. In addition, the heat transfer in the semi-elliptical chamber degrades rapidly away from the stagnation region, while the longitudinal vortices enhance the heat transfer further, making the heat transfer coefficient distribution more uniform. The Nusselt number decreases with increase of VR and TR for both the semi-elliptical chamber and the alternating elliptical chamber. The alternating elliptical chamber enhances the heat transfer and moves the stagnation point up for all VR and TR, and the heat transfer enhancement is more obvious at high cross-flow velocity ratio.

Numerical Investigation of Impingement Heat Transfer on a Flat and Square Pin-Fin Roughened Plates

2013 ◽  
Author(s):  
Chaoyi Wan ◽  
Yu Rao ◽  
Xiang Zhang
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Flat Plate ◽  
Numerical Investigation ◽  
Pressure Loss ◽  
Transfer Characteristic ◽  
Number Range ◽  
Pin Fin ◽  
Pressure Distributions ◽  
Impingement Heat Transfer

A numerical investigation of the heat transfer characteristics within an array of impingement jets on a flat and square pin-fin roughened plate with spent air in one direction has been conducted. Four types of optimized pin-fin configurations and the flat plate have been investigated in the Reynolds number range of 15000–35000. All the computation results have been validated well with the data of published literature. The effects of variation of jet Reynolds number and different configurations on the distribution of the average and local Nusselt number and the related pressure loss have been obtained. The highest total heat transfer rate increased up to 162% with barely any extra pressure loss compared with that of the flat plate. Pressure distributions and streamlines have also been captured to explain the heat transfer characteristic.

Numerical Investigation of Inlet Swirl in a Turbine Cascade

2012 ◽  
Author(s):  
Gregor Schmid ◽  
Heinz-Peter Schiffer
Keyword(s):  
Heat Transfer ◽  
Numerical Investigation ◽  
Leading Edge ◽  
Turbine Cascade ◽  
Lean Burn ◽  
Image Velocimetry ◽  
Turbine Vane ◽  
Inlet Swirl ◽  
Inflow Conditions ◽  
Probe Measurements

New combustion concepts towards lean burn aim at reducing peak temperatures and therefore emissions, especially nitrogen oxides. High swirl is required in order to enhance the mixing of fuel and air and thus, improve combustion and flame stability. In a numerical investigation of a turbine vane cascade the effect of such inlet swirl on aerodynamic losses, secondary flow pattern and heat transfer is investigated. The computations are conducted prior to particle image velocimetry and five-hole-probe measurements in a cascade of six vane passages and swirl generators upstream of each passage. The analysis covers three constituent parts: First, different swirl intensities are simulated which resemble the situation in a real combustion chamber. Second, different clocking positions are investigated — the swirl cores are either aligned with the vane leading edge or with midpassage — and finally, swirl orientation as clockwise, anticlockwise and counter rotating swirl is analysed. Two-dimensional inlet boundary conditions are applied to model the discrete swirl cores. Furthermore, a comparison with circumferentially averaged as well as with axial inflow conditions is made. Increasing the swirl number at the inlet boundary results in reduced heat transfer coefficient within the vane passage and higher pressure loss. Heat transfer through vanes and endwalls is maximal if the swirl generators are aligned with the vane leading edge and counter rotating swirl.

Experimental and Numerical Impingement Heat Transfer in an Airfoil Leading-Edge Cooling Channel With Crossflow

2007 ◽  
Author(s):  
M. E. Taslim ◽  
D. Bethka
Keyword(s):  
Heat Transfer ◽  
Mass Flow ◽  
Convective Heat Transfer Coefficient ◽  
Internal Heat ◽  
Leading Edge ◽  
Impinging Jet ◽  
Suction Side ◽  
Experimental Results ◽  
Transfer Coefficients ◽  
Impingement Heat Transfer

To enhance the internal heat transfer around the airfoil leading-edge area, a combination of rib-roughened cooling channels, film cooling and impingement cooling is often employed. Experimental data for impingement on various leading-edge geometries are reported by these and other investigators. Effects of strong crossflows on the leading-edge impingement heat transfer, however, have not been studied to that extent. This investigation dealt with impingement on the leading-edge of an airfoil in the presence of crossflows beyond the crossflow created by the upstream jets (spent air). Measurements of heat transfer coefficients on the airfoil nose area as well as the pressure and suction side areas are reported. The tests were run for a range of axial to jet mass flow rates (Maxial/Mjet) ranging from 1.14 to 6.4 and and jet Reynolds numbers ranging from 8000 to 48000. Comparisons are also made between the experimental results of impingement with and without the presence of crossflow and between representative numerical and measured heat transfer results. It was concluded that the presence of the external crossflow reduces the impinging jet effectiveness both on the nose and side walls, even for an axial to jet mass flow ratio as high as 5, the convective heat transfer coefficient produced by the axial channel flow was less than that of the impinging jet without the presence of the external crossflow, and the agreement between the numerical and experimental results was reasonable with an average difference ranging from −8% to −20%.

Experimental and Numerical Impingement Heat Transfer in an Airfoil Leading-Edge Cooling Channel With Cross-Flow

2008 ◽  
Vol 131 (1) ◽  
Author(s):  
M. E. Taslim ◽  
D. Bethka
Keyword(s):  
Heat Transfer ◽  
Mass Flow ◽  
Convective Heat Transfer Coefficient ◽  
Cross Flow ◽  
Internal Heat ◽  
Leading Edge ◽  
Impinging Jet ◽  
Experimental Results ◽  
Transfer Coefficients ◽  
Impingement Heat Transfer

To enhance the internal heat transfer around the airfoil leading-edge area, a combination of rib-roughened cooling channels, film cooling, and impingement cooling is often employed. Experimental data for impingement on various leading-edge geometries are reported by these and other investigators. The effects of strong cross-flows on the leading—edge impingement heat transfer, however, have not been studied to that extent. This investigation dealt with impingement on the leading edge of an airfoil in the presence of cross-flows beyond the cross-flow created by the upstream jets (spent air). Measurements of heat transfer coefficients on the airfoil nose area as well as the pressure and suction side areas are reported. The tests were run for a range of axial to jet mass flow rates (Maxial∕Mjet) ranging from 1.14 to 6.4 and jet Reynolds numbers ranging from 8000 to 48,000. Comparisons are also made between the experimental results of impingement with and without the presence of cross-flow and between representative numerical and measured heat transfer results. It was concluded that (a) the presence of the external cross-flow reduces the impinging jet effectiveness both on the nose and sidewalls; (b) even for an axial to jet mass flow ratio as high as 5, the convective heat transfer coefficient produced by the axial channel flow was less than that of the impinging jet without the presence of the external cross-flow; and (c) the agreement between the numerical and experimental results was reasonable with an average difference ranging from −8% to −20%.

Parametric Study on Micro-Roughness Shapes for Enhanced Jet Impingement Heat Transfer

2020 ◽  
Author(s):  
Ramaswamy Devakottai ◽  
Srivatsan Madhavan ◽  
Prashant Singh ◽  
Srinath V. Ekkad
Keyword(s):  
Heat Transfer ◽  
Turbine Blades ◽  
Leading Edge ◽  
Jet Impingement ◽  
Diameter Ratio ◽  
External Diameter ◽  
Concentric Cylinder ◽  
Pin Fin ◽  
Plate Spacing ◽  
Impingement Heat Transfer

Abstract Development of efficient cooling technologies are imperative to support the constant push for higher turbine inlet temperatures to achieve increased overall turbine efficiency. High-pressure stage turbine blades are subjected to hostile environment involving high temperature turbulent flow exiting from the combustor section. The blade leading edge is subjected to flow stagnation and hence requires special attention in terms of both, internal and external cooling. This study is focused on improving the internal side heat transfer coefficient by installing novel micro-roughness elements on the target wall. The study is based on Singh, Prashant, et al. “Effect of micro-roughness shapes on jet impingement heat transfer and fin-effectiveness.” International Journal of Heat and Mass Transfer 132 (2019): 80–95, where different micro-roughness shapes were investigated experimentally and numerically. The authors proposed that the novel concentric-cylinder shaped roughened geometry exhibited highest fin-effectiveness. Present study reports the effect of three micro-roughness shapes, viz. cylindrical, cubic and concentric cylinder. Conjugate heat transfer study was performed, and the heat transfer performance was reported in the form of local Nusselt number and globally averaged fin-effectiveness. An array jet configuration of 5 × 5 jets with a jet-to-jet spacing of X/Djet = Y/Djet = 3 and jet-to-target plate spacing of Z/Djet = 1 was maintained for jet-diameter based Reynolds number (ReDjet) ranging from 3,000 to 12,000. Investigation on the effect of pin-fin shapes shows that the concentric-shaped micro pin-fin element had the highest fin-effectiveness of 2.45 at ReDjet = 12,000. Further, pin-fin optimization studies were performed for the concentric cylinder pin-fin shape, where the effect of pin-fin height and the effect of internal to external diameter ratio was studied. The pin-fin effectiveness increased with increase in height and diameter ratio, and a maximum fin effectiveness was observed for maximum pin-fin height.

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