Detailed Heat Transfer Distributions of Narrow Impingement Channels for Cast-In Turbine Airfoils

2014 ◽  
Vol 136 (9) ◽  
Author(s):  
Alexandros Terzis ◽  
Peter Ott ◽  
Jens von Wolfersdorf ◽  
Bernhard Weigand ◽  
Magali Cochet
Keyword(s):  
Heat Transfer ◽  
Reynolds Numbers ◽  
Transfer Model ◽  
Target Plate ◽  
Cooling Effectiveness ◽  
Transfer Rates ◽  
Impingement Cooling ◽  
Turbine Airfoils ◽  
Transient Liquid Crystal Technique ◽  
Plate Distance

The current capabilities of the foundry industry allow the production of integrally cast turbine airfoils. Impingement cooling effectiveness can be then further increased due to the manufacturing feasibility of narrow impingement cavities in a double-wall configuration. This study examines experimentally, using the transient liquid crystal technique, the cooling performance of narrow cavities consisting of a single row of five impingement holes. Heat transfer coefficient distributions are obtained for all channel interior surfaces over a range of engine realistic Reynolds numbers varying between 10,900 and 85,900. Effects of streamwise jet-to-jet spacing (X/D), channel width (Y/D), jet-to-target plate distance (Z/D), and jet offset position (Δy∕D) from the channel centerline are investigated composing a test matrix of 22 different geometries. Additionally, the target plate and sidewalls heat transfer rates are successfully correlated within the experimental uncertainties providing an empirical heat transfer model for narrow impingement channels. The results indicate similarities with multijet impingement configurations; however, the achievable heat transfer level is about 20% lower compared to periodic multijet impingement correlations found in open literature.

Experimental Study on Racetrack-Shaped Holes Impingement Cooling With Bump Type Roughening Element

2012 ◽  
Author(s):  
Chiyuki Nakamata ◽  
Yoji Okita ◽  
Takashi Yamane ◽  
Yoshitaka Fukuyama ◽  
Toyoaki Yoshida
Keyword(s):  
Experimental Study ◽  
Flow Condition ◽  
Reynolds Numbers ◽  
Main Flow ◽  
The Other ◽  
Relative Location ◽  
Target Plate ◽  
Cooling Effectiveness ◽  
Impingement Cooling ◽  
Cooling Air

Cooling effectiveness of an impingement cooling with array of racetrack-shaped impingement holes is investigated. Two types of specimens are investigated. One is a plain target plate and the other is a plate roughened with bump type elements. Sensitivity of relative location of bump to impingement hole on the cooling effectiveness is also investigated. Experiments are conducted under three different mainflow Reynolds numbers ranging from 2.6×105 to 4.7×105, with four different cooling air Reynolds numbers for each main flow condition. The cooling air Reynolds numbers are in the range from 1.2×103 to 1.3×104.

Recent Trends of Impingement Cooling System Enhancement for Gas Turbine

2013 ◽  
Vol 465-466 ◽  
pp. 496-499
Author(s):  
Mohd Firdaus Bin Abas ◽  
Abdullah Aslam ◽  
Hamidon bin Salleh ◽  
Nor Adrian Bin Nor Salim
Keyword(s):  
Heat Transfer ◽  
Cooling System ◽  
Turbine Blades ◽  
Impinging Jets ◽  
Target Plate ◽  
Impingement Cooling ◽  
Impingement Jet ◽  
Rib Turbulators ◽  
Recent Trends ◽  
Plate Distance

Efforts have been given to improve the turbine blades ability to withstand high temperature for a long period of time by implementing effective cooling system. There are many aspects that should be considered when implementing impingement cooling. This paper will only cover two trending aspects in impingement cooling implementation; the jet-to-target plate distance and the application of ribs in promoting better impingement cooling performance. For target plate distance to impingement jet diameter value, H/d > 1, the area-averaged Nusselt number also decreases as the H/d value increases. This may have been due to a reduction of the amount of momentum exerted by the impinging jets onto the target plate. For H/d < 1, the results have been proven otherwise. Heat transfer in impingement/effusion cooling system in crossflow with rib turbulators showed higher heat transfer rate than that of a surface without ribs because the ribs prevent the wall jets from being swept away by the crossflow and increase local turbulence of the flow near the surface. It could be concluded that both H/d ratio and ribs installation play an important role in enhancing impingement cooling systems heat transfer effectiveness.

Effects of Jet-to-Target Plate Distance and Reynolds Number on Jet Array Impingement Heat Transfer

2013 ◽  
Author(s):  
Junsik Lee ◽  
Zhong Ren ◽  
Jacob Haegele ◽  
Geoff Potts ◽  
Jae Sik Jin ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Strong Dependence ◽  
Target Surface ◽  
Reynolds Numbers ◽  
Target Plate ◽  
Stagnation Points ◽  
Nusselt Numbers ◽  
Impingement Heat Transfer ◽  
Plate Distance

Data which illustrate the effects of jet-to-target plate distance and Reynolds number on the heat transfer from an array of jets impinging on a flat plate are presented. Considered are Reynolds numbers Rej ranging from 8,200, to 52,000, with isentropic jet Mach numbers of approximately 0.1 to 0.2. Jet-to-target plate distances Z of 1.5D, 3.0D, 5.0D, and 8.0D are employed, where D is the impingement hole diameter. Steamwise and spanwise hole spacings are 8D. Local and spatially-averaged Nusselt numbers show strong dependence on the impingement jet Reynolds number for all situations examined. Experimental results also illustrate the dependence of local Nusselt numbers on normalized jet-to-target plate distance, especially for smaller values of this quantity. The observed variations are partially due to accumulating cross-flows produced as the jets advect downstream, as well as the interactions of the vortex structures which initially form around the jets, and then impact and interact as they advect away from stagnation points along the impingement target surface. The highest spatially-averaged Nusselt numbers are present for Z/D = 3.0 for Rej of 8,200, 20,900, and 30,000. When Rej = 52,000, spatially-averaged Nusselt numbers increase as Z/D decreases, with the highest value present at Z/D = 1.5.

Effect of Varying Jet Diameter on the Heat Transfer Distributions of Narrow Impingement Channels

2014 ◽  
Vol 137 (2) ◽  
Author(s):  
Alexandros Terzis ◽  
Peter Ott ◽  
Magali Cochet ◽  
Jens von Wolfersdorf ◽  
Bernhard Weigand
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Reynolds Numbers ◽  
Considerable Effect ◽  
Cooling Performance ◽  
Single Row ◽  
Discharge Coefficients ◽  
Turbine Airfoils ◽  
Transient Liquid Crystal Technique ◽  
Double Wall

The development of integrally cast turbine airfoils allows the production of narrow impingement channels in a double-wall configuration, where the coolant is practically injected within the wall of the airfoil providing increased heat transfer capabilities. This study examines the cooling performance of narrow impingement channels with varying jet diameters using a single exit design in an attempt to regulate the generated crossflow. The channel consists of a single row of five inline jets tested at two different channel heights and over a range of engine representative Reynolds numbers. Detailed heat transfer coefficient distributions are evaluated over the complete interior surfaces of the channel using the transient liquid crystal technique. Additionally, local jet discharge coefficients are determined by probe traversing measurements for each individual jet. A 10%-increasing and a 10%-decreasing jet diameter pattern are compared with a baseline geometry of uniform jet size distribution, indicating a considerable effect of varying jet diameter on the heat transfer level and the development of the generated crossflow.

Effects of Jet-To-Target Plate Distance and Reynolds Number on Jet Array Impingement Heat Transfer

2013 ◽  
Vol 136 (5) ◽  
Author(s):  
Junsik Lee ◽  
Zhong Ren ◽  
Jacob Haegele ◽  
Geoffrey Potts ◽  
Jae Sik Jin ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Strong Dependence ◽  
Target Surface ◽  
Reynolds Numbers ◽  
Target Plate ◽  
Stagnation Points ◽  
Nusselt Numbers ◽  
Impingement Heat Transfer ◽  
Plate Distance

Data which illustrate the effects of jet-to-target plate distance and Reynolds number on the heat transfer from an array of jets impinging on a flat plate are presented. Considered are Reynolds numbers Rej ranging from 8200 to 52,000 with isentropic jet Mach numbers of approximately 0.1 to 0.2. Jet-to-target plate distances Z of 1.5D, 3.0D, 5.0D, and 8.0D are employed, where D is the impingement hole diameter. Streamwise and spanwise hole spacings are 8D. Local and spatially-averaged Nusselt numbers show strong dependence on the impingement jet Reynolds number for all situations examined. Experimental results also illustrate the dependence of local Nusselt numbers on normalized jet-to-target plate distance, especially for smaller values of this quantity. The observed variations are partially due to accumulating cross-flows produced as the jets advect downstream, as well as the interactions of the vortex structures, which initially form around the jets and then impact and interact as they advect away from stagnation points along the impingement target surface. The highest spatially-averaged Nusselt numbers are present for Z/D = 3.0 for Rej of 8200, 20,900, and 30,000. When Rej = 52,000, spatially-averaged Nusselt numbers increase as Z/D decreases, with the highest value present at Z/D = 1.5.

Detailed Heat Transfer Distributions of Narrow Impingement Channels With Varying Jet Diameter

2014 ◽  
Author(s):  
Alexandros Terzis ◽  
Magali Cochet ◽  
Jens von Wolfersdorf ◽  
Bernhard Weigand ◽  
Peter Ott
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Reynolds Numbers ◽  
Considerable Effect ◽  
Cooling Performance ◽  
Single Row ◽  
Discharge Coefficients ◽  
Turbine Airfoils ◽  
Transient Liquid Crystal Technique ◽  
Double Wall

The development of integrally cast turbine airfoils allows the production of narrow impingement channels in a double-wall configuration, where the coolant is practically injected within the wall of the airfoil providing increased heat transfer capabilities. This study examines the cooling performance of narrow impingement channels with varying jet diameters using a single exit design in an attempt to regulate the generated crossflow. The channel consist of a single row of five inline jets tested at two different channel heights and over a range of Reynolds numbers. Detailed heat transfer coefficient distributions are evaluated over the complete interior surfaces of the channel using the transient liquid crystal technique. Local jet discharge coefficients are determined by probe traversing measurements for each individual jet. A 10%-increasing and a 10%-decreasing jet diameter pattern is compared with a baseline geometry of uniform jet size distribution indicating a considerable effect of varying jet diameter on the heat transfer level and the development of the generated crossflow.

Heat Transfer in Separated, Reattached, and Redevelopment Regions Behind a Double Step at Entrance to a Flat Duct

1967 ◽  
Vol 89 (2) ◽  
pp. 163-167 ◽  
Author(s):  
E. G. Filetti ◽  
W. M. Kays
Keyword(s):  
Heat Transfer ◽  
Local Heat Transfer ◽  
Reynolds Numbers ◽  
Local Heat ◽  
Duct Flow ◽  
Double Step ◽  
Maximum Heat ◽  
Transfer Rates ◽  
Maximum Heat Transfer ◽  
Flow Cross

Experimental data are presented for local heat transfer rates near the entrance to a flat duct in which there is an abrupt symmetrical enlargement in flow cross section. Two enlargement area ratios are considered, and Reynolds numbers, based on duct hydraulic diameter, varied from 70,000 to 205,000. It is found that such a flow is characterized by a long stall on one side and a short stall on the other. Maximum heat transfer occurs in both cases at the point of reattachment, followed by a decay toward the values for fully developed duct flow. Empirical equations are given for the Nusselt number at the reattachment point, correlated as functions of duct Reynolds number and enlargement ratio.

Predictions of the Effect of Roughness on Heat Transfer From Turbine Airfoils

1998 ◽  
Author(s):  
Anil K. Tolpadi ◽  
Michael E. Crawford
Keyword(s):  
Heat Transfer ◽  
Side Surface ◽  
Suction Side ◽  
Reynolds Numbers ◽  
Surface Finishing ◽  
Transfer Coefficients ◽  
Average Roughness ◽  
Wide Range ◽  
Turbine Airfoils ◽  
Good Agreement

The heat transfer and aerodynamic performance of turbine airfoils are greatly influenced by the gas side surface finish. In order to operate at higher efficiencies and to have reduced cooling requirements, airfoil designs require better surface finishing processes to create smoother surfaces. In this paper, three different cast airfoils were analyzed: the first airfoil was grit blasted and codep coated, the second airfoil was tumbled and aluminide coated, and the third airfoil was polished further. Each of these airfoils had different levels of roughness. The TEXSTAN boundary layer code was used to make predictions of the heat transfer along both the pressure and suction sides of all three airfoils. These predictions have been compared to corresponding heat transfer data reported earlier by Abuaf et al. (1997). The data were obtained over a wide range of Reynolds numbers simulating typical aircraft engine conditions. A three-parameter full-cone based roughness model was implemented in TEXSTAN and used for the predictions. The three parameters were the centerline average roughness, the cone height and the cone-to-cone pitch. The heat transfer coefficient predictions indicated good agreement with the data over most Reynolds numbers and for all airfoils-both pressure and suction sides. The transition location on the pressure side was well predicted for all airfoils; on the suction side, transition was well predicted at the higher Reynolds numbers but was computed to be somewhat early at the lower Reynolds numbers. Also, at lower Reynolds numbers, the heat transfer coefficients were not in very good agreement with the data on the suction side.

Effect of Jet-to-Jet Distance and Pipe Position on Flow and Heat Transfer Features of Active Clearance Control Systems

2021 ◽  
Author(s):  
Lorenzo Cocchi ◽  
Alessio Picchi ◽  
Bruno Facchini ◽  
Riccardo Da Soghe ◽  
Lorenzo Mazzei ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Target Surface ◽  
Reynolds Numbers ◽  
Metal Plate ◽  
Target Distance ◽  
Target Plate ◽  
Ir Camera ◽  
Supply Pipe ◽  
Heating Up ◽  
Clearance Control

Abstract The goal of the present work is to investigate the effect of supply pipe position on the heat transfer features of various active clearance control (ACC) geometries, characterized by different jet-to-jet distances. All geometries present 0.8 mm circular impingement holes arranged in a single row. The jets generated by such holes cool a flat target surface, which is replicated by a metal plate in the experimental setup. Measurements are performed using the steady-state technique, obtained by heating up the target plate thanks to an electrically heated Inconel foil applied on the side of the target opposite to the jets. Temperature is also measured on this side by means of an IR camera. Heat transfer is then evaluated thanks to a custom designed finite difference procedure, capable of solving the inverse conduction problem on the target plate. The effect of pipe positioning is studied in terms of pipe-to-target distance (from 3 to 11 jet diameters) and pipe orientation (i.e. rotation around its axis, from 0° to 40° with respect to target normal direction), while the investigated jet Reynolds numbers range from 6000 to 10000. The obtained results reveal that heat transfer is maximized for a given pipe-to-target distance, dependent on both jet-to-jet distance and target surface extension. Pipe rotation also affects the cooling features in a non-monotonic way, suggesting the existence of different flow regimes related to jet inclination.

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.

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