Impingement cooling for modern combustors: experimental analysis of heat transfer and effectiveness

Facchini, Bruno; Surace, Marco

doi:10.1007/s00348-005-0100-y

Cited by 17 publications

(6 citation statements)

References 17 publications

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“…For both cases, (C D ) is increased slightly with a constant level from (Re j = 30T 5000, BR=1 to Re j = 10000, BR = 1.9). The present test results agree well with the results given by [6] of impingement/effusion cooling and [16] for impingement cooling case of combustion chamber. Both results showed that the discharge coefficient increased slightly with increasing BR.…”

Section: Pressure Losses and Discharge Coefficientsupporting

confidence: 90%

Heat Transfer and Flow Performance of Impingement and Impingement/Effusion Cooling Systems

Yousif¹,

Dabagh²,

Aun³

2015

ETJ

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The current experimental study is made to investigate the heat transfer characteristics and pressure losses for both impingement and impingement/effusion cooling systems. The experiments are carried out on a metal test plate. The numerical work is made to analyze the flow behavior in the test section. The benefit of introducing the present experimental method is the capability of investigating and analyzing the performance of both impingement and impingement/effusion cooling systems by the same test rig. The impinging jet device configurations are designed as inline round multihole arrays with jet to jet spacing of 4 jet hole diameter. The effusion holes configurations are inline round multi-hole arrays. Staggered arrangement between jet and effusion holes is maintained. The Jet Reynolds numbers (Re j ) of 5000 to 15000 and jet height to diameter ratio ( H D ⁄ ) of 1.5, 2.0, and 3.0 are maintained. For impingement/effusion case, the best wall cooling effectiveness is obtained at (H D ⁄ = 2), and maximum increment in the wall cooling effectiveness over that of impingement case is 23% at (Re j = 5000), 16 % at (Re j = 7500), and 14% at (Re j = 15000). Jet spacing in impingement case and blowing ratio in impingement/effusion case show an evident effect on the discharge coefficients.

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Section: Pressure Losses and Discharge Coefficientsupporting

confidence: 90%

Heat Transfer and Flow Performance of Impingement and Impingement/Effusion Cooling Systems

Yousif¹,

Dabagh²,

Aun³

2015

ETJ

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“…Brevet et al [18] optimized the spanwise pitch on the basis of cooling efficiency estimated per unit area of impingement surface. More recently, liquid crystal thermography was used to study local heat transfer distribution due to impingement of arrays of multiple jets with spent air exiting in one direction [19][20][21][22][23]. The distribution of heat transfer coefficient due to arrays of impinging jets involving an increase in spacing between the jets in the streamwise direction and an increase in jet-hole diameters in the streamwise direction using liquid crystal thermography was studied by Gao et al [24].…”

Section: Introductionmentioning

confidence: 98%

Influence of Spanwise Pitch on Local Heat Transfer for Multiple Jets with Crossflow

Katti

Prabhu

2008

Journal of Thermophysics and Heat Transfer

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The influence of spanwise jet-to-jet spacing on local heat transfer distribution due to multiple impinging circular air jets from an in-line rectangular array on a surface parallel to the jet plate is studied experimentally. The length-todiameter ratio of the nozzles of the jet plate is 1.0. The flow, after impingement, is constrained to exit in one direction from the confined passage formed between the jet plate and the target plate. Mean jet Reynolds numbers based on the nozzle-exit diameter d covered are 3000, 5000, 7500, and 10,000, and jet-to-plate spacings studied are d, 2d, and 3d. Spanwise pitches considered are 2d, 4d, and 6d, keeping the streamwise pitch at 5d. For all configurations, the jet plates have ten spanwise rows in the streamwise direction and six jets in each spanwise row. The flat heat transfer surface is made of thin stainless steel metal foil. Local temperature distribution on the target plate is measured using thermal infrared camera. Wall static pressure on the target plate is measured in the streamwise direction to estimate crossflow velocities and individual jet velocities. Heat transfer characteristics are explained on the basis of flow distribution. A simple correlation is developed to predict the streamwise distribution of the Nusselt number averaged over each spanwise strip resolved to one jet hole as a function of jet-flow and crossflow distributions.diameter of the jet, m G act = actual jet mass velocity based on jet-hole area, kg=s m 2 G c = channel crossflow mass velocity based on channel cross-sectional area, kg=s m 2 G ideal = theoretical jet mass velocity based on jet-hole area, kg=s m 2 G j = individual jet mass velocity based on jet-hole area, kg=s m 2 G j = mean jet mass velocity based on jet-hole area for the array, kg=s m 2 h = heat transfer coefficient, W=m 2 K k = thermal conductivity of the jet fluid, W=m K l=d = aspect ratio of the nozzle _ m j = mean mass flow rate from the nozzle, kg=s N c = number of streamwise rows of jets Nu = local Nusselt number (hd=k) Nu o;multijet = stagnation Nusselt number due to a jet in each spanwise row Nu o;single jet = stagnation Nusselt number due to a single jet estimated from the correlation corresponding to the jet-row Reynolds number Nu segment = Nusselt number averaged over each segment Nu strip = Nusselt number averaged over each spanwise strip resolved to one jet hole P = absolute static pressure at the nozzle exit, Pa P a = atmospheric pressure, Pa P o = absolute static pressure in the plenum or at the nozzle inlet, Pa Pr = Prandtl number Q = heater input power, W q 00 = net heat flux imposed on the target plate, W=m 2 R = characteristic gas constant of air, J=kg K Re = mean jet Reynolds number of flow exiting the nozzle (4 _ m j =d) Re j = individual spanwise-row jet Reynolds number T amb = ambient air temperature, K T j = reference jet fluid temperature on the target plate, K T o= plenum air temperature, K T w = target-plate surface temperature, K V j = mean jet velocity at the nozzle exit, m=s x = distance in the streamwi...

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“…The analysis of the heat transfer distribution on the inner side of the effusion plate is supported by CFD simulations: the combination of measured and calculated data enables a complete analysis of thermal and fluid-dynamic phenomena, and thus provides significant information on the unique behaviour of each geometry. A similar approach have been already followed by the authors in the past for the investigation of different cooling configurations based on impinging jets [14,15,16].…”

Section: Introductionmentioning

confidence: 99%

Experimental and numerical investigation on the role of holes arrangement on the heat transfer in impingement/effusion cooling schemes

Andreini

Cocchi

Facchini

et al. 2018

International Journal of Heat and Mass Transfer

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In the present work, two different impingement/effusion geometries have been investigated, both having staggered hole configuration and an equal number of impingement and effusion holes. The first geometry, which is designed in case of low coolant availability, has impingement hole pitch-to-diameter ratios of 10.5 in both orthogonal directions, a jet-to-target plate spacing of 6.5 hole diameters, with effusion holes inclined of 20 • with respect to the target surface. The second geometry, which is designed in case of high coolant availability, has impingement hole pitch-to-diameter ratios of 3.0, a jet-to-target plate spacing of 2.5 diameters and normal effusion holes. For each geometry, two relative arrangements between the impingement and effusion holes have been investigated, as well as various Reynolds numbers for the sparser geometry.The experimental investigation has been performed by applying a transient technique, using narrow band thermochromic liquid crystals (TLCs) for surface temperature measurement. A CFD analysis has also been performed in order to support interpretation of the results. Results show unique heat transfer patterns for every investigated geometry. Weak jet-jet interactions have been recorded for the sparser array geometry, while intense secondary peaks and a complex heat transfer pattern are observed for the denser one, which is also strongly influenced by the presence and position of effusion holes. For both the geometries, effusion holes increase heat transfer with respect to impingement-only, which can be mainly attributed to a reduction in flow recirculation for the sparser geometry and to the suppression of spent coolant flow for the denser one.

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Impingement cooling for modern combustors: experimental analysis of heat transfer and effectiveness

Cited by 17 publications

References 17 publications

Heat Transfer and Flow Performance of Impingement and Impingement/Effusion Cooling Systems

Heat Transfer and Flow Performance of Impingement and Impingement/Effusion Cooling Systems

Influence of Spanwise Pitch on Local Heat Transfer for Multiple Jets with Crossflow

Experimental and numerical investigation on the role of holes arrangement on the heat transfer in impingement/effusion cooling schemes

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