Comparisons of pins/dimples/protrusions cooling concepts for a turbine blade tip-wall at high Reynolds numbers / Gongnan Xie in Journal of heat transfer, Vol. 133 N° 6 (Juin 2011)  

Public ISBD [article]  inJournal of heat transfer > Vol. 133 N° 6 (Juin 2011) . - pp. [061902/1-9] Titre : Comparisons of pins/dimples/protrusions cooling concepts for a turbine blade tip-wall at high Reynolds numbers Type de document : texte imprimé Auteurs : Gongnan Xie, Auteur ; Bengt Sundén, Auteur ; Weihong Zhang, Auteur Année de publication : 2011 Article en page(s) : pp. [061902/1-9] Note générale : Physique Langues : Anglais (eng) Mots-clés : Heat transfer enhancement Blade tip-wall Pins Dimples Protrusions Numerical simulation Index. décimale : 536 Chaleur. Thermodynamique Résumé : The blade tip region encounters high thermal loads because of the hot gas leakage flows, and it must therefore be cooled to ensure a long durability and safe operation. A common way to cool a blade tip is to design serpentine passages with a 180 deg turns under the blade tip-cap inside the turbine blade. Improved internal convective cooling is therefore required to increase blade tip lifetime. Pins, dimples, and protrusions are well recognized as effective devices to augment heat transfer in various applications. In this paper, enhanced heat transfer of an internal blade tip-wall has been predicted numerically. The computational models consist of a two-pass channel with 180 deg turn and arrays of circular pins, hemispherical dimples, or protrusions internally mounted on the tip-wall. Inlet Reynolds numbers are ranging from 100,000 to 600,000. The overall performance of the two-pass channels is evaluated. Numerical results show that the heat transfer enhancement of the pinned-tip is up to a factor of 3.0 higher than that of a smooth tip while the dimpled-tip and protruded-tip provide about 2.0 times higher heat transfer. These augmentations are achieved at the cost of an increase of pressure drop by less than 10%. By comparing the present cooling concepts with pins, dimples, and protrusions, it is shown that the pinned-tip exhibits best performance to improve the blade tip cooling. However, when disregarding the added active area and considering the added mechanical stress, it is suggested that the usage of dimples is more suitable to enhance blade tip cooling, especially at low Reynolds numbers. DEWEY : 536 ISSN : 0022-1481 En ligne : http://asmedl.aip.org/vsearch/servlet/VerityServlet?KEY=JHTRAO&ONLINE=YES&smode= [...] [article] Comparisons of pins/dimples/protrusions cooling concepts for a turbine blade tip-wall at high Reynolds numbers [texte imprimé] / Gongnan Xie, Auteur ; Bengt Sundén, Auteur ; Weihong Zhang, Auteur . - 2011 . - pp. [061902/1-9]. Physique Langues : Anglais (eng) in Journal of heat transfer > Vol. 133 N° 6 (Juin 2011) . - pp. [061902/1-9] Mots-clés : Heat transfer enhancement Blade tip-wall Pins Dimples Protrusions Numerical simulation Index. décimale : 536 Chaleur. Thermodynamique Résumé : The blade tip region encounters high thermal loads because of the hot gas leakage flows, and it must therefore be cooled to ensure a long durability and safe operation. A common way to cool a blade tip is to design serpentine passages with a 180 deg turns under the blade tip-cap inside the turbine blade. Improved internal convective cooling is therefore required to increase blade tip lifetime. Pins, dimples, and protrusions are well recognized as effective devices to augment heat transfer in various applications. In this paper, enhanced heat transfer of an internal blade tip-wall has been predicted numerically. The computational models consist of a two-pass channel with 180 deg turn and arrays of circular pins, hemispherical dimples, or protrusions internally mounted on the tip-wall. Inlet Reynolds numbers are ranging from 100,000 to 600,000. The overall performance of the two-pass channels is evaluated. Numerical results show that the heat transfer enhancement of the pinned-tip is up to a factor of 3.0 higher than that of a smooth tip while the dimpled-tip and protruded-tip provide about 2.0 times higher heat transfer. These augmentations are achieved at the cost of an increase of pressure drop by less than 10%. By comparing the present cooling concepts with pins, dimples, and protrusions, it is shown that the pinned-tip exhibits best performance to improve the blade tip cooling. However, when disregarding the added active area and considering the added mechanical stress, it is suggested that the usage of dimples is more suitable to enhance blade tip cooling, especially at low Reynolds numbers. DEWEY : 536 ISSN : 0022-1481 En ligne : http://asmedl.aip.org/vsearch/servlet/VerityServlet?KEY=JHTRAO&ONLINE=YES&smode= [...]

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Energy absorption performance of staggered triangular honeycombs under in - plane crushing loadings / Deqiang Sun in Journal of engineering mechanics, Vol. 139 N° 2 (Février 2013)  

Public ISBD [article]  inJournal of engineering mechanics > Vol. 139 N° 2 (Février 2013) . - pp.153–166. Titre : Energy absorption performance of staggered triangular honeycombs under in - plane crushing loadings Type de document : texte imprimé Auteurs : Deqiang Sun, Auteur ; Weihong Zhang, Auteur Année de publication : 2013 Article en page(s) : pp.153–166. Note générale : Applied mechanics Langues : Anglais (eng) Mots-clés : Staggered triangular honeycombs Finite-element analysis Energy absorption per unit volume Minimum dynamic cushioning coefficient Résumé : The finite-element methodology is presented to evaluate the energy absorption performance of staggered triangular honeycombs under in-plane crushing loadings at impact velocities of 50–300 m/s. The minimum dynamic cushioning coefficient is proposed to characterize the maximum energy absorption efficiency of staggered triangular honeycombs. When all configuration parameters are constant, the energy absorption per unit volume is proportional to the square of the impact velocity; for a given impact velocity, the energy absorption per unit volume is related to the ratio of the cell wall thickness to the edge length by a power law and to the expanding angle by complicated analytical equations. The maximum energy absorption efficiency is insensitive to the impact velocity. Only for the smaller ratio of the cell wall thickness to the edge length does the maximum energy absorption efficiency increase with the increasing expanding angle. At a given impact velocity there is a threshold ratio of the cell wall thickness to the edge length. The maximum energy absorption efficiency decreases abruptly when the ratio is larger than the threshold. The threshold ratio is approximately equal to 0.04. ISSN : 0733-9399 En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%29EM.1943-7889.0000475 [article] Energy absorption performance of staggered triangular honeycombs under in - plane crushing loadings [texte imprimé] / Deqiang Sun, Auteur ; Weihong Zhang, Auteur . - 2013 . - pp.153–166. Applied mechanics Langues : Anglais (eng) in Journal of engineering mechanics > Vol. 139 N° 2 (Février 2013) . - pp.153–166. Mots-clés : Staggered triangular honeycombs Finite-element analysis Energy absorption per unit volume Minimum dynamic cushioning coefficient Résumé : The finite-element methodology is presented to evaluate the energy absorption performance of staggered triangular honeycombs under in-plane crushing loadings at impact velocities of 50–300 m/s. The minimum dynamic cushioning coefficient is proposed to characterize the maximum energy absorption efficiency of staggered triangular honeycombs. When all configuration parameters are constant, the energy absorption per unit volume is proportional to the square of the impact velocity; for a given impact velocity, the energy absorption per unit volume is related to the ratio of the cell wall thickness to the edge length by a power law and to the expanding angle by complicated analytical equations. The maximum energy absorption efficiency is insensitive to the impact velocity. Only for the smaller ratio of the cell wall thickness to the edge length does the maximum energy absorption efficiency increase with the increasing expanding angle. At a given impact velocity there is a threshold ratio of the cell wall thickness to the edge length. The maximum energy absorption efficiency decreases abruptly when the ratio is larger than the threshold. The threshold ratio is approximately equal to 0.04. ISSN : 0733-9399 En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%29EM.1943-7889.0000475

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