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Development and validation of a three-dimensional multiphase flow computational fluid dynamics analysis for journal bearings in steam and heavy duty gas turbines / Stephan Uhkoetter in Transactions of the ASME . Journal of engineering for gas turbines and power, Vol. 134 N° 10 (Octobre 2012) 

Public ISBD [article]  in Transactions of the ASME . Journal of engineering for gas turbines and power > Vol. 134 N° 10 (Octobre 2012) . - 08 p. Titre : Development and validation of a three-dimensional multiphase flow computational fluid dynamics analysis for journal bearings in steam and heavy duty gas turbines Type de document : texte imprimé Auteurs : Stephan Uhkoetter, Auteur ; Stefan aus der Wiesche, Auteur ; Michael Kursch, Auteur Année de publication : 2012 Article en page(s) : 08 p. Note générale : gas turbines Langues : Anglais (eng) Mots-clés : hydrodynamic  journal  bearing  analysis;  Reynolds  equation;  cover  turbulence;  heat  transfer;  cavitation Index. décimale : 620.1 Essais des matériaux. Défauts des matériaux. Protection des matériaux Résumé : The traditional method for hydrodynamic journal bearing analysis usually applies the lubrication theory based on the Reynolds equation and suitable empirical modifications to cover turbulence, heat transfer, and cavitation. In cases of complex bearing geometries for steam and heavy-duty gas turbines, this approach has its obvious restrictions in regard to detail flow recirculation, mixing, mass balance, and filling level phenomena. These limitations could be circumvented by applying a computational fluid dynamics (CFD) approach, resting closer to the fundamental physical laws. The present contribution reports about the state of the art of such a fully three-dimensional multiphase-flow CFD approach, including cavitation and air entrainment for high-speed turbomachinery journal bearings. It has been developed and validated using experimental data. Due to the high ambient shear rates in bearings, the multiphase-flow model for journal bearings requires substantial modifications in comparison to common two-phase flow simulations. Based on experimental data, it is found, that particular cavitation phenomena are essential for the understanding of steam and heavy-duty-type gas turbine journal bearings. DEWEY : 620.1 ISSN : 0742-4795 En ligne : http://asmedl.org/getabs/servlet/GetabsServlet?prog=normal&id=JETPEZ000134000010 [...] [article] Development and validation of a three-dimensional multiphase flow computational fluid dynamics analysis for journal bearings in steam and heavy duty gas turbines [texte imprimé] / Stephan Uhkoetter, Auteur ; Stefan aus der Wiesche, Auteur ; Michael Kursch, Auteur . - 2012 . - 08 p. gas turbines Langues : Anglais (eng) in Transactions of the ASME . Journal of engineering for gas turbines and power > Vol. 134 N° 10 (Octobre 2012) . - 08 p. Mots-clés : hydrodynamic  journal  bearing  analysis;  Reynolds  equation;  cover  turbulence;  heat  transfer;  cavitation Index. décimale : 620.1 Essais des matériaux. Défauts des matériaux. Protection des matériaux Résumé : The traditional method for hydrodynamic journal bearing analysis usually applies the lubrication theory based on the Reynolds equation and suitable empirical modifications to cover turbulence, heat transfer, and cavitation. In cases of complex bearing geometries for steam and heavy-duty gas turbines, this approach has its obvious restrictions in regard to detail flow recirculation, mixing, mass balance, and filling level phenomena. These limitations could be circumvented by applying a computational fluid dynamics (CFD) approach, resting closer to the fundamental physical laws. The present contribution reports about the state of the art of such a fully three-dimensional multiphase-flow CFD approach, including cavitation and air entrainment for high-speed turbomachinery journal bearings. It has been developed and validated using experimental data. Due to the high ambient shear rates in bearings, the multiphase-flow model for journal bearings requires substantial modifications in comparison to common two-phase flow simulations. Based on experimental data, it is found, that particular cavitation phenomena are essential for the understanding of steam and heavy-duty-type gas turbine journal bearings. DEWEY : 620.1 ISSN : 0742-4795 En ligne : http://asmedl.org/getabs/servlet/GetabsServlet?prog=normal&id=JETPEZ000134000010 [...]

A mobile test rig for micro gas turbines based on a thermal power measurement approach / Stefan aus der Wiesche in Transactions of the ASME . Journal of engineering for gas turbines and power, Vol. 134 N° 11 (Novembre 2012) 

Public ISBD [article]  in Transactions of the ASME . Journal of engineering for gas turbines and power > Vol. 134 N° 11 (Novembre 2012) . - 08 p. Titre : A mobile test rig for micro gas turbines based on a thermal power measurement approach Type de document : texte imprimé Auteurs : Stefan aus der Wiesche, Auteur Année de publication : 2012 Article en page(s) : 08 p. Note générale : gas turbines Langues : Anglais (eng) Mots-clés : micro  gas  turbines;  thermal  measurement Résumé : It is widely considered that micro gas turbines are potential devices for future energy needs. However, many micro gas turbine development projects have failed, particularly those with a very low power level below 10 kW. The financial and experimental capabilities for micro gas turbine development projects are typically extremely limited; hence, there is a need for low cost mobile test rigs. To close this gap, a robust mobile test rig for turboshaft micro gas turbines was developed and validated. The shaft power can be determined using a thermal measurement approach. This circumvents any issues associated with high voltage and electric current levels. The shaft power can be obtained by a straightforward parameter identification procedure based on simple temperature measurements. This approach is feasible because an analytical expression for the transient temperature field can be obtained. The test rig and thermal power measurement concept were fully validated by a commercial micro gas turbine; good agreement was obtained between the experimental results and the theoretical process data. DEWEY : 620.1 ISSN : 0742-4795 En ligne : http://asmedl.org/getabs/servlet/GetabsServlet?prog=normal&id=JETPEZ000134000011 [...] [article] A mobile test rig for micro gas turbines based on a thermal power measurement approach [texte imprimé] / Stefan aus der Wiesche, Auteur . - 2012 . - 08 p. gas turbines Langues : Anglais (eng) in Transactions of the ASME . Journal of engineering for gas turbines and power > Vol. 134 N° 11 (Novembre 2012) . - 08 p. Mots-clés : micro  gas  turbines;  thermal  measurement Résumé : It is widely considered that micro gas turbines are potential devices for future energy needs. However, many micro gas turbine development projects have failed, particularly those with a very low power level below 10 kW. The financial and experimental capabilities for micro gas turbine development projects are typically extremely limited; hence, there is a need for low cost mobile test rigs. To close this gap, a robust mobile test rig for turboshaft micro gas turbines was developed and validated. The shaft power can be determined using a thermal measurement approach. This circumvents any issues associated with high voltage and electric current levels. The shaft power can be obtained by a straightforward parameter identification procedure based on simple temperature measurements. This approach is feasible because an analytical expression for the transient temperature field can be obtained. The test rig and thermal power measurement concept were fully validated by a commercial micro gas turbine; good agreement was obtained between the experimental results and the theoretical process data. DEWEY : 620.1 ISSN : 0742-4795 En ligne : http://asmedl.org/getabs/servlet/GetabsServlet?prog=normal&id=JETPEZ000134000011 [...]

The effect of the location of nucleation sites on the thermal-hydraulic stability of a short-tube natural circulation loop / Marek Kapitz in Transactions of the ASME . Journal of engineering for gas turbines and power, Vol. 134 N° 6 (Juin 2012) 

Public ISBD [article]  in Transactions of the ASME . Journal of engineering for gas turbines and power > Vol. 134 N° 6 (Juin 2012) . - 08 p. Titre : The effect of the location of nucleation sites on the thermal-hydraulic stability of a short-tube natural circulation loop Type de document : texte imprimé Auteurs : Marek Kapitz, Auteur ; Stefan aus der Wiesche, Auteur Année de publication : 2012 Article en page(s) : 08 p. Note générale : Génie mécanique Langues : Anglais (eng) Mots-clés : Nucleation  sites  Thermal-hydraulic  stability  Artificial  nucleation  sites Index. décimale : 620.1 Essais des matériaux. Défauts des matériaux. Protection des matériaux Résumé : The use of small two-phase natural circulation loops is an attractive option for efficient cooling applications and innovative steam generators. An experimental study was conducted to examine how the thermal-hydraulic stability and operating conditions of these devices are affected by nucleation sites. A very smooth glass tube with artificial nucleation sites was used as a boiling channel. The mass flow rate was obtained as a function of heat flux and nucleation site location. Nucleation sites have a strong impact on stability behavior, particularly for low heat flux levels. The observed flow instabilities were analyzed with regard to nonlinear effects and chaotic behavior. DEWEY : 620.1 ISSN : 0742-4795 En ligne : http://asmedl.org/getabs/servlet/GetabsServlet?prog=normal&id=JETPEZ000134000006 [...] [article] The effect of the location of nucleation sites on the thermal-hydraulic stability of a short-tube natural circulation loop [texte imprimé] / Marek Kapitz, Auteur ; Stefan aus der Wiesche, Auteur . - 2012 . - 08 p. Génie mécanique Langues : Anglais (eng) in Transactions of the ASME . Journal of engineering for gas turbines and power > Vol. 134 N° 6 (Juin 2012) . - 08 p. Mots-clés : Nucleation  sites  Thermal-hydraulic  stability  Artificial  nucleation  sites Index. décimale : 620.1 Essais des matériaux. Défauts des matériaux. Protection des matériaux Résumé : The use of small two-phase natural circulation loops is an attractive option for efficient cooling applications and innovative steam generators. An experimental study was conducted to examine how the thermal-hydraulic stability and operating conditions of these devices are affected by nucleation sites. A very smooth glass tube with artificial nucleation sites was used as a boiling channel. The mass flow rate was obtained as a function of heat flux and nucleation site location. Nucleation sites have a strong impact on stability behavior, particularly for low heat flux levels. The observed flow instabilities were analyzed with regard to nonlinear effects and chaotic behavior. DEWEY : 620.1 ISSN : 0742-4795 En ligne : http://asmedl.org/getabs/servlet/GetabsServlet?prog=normal&id=JETPEZ000134000006 [...]