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Influence of film cooling unsteadiness on turbine blade leading edge heat flux / James L. Rutledge in Transactions of the ASME . Journal of engineering for gas turbines and power, Vol. 134 N° 7 (Juillet 2012) 

Public ISBD [article]  in Transactions of the ASME . Journal of engineering for gas turbines and power > Vol. 134 N° 7 (Juillet 2012) . - 10 p. Titre : Influence of film cooling unsteadiness on turbine blade leading edge heat flux Type de document : texte imprimé Auteurs : James L. Rutledge, Auteur ; Paul I. King, Auteur ; Richard B. Diver, Auteur Année de publication : 2012 Article en page(s) : 10 p. Note générale : Génie mécanique Langues : Anglais (eng) Mots-clés : Hot  gas  path  Turbine  engine  Heat  transfer Index. décimale : 620.1 Essais des matériaux. Défauts des matériaux. Protection des matériaux Résumé : Film cooling in the hot gas path of a gas turbine engine can protect components from the high temperature main flow, but it generally increases the heat transfer coefficient h partially offsetting the benefits in reduced adiabatic wall temperature. We are thus interested in adiabatic effectiveness eta and h which are combined in a formulation called net heat flux reduction (NHFR). Unsteadiness in coolant flow may arise due to inherent unsteadiness in the external flow or be intentionally introduced for flow control. In previous work it has been suggested that pulsed cooling flow may, in fact, offer benefits over steady blowing in either improving NHFR or reducing the mass flow requirements for matched NHFR. In this paper we examine this hypothesis for a range of steady and pulsed blowing conditions. We use a new experimental technique to analyze unsteady film cooling on a semicircular cylinder simulating the leading edge of a turbine blade. The average NHFR with pulsed and steady film cooling is measured and compared for a single coolant hole located 21.5° downstream from the leading edge stagnation line, angled 20° to the surface and 90° to the streamwise direction. We show that for moderate blowing ratios at blade passing frequencies, steady film flow yields better NHFR. At higher coolant flow rates beyond the optimum steady blowing ratio, however, pulsed film cooling can be advantageous. We present and demonstrate a prediction technique for unsteady blowing at frequencies similar to the blade passing frequency that only requires the knowledge of steady flow behavior. With this important result, it is possible to predict when pulsing would be beneficial or detrimental. DEWEY : 620.1 ISSN : 0742-4795 En ligne : http://asmedl.org/getabs/servlet/GetabsServlet?prog=normal&id=JETPEZ000134000007 [...] [article] Influence of film cooling unsteadiness on turbine blade leading edge heat flux [texte imprimé] / James L. Rutledge, Auteur ; Paul I. King, Auteur ; Richard B. Diver, Auteur . - 2012 . - 10 p. Génie mécanique Langues : Anglais (eng) in Transactions of the ASME . Journal of engineering for gas turbines and power > Vol. 134 N° 7 (Juillet 2012) . - 10 p. Mots-clés : Hot  gas  path  Turbine  engine  Heat  transfer Index. décimale : 620.1 Essais des matériaux. Défauts des matériaux. Protection des matériaux Résumé : Film cooling in the hot gas path of a gas turbine engine can protect components from the high temperature main flow, but it generally increases the heat transfer coefficient h partially offsetting the benefits in reduced adiabatic wall temperature. We are thus interested in adiabatic effectiveness eta and h which are combined in a formulation called net heat flux reduction (NHFR). Unsteadiness in coolant flow may arise due to inherent unsteadiness in the external flow or be intentionally introduced for flow control. In previous work it has been suggested that pulsed cooling flow may, in fact, offer benefits over steady blowing in either improving NHFR or reducing the mass flow requirements for matched NHFR. In this paper we examine this hypothesis for a range of steady and pulsed blowing conditions. We use a new experimental technique to analyze unsteady film cooling on a semicircular cylinder simulating the leading edge of a turbine blade. The average NHFR with pulsed and steady film cooling is measured and compared for a single coolant hole located 21.5° downstream from the leading edge stagnation line, angled 20° to the surface and 90° to the streamwise direction. We show that for moderate blowing ratios at blade passing frequencies, steady film flow yields better NHFR. At higher coolant flow rates beyond the optimum steady blowing ratio, however, pulsed film cooling can be advantageous. We present and demonstrate a prediction technique for unsteady blowing at frequencies similar to the blade passing frequency that only requires the knowledge of steady flow behavior. With this important result, it is possible to predict when pulsing would be beneficial or detrimental. DEWEY : 620.1 ISSN : 0742-4795 En ligne : http://asmedl.org/getabs/servlet/GetabsServlet?prog=normal&id=JETPEZ000134000007 [...]

Time averaged net heat flux reduction for unsteady film cooling / James L. Rutledge in Transactions of the ASME . Journal of engineering for gas turbines and power, Vol. 132 N° 12 (Décembre 2010) 

Public ISBD [article]  in Transactions of the ASME . Journal of engineering for gas turbines and power > Vol. 132 N° 12 (Décembre 2010) . - 06 p. Titre : Time averaged net heat flux reduction for unsteady film cooling Type de document : texte imprimé Auteurs : James L. Rutledge, Auteur ; Paul I. King, Auteur ; Richard Rivir, Auteur Année de publication : 2011 Article en page(s) : 06 p. Note générale : Génie Mécanique Langues : Anglais (eng) Mots-clés : Cooling  Flow  Gas  turbines Index. décimale : 620.1 Essais des matériaux. Défauts des matériaux. Protection des matériaux Résumé : Film cooling flow for reduction in heat flux to a gas turbine engine hot gas path component is generally assumed to be steady. However, unsteady film cooling may occur due to naturally occurring flow unsteadiness or may be induced intentionally. Analysis of pulsed or otherwise unsteady film coolant flow necessitates a reformulation of the existing steady-state technique for net heat flux reduction (NHFR). We show that addition of a cross-coupled term to the traditional steady form of the NHFR equation with time averaged quantities accounts for the unsteady effects. In the experimental technique to determine the time averaged NHFR, we present a new parameter gamma to capture the combined influence of the average adiabatic effectiveness and the coupling between eta[prime] and h[prime]. Measurement of gamma is shown to be straightforward but requiring careful considerations beyond those required to measure eta with steady film cooling. DEWEY : 620.1 ISSN : 0742-4795 En ligne : http://scitation.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=JETPEZ00013 [...] [article] Time averaged net heat flux reduction for unsteady film cooling [texte imprimé] / James L. Rutledge, Auteur ; Paul I. King, Auteur ; Richard Rivir, Auteur . - 2011 . - 06 p. Génie Mécanique Langues : Anglais (eng) in Transactions of the ASME . Journal of engineering for gas turbines and power > Vol. 132 N° 12 (Décembre 2010) . - 06 p. Mots-clés : Cooling  Flow  Gas  turbines Index. décimale : 620.1 Essais des matériaux. Défauts des matériaux. Protection des matériaux Résumé : Film cooling flow for reduction in heat flux to a gas turbine engine hot gas path component is generally assumed to be steady. However, unsteady film cooling may occur due to naturally occurring flow unsteadiness or may be induced intentionally. Analysis of pulsed or otherwise unsteady film coolant flow necessitates a reformulation of the existing steady-state technique for net heat flux reduction (NHFR). We show that addition of a cross-coupled term to the traditional steady form of the NHFR equation with time averaged quantities accounts for the unsteady effects. In the experimental technique to determine the time averaged NHFR, we present a new parameter gamma to capture the combined influence of the average adiabatic effectiveness and the coupling between eta[prime] and h[prime]. Measurement of gamma is shown to be straightforward but requiring careful considerations beyond those required to measure eta with steady film cooling. DEWEY : 620.1 ISSN : 0742-4795 En ligne : http://scitation.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=JETPEZ00013 [...]