| Titre : | Discharge coefficient of film cooling holes | | Type de document : | texte imprimé | | Auteurs : | Saad Benmansour, Auteur ; N. Hay, Directeur de thèse ; D. Lampard, Directeur de thèse | | Editeur : | Nottingham : University of Nottingham | | Année de publication : | 1981 | | Importance : | 137 f. | | Présentation : | ill. | | Format : | 30 cm. | | Note générale : | Mémoire de Master : Génie Mécanique : Royaume-Uni, University of Nottingham : 1981
Bibliogr. f. 138 - 143 . Annexe f. 144 - 208 | | Langues : | Anglais (eng) | | Mots-clés : | Film cooling holes
Jet engines
Discharge coefficient | | Index. décimale : | Ms00281 | | Résumé : | Film cooling is a method of protecting a surface which is exposed to a hot gas flow by covering it with a film of cold gas.
The coolant film is injected through rows of holes in the cooled surface.
The most important application of this method is its use in cooling turbine blades and nozzle guide vanes in jet engines, which are subjected to very hot flows from the engine combustion chambers.
It is shown that there is a lack of information about the behaviour of the discharge coefficient of holes and also about the effects on it of the various possible parameters investigated.
The work presented here, was conducted in a specially constructed isothermal rig, to determine which are the parameters having a strong effect on the discharge coefficient of film cooling holes.
The flow direction in the coolant channel was considered parallel to the mainstream flow, such as encountered in nozzle guide vanes and perpendicular to the mainstream such as in the rotor blade situation.
The flow parameters covered in both configurations were the mainstream mach number M ͚, ranging from 0.0 to 0.5 the coolant mach number Mc, ranging from 0.0 to 0.4 and the pressure ratio Pc⁺/P ͚ from 1.0 to 2.0.
The Reynolds number in the holes was kept around 0.6 x 10⁵.
The geometric parameters varied, were α the angle of inclination of the holes, between 30° and 90°, and the length to diameter ratio L/D between 2 and 6.
The results showed that the discharge coefficient was mainly affected by the pressure ratio Pc⁺/P ͚ and the coolant mach number Mc.
For a pressure ratio up to 1.5, the discharge coefficient decreased by about 25% when Mc increased from 0.0 to 0.4 for both flow configurations and α = 30° and 90°.
For higher values of pressure ratio, Cd remains approximately constant, except for α = 30° in the parallel flow configuration, in which Cd increased by up to 30% in all the range of pressure ratio (1.05 -> 2.0).
The effect of the length to diameter ratio L/D was negligible in the range considered 2 < L/D < 6.
Similarly, the mainstream mach number did not have a significant effect on Cd for Pc⁺/P ͚, the discharge coefficient decreased by up to 15% for parallel flow configuration and about 20% for perpendicular flow configuration when M ͚ increased from 0.0 to 0.5.
It was also found that a row of four holes could be considered as representative of a gas turbine blade situation.
Finally, the experimental results were compared with a simplified prediction of Cd.
Acceptable agreement had been achieved at low pressure ratio. |
Discharge coefficient of film cooling holes [texte imprimé] / Saad Benmansour, Auteur ; N. Hay, Directeur de thèse ; D. Lampard, Directeur de thèse . - Nottingham : University of Nottingham, 1981 . - 137 f. : ill. ; 30 cm. Mémoire de Master : Génie Mécanique : Royaume-Uni, University of Nottingham : 1981
Bibliogr. f. 138 - 143 . Annexe f. 144 - 208 Langues : Anglais ( eng) | Mots-clés : | Film cooling holes
Jet engines
Discharge coefficient | | Index. décimale : | Ms00281 | | Résumé : | Film cooling is a method of protecting a surface which is exposed to a hot gas flow by covering it with a film of cold gas.
The coolant film is injected through rows of holes in the cooled surface.
The most important application of this method is its use in cooling turbine blades and nozzle guide vanes in jet engines, which are subjected to very hot flows from the engine combustion chambers.
It is shown that there is a lack of information about the behaviour of the discharge coefficient of holes and also about the effects on it of the various possible parameters investigated.
The work presented here, was conducted in a specially constructed isothermal rig, to determine which are the parameters having a strong effect on the discharge coefficient of film cooling holes.
The flow direction in the coolant channel was considered parallel to the mainstream flow, such as encountered in nozzle guide vanes and perpendicular to the mainstream such as in the rotor blade situation.
The flow parameters covered in both configurations were the mainstream mach number M ͚, ranging from 0.0 to 0.5 the coolant mach number Mc, ranging from 0.0 to 0.4 and the pressure ratio Pc⁺/P ͚ from 1.0 to 2.0.
The Reynolds number in the holes was kept around 0.6 x 10⁵.
The geometric parameters varied, were α the angle of inclination of the holes, between 30° and 90°, and the length to diameter ratio L/D between 2 and 6.
The results showed that the discharge coefficient was mainly affected by the pressure ratio Pc⁺/P ͚ and the coolant mach number Mc.
For a pressure ratio up to 1.5, the discharge coefficient decreased by about 25% when Mc increased from 0.0 to 0.4 for both flow configurations and α = 30° and 90°.
For higher values of pressure ratio, Cd remains approximately constant, except for α = 30° in the parallel flow configuration, in which Cd increased by up to 30% in all the range of pressure ratio (1.05 -> 2.0).
The effect of the length to diameter ratio L/D was negligible in the range considered 2 < L/D < 6.
Similarly, the mainstream mach number did not have a significant effect on Cd for Pc⁺/P ͚, the discharge coefficient decreased by up to 15% for parallel flow configuration and about 20% for perpendicular flow configuration when M ͚ increased from 0.0 to 0.5.
It was also found that a row of four holes could be considered as representative of a gas turbine blade situation.
Finally, the experimental results were compared with a simplified prediction of Cd.
Acceptable agreement had been achieved at low pressure ratio. |
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