Internal crossflow is an important element to actual gas turbine blade cooling; however, there are very few studies in open literature that have documented its effects on turbine blade film cooling. Experiments measuring adiabatic effectiveness were conducted to investigate the effects of perpendicular crossflow on a row of 45 degree compound angle, cylindrical film cooling holes. Tests included a standard plenum condition, a baseline crossflow case consisting of a smooth-walled channel, and various crossflow configurations with ribs. The ribs were angled to the direction of prevailing internal crossflow at 45 and 135 degrees and were positioned at different locations. Experiments were conducted at a density ratio of DR=1.5 for a range of blowing ratios including M=0.5, 0.75, 1.0, 1.5, and 2.0. Results showed that internal crossflow can significantly influence adiabatic effectiveness when compared to the standard plenum condition. The implementation of ribs generally decreased the adiabatic effectiveness when compared to the smooth-walled crossflow case. The highest adiabatic effectiveness measurements were recorded for the smooth-walled case in which crossflow was directed against the spanwise hole orientation angle. Tests indicated that the direction of perpendicular crossflow in relation to the hole orientation can significantly influence the adiabatic effectiveness. Among the rib crossflow tests, rib configurations that directed the coolant forward in the direction of the mainstream resulted in higher adiabatic effectiveness measurements. However, no other parameters could consistently be identified correlating to increased film cooling performance. It is likely that a combination of factors are responsible for influencing performance, including internal local pressure caused by the ribs, the internal channel flow field, jet exit velocity profiles, and in-hole vortices. / text

Dans la chambre de combustion, les températures auxquelles les parois sont soumises sont supérieures aux températures de fusion des matériaux. Afin de protéger les parois, une partie de l'air froid provenant du compresseur est injectée par des milliers de perforations (multiperforation). Cependant, face à l'enjeu de la pollution, les motoristes considèrent des solutions qui limitent la quantité d'air disponible pour le refroidissement. Son optimisation s'avère donc capital. Néanmoins, la très petite taille des perforations rend les simulations numériques coûteuses, et des modèles homogènes permettant de s'affranchir du maillage des trous ont gagné de l'importance. De plus, des études récentes ont mis en évidence l'intérêt d'une injection d'air de refroidissement non-alignée avec l'écoulement chaud (solution baptisée dilution giratoire). Cette thèse se propose, d'une part de développer un modèle homogène adapté à ce type nouveau d'injection et d'autre part de contribuer à la compréhension de la multiperforation giratoire. / Ln the combustion chamber, temperatures up to 2000K are reached, which exceeds by far the melting point of the liner materials. ln order to protect the liner, cool air from the combustion chamber outer casing is injected into the combustor through a large number of sub-millimeter closely-spaced holes (effusion cooling). However, strict environmental legislation has led jet-engine manufacturers to consider techniques that reduce the quantity of air available for cooling. Therefore, cooling system must be carefully designed. However, the size of the holes makes detailed numerical simulations unaffordable. Aerothermal models that mimic effusion cooling behavior are a promising solution. On the Other hand, up to now, far too little attention has been paid to a novel effusion cooling technique (compound angle effusion cooling), where cold air injection is not aligned With the hot air flow direction. The aim of this dissertation is twofold: to establish an effusion cooling model and to investigate the flow field of compound angle effusion cooling.

This experimental study consists of two parts. For the first part, the film cooling effectiveness for a single row of seven cylindrical holes with a compound angle is measured on a flat surface using five different measurement techniques: steady-state liquid crystal thermography, transient liquid crystal thermography, pressure sensitive paint (PSP), thermocouples, and infrared thermography. A comparison of the film cooling effectiveness from each of the measurement techniques is presented. All methods show a good comparison, especially for the higher blowing ratios. The PSP technique shows the most accurate measurements and has more advantages for measuring film cooling effectiveness. Also, the effect of blowing ratio on the film cooling effectiveness is investigated for each of the measurement techniques. The second part of the study investigates the effect of hole geometries on the film cooling effectiveness using pressure sensitive paint. Nitrogen is injected as the coolant air so that the oxygen concentration levels can be obtained for the test surface. The film effectiveness is then obtained by the mass transfer analogy. Five total hole geometries are tested: fan-shaped laidback with a compound angle, fan-shaped laidback with a simple angle, a conical configuration with a compound angle, a conical configuration with a simple angle, and the reference geometry (cylindrical holes) used in part one. The effect of blowing ratio on film cooling effectiveness is presented for each hole geometry. The spanwise averaged effectiveness for each geometry is also presented to compare the geometry effect on film cooling effectiveness. The geometry of the holes has little effect on the effectiveness at low blowing ratios. The laterally expanded holes show improved effectiveness at higher blowing ratios. All experiments are performed in a low speed wind tunnel with a mainstream velocity of 34 m/s. The coolant air is injected through the coolant holes at four different coolant-to-mainstream velocity ratios: 0.3, 0.6, 1.2, and 1.8.