| To increase the temperature of turbine inlet is an important method for improving turbine performance and its economics. However, the inlet temperature increasing is restricted by the heat resistance ability of blade material. Therefore, some effective manners must be taken to protect the turbine blades from high temperature erosion. Among these methods, film cooling technique has been used for gas turbine blades and became a major cooling method for turbine rotor. In film cooling, cooling medium was injected to main stream in lateral jet through slots and/or little holes on the surface of high temperature turbine rotor. Under the effect of pressure and friction of the main stream, the jet curved and covered the surface of high temperature parts, and then low temperature gas film was formed, which can perform the action of isolation and cooling.The effectiveness of film cooling is mainly dependent on the shape of hole geometry, such as jet angle, hole diameter, length-to-diameter ratio, pitch, outlet configuration, blade geometry, and aerodynamic parameters. Many studies have shown the presence of uneven outlet velocity and complicated flow fields configuration, and the different film configuration has significant effects on the film. Therefore, it is very important to understand the flow filed feather of different hole mouth and mechanism of heat transfer for the optimum design of turbine blades and practical holes. The present studies are manly focused on cylindrical hole relatively to other types of hole. Recently, some researchers has tried to adopt novel holes, such as converged-slot hole, crescent hole, and trenched hole, in the optimum design of film holes and get better performance of cooling . In this dissertation, numerical simulation method was adopted to study cylindrical hole, forward diffused hole, crescent hole, trenched forward diffused hole, converged-slot hole and trenched cylindrical hole in film cooling effectiveness and flow fields of jet downstream and spanwise, and comparison among these holes were analyzed in detail, thereby the principle of strengthen cooling of novel hole was clarified. With regard to converged-slot hole, further study was carried out about the effect of length-to-diameter ratio, pitch-to-diameter ratio and injection angle on converged-slot hole cooling effectiveness. In addition, film cooling characteristics of a turbine blade's leading edge with two rows cooling orifices were investigated in this dissertation. The computed results were presented in the form of effectiveness contours on the blade surface and compared with experimental results. Complicated characteristic of flow fields and cooling on the stagnation area of blade leading edge, the effect of injection angle and hole pitch on film cooling effectiveness were investigated in detail. The main content and conclusion in this dissertation were listed as follows:(1)A numerical code for the calculation of turbine blade film cooling was accomplished by the two-layer k ?εturbulence model. Coordinate system is set up by the differential equation and by adoption of the multi-block grids accelerated compute procedure. The trait of numerical code was provided with account precision high, generate grid and compute convergence rapidly, so it preferably simulated flat plate film cooling and main flow and film cooling character in leading edge of turbine blade.(2)Numerical simulation about film cooling effectiveness in downstream and spanwise and flow fields of crescent hole, converged-slot hole were carried out. Comparison between novel hole and cylindrical hole was carried out, and the principal of high effectiveness of novel hole was thoroughly analyzed. It was shown that the expanded exit of crescent hole reduced the vortex intensity especially high blowing ratio, cooling gas expanded laterally in spanwise and uniformly covered plate surface, and the interaction between mainstream and the jet uniformed duo to exit geometry of crescent hole, so film coverage, averaged film cooling effectiveness and film uniformity of crescent hole were best among the cylindrical hole and forward diffused hole. In vertical jet direction the walls of converged-slot hole diverge, and in jet direction the walls converge, so that jet in film hole enough was developed and flow separation was disappeared. Because of special jet structure of converged-slot hole, the flow accelerated from inlet to outlet made suitable pressure gratitude, so the ejected coolant film was continuous and the film didn't lift off from blade surface. Consequently, the typical two counter rotating vortices were restrained and the film cooling protection effect was improved.(3)With regard to converged-slot hole, further study was developed about the effect of length-to-diameter ratio, pitch-to-diameter ratio and injection angle on converged-slot hole cooling effectiveness in this dissertation. It was found that cooling effectiveness of converged-slot hole increased along with length-to-diameter increasing for any blowing ratios. Furthermore, the film cooling effectiveness had the different degree raising along the span direction between adjacent holes within the somewhere downstream the holes for fixed length-to-diameter, and extent of rising a little at low blowing ratio, and that extent of rising for cooling effectiveness corresponding augment along with blowing ratio increasing. Results also showed that cooling effectiveness for small injection angle was very high. Furthermore, the improvement realized by the small jet angle compared to the other jet angle holes is more important at the higher blowing ratio than it is at the lower one. For short hole pitch, intensive disturbance was happened at nearby injection outlet and between two holes, and hence effect of row made single hole. It caused film cooling distributed convergence, and the improvement for cooling effectiveness realized by downstream the holes, but film coverage was poor. The broad coverage realized by the increase hole pitch, and but cooling effectiveness was low by comparison with short pitch at injection outlet. In addition, interference of film was very clear at a bit far downstream the holes. (4) Numerical simulation about film cooling effectiveness in downstream and spanwise and flow fields of six kinds of trench hole were carried out. Results of several special of trench hole were detailed analyzed, as well as the mechanism of transverse trench was thoroughly analyzed. It was shown that effectiveness in downstream and spanwise of all of trench hole was better than that of cylindrical hole at any blowing ratio, and this trend was got over evidence along with increasing of blowing ratio. Film cooling effectiveness of several kinds of trench hole was almost consistent at low blowing ratio, change trend of effectiveness of different trench hole was unlikeness along with increasing blowing ratio. The effect of trenched size on film cooling performance was very complicated. In this dissertation, temperature of trench hole with moderate depth and maximal width was very low at large-scale of film hole downstream, and jet center axes was near from wall at hole exit, so its film effective coverage, average cooling effectiveness and film uniformity were best among other cases. Furthermore, film cooling effectiveness in downstream and spanwise direction increased along with increasing of blowing ratio. However, temperature of trench hole with maximal depth was high at large-scale of film hole downstream and jet tended to lift-off wall, so film cooling effectiveness was reduced.(5)Film cooling characteristics of a turbine blade's leading edge with two rows cooling orifices were investigated in this dissertation. Complicated characteristic of flow fields and cooling on the stagnation area of blade leading edge, the effect of injection angle and hole pitch on film cooling effectiveness were studied in detail. Results showed that the first row of orifices located nearby leading stagnation line existed suitable pressure gratitude, which was beneficial to cooling gas uniformly development towards downstream of the orifices. The second row of coolant, which is situated in a low-pressure region, created counter rotating vortex pairs at back of the coolant hole on account of coolant jet interrupting mainstream during both interaction. The net result is that coolant jet tended to lift-off surface development towards downstream of the holes. Because mainstream and coolant jet mixed, coolant tended to stay near surface again during development towards downstream of the holes. Vortex pairs were weakened in virtue of reducing injection angle, and therefore coolant jet core tended to near the surface, which was propitious to covering surface. For different blowing ratios, cooling effectiveness of two rows was opposite proportion to pitch, that is cooling effectiveness declined along with increasing pitch, and but the drop extent of efficiency was difference.
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