Gaz türbin kanatlarının soğutulmasında film soğutması yaygın olarak kullanılmaktadır. Bu makalede, dört farklı eğrisel yüzey ile bir düz yüzey üzerinde film soğutma etkenliği sayısal olarak incelenmiştir. Modeller bir sırada onbir enjeksiyon deliğinden oluşmuştur. Delik geometrileri tüm modellerde dikdörtgendir ve aynı kesit alanına sahiptir. Üfleme oranları 0.5 ile 2.0 arasında ve delik enjeksiyon açıları ana akış yönü ile 30° alınmıştır. Modellerde rüzgâr tüneli ve delikler için sırasıyla hexahedral ve tetrahedral elemanlar kullanılarak ağ yapısı oluşturulmuştur. Sayısal modellerde optimum ağ kullanılmıştır. Enjeksiyon delik kesitlerinde ve jetler ile ana akışın karıştığı bölgelerde diğer bölgelere göre daha sık ağ aralığı kullanılmıştır. Modellerimizde k-ε türbülans modeli, enerji denklemi, ana akış ve soğutucu akışkan olarak hava ve duvarlar için standart duvar fonksiyonları seçilmiştir. Ayrıca sistemin kararlı, duvarlarda ısı kaybının olmadığı ve havanın ideal gaz olduğu kabulleri yapılmıştır. Düşük üfleme oranlarında ana akış, jeti daha kolay bükebilmekte ve böylece jet yüzey üzerine yapışabilmektedir. Bu nedenle düşük üfleme oranlarında film soğutma etkenlikleri yüksek elde edilmiştir. Delik geometrisi, eğrisel yüzeyin eğimi ve üfleme oranının film soğutma etkenliğine önemli etkileri vardır. Sonuçlar, verilen bir yüzey eğriliğinin hem ana akış hemde ana akışa dik yönde film soğutma etkenliğinin, yukarıda ifade edilen parametrelerin uygun seçimine bağlı olduğunu göstermiştir. İyi bir film soğutma için optimum yüzey eğriliği yada gaz türbini kanat eğriliğine uygun enjeksiyon delik geometrisi ve üfleme oranı seçilmelidir.

Gas turbine designers want the gas turbines to have high efficiency. High efficiency is one of the reasons for choosing gas turbines. High turbine inlet temperatures are required to obtain high cycle efficiency in modern gas turbines. The turbine inlet temperature is limited by current blade and vane materials. Some damages and deformations are observed in the blade and vane materials at high temperature. Thus, blade and vane materials should be resistible to such high temperatures. The resistible production of blade and vane materials at high temperatures is related with the improvements of material technology. The current blade and vane materials are made of special alloys and coatings. Moreover, the manufacturing of new blade materials takes a very long time. Therefore, the resistible manufacturing of blades at high temperature is an expensive method. Cooling with air is a less expensive method for the protection of blade and vane materials from high temperatures. Therefore, air is used for cooling on gas turbine vanes and blades as commonly. Film cooling is one of the most commonly used blade and vane cooling methods. Although the film cooling is used commonly it has lots of unknown aspects. Therefore, many researchers are interested in this cooling method. In film cooling, cooling air is injected from holes which are opened with a certain angle to the blade surface and the film layer appears on the blade surface. In this paper, effectiveness of the film cooling on four different curved surfaces and a flat surface was investigated numerically. Models consist of eleven injection holes aligned in a single row. The hole geometries are rectangle and they have the same crosssectional area in all models. The blowing ratios vary between 0.5 and 2.0 and the injection angle is 30o. The main flow velocity value is 15 m/s and the injected fluid velocities are calculated from the blowing ratio equation. The main flow temperature is 288 K in the wind tunnel. The injected cooling air temperature is selected as 328 K. The flat plate, curved surfaces and wind tunnel are modeled in 3-D by using GAMBIT and these models were solved with the FLUENT CFD (computational fluid dynamics) software programme. In models, the wind tunnel and the holes are meshed with hexahedral and tetrahedral map respectively. Optimum mesh has been used in computational models. For the injection hole sections, a finer mesh structure has been used in comparison with that of the other sections. Standard k-ε turbulence model with standard wall function for walls have been selected. The standard k- ε model is a semi-empirical model based on model transport equations for the turbulent kinetic energy (k) and its dissipation rate (ε). The model transport equation for k is derived from the exact equation, while the model transport equation for ε was obtained using physical reasoning and bears little resemblance to its mathematically exact counterpart. In the derivation of the k-ε model, it was assumed that the flow is fully turbulent, and the effects of molecular viscosity are negligible. A wall function is used between the turbulent zone and the wall,. Therefore, the distance from the wall at the cells adjacent to the wall is determined by considering the range over which the log law is valid. Steady state solutions have been obtained assuming no heat loss at the injection hole surfaces. Furthermore, it has been accepted that the system is determined, there is no loss of heat in the walls and the air behaves like an ideal gas. The main flow bends the jet at the low blowing ratios easily and so, the jet gets stuck on blade surface. At high blowing ratios, jet goes in the main flow more easily. This shows that the momentum of jet is better than the momentum of main flow. In that case, the separations from the blade surface have appeared. The hole geometry, the slope of the curved surface and the blowing ratio have important effects on the film cooling effectiveness. The results show that the film cooling effectiveness of a given curved surface both along the mainstream and spanwise direction depends on the optimum selection of the parameters mentioned above. The best surface is C and the best blowing ratio is 0.5 in the mainstream and in the lateral direction in this study. Either optimum surface curvature or appropriate injection hole geometry and blowing ratio for the blade curvature of gas turbine need to be selected for a good film cooling effectiveness.