Investigation On Endwall Film Cooling And Tip Leakage Of Gas Turbine Blade

Gas turbine is the "heart" of the aircraft. As the key technique,gas turbine techniques are always preferentially developed and strictly confidential in the developed countries, because they are important symbols of military strength and comprehensive national power of a country. In recent years, our country is facing seriously territorial disputes. Therefore, a powerful air force is necessary to achieve the "China Dream" and the "dream of a strong military". The Chinese government attaches great importance to developing the next generation fighter.The growing requirement of higher thermal efficiency of gas turbines leads to increase continuously turbine inlet temperature. Nowadays, the turbine inlet temperatures of advanced gas turbines have been much higher than the melting points of existing high temperature alloys. To protect the high temperature components, it seems to be more important to research advanced cooling techniques than high temperature materials. In this paper, the characteristics of endwall film cooling and tip leakage of gas turbine blade are investigated, and main works can be classified into the following three parts.Part 1: focusing on the film cooling characteristics of one film hole. The film cooling characteristics of three types of film holes with new configurations are investigated using numerical simulations with commercial CFD software. Here, the three types of film holes are: 1) fanshaped hole with round exit (RE); 2) fanshaped hole with laidback and round exit (LBRE); 3) fanshaped hole with laidback and sharp-angle exit (LBSE). It is clear that the three configurations of film holes are different from the traditional cylindrical film hole. Fanshaped hole with LBSE is firstly proposed by this work, and it has been validated as the best configuration of film holes through the comparison of film cooling effectiveness and areodynamical performances with the other two configurations. Through a comparison of the film cooling effectiveness with different blowing ratios, it can be confirmed that the film cooling effectiveness achieves the best, when blowing ratio is at 1.5. Through the investigation on the conductivities of alloy, ceramic and foam glass, it can be concluded that the heat conductivity is an important factor to influence on the film cooling effectiveness. This work suggests firstly two exponential equations to fit the film cooling effectiveness with Biot number and space, i.e.,?f = f(Bi) and ?f =f(x, Bi). The rationality of the fitting equations is validated.Part 2: researching on the characteristics of endwall film cooling of turbine cascade, and discovering firstly the similarity phenomena of temperature field in this process. The similarity phenomena of temperature distributions at the film cooled endwall surface are discovered through the experiments conducted in the hot gas wind tunnel using an infrared thermal imaging system. The similarity phenomena are regenerated using the numerical approach validated by the experimental data.According to the simulation results at different mainstream and coolant temperatures,it can be discovered that both the maximal and minimal temperatures of similar contours basically meeting linear relationships. The reason of the similarity phenomena is analyzed, and the conditions how the similarity phenomena existing are discussed. The way to quantitatively describe the similarity phenomena is firstly presented in this paper, including defining three new parameters, i.e. the similarity degree between different contours, corresponding deviation and maximal deviation from a certain reference contour. Two ways, indirect and direct prediction methods, to predict the endwall temperature distribution are proposed, and how to calculate the error of the prediction is also exhibited. Using the predication methods, the cost and time for the experimental and numerical investigations could be significantly reduced.Part 3: investigating on the tip leakage of turbine blades. There have been three experimental approaches in the previous investigations to capture the characteristics of the tip leakage: (1) both the blade and shroud were stationary (BSSS); (2) the blade was stationary but the shroud was operated by a rectilinear movement (BSSRM); (3)the blade was rotating and the shroud was in steady (BRSS), which is a real status of turbine operation. The differences of tip leakage flows between the three approaches are discussed through the numerical strategy validated by our previous experiments.The numerical simulations are carried out at three rotation rates (1000r/min,2500r/min and 4000r/min), and a blowing ratios of 1.5. Through comparisons, three conclusions can be drawn: (1) BSSM experiment method is closer to the real status,BRSS, however there are some evident differences between BSSS and BRSS cases;(2) a method based on correcting the wall viscous shear stress via shroud wall roughness is proposed to revise the experimental data obtained in BSSS case, so that the difference of BSSS case from the real case, BRSS, is reduced...