Flow Characteristics In Passages With Rib-Turbulators And Film-Holes' Extractions

Passages with rib-turbulators and film holes' extractions are presented inside the state-of-the-art turbine blades, which cooled by combination of the internal convection and the film cooling on surface of the airfoil. Comprehensive understanding of how the rib geometries affect the discharge coefficients of the film holes and how the holes' extractions affect the pressure losses of the passage, would allow designers to optimize the layout of the internal cooling passages of the blades for acquiring higher cooling performances. This dissertation aimed at solving these two questions experimentally and numerically.Experimental investigations were carried out on sets of proportionally enlarged models. The internal passage is rectangular cross-sectioned with two opposite ribbed walls, and the rib-turbulators are staggered arranged. The cylindrical film holes are 45° inclined and perpendicular oriented, there are totally fourteen holes placed on one ribbed wall. Geometrical parameters such as rib angle (45°, 60°, 90° and 120°), rib height (h/e=1.0, 2.0), location of the hole relative to rib on the discharge coefficients and pressure loss characteristics are all studied systematically. And effects of different aspect ratios of the passages (0.5, 1.0, 2.0) are also studied. Reynolds numbers (based on average velocity at passage inlet and hydraulic diameter of the passage) are changing from 20000 to 80000 and the extraction ratios (suction ratios, SR) are changing from 0.30 to 0.60 for each test model. So the influences of Reynolds numbers, suction ratios and etc. on the discharge coefficients and pressure loss characteristics are also presented.Flow fields of typical passages are visualized with the flow visualization techniques and measured with hot-wire anemometer. In addition, numerical simulations are performed to exhibit more detailed flow fields. All of such knowledge would improve our understanding of the flow characteristics.With above research work accomplished, some main results are shown as following: 1. The rib geometries have remarkable influence on the dischargecoefficients of the film holes, by affecting the second flow pattern in the passage and reattachment point of the main flow; 2. The discharge coefficient is increasing along the passage, and reached the maximum value near the passage outlet; 3. The Reynolds number of the film hole and the momentum ratio are the main factors that determine the discharge coefficients; 4. The film hole extraction has the effect of increasing the static pressure, so the pressure loss characteristics of the passage with film hole extraction is obviously different in comparison with that without extraction; 5. A new model for predicting the static pressure loss coefficients in the passage with rib-turbulators and film holes is presented, and its predictions are consistent with the experimental results.