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Film–Cooling Hole Blockage by Sand |
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Project Funded by: Pratt & Whitney |
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Turbine blades in gas turbine engines operate at temperatures well above the melting temperature of the blade material. The turbine relies on lower temperature cooling air to both convect away the heat from inside the turbine blades, but also to protect it through film-cooling on the outside of the blade. These turbine blades are designed with complex internal passages that feed into film cooling holes and pin fin arrangements. |
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In many situations, including desert conditions, takeoff conditions can be very dusty as shown in Figure 1. Ingestion of this dust into the cooling passages can be detrimental to cooling performance given this dust can block the internal passages and external film-cooling holes. Depending on how much sand is ingested and what size the grains are, differing amounts of blockage can occur. Figure 2 shows a turbine blade that has been partially clogged from sand ingestion. If the impacts of sand blockage are not taken into account during the design phase, there could be substantial impact. |
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Figure 1. Sand ingestion is a major concern in modern engine design. |
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Figure 2. Sand ingestion in turbine blades can block the cooling holes leaving the blade vulnerable to high temperature air. |
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A test rig has been designed to simulate the high temperatures in the gas turbine engine while flowing sand through the cooling passages, shown in Figure 3. Figure 4 shows the two coupons that were designed to replicate characteristics of the leading edge of a turbine airfoil. This study uses different sand grains (Figure 5) to test for a range of sand flow rates in order to determine a correlation with blockage effects. |
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Figure 4. The 60-hole and 36-hole test coupons were designed to simulate the leading edge showerhead. |
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Figure 3. The test rig for the sand ingestion tests included a sand delivery system. |
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Figure 5. Dusts similar in composition to those found in arid regions melt at moderate temperatures. |