Weave Topology Effects on Gas Turbine Cooling Technology PDF Download

Author: Ryan Edelson
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Languages : en
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Book Description
As hot section gas turbine technology continually improves, it is necessary to fully understand how these technologies impact traditional cooling features. Ceramic matrix composites (CMCs) are a material of great interest in hot section components, as the material's favorable weight and thermal properties at high temperatures have the potential to reduce cooling flows and increase efficiency. However, in order to fully implement this technology, it is critical to understand how the macro scale weave topology affects the fluid dynamics and heat transfer of cooling flows. Particularly, it is of interest to characterize how this weave surface impacts internal convective heat transfer, as well as overall film cooling effectiveness, in order to better predict cooling flow requirements for hot section components made from CMCs. This thesis begins with a study that investigated CMC weave surface topology effects on internal channel pressure loss and heat transfer. Weave surface topology was additively manufactured at three different orientations and used as the walls of an internal channel. Experiments measured bulk pressure loss and heat transfer for a range of Reynolds numbers, while computational fluid dynamics simulations measured bulk and local pressure loss and heat transfer at one specific Reynolds number. Results showed that the weave surface topology increased pressure loss and heat transfer compared to a smooth surface. Additionally, orienting the long weave strands perpendicular to the flow caused greater augmentations than when they were parallel to the flow due to secondary flow vortical structures. As a follow up study, test coupons with film cooling holes relevant to true engine scale were additively manufactured. These test coupons contained weave surfaces, representative of CMCs, on the top wall of the internal coolant supply channel, external film cooled surface or both internal and external surfaces. The coupons were tested over a range of blowing ratios to evaluate the effects of the weave geometry on overall effectiveness, with and without film cooling. Overall effectiveness values without film cooling indicated that the internal CMC coupon with a smooth external surface resulted in significantly increased overall effectiveness levels when compared to the test coupons with an external weave surface. This overall effectiveness increase was because the smooth external surface reduced convective heat transfer between the test coupon and the mainstream flow when compared to an external weave surface. Overall effectiveness results with film cooling showed that increases in blowing ratio caused increases in overall effectiveness for all coupons. Overall effectiveness measurements indicated that the weave surface caused increased mixing between the coolant and mainstream flows compared to a smooth external surface. This increased mixing caused decreased levels of overall effectiveness for coupons with an external weave surface compared to a smooth external surface. The weave surface on the top wall of the internal coolant supply channel increased the heat transfer coefficient of the internal channel and increased in-hole convection when compared to a smooth surface, also increasing levels of overall effectiveness. As such the internal CMC coupon, with a smooth external surface and internal weave surface, saw the highest overall effectiveness levels. This study provided valuable knowledge for turbine designers who wish to implements film cooling into components made of CMC. The results prominently indicated the importance of considering the weave surface topology of the CMC when implementing this new material.