The advantage of higher turbine inlet temperatures as a way to increase cycle efficiency is potentially outweighed by the efficiency losses caused by the increased secondary air extracted from the compressor discharge to cool turbine components. Higher cooling effectiveness schemes could be used, but pressure head required to drive the coolant flow through the hot section components may be higher than those available due to combustor pressure losses. This paper looks to determine the potential effects on the overall cycle efficiency caused by an intentional pressure drop across the combustor, allowing more aggressive cooling schemes with a lower amount of cooling air, based on data of state of the art cooling schemes (coolant flow ratio, pressure head and cooling effectiveness) and a parametric analysis of a simple cycle turbine. Results suggest that coolant flow reduction can actually result in a lower pressure drop across the cooling passages, given the decreased flow velocity ending up in higher efficiency and specific work. Enhanced cooling schemes can also allow higher turbine inlet temperatures for a given coolant flow, resulting in improved performance.

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