Approaches to Facilitate Using HPT SiC/SiC CMC Vanes and Rotor Blades

The work will evaluate the benefit of cooling compressor discharge air. T3 air, for use in cooling High Pressure Turbine(HPT) first stage vane and blades for future high OPR and high power density aircraft engines. SiC/SiC CMC materials have higher temperature capability than Superalloys, but require minimum cooling to achieve high performance. Surface temperature rises as OPR increases, if T3 air is not cooled. Cooling T3 air will be evaluated to show its effect on blade row average temperature, and on blade stresses. Detailed stress analysis will be done for first and second stage vanes and blades. For the first stage thermal stressed are expected to be the dominant stress. While cooling T3 air is expected to have a higher overall effectiveness, a small effectiveness increase might result in higher component stresses. The effect on efficiency of axial velocity variations between first and second HPT stages will be determined. As OPR and T41 increase the mass flow at constant thrust decreases, which decreases axial velocity below current levels. As OPR increases for stress constrained SiC/SiC CMC components the variation in axial velocity between first and second stages increases. A reduction in blade span increases axial velocity, but increases clearance loss due to a higher clearance-to-span ratio. A reduction in blade span increases friction losses. The analysis of axial velocity effects will address this issue.

This work furthers NASA's goal of reduced emissions from commercial aircraft. The proposed work will identify approaches to improve engine efficiency and reduce the weight of the high pressure core. The work will quantify reduction in fuel burn from these approaches. Over the long term these approaches will help enable expanded air travel with fewer emissions.

This work is relevant to the entire gas turbine industry. Land based combined cycle gas turbines seek to increase efficiency by increasing T41 without increasing NOx, and cooled T3 air can help to achieve this goal. Simple cycle gas turbines, and military aircraft engines have the same interest in efficiency and weight as commercial engines.

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