Background
Decarbonization of gas turbine engines used in aircraft propulsion and electrical power generation is a significant technical concern to achieve climate security. One means of achieving decarbonization of gas turbine engines is using hydrogen fuel. There have been numerous studies showing the viability of hydrogen fueled gas turbines, with the major advantage of hydrogen being that the exhaust from the engine is free of carbon biproducts. However, one of the challenges of using hydrogen fuels is the higher localized combustion temperatures and higher heat transfer to the turbine blades due to increased water content in the combustion products. Consequently, an important technological challenge for gas turbines operating with hydrogen fuel is to provide improved cooling to the turbine components so they can operate effectively with higher heat transfer from mainstream flows. The goal of this project is to design and build a turbine blade prototype which incorporates advanced cooling technologies and test it in a hydrogen-fueled, high-temperature combustor flow.
Approach
For this research project, an internally and film-cooled airfoil is being designed by UT Austin, taking advantage of recent advances in metal additive manufacturing (AM). The cooling performance for this airfoil will first be evaluated at low temperatures using the turbine airfoil testing facilities at UT Austin, then verified at high temperatures using the combustor test facility at SwRI. The external environment will be combustion products from 100% hydrogen fuel combustion with dry air as the coolant.
Accomplishments
A film-cooled airfoil strut has been designed and the effectiveness of the internal cooling passage design and film hole placement has been studied using computational fluid dynamics (CFD). Only a single cooling hole pitch was modeled with periodic boundaries for faster computation time. The strut includes internal cooling passages, showerhead film cooling holes, shaped film cooling holes, and pin fin cooling. UT Austin conducted adiabatic film cooling effectiveness tests on the strut design in their low temperature, low speed wind tunnel. Results from testing have not yet been post processed to remove the effects of conduction through the strut material. The preliminary results without the conduction correction show adiabatic film cooling effectiveness of 60 to 80%. Correcting for conduction is expected to reduce this range to 40 to 60% adiabatic effectiveness. Inconel test struts for high temperature testing have been additively manufactured by UT Austin’s metal AM printers with good resolution of the hole geometries and cooling configurations. UT Austin conducted a computed topography (CT) scan of one of the Inconel struts that showed negligible clogging of the holes with no obvious deformities.
Figure 1: Results from CFD analysis of the film-cooled strut showing temperature contours in and around the test article.
Figure 2: Preliminary adiabatic effectiveness results of strut from low speed, low temperature testing at UT. Note – these results have not yet been corrected for conduction and so are unrealistically high.
Figure 3: CT scan of additively manufactured Inconel strut shows clear holes and channels and no obvious deformities.