Transportation Energy Conversion

GE Research has proposed transformational material solutions to potentially enable a gas turbine blade alloy-coating system capable of operating at a turbine inlet temperature of 1800 °C for more than 30,000 hours.

Pennsylvania State University (PSU) will develop an integrated computational and experimental framework for the design and manufacturing of ULtrahigh TEmperature Refractory Alloys (ULTERAs). PSU will generate alloy property data through high-throughput computational and machine learning models; design ULTERAs through a neural network inverse design approach; manufacture the designed alloys utilizing field assisted sintering technology and/or additive manufacturing; and demonstrate the performance through systematic characterization in collaboration with industry.

A turbine engine's combustion environment can rapidly degrade high temperature alloys, which means they must be coated. This coating must be able to expand with the alloy so it adheres during temperature cycling, prevent combustion gases from permeating to the underlying alloy, and possess ultra-low thermal conductivity to protect the alloy from high surface temperatures. The University of Virginia will develop a novel coating for high temperature alloys that enables both a dramatic increase in upper use temperature for turbine engine blades and increased engine efficiency.

Current Ni-based alloys used in turbine blade applications are operating at 1100°C, which is approximately 90% of their melting temperatures. Refractory alloys, such as niobium (Nb) alloys, can withstand higher temperatures.

Thermal barrier coatings (TBCs) on turbine blades are designed to protect the blade from reaching temperatures higher than the operational capability of the base metal. Pacific Northwest National Laboratory aims to develop a new type of TBC that performs dual functions. The coating will act as a barrier to conventional heat transfer and have ability to alter the wavelength of light radiated from the hot turbine blade surface. This normally wasted energy will be absorbed in the turbine exhaust where it can then produce additional electrical power or thrust.

The National Energy Technology Laboratory (NETL) will develop lightweight, cost-effective, precipitation-strengthened refractory high entropy alloys (RHEAs) for additive manufacturing. The advantage is an alloy with all phases in thermodynamic equilibrium, promoting high microstructural stability. The alloys will be comprised of a ductile high entropy solid solution matrix strengthened by fine precipitates of the high entropy carbides. NETL will use high throughput, multi-scale computer modeling, and machine learning to identify novel alloys within the large compositional space.

Current alloys used in gas turbines operate at about 90% of their melting temperature, which sets a limit on achieving higher temperatures. Refractory metal alloys (RMA) have the capability to enable continuous operation at 1300°C and with compatible coatings along with cooling systems to allow for gas inlet temperatures to reach 1800°C. The high RMA melting temperatures present challenges for traditional manufacturing methods, however.

The Zero-carbon Ammonia-Powered Turboelectric (ZAPTurbo) Propulsion System is a very high efficiency and lightweight turboelectric system that uses green ammonia as a fuel and coolant via regenerative cooling. Coke-free heating of this carbon-free ammonia fuel enables a high level of waste-heat recovery that will be used for the endothermic cracking of ammonia prior to its combustion, significantly increasing the cycle efficiency. The proposed propulsion system includes an efficient AC electric powertrain for turboelectric cruise, with battery boost for takeoff and climb flight phases.

Increasing the efficiency of power generation and air transportation can only be achieved by increasing the temperature at which generation/propulsion turbines operate. The emerging Refractory High Entropy Alloys (RHEAs) can enable much higher operating temperatures than the state-of-the-art. Identifying the alloys' chemistry is difficult due to the vastness of the RHEA chemical space.

The University of Maryland will leverage a newly invented, ultrafast high-temperature sintering (UHS) method to perform fast exploration of new environmental-thermal barrier coatings (ETBCs) for 1300°C-capable refractory alloys for harsh turbine environments. UHS enables ultrafast synthesis of high-melting oxide coatings, including multilayers, in less than a minute, enabling rapid evaluation of novel coating compositions.