Thermofluids Discovery Laboratory

Contrail formation is one of the most significant non-CO2 climate impacts of aircraft operations, outweighing the radiative forcing from CO2 emissions by almost a factor of two. Understanding differences in microphysical evolution and optical characteristics between contrails produced by traditional and carbon-free aviation fuels is, therefore, crucial to ensuring the successful development of climate-friendly propulsion systems.

While ammonia is considered a promising hydrogen-based fuel alternative, its contrail formation and persistence characteristics remain uncertain owing to unique thermodynamic conditions in the aircraft's wake. While soot, acting as a primary nucleation site in contrails produced by traditional fuels, is absent in the ammonia-system's exhaust, water vapor emissions are significantly increased, and contrail nucleation may still occur on ambient aerosol populations at upper tropospheric levels.

To assess the climate impacts of ammonia-powered contrails, a specialized CFD contrail module has been developed within the atmospheric code Meso-NH, based on the microphysical parameterization LIMA (Liquid Ice Multiple Aerosols) and coupled with anelastic and pseudo-incompressible formulations. To reconcile the significantly varying spatial and temporal scales throughout a contrail's lifetime, the model couples two temporal LES domains specialized to the jet, vortex, and early-dissipation regimes by superimposing synthetic atmospheric and wake-turbulence fields. The development of this model paves the way to enabling the first detailed simulation-backed comparison of optical and persistence characteristics between contrails produced by ammonia and kerosene.

A power plant’s ice condenser system consists of thousands of “baskets” filled with borated ice. Each basket must be individually lifted and weighed during routine inspections. However, the process used to replenish the gradually melting ice can cause neighboring baskets to freeze together, preventing their individual inspection without labor-intensive work to separate them.

We developed a better way to separate the ice baskets to allow for easier inspections. We designed a deicing system that uses a precision laser to cut through the sheets of ice that connect adjacent baskets, allowing the baskets to be safely separated and inspected. Our tool can function more than 40 feet below the surface in freezing conditions and in the tight spaces between the ice baskets.

CLEAN (CarbonLess Electric AviatioN) is a NASA-sponsored University Leadership Initiative project working toward a zero-emission, 150-passenger airliner powered by an ammonia-fueled hybrid-electric engine. Within the project, our Aircraft Structure and Aero-System (ASAS) sub-team, a collaboration between the University of South Florida, Tennessee Tech University and Tennessee State University, is designing an airframe that can carry the heavier engine and still fly more than 2,100 nautical miles, comparable to a Boeing 737-400.

The concept shown in this animation combines two NASA ideas, the truss-braced wing of the NASA/Boeing SUGAR Volt and the aft-mounted Electrofan of NASA’s SUSAN concept. Two turbofans under the wings and one Electrofan at the tail share the propulsion load, which lightens the slender braced wing and lets the aft fan ingest the fuselage boundary layer to reduce drag. Our team is now optimizing the wing and propulsion together for the CLEAN engine, with CFD validation and a truss design to follow.