The use of a liquid-organic hydrogen carrier (LOHC)—specifically, 1,2,3,4-tetrahydroquinoline (THQ)—as an endothermic fuel for thermal protection of hypersonic aircraft engines is being proposed by a team at the University of Pennsylvania. Fuel has released a paper on their research.
At 60 bar and temperatures between 500 and 600 °C, the conversion and endothermic heats of reaction were determined over a Pd-Al2O3 catalyst. At 600 °C, heats of reaction as high as 950 kJ kg1 were produced, with conversions of more than 80%. The catalyst remained stable for at least many hours with no signs of coking.
Even at 500 °C on this catalyst, the reaction of methylcyclohexane produced tars that soon choked the reactor. These findings show that LOHC might be used as an endothermic cooling option.
Endothermic fuels have been proposed as a heat control solution for hypersonic aircraft since the 1960s. The basic idea is to transmit heat to a cold fluid fuel as a heat sink; when the temperature of the fuel rises, endothermic reactions occur, and the compound breaks down into simpler components that may be utilized as propulsion fuel.
According to a critical assessment published earlier this year by Dinda et al., despite the interest in the potential, coke formation and buildup in the fuel lines are two of the main restrictions for regenerative cooling using hydrocarbon fuels. Cao et alnew .’s paper proposes a different technique to avoid the well-known issue set.
