High-Fidelity Model for Endothermic Jet Fuel Cracking and Coking

Several advanced propulsion designs run up against material limitations, i.e. with some otherwise attractive designs, at certain operating conditions the heat load in certain locations of the structure can be so large the surface temperature can exceed safety limits for structural failure.

One way to reduce the surface temperature is to flow fuel through channels inside the structure, i.e. to use the fuel as a coolant. If the heat load is small, the heat can be carried away as sensible heat of the liquid fuel, or, at higher heat loads, by boiling the fuel. At more interesting heat loads, these thermophysical mechanisms of heat removal are insufficient, and instead we must use the much larger heat absorbing capacity of endothermic chemical reactions. Because the energetics of chemical reactions are an order of magnitude larger than the energies associated with physical changes, this potentially could allow much higher heat loading than if the cooling is purely physical, allowing more efficient engine designs.

However, some undesirable side reactions can occur. The most detrimental are side reactions which create solid deposits. If deposits accumulate, they would affect the heat transfer, might affect the chemistry, and in the worst case could plug the cooling channels. At present the details of all these chemical reactions are unknown, and there is no reliable computer simulator one could use to help guide development of an efficient and safe design that would be robust over the whole possible range of operating conditions, including variations in fuel composition.

The goal of this research is to develop a computer simulation of the chemical and physical phenomena occurring in the cooling channels, with a focus on the cracking reactions which dominate the heat absorption and the reactions which could lead to coke formation. Our main approach will be to use the Reaction Mechanism Generator (RMG) to construct a detailed chemical kinetic model for this system. The coking model will build on existing models in the literature.

This project is done in collaboration with and is sponsored by Mitsubishi Heavy Industries.