Zero-Carbon Engine Core with Supercritical Carbon Dioxide Power Cycle for Onboard Power (ALFA)

Over the past two decades, zero-emission aviation has focused on drop-in synthetic fuels to replace fossil-based jet fuels in progress towards net-zero emission of carbon dioxide. This project targets an alternative, scalable pathway to zero-emission aviation using electricity-derived (or green) ammonia as a hydrogen carrier. Here emission of carbon dioxide and non-volatile particulate matter is completely eliminated, and new technology is introduced that can significantly reduce, or even eliminate, emissions of nitrogen oxides and contrail-forming water vapor. Thus, ALL emissions are targeted in this project, not just that of carbon dioxide.

In this proposed scenario, liquid ammonia is used to refuel each airplane, and portion of that ammonia is cracked onboard to nitrogen and hydrogen. Here, ammonia is not only used as a hydrogen carrier, but leveraged for multiple purposes to nearly eliminate ALL emissions and improve engine efficiency. In addition, a closed-Brayton power cycle is incorporated into the proposed concept to utilize exhaust waste heat to minimize engine power extraction and specific fuel consumption.

Any new technology for aviation needs to address several concerns concurrently: (1) technical requirements for commercial aviation, (2) over-arching concern for safety, (3) extent and cost for upgrading the global fleet of airplanes and airports, and (4) global supply chain. Even though the first concern is the primary focus of this project, no new technology will be successfully transitioned to market without sufficient attention to the other three, and there needs to be holistic optimization of all four. For this reason, with significant attention on technology transition, this project addresses all four barriers to adoption. A single-aisle Boeing airframe with a GE engine will be utilized as the reference model for which the proposed technologies will be optimized, and values of key performance metrics for the proposed configuration will be compared against those for the reference configuration. As needed, specific gates of Orlando International Airport will be utilized in cost estimates to be performed.

For potential fleet implementation in the 2040s, the project team consists of members who can assist in follow-up technology transition and ground/flight demonstration.