MEGAWATT project

Demonstration of Massive Electric Generation for Aircraft and Wake Adaptive Thruster Technologies

JAXA is working on a technology demonstration project called MEGAWATT from FY2023, aiming to take an initiative on the era of passenger jet fleet with megawatt-class electric hybrid propulsion systems by integrating key technologies from Japanese industries. The mission of MEGAWATT is to develop and demonstrate electric hybrid propulsion system for jet aircraft as a highly matured integrated system capable of treating high electric power, thereby enabling Japanese companies to lead the way in electrification businesses by leveraging their innovative technologies. The outcome through this activity will be transferred to Japanese industries and aircraft OEMs, contributing to international standardization efforts, the electrification of next-generation passenger fleet as well as the carbon neutrality.

Wake Adaptive Thruster (WAT) concept

The concept of improving the efficiency of the propulsion system using the BLI (Boundary Layer Ingestion) effect by attaching a propulsion fan on the tail of the fuselage has been proposed, but it has not yet been realized.

There are two main reasons for this. The first is that the airflow near the tail of the fuselage is quite complicated and distorted, making it risky for a conventional turbofan engine to ingest it. Second, when the aircraft is rotated during takeoff, the cowling of the tail fan must not touch the ground, so there is restriction on the diameter of the tail fan, making it impossible to achieve the expected level of improvement. For the former, the feasibility can be improved by adopting electric fans, so recent proposals for the BLI aircraft are based on the use of electric fans. On the other hand, no drastic solution has been found regarding the latter.

To solve the above issues, JAXA is proposing a new aerodynamic configuration, the WAT (Wake Adaptive Thruster) concept.

On board electric power generation in passenger air fleet

Modern airfleet uses a lot of electricity, but its aim is not to generate propulsive power, but to be utilized as power for various systems such as air conditioning, galleys, and anti-icing.　Normally, electricity on the airfleet is generated by an electric generator attached to the gas　turbine engine. As the electric power requirement of aircraft systems increases with each succeeding generation, the capacity of engine-mounted electric generators tends to increase exponentially. Current engine-mounted electric generators are driven by shaft power extracted from the high-pressure spool, but the power that can be extracted from that spool shaft is approaching its limit. To realize a new type of electric generator which extracts power from a low-pressure spool is the key to obtaining the power required by electric propulsion fans.

Key technologies from Japanese domestic industries will lead to a breakthrough in the realization of electric hybrid passenger fleet.

Topics of research and development in the MEGAWATT project

MEGAWATT will develop the main subsystems that are parts of the electric hybrid propulsion system and will conduct assessment of the following designs and technology demonstrations by using ground test facilities.

1. Regarding JAXA's unique WAT concept, the effectiveness will be validated through CFD and transonic wind tunnel tests. The results obtained from the technology demonstrations will be used to estimate the performance of the actual electric hybrid aircraft.
2. MW(MegaWatt)-class electric generator, motor and several devices will be developed and preliminary tests to confirm the validity of the performance of the components, which will be supplied to the demonstrations, will be conducted.
3. In-flight electric power generation system will be developed, and an integrated demonstration test will be conducted to confirm that large amounts of electric power can be generated from the generator which is directly connected to the engine low-pressure spool. Furthermore, protection functions will be checked whether it will be reliably activated to prevent generator failures from propagating to the entire engine system.
4. The electric fan drive system will be developed with a high-altitude environment facility. The ability to generate torque and rotation speed required for an actual aircraft even in a low-pressure environment will be demonstrated, and the aerodynamic loss caused by the cooling system for the electric motor will be validated as well.
5. The achievements of the project will be shared to Japanese domestic industries and global stake holders, in addition, the knowledge will be used for international standardization.

May 21, 2024