Aerospace

Deflecting vanes are a common means of attitude control for electric ducted fan (EDF) vehicles. However, vane forces are mostly measured at a single operating condition, and the usable deflection range is usually assumed. A four-vane vectoring module fitted to a 70 mm EDF was tested on a static rig. Axial and normal forces were measured at six vane angles up to 25° and eight throttle settings from 10% to 80%. Rotational speed and exhaust velocity were measured, and smoke visualized the deflected jet. The vanes turned the force through less than the commanded angle. At each commanded angle, this shortfall varied by no more than 1.5° with throttle from 40%. At 20°, the effective vectoring angle was 16.0° to 17.2°. The thrust vectoring efficiency peaked at 20° at every throttle setting, from 40% to 20.9%. Beyond 20°, the normal force decreased and the resultant continued to fall. Hence, 20° was the best setting tested. At 80% throttle and 20°, the normal force was 1.56 N, and the resultant was 72% of the 7.89 N reference thrust. For control design, one relation between commanded and effective angle holds from 40% throttle, and commands beyond 20° add no control force.

The Brayton cycle based on supercritical carbon dioxide (S-CO₂) is widely used in turbomachinery. In this paper, the rotordynamic coefficients are systematically investigated for the labyrinth seal working with S-CO₂ based on NIST REFPROP database. A three-dimensional numerical model of the labyrinth seal was developed using computational fluid dynamics (CFD). The rotordynamic characteristics of the labyrinth seal for different boundary conditions and various geometries were studied over a wide frequency range of 20–260 Hz. Results show that the direct complex stiffness coefficient exhibits strong frequency dependence in the low-frequency region, while the cross-coupled complex stiffness coefficient and average direct damping coefficient exhibit relatively slight frequency dependency. The effective damping coefficient increases with the increasing inlet pressure, rotational speed, blade quantities, and decreasing inlet temperature. The effective damping coefficient has a strong frequency dependency at low whirling frequencies less than 80 Hz and increases slightly with the decreasing sealing clearance. At high whirling frequencies above 80 Hz, the effective damping coefficient increases with the increasing sealing clearance. The effective damping coefficient of the labyrinth seal with S-CO₂ is about 167~202% of that with air modeled as an ideal gas, indicating a more favorable contribution of the seal to rotordynamic stability. The frequency-dependent trends of the rotordynamic coefficients under real gas conditions differ significantly from those under ideal gas conditions, highlighting the importance of real gas effects for accurately predicting the rotordynamic performance and stability of S-CO₂ labyrinth seals.

Aviation accounts for 2% of global carbon emissions. As global carbon emissions increase, the more-electric aircraft (MEA) concept has been proposed in recent years to reduce emissions from aviation. The MEA trend involves replacing conventional hydraulic, mechanical and pneumatic components with more electrical components, eliminating some uses of non-electrical energy. Starting from the background and concept of MEA, this review introduces its basic concepts and architectures, together with the energy-supply requirements of onboard electrical systems. It reviews progress in high-power-density power supplies, energy utilisation, thermal management, onboard energy storage and fault safety. By comparing existing technical results, the review identifies interactions among generation, power conversion, thermal management and energy storage. It analyses their effects on onboard electrical power system mass, mission energy consumption and power supply reliability. The functional differences between MEA and electrified aircraft propulsion (EAP) are used to clarify the shared basis of their electrical technologies and the conditions for applying them. Finally, the review identifies priorities for MEA development. These include higher power density and efficiency in generation and conversion equipment, lightweight thermal management, energy recovery and high-specific-energy storage. Further priorities are intelligent power management, post-fault supply restoration, battery installation protection and verification of airworthiness compliance.