Session: 01-14: Whole Engine Performance and Novel Concepts I

Submission Number: 177272

The Role of Diffusion in an Integrated Fan-Heat Exchanger Configuration 

Many studies highlight the potential of hydrogen-powered fuel cells as a promising pathway toward cleaner regional aviation. However, this solution comes with several concerns, such as heat dissipation. Integrating a heat exchanger into the flow path of a propulsor can turn this challenge into an opportunity, leveraging the Meredith effect to generate additional thrust. A critical aspect of this concept is the transition duct between the fan and the heat exchanger, as they operate at different Mach number ranges. The efficiency of the diffusion process within this duct has a direct impact on the overall cycle performance. High levels of diffusion also introduce significant challenges in fan design and integration, posing key questions about the overall feasibility of the concept.

The propulsive system consists of two e-fans mounted under each wing, driven by electrical power provided by the fuel cell system. Cruise is the aerodynamic design point, while take-off and top-of-climb are analyzed to ensure the complete dissipation of the heat produced by the fuel-cells during these flight phases.

To evaluate the cycle-level performance, a 1D cycle sizing model is developed. Initially, conical diffusers combined with non-inclined heat exchangers are analyzed. This configuration shows limited feasibility due to maximum diameter constraints and off-design heat dissipation issues. More promising results are obtained with an inclined heat exchanger arrangement, in which part of the diffusion is achieved using flow-turning guide vanes. This setup mitigates diameter limitations, enhances diffusion potential, and enables lower Mach numbers at the heat exchanger inlet. Furthermore, a sensitivity analysis on guide vanes diffusion losses is conducted to explore different trade-offs and identify promising configurations.

Based on the cycle-level results, a baseline fan design is developed using a 2D preliminary throughflow analysis, ensuring consistency with the 1D cycle and sizing parameters. Within the fan stage, the required diffusion introduces operability challenges, particularly near the hub line. For this reason, a full performance map is generated, and off-design conditions are assessed. typical fan design parameters are investigated to explore the potential benefits of redistributing the diffusion within the fan stage itself, thereby reducing the load on the downstream diffuser. Therefore, a second fan configuration is developed, this alternative design considered approaches such as lowering the fan face Mach number and achieving more diffusion ahead of the stator.

Presenting Author: Giovanni Ciprian German Aerospace center (DLR)

Presenting Author Biography: Will be provided before the conference

Authors:

Giovanni Ciprian German Aerospace center (DLR)
Mavroudis Kavvalos German Aerospace Center (DLR)
Rainer Schnell German Aerospace Center (DLR)
Niccolò Ferrari Technical University Vienna
Ernesto Benini University of Padova