Assessment of Variable Inlets and Active Aerodynamic Components in Nacelles for Subsonic Hydrogen Fuel Cell Propulsion

Kurzfassung

Concerns over global warming have driven research into alternative sustainable aircraft propulsion, with electrified and hydrogen-based systems among the options under development. However, these technologies face challenges related to energy density, manufacturing and safety. They also remain costly, requiring further research. A critical challenge in these systems is heat dissipation, which varies across flight phases, making cooling system optimization essential. This study aims to explore and quantify the potential benefits and challenges of implementing adaptive inlets and morphable nacelle components to enhance cooling efficiency and reduce drag. The focus of this study is on fuel cell based hydrogen-electric propulsion systems, particularly in tractor-propeller configurations similar to the ATR 72-600 aircraft. The primary design criteria is the required air mass flow rate within the cooling system. The nacelle’s three key aerodynamic components are the inlet, internal ducting, and outlet (nozzle). The analytical and numerical methods that measure the sensitivity of their geometric characteristics to the flow characteristics are analyzed. Their impact on flow uniformity, separation, spillage, friction losses, ducting curvature sensitivity, and the effects of Y-duct geometry are evaluated. Then, the flow characteristics are established in a three-dimensional plane considering an interaction with Actuator Line Method to simulate the effects of the close wake of the propeller. To achieve this, CFD simulations are conducted to analyze the sensitivity of flow behavior to the geometric characteristics of the nacelle, particularly due to the limitations that presents analytical modeling. The methods are validated against the experimental methods in existing literature. The research seeks to provide insights into the feasibility of hydrogen-based fuel cell propulsion systems for future sustainable aviation by assessing and quantifying the aerodynamic performance improvements and trade-offs of nacelle inlets, air ducts, and nozzles. The results obtained present mass flow rate variations between 69% and 60% for outlet cross sectional area variations of 25%. In consequence the heat dissipation of the heat exchanger varies in a proportional manner as the mass flow rate, but the increase in drag is up to 2.8 times higher in the configuration with higher mass flow rate at higher speeds, proving the potential benefits in drag reduction from this preliminary research.