Efficiency of models for numerical simulation of propeller-driven flow around nacelles of fuel-cell driven engines

Abstract

Aircraft propulsion systems face significant challenges during take off, where peak motor performance coincides with insufficient cooling due to the absence of sufficient airflow. This issue is particularly relevant for electric propulsion and fuel cell systems. Therefore, a crucial aspect of electrifying aero engines is the analysis of nacelle integrated thermal management systems. It becomes essential to develop cost effective and validated computational tools capable of simulating the impact of propellers on the flow properties around cooling nacelle systems. Given that computational expenses are directly linked to the fidelity of the numerical model, finding an optimal balance between accuracy and cost is of great interest. The objective of this thesis is to provide simulations that strike a proper balance between precision and computational efficiency, enabling the analysis of nacelle integrated cooling systems. To address this challenge, the study investigates various numerical techniques such as the Actuator Line Method (ALM), Actuator Disk Method (ADM), and Panel Method (PM) to explore the flow dynamics around an aircraft’s propeller-nacelle configuration. The primary goal is to develop a versatile tool that can be applied to different conditions and nacelle geometries. A secondary goal is to gather data that can be utilized as an input to evaluate the inlet and outlet flow, pressure, and velocity within the nacelle intercooler’s internal duct. To this end, the study simulates the flow around the propeller-nacelle assembly of a regional aircraft. The results provide crucial information necessary for future internal duct studies and are part of the DLR-EL project with the name ’H2 Electra’. The primary objective was successfully achieved. A comprehensive comparison of the simulation methods, with respect to the balance between solution quality and computational cost, has been conducted. Finally an ALM has been chosen and a solver based on this method was implemented for 3D CFD simulations involving external geometry interactions. Insights across various simulation scenarios were extracted, including near-zero and 40m/s inlet velocities. Additionally, a validation case was conducted, which, despite being only partially successful due to mesh refinement constraints, offers valuable lessons for future work. The secondary objective was also successfully achieved. These results serve as a valuable foundation for future simulations of the internal duct within the nacelle wing cooling system configuration.