Impact of Installation Effects on Optimal Propeller Design: Application to a Boundary-Layer-Ingesting Propeller

Abstract

Propellers have gained traction in recent years and are subsequently being integrated into unconventional airframe configurations as part of conceptual designs for developing sustainable aircraft. Close coupling of the propeller and airframe enhances the non-uniformity of the inflow to the propeller. This non-uniform inflow introduces unsteady loading, affecting the propeller's performance. This paper investigates the impact of accounting for installation effects during propeller blade design within an optimization toolchain. This toolchain is applied to a propeller mounted at the rear of a fuselage utilizing Boundary Layer Ingestion (BLI). The proposed design methodology utilizes existing analysis methods to assess the installed aerodynamic and structural performance of the propeller. A gradient-based optimizer is coupled to these analysis methods to design two distinct blades for a multi-segment mission with the objective to maximize the aerodynamic performance. The geometry of the first propeller blade is optimized for the uniform inflow and consequently optimized to operate in the non-uniform inflow. The second blade is from the outset designed for the non-uniform inflow condition. The implementation of the proposed design methodology captures the sensitivity of the inflow field within the design loop, resulting in two distinct blade designs. Upon comparing these blades in BLI inflow conditions to meet identical performance requirements, it was observed that the blade designed to account for installation effects featured a higher inboard chord distribution and consumed 1.58% less energy compared to the blade optimized for uniform inflow for the considered mission profile.